# Older air compressor wiring help



## lash-1295 (Dec 7, 2009)

Registered Member

Join Date: Dec 2009
Location: texas
Posts: 1 









*Air compressor wiring (speedaire)(dayton)* 
Can anyone on here help with the wiring on a speedaire(dayton) air compressor? There are no tags on the motor or compressor so Grainger cannot help with wiring diagrams. There is some sort of switch or treminal block missing in the junction box. The wiring was done by previous owner. I tried wiring the two wires with the missing connection directly together but it blows the breaker. With them disconnected nothing happens at all. The wires appear to come from the low oil cut off switch. Any Ideas. The ground wire is not wired to anything at all in the present configuration.


























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## Thurman (Feb 9, 2009)

Well, it appears that the electricians over at their forum didn't offer much help. I'd like to see a picture of the whole compressor, particularly if it is belt-driven. I'm thinking that you may have a larger unit requiring three-phase electricity. That control box seems to have at least one heater element in it, and possibly two small relay contacts. That is why I'm suspecting three-phase electric supply. A photo taken further back would also show where the yellow wires go/come from. So, maybe a pic of the entire unit, and one of the control box from further back would offer more info. Thanks, David


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## micromind (Mar 9, 2008)

It's pretty hard to tell from the pics, but it looks like the starter is set up for single phase. A single phase motor needs only one overload, a 3 phase needs at least two, preferably 3. 

I think this system can be made to work, but we'll need a few more pics. Get a shot of the whole starter, and make it right-side-up. The sideways ones are hard to read. 

It's been so long since I've worked with a Furnas starter, I'll need a good look at it. 

Make sure that the coil is 240 volt, it'll likely say 120/240 or 240/480. 

Basically, the pressure switch, the overload switch, and the low-oil switch are wired in series with the coil. When the coil is energized, the contacts are pulled in, and the motor is powered up. 

Rob


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## lash-1295 (Dec 7, 2009)

Ok, Quick update here. First of all I guess the guys over at the other forum were none to happy with me. LOL. Guess it was more clear to them than to me that their forum was only for "professional" electricians. OOPs. I had an "electrician" come and look at the compressor and he couldn't make heads or tails of it. I made a call to a compressor shop and talked to a salty old repair man who seems to have me on the right track. I was able to wire the motor directly to the 220 outlet and it works like a charm. But obviously I still need to wire back in all of the shut off and safety switches. He said it sounded like I was missing a starter coil or a "heater". Did a little more poking around and discovered that underneath the terminal block at the top there is a set of four spring loaded contacts that are just setting loose at the moment. It looks like the part that is missing connects to this block of contacts. On the left side of this contact block the is a white "thing" that looks like it pushes down on the left side of this block to "rock" the contacts on and off. I realize a picture is worth a thousand words so I will get bigger better pictures asap. 

Thanks for the help so far.


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## lash-1295 (Dec 7, 2009)




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## nap (Dec 4, 2007)

you are missing the coil for the contactor. It is what pushes the contacts together to turn this on.

You may not be able to find the parts for that starter anymore. That style is not made anymore that I am aware of and parts would be tough to find.

I would suggest pricing out a new motor starter at an electrical supply house.

they will need the voltage of the motor, the control circuit voltage, the # of phases (appears to be single phase), the FLA of the motor,

and what else micromind? I am sure I am forgetting something.


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## lash-1295 (Dec 7, 2009)

Thanks for the advice. One small problem though. There are no and I mean none at all id plates on the motor or the compressor. So I have no idea how to get any of those voltage requirements. Any suggestions?

Thanks for the help so far.<br><br>


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## micromind (Mar 9, 2008)

nap is right on the dot. That starter is pretty old, parts will be nearly impossible to find. 

A new starter is in order, it would be easiest to get one with a 240 volt coil. No neutral that way. 

Wherever you get it from, you'll need the HP of the motor, # of phases (I'm betting single phase too), and the full-load amps (for sizing the heaters). It needs to be 2 pole (more is OK, but a waste of money), and doesn't need the auxiliary contact. 

There are pretty much 3 types of starters; NEMA, IEC, and Definite Purpose. 

The NEMA type is pretty much bullet-proof. They're the toughest ones, and the most expensive. They'll take an incredible amount of abuse, and just keep on working. These are referred to by size. For example, a size 2 will start a 25 HP motor on 460 volts 3 phase, a 15 at 230 volts, a 10 at 200 volts, a 7-1/2 at 230 volts single phase, and a 3 at 115 volts. 

The IEC type is not as tough, but it'll work OK for an air compressor. Some of these come in two parts, the contactor and the overload. Easy to assemble. These are rated in amps, but have HP rating as well. Always use the HP ratings. 

The Definite Purpose type is similar to the IEC type, but it's the leas toughest. Also the least expensive. It'll work for an air compressor if it doesn't get started and stopped very much. It'll work OK in a home garage, but not in a commercial/industrial application. They're made for A/C units where the motor starts fast. An air compressor starts a bit slower, and is harder on the starter. 

If we know the HP of the motor, we can help you pick the right starter. 

Rob


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## micromind (Mar 9, 2008)

The new pic helps. That's a Baldor motor, likely either a 3 or 5 HP. Measure the shaft diameter (likely 1-1/8") and how high the center of the shaft is from the bottom of the base (likely 4-1/2"). 

Next, remove the spring shaped thing from the overload block. (Right below the white button). It'll have some sort of number stamped on it. If I remember right, Furnas uses a letter then a number. Like F34, or something. This will tell us the full-load amps, and confirm the HP. 

Failing this, hook it up, and measure current at around 100 PSI. If it's 3 HP, it'll be around 16 amps, if it's a 5, about 25 amps. 

Keep at it, eventually we'll get it running.

Rob


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## lash-1295 (Dec 7, 2009)

Was told it was a 5 hp single phase so what I am missing is the full load amps. Any idea how to determine that? The only labels I can find at all are on the low oil cutoff and I think on the pressure switch itself.

Thanks


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## lash-1295 (Dec 7, 2009)

You guys are awesome thanks alot. The copper plate reads H-40 on the side. So 17.7 to 18.4 full load amps?


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## lash-1295 (Dec 7, 2009)

Micromind you called it 1 1/8" shaft 4 1/2" inches high


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## micromind (Mar 9, 2008)

That motor is a NEMA type. It's pretty tough. Just as a wild guess, I'd get overload heaters at 25 amps. That motor very likely has a service factor of 1.15. This means that it can tolerate a bit of overload indefinitely. 

I'd use a 50 amp breaker. The code allows a maximum of a 70, and if the 50 trips, that's what I'd use. #10 will be the minimum wire size, unless it's NM cable (Romex), then 8/2 would be minimum. 

An air compressor doesn't overload the motor unless something is wrong. The load on the motor goes up as pressure increases. I'd bet a lot that the pump is two-stage. The maximum operating pressure of such a pump is 175 PSI. Anything less than that is less load on the motor. 

If it is 5 HP, you'll need a NEMA size 1P starter. This is a two pole model designed for single phase motors. It might be a bit hard to find though, a size 2 three pole will work as well. 

The IEC and Definite Purpose size will be 30 amp. They're available in two or 3 pole. Usually, 3 pole is easier to find, but a bit more expensive. If you went a size or two larger, it'll last longer. There's absolutely no need to up-size a NEMA starter though. 

A used NEMA starter would be OK, I'd be a bit hesitant about a used IEC or Definite Purpose type though.

Rob


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## micromind (Mar 9, 2008)

The H40 is just a number. The actual current will be a bit different fir different size-type of starters. I'll try to find a current table, but it might take a while, if I can find one at all. 

Rob


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## lash-1295 (Dec 7, 2009)

Does this help?


H40 Furnas Furnas "H Series" Heater Element - Reconditioned 
 

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*
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*

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*Weight:* 0.10LB
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*Condition: * Reconditioned 
*Manufacturer List Price: * $11.60 

H40 "Standard Trip" Furnas Heater Element for Metal Alloy Relays, Sizes 1, 1 3/4, 2 and 2 1/2 Starters. Full Load Motor Amps Range 17.7 - 18.4 - Furnas Catalog Number: H40


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## micromind (Mar 9, 2008)

Yes, it does.

18 amps is slightly high for a 3 HP, but it's way low for a 5. I'm betting on the 3. 

Whatever starter you get, use overloads for 18 amps. 

This also helps on the starter as well. A NEMA size 1 will operate a 3 HP single phase motor, two pole or 3 pole. 

A 23 amp IEC starter is good for 3 HP, as is a 25 amp Definite Purpose starter. A size or two larger will last longer. 

Rob


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## lash-1295 (Dec 7, 2009)

Sorry but I need a little help understanding. Two poles means? If I buy the whole box with the starter will it come with a wiring diagram?


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## nap (Dec 4, 2007)

twp poles equates to two sets of contacts so you can basically open or close two separate wires.

and yes, a motor starter does come with wiring diagram in the thing but it does not figure in a pressure switch or oil level switch (if used). those will have to be added to the circuit in the control circuit.


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## lash-1295 (Dec 7, 2009)

So I just talked to local repair tech and he suggested just wiring it through the pressure switch and using that as the starter while he looks to see what he has for starters. Any thoughts on that?


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## Stubbie (Jan 7, 2007)

Just looked in on this thread and I noticed that this furnas contactor as said needs replacing but I'm wondering with so many parts missing the contacts cover is off or missing, the coil is missing and the cover is off or gone. I think on the cover there may have been a momentary start button or rocker toggle? Just mentioning as that may need to be addressed in the new wiring.


Also e bay sometimes has some very good deals on this type of motor starter.


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## nap (Dec 4, 2007)

it will work for now but the contacts on a pressure switch are often not rated for the current draw of a motor. That is exactly why you use a starter; so you control the motor power wiring with a control circuit that either has a lower voltage or has a lower current flow.

anyway, what will happen is the contacts could weld closed and you may not notice until the pop off valve opens or they could burn bad enough not not start the motor.


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## nap (Dec 4, 2007)

Stubbie said:


> Just looked in on this thread and I noticed that this furnas contactor as said needs replacing but I'm wondering with so many parts missing the contacts cover is off or missing, the coil is missing and the cover is off or gone. I think on the cover there may have been a momentary start button or rocker toggle? Just mentioning as that may need to be addressed in the new wiring.
> 
> 
> Also e bay sometimes has some very good deals on this type of motor starter.


actually there could have been stop start buttons which does need to be present to make all of this work. 

good catch.


lash, if there are no momentary buttons elsewhere, you need to incorporate start button and a stop buttons. They should be momentary. The start is a normally open contact and the stop is a normally closed contact.


micromind; why didn't you remind me when I asked you?

great job with the explanation and info by the way.:thumbup:


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## lash-1295 (Dec 7, 2009)

Thanks guys. I will make sure of that when I decide on the new starter. The cover is indeed missing so I will replace the box as well. I bought this from a guy who inherited it from his dad. He initially wanted $125 but by the time I met him the next morning he wanted $250 because he said he have an offer for that much on the phone. What do you think did I over pay?


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## micromind (Mar 9, 2008)

Sorry, nap. I guess I was too busy with the techno-babble. lol.

Baldor is one of the very top motor manufacturers. 

The pump looks like a Champion. They seem to last forever as well. 

I know it's sort of old, but back then compressors were built to last. I think you got a pretty good deal. A similar compressor goes for around $1500 new. 

Rob

P.S. I don't think the pressure switch alone will handle a 3 HP motor. At least not for very long. Most of them are rated for 2 HP at 240 volts. It'd be a good idea to include the low oil switch in the circuit as well. It won't handle any HP, just control of a starter.


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## Stubbie (Jan 7, 2007)

nap said:


> actually there could have been stop start buttons which does need to be present to make all of this work.
> 
> good catch.
> 
> ...


Yeah... I'm not going to try to compete with micro on his technical knowledge. 

Yes I meant to say start/stop buttons but heck who wants to turn this baby off ???? I think.. though I am not positive... that furnas used a black rocker type momentary switch to operate the starter . There is a chance you might find a picture of the starter on a surplus electrical site or may be has one up for sale. Might check and see would make the change over a tad easier but not much. I'm not so sure if push come to shove you could fuse the motor for overload and use a definite purpose contactor to start it in conjuction with the pressure switch. But that's the kansas farmer in me....

Is that an oil level switch on the compressor ?


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## nap (Dec 4, 2007)

Stubbie said:


> Yeah... I'm not going to try to compete with micro on his technical knowledge.
> 
> Yes I meant to say start/stop buttons but heck who wants to turn this baby off ???? I think.. though I am not positive... that furnas used a black rocker type momentary switch to operate the starter . There is a chance you might find a picture of the starter on a surplus electrical site or may be has one up for sale. Might check and see would make the change over a tad easier but not much. I'm not so sure if push come to shove you could fuse the motor for overload and use a definite purpose contactor to start it in conjuction with the pressure switch. But that's the kansas farmer in me....
> 
> Is that an oil level switch on the compressor ?


ya mean like this?










Unless he runs across somebody with some old parts, I don't think he is going to get the rest of this starter. I think his best bet would be just replace with new.

and the switch to the near right of center of the compressor; it looks like a micro-switch (actuator pointed to to the left.) I do not know what that would be for.

MM, any ideas?


lash; to the value of the compressor:

I don't think you are going to like the cost of a new starter but at $125, if that thing works, you got a steal. I think at $250 you still did good..

I cannot tell but is it single or dual cyl and is it single or dual stage? There are a lot of pipes running around. . Peerless' newer 2 stage compressors put the cylinders in a V configuration. I don't know if they did side by side configuration with their older compressors so that is why I ask.

any tags that give a CFM or LPM rating on the thing?


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## Stubbie (Jan 7, 2007)

I'm pretty sure that micro switch is for oil level shutdown. If the oil level gets too low the rod that holds the switch closed moves so far down that the actuator stem frees and opens the latching circuit.

Was that furnas starter for sale and was it rated properly?

I would have gave 250 for this compressor but I have all the stuff to get it back going again. A new starter with enclosure box is not the cheapest thing and your going to have anther 150 in it at best...unless you find something surplus but your going to have to know what you are looking for.

Right now if there is a bottom drain I would open it and get the water out of the tank might be a bunch in there.


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## micromind (Mar 9, 2008)

That's almost certainly a two stage pump. It looks a lot like a Champion, but it's hard to tell. 

There are two cylinders, a larger one and a smaller one. On this pump, they're in-line, others are V. The larger cylinder is the first stage, it draws air in through the filter, and compresses it to about 40 PSI or so. 

The air exits this cylinder and goes into the finned tubing. This is the intercooler. It if then fed into the smaller cylinder, and exits into the tank. The smaller cylinder is closest to the flywheel, because it runs hotter. 

The maximum pressure on this pump is 175 PSI. It'll very likely produce around 10 CFM at 175 PSI. Use straight 30 weight oil in it, not 10-40 or any multi-weight. 'Air Compressor Oil' is almost always 30 Wt, and will work fine. Be careful if you use synthetic oil. It doesn't get along with mineral oil very well, and the crankcase will need to be flushed out first. It also will eat away at polycarbonate (the plastic used on filters and such). 

The micro-switch looks a lot like a low-oil shutdown. Just wire it in series with the pressure switch. It'd be a good idea to test it first, they're notorious for failing. With the crankcase full of oil, the contacts should be closed (have continuity). 

Rob

P.S. Ebay is your friend when looking for a starter. They're unbelievably expensive new.


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## lash-1295 (Dec 7, 2009)

http://cgi.ebay.com/Square-D-starte...emQQptZLH_DefaultDomain_0?hash=item20ae6e766d

Can't read the labels on this but could it be about what I am looking for? I need to contact them for more detail if you think I am on the right track. The switch in question is indeed a low oil cutoff. There is a cork float behind the sight glass that floats the copper rod up and closes the contact. I think the copper button on the side is supposed to be a reset but it is frozen I just took the cover off and cleared the lever by hand until the rod floated up. By the way I have it wired directly to the motor at the moment and everything seem to work. I had to fix what I believe is called the "unloader" valve. It is located on the front of the pump and uses a ball bearing between a spring and a copper rod. It was leaking all of the air out and would not shut off as it is supposed to do. I took it apart and oiled it with compressor oil and now it just lets a small amount of air out and then shuts off. I believe it is supposed to make it easier for the pump to start by dumping air pressure in the pump. I can't find any numbers on the pump. It is a dual stage. By the way it is the quietest compressor I have ever been around. It makes about 1/10th of the sound of my oilless compressor. Label inside pressure switch say 145 cut in and 175 shutoff pressures. By the way what kind of grease should go in the motor if those are grease serts? Tank has been drained. About a pint of water.


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## micromind (Mar 9, 2008)

The starter you're looking at might work, I can't tell what the coil voltage is, but 240 would be best. Since there's a white wire in it going to the overload block, I suspect it's 120. If so, you'll need to either run a neutral along with the power circuit, get a 240 coil, or install a control power transformer. 

The hand-off-auto switch in not needed, but it can be easily removed, or left on and used as a control switch.

Square D is a good brand, so is Allen Bradley. The overload heaters for Square D are likely easier to get than the Allen Bradley. The square D heater will be a B28.0, the Allen Bradley will be a W59. A two pole starter for single phase motors uses one heater, a 3 pole uses 3 heaters even it the motor is single phase. They cost about $15 each. 

Rob


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## lash-1295 (Dec 7, 2009)

So is it acceptable to use a 120v switch if I use the ground?


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## nap (Dec 4, 2007)

lash-1295 said:


> So is it acceptable to use a 120v switch if I use the ground?


??????????????


I hope you do not mean "use the ground in place of a neutral so as to have 120 volts" Because if it is, the answer is emphatic "NO".

You need to be using the ground for it's intended purpose anyway. You cannot use the ground as a neutral. You need to bring a proper neutral to the controller to allow the use of a 120 volt coil and control circuit.


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## micromind (Mar 9, 2008)

Like nap stated, the ground cannot be used to carry current. Not even a little bit. 

If you use a starter with a 120 volt coil, you'll need a total of 4 wires from the panel to the starter. Two hots, a neutral, and a ground. 

If you use a starter with a 240 volt coil, you'll need a total of 3 wires from the panel to the starter. Two hots, and a ground. 

The only other options are to replace the 120 volt coil with a 240 volt one, or install a control power transformer. This transformer needs to be designed for motor controls, a regular transformer will work only if it's grossly oversized. 

Rob

P.S. A 240 volt coil for a typical size 1 starter will cost about $80-100, a control transformer will cost about $70, but you'll need to mount it in some sort of box. A 6"X6"X6" will work. Ebay will be less.


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## J. V. (Jun 1, 2007)

http://www.weg.net/files/products/W...arters-esw-series-usa300-brochure-english.pdf

Here is an example of a single phase fully assembled starter for around $100.00. Nema 1 enclosure, 5 HP rated contactor rated @240 VAC, user must select OLR and coil voltage, and prewired with wiring instructions. The OP could use the pressure switch in lieu of the rocker or push button start/stop. However, a disconnect may be required?

You guys did all the research, I just thought I might be able to help with the starter selection and give the OP an idea of what he should be looking for.


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## lash-1295 (Dec 7, 2009)

Guess that did not sound too good the way I wrote it. LOL. 
Thanks for the clarification.


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## nap (Dec 4, 2007)

J. V. said:


> http://www.weg.net/files/products/W...arters-esw-series-usa300-brochure-english.pdf
> 
> Here is an example of a single phase fully assembled starter for around $100.00. Nema 1 enclosure, 5 HP rated contactor rated @240 VAC, user must select OLR and coil voltage, and prewired with wiring instructions. The OP could use the pressure switch in lieu of the rocker or push button start/stop. However, a disconnect may be required?
> 
> You guys did all the research, I just thought I might be able to help with the starter selection and give the OP an idea of what he should be looking for.


actually the pressure switch would not be used in lieu of the start/stop. The P/S would need to be wired inline properly so it would shut down the compressor but not drop out the run circuit so the comp would restart automatically when pressure drops. The stop would drop out the run circuit totally.

the oil pressure switch could be hooked in either way since it must be reset to restart the machine but I would still wire it in to totally shut down the run circuit.


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## micromind (Mar 9, 2008)

The starter from the site that J.V. provided would be #ESWS-25V24E-RM33. If you want an on-off switch, get the field kit modification # KESWFP. It's easy to wire, if the instructions are unclear, there's about 10 of us around here who can walk you through it. 

The overload in this starter is an IEC type, it doesn't use heaters. It has a dial that you set with a screwdriver to the full-load current of the motor. Yours is 18 amps. 

The only slight drawback to this starter is it has class 10 overloads. These are sort of fast-acting. If the compressor comes up to speed in less than 5 seconds (it very likely does), it'll be OK. If it takes longer, the overloads might trip unnecessarily. 

Rob


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## J. V. (Jun 1, 2007)

nap said:


> actually the pressure switch would not be used in lieu of the start/stop. The P/S would need to be wired inline properly so it would shut down the compressor but not drop out the run circuit so the comp would restart automatically when pressure drops. The stop would drop out the run circuit totally.
> 
> the oil pressure switch could be hooked in either way since it must be reset to restart the machine but I would still wire it in to totally shut down the run circuit.


Why not? The pressure switch can and will control the starter without any operator interface (start/stop). You want the pressure switch to drop out the contactor. The OPS would be wired in series with the pressure switch. 

There is no requirement for a start/stop button or switch. Maybe a disconnect, but not a start/stop.


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## lash-1295 (Dec 7, 2009)

See next


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## lash-1295 (Dec 7, 2009)

http://cgi.ebay.com/NEW-Siemens-Sin...emQQptZLH_DefaultDomain_0?hash=item4ce5b68cfe

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260430630230&ssPageName=STRK:MEWAX:IThttp://cgi.ebay.com/NEW-Siemens-Sin...emQQptZLH_DefaultDomain_0?hash=item4ce5b68cfe

Would one of these work if I have them put in the proper size heaters?


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## spark plug (May 5, 2009)

lash 1295 (Poster #7) Look for Motor ratings; Voltage, FLA & LRA (Probably the one item NAP skipped?) Ph. Single or 3ph. Size of motor/RPM. inside the Humongous cover.


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## spark plug (May 5, 2009)

J. V. said:


> Why not? The pressure switch can and will control the starter without any operator interface (start/stop). You want the pressure switch to drop out the contactor. The OPS would be wired in series with the pressure switch.
> 
> There is no requirement for a start/stop button or switch. Maybe a disconnect, but not a start/stop.


But most (quality) magnetic starters I've seen come with START/STOP buttons. Except they have to be wired properly. And what if not. That's a story for another thread.:laughing:


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## nap (Dec 4, 2007)

a motor starter only comes with a stop start button if that is how you order it. There are many times where I have a motor starter and the stop start station is nowhere near the motor starter so having one on the starter is an unnecessary expense. 

A lot of times, there will be an on/off/auto selector on a motor starter as well but again, only if it is needed or wanted.

when operating motors with other controls, having a stop start on the starter is not the norm.


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## nap (Dec 4, 2007)

J. V. said:


> Why not? The pressure switch can and will control the starter without any operator interface (start/stop). You want the pressure switch to drop out the contactor. The OPS would be wired in series with the pressure switch.
> 
> There is no requirement for a start/stop button or switch. Maybe a disconnect, but not a start/stop.


You wire it how you want to wire it and I wire it how I like. If you put the air pressure switch in the wrong place, it will drop out the coil and you would need to hit the start button to restart the machine. That is where I would put the oil pressure switch so I would have to restart the machine manually for the loss of oil pressure since that is something the operator should attend to.

with the air pressure, you would want the compressor to cycle on and off as needed. Like I said, if you put that in the wrong place in the circuit, it will not do that.

as to requirement for on/off. How do you propose turning it on and off?


I do not like to use breakers for switches. I would not plug this in so that means I would put an on/off switch on the thing.

a disconnect may or may not be required but that would depend on where the breaker is from the compressor. If you need a disco, I would use a combination starter/disco.


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## micromind (Mar 9, 2008)

Either of those starters will work just fine. Easy to install and connect, and with the proper heater, it'll protect the motor. 

If you want an on-off switch, a basic light switch will work. Mount it in a single-gang handy box (1-7/8" or 2-1/8" deep). If you'd like, the handy box can be mounted directly to the starter box using a 1/2" chase nipple and a locknut, and a couple of 8/32 X 1/2" machine screws.

Just wire the switch in series with the rest of the control circuit. If you need help with the controls, any one of about a dozen of us around here can walk you through it. 

Rob


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## lash-1295 (Dec 7, 2009)

Ok.

Just ordered it. I will go with the light switch. Thanks for the advice. I will let you know when I get it.


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## J. V. (Jun 1, 2007)

nap said:


> You wire it how you want to wire it and I wire it how I like.
> 
> *Okay*
> 
> ...


*Agree on both points. Combination starters cost ALOT of money. A simple AC disconnect like used outside next to a condenser unit would work just fine and cost less than $20.00.*

*I had no intention to hijack or disrupt this thread. However, there was some clarification required between nap and myself before I could let it go. Thanks and good luck on this project.*


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## spark plug (May 5, 2009)

nap said:


> a motor starter only comes with a stop start button if that is how you order it. There are many times where I have a motor starter and the stop start station is nowhere near the motor starter so having one on the starter is an unnecessary expense.
> 
> A lot of times, there will be an on/off/auto selector on a motor starter as well but again, only if it is needed or wanted.
> 
> when operating motors with other controls, having a stop start on the starter is not the norm.


So I've come across one where it was operating with an automatic sensor on a forced air system. In addition it had an ON/OFF/Auto combination. And it was wired wrong, anyway. One of my supervisors said he knows 100% that it's a burned coil. So, on blind faith I went out and got another coil. Installed the coil and it still didn't work. That's when I REALLY started checking. Found an open circuit in the sensor. And the magnetic starter was wired wrong. Pressing the manual ON button didn't do a thing.


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## Stubbie (Jan 7, 2007)

I might as well jump into the fray..... My opinion is that with this compressor a hard wire installation is best.... it isn't likely to be portable. Second IMO the manufacturer had a start stop button option on the starter like the image previously posted.... That doesn't mean it was required. It is prudent to have a stop ability at the air compressor so that you have a readily available stop if your going to have your hands around those moving parts of the pulley and belt during maintenance. At any rate I think a disconnect would be prudent.. close by, at the least, and I think this has been suggested already by JV.
The problem with air compressors is their ability to restart without warning. No matter how you wire it this auto start is inherent to the compressor but I sure as heck would want to have a stop ability where I could reach it if I was doing maintenance on the thing or if I just wanted to turn it off after use. 

Anyway here is a pretty good one to try and get. Nema 1 starter .. with start/stop kit installed.... might give the seller a call and make sure of coil voltage should state Vo3 if 240 volts. But 120 volt coil wouldn't be a big deal either.It should have Class 20 overloads. Square d web site I would think have all the info on this starter...I'd just search class 8536.

This is a 3 pole starter and I believe it will start a single phase 5 hp if you configure it correctly..which is pretty simple . The original one on the compressor is a 3 pole starter configured with a nifty kit to single phase. There was a mounting block that could be added to the right of the coil that housed the other two overloads when used as 3 phase contacter.


http://cgi.ebay.com/Square-D-Nema-size-1-starter_W0QQitemZ250547106888QQihZ015QQcategoryZ42895QQcmdZViewItemQQ_trksidZp3286.m7QQ_trkparmsZalgo%3DLVI%26itu%3DUCI%26otn%3D4%26ps%3D63


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## lash-1295 (Dec 7, 2009)

Well since I am the guy who asked for help in the first place I guess I am in no position to be the expert here, but when I ordered the switch I asked if they thought I should order the start/stop switch. The tech said that I didn't need it and it would not work correctly for a compressor anyway. I didn't press him for details but I asked him about MM's suggestion of a light switch and he said that is what he would use instead of the on/off switch. Don't mean to take sides just relaying what I was told. Thanks for all the help. I could have bought a 120v coil locally for $40 and I though about it but adding the proper heaters would have brought it up to the same price not to mention it will be nice having a wiring diagram (if I can read it) LoL. I am hoping I can wire it up and just let you guysf look at pictures and verify my work. I sure can't wait to get this thing done so I can get back to work on the 68 Mustang convertible that is the reason for this compressor in the first place.


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## Stubbie (Jan 7, 2007)

Sorry lash I just saw where you have ordered your starter. I'm not sure what the tech was saying about a start/stop not working correctly. But I don't want into that argument.

Hopefully there won't be any other issues with your air compressor once you get the new starter installed.


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## lash-1295 (Dec 7, 2009)

Dang, I wish I had seen that one before I ordered. Especially if it stays cheap. If you haven't guessed I am trying to do this as cheaply as possible. Don't know how I missed that one. Thanks anyway Stubbie


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## nap (Dec 4, 2007)

Stubbie said:


> Sorry lash I just saw where you have ordered your starter. I'm not sure what the tech was saying about a start/stop not working correctly. But I don't want into that argument.
> .


I would think the guy was speaking of the 3 wire stop/start configuration.

speaking of; do you have any diagrams with a 3 wire SS station with an air pressure switch involved so as to not reset the SS function? I went to PM's with JV to discuss and need a diagram showing what I was speaking of doing.

oil pressure acts same as "stop"

air pressure does not drop out the run circuit but does shut down the compressor


yes, extra relay as far as I see it. but hey, it's just another rung on the ladder, right?

and your drawings are sooooo nice.


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## Stubbie (Jan 7, 2007)

Sorry NAP stepped out for Pizza and hot wings....

Nope I don't have that exact diagram....Just looked for one in my files. I have several 3 wire control drawings though with latching circuits that are generic circuits. Meaning I do not show exact wire connections at the starter as it varies considerably. But I did post one that is close at the end of this post.

But essentially what you would do is place you pressure switch with L1 going to your stop button and L2 going to one side of your starter coil. The oil pressure switch would be in series with the stop circuit. I think that is what you are wanting. This would energize the coil when you push start which is a momentary switch. This pulls in the starter coil and closes the auxillary contact on the starter that completes the latch circuit. When you release start... the latch circuit will continue to hold the coil in and run the motor. The latch circuit must be broken to stop the motor/compressor. That will happen if the oil pressure switch opens or the stop button is pushed. But better to have the oil pressure switch kill all power to the control circuit.... So place it in series with the stop button and it will be mechanically opened by a low oil float and shaft. If it opens then the motor stops and you cannot start the motor until the oil switch issue is resolved. Once it is you simply push start and your up and running again. You would not reset anything on the run circuit.

The closest I could get to a drawing of your circuit is this one for a dust collector like below just consider the high dust switch your oil pressure switch. Unfortunately this is a low voltage 3 wire control and not 240 volt coil. So not quite correct. Maybe will get your point across. What you are describing is very likely what you would find in a commercial or industrial setting controlling the air compressor if you wanted several start/stop stations located remote from the compressor or even just one at the compressor. Even though this shows a definite purpose 3 pole contactor it really is functioning the same as a motor starter it's just using a pole of the contactor to latch the circuit...whereas a magnetic motor starter would use a auxillary contact. Your pressure switch would be in the place of the transformer controlling a 240 volt coil.


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## spark plug (May 5, 2009)

Stubbie (Poster #49) You mention that it would be worthwhile to "Hardwire" the compressor. also, that compressors have a tendency to suddenly start. And that while doing maintenance it would be good to have a cutoff switch, such as the OFF button on the magnetic starter. First off, the reason the compressor starts "Suddenly", is when it's controlled by the pressure switch (connected in parallel with the coil) and the pressure drops to allow the compressor to run. For this very reason, IMHO it's not sufficient to rely on the magnetic starter alone. You would need a separate Manual cutoff switch "within sight". I'm not sure but I think this is also a Code requirement.:yes::no:


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## nap (Dec 4, 2007)

an off switch in the situation you just stated is not a legal disconnect. A disco must cut the power that runs the unit altogether. If the breaker is deemed appropriate as a disco (distance, line of sight, lockable, whatever), in the discussion involved, that would be the only disco in the system so far.


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## spark plug (May 5, 2009)

Stubbie (Poster #54) When I first posted (#55) I did not read (yet) your post #54. That is the ideal way to wire a control circuit on a compressor (or similarly any other piece of equipment. But I encountered a problem where, a magnetic starter was miswired. And it took some effort :laughing: (removing the cover and tracing the wiring) to find the problem. That the automatic connection (a sensor) was wired to the manual override button (which is a momentary switch). And everyone wondered why the blower doesn't work.


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## Stubbie (Jan 7, 2007)

Nap is correct a unit switch on the compressor that does not open both hot conductors is not a legal disconnect even if another disconnecting means is present. But its a legal....off/stop ! ...... However all joking aside in a residential garage I'd just use the breaker if I was going to work on the thing. You could lock the breaker in the open position if needed...or a simple AC disconnect works...close by....... but I like the Hubbell ones that are really expensive with the red off handles and horn that sounds on delay if the disconnect is fooled with.....:laughing: Whoops guess I'm still joking.

My point is I want a stop/start option on the air compressor but that's me and some people say I'm weird...:wink:


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## Stubbie (Jan 7, 2007)

Nap 

I left out a rather important feature of the start /stop switch ( I think). I believe this type switch is an assembly and comes with a relay designed for use with a air pressure switch. Not just any ole start /stop button. It has a contact in the relay that closes when the start switch is pushed which stays energized until you push the stop button. This is what allows the start switch to be momentary and still allows the pressure switch to cycle the motor once you release it. The diagram as shown would not allow the pressure switch to cycle the motor. Sorry for that omission it might be best if I draw the circuit maybe in the next few days as my example drawing just isn't showing what your wanting.


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## nap (Dec 4, 2007)

How I would do it:

the 3 wire start stop operates an aux relay but does have the motor overload in series. paralled with the start contact, a N/O contact from the aux relay and the oil pressure switch.

then, in another circuit I would series the oil pressure switch, a N/O contact from the relay (listed above) and the motor starter coil.

that way, the oil pressure or the stop switch would drop out the latched aux relay but the oil pressure switch would cycle the motor starter coil without dropping out the latched start stop circuit.










http://public.bay.livefilestore.com...dha1KA2_V_ArkLrd3HQ6w/air comp 2.jpg?download

what do you think? (not considering the quality of the drawing)

Now, if he has an electric unloader, we can work that in so the comp runs continuously but dumps the loader when high pressure is reached. We can even figure in a timer so it will only run unloaded for 5 minutes or so and then shut down the motor (but leaves the latched circuit energized still so the system will still cycle automatically)? Huh?? maybe?


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## Stubbie (Jan 7, 2007)

I think that works but I think you meant to say air pressure switch cycles the starter coil powering the compressor motor. 

Seems though you would not have to have two circuits if you have a relay. If you put the oil pressure switch in series with the control circuit on L1 and then wire the relay to the start switch. When the momentary start switch is pushed closed it closes the relay contact which is then held closed being in series with the stop button. Then connect the relay to one pole on the pressure switch then the other side of the pressure switch to the starter coil NO contact. Connect L2 to the other pole of the pressure switch (if two pole) and then the other side of the pressure switch to the closed contact of the OL then other side of OL to the other side of the starter coil. The pressure switch is now in series with the closed (latched) contact and will cycle the motor. Pushing the stop button deenergizes the relay coil and drops the starter coil out. The pressure switch can no longer cycle the compressor.
This might actually be what your saying only my way of explaining it. Anyway the oil pressure switch opens the latched circuit on L1 if the mechanical shaft allows the oil level switch to open and this drops the relay coil out and consequently the starter coil. Until the oil is filled the motor cannot start.

Gosh I'm rusty at this stufff.....

You know we would ruin our fun but a simple on off switch would be a lot less headache .... Rob is laughing at us....


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## nap (Dec 4, 2007)

the MS in the circle is the coil for the motor starter. the air pressure switch does cycle the motor starter. the upper line has an aux relay. that circuit is designed to allow the run circuit to stay energized when the air pressure circuit cycles.

as to the oil pressure switch: you could put it anywhere in the top line except the mainline between where the paralleled branch than contains the contact for the relay (R1-1) taps off and back on. All that is to do is the same thing the stop switch does; open the holding circuit and allow the relay to drop out. I put it in series with the contact R1-1 simply because that is my preference.

actually, if you put it in the lead of that circuit (in immediate series with the stop button), it would be better since, the way I have it, you could push the start button and the motor would run until you released the start button. If you put it on the mainline, it would prevent even that amount of start.

and you are going to have to draw the rest. You know what they say about a picture being worth a thousand words.:thumbsup:


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## Stubbie (Jan 7, 2007)

> and you are going to have to draw the rest. You know what they say about a picture being worth a thousand words.:thumbsup:


Why is it that I knew you were going to ask me that.....

Ok, I'll draw your circuit and post it in a day or so. 

Have a good day


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## J. V. (Jun 1, 2007)

This is my simple drawing for the DIY OP.


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## nap (Dec 4, 2007)

include a maintained on/off switch (toggle would be fine) rather than the momentary stop switch and that will work. That is what some/many/most (take your pick 'cuz I didn't keep track) have suggested. That is s simple 2 wire control and is fine. 


Not like mine will but it will work:wink:

I just like to make things the average guy cannot work on. Job security and all.:laughing:

boy that drawing looks familiar:whistling2:


whoops! I see you did label the switch as maintained. I just saw the diagrammatic representation which is of a momentary switch.


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## Stubbie (Jan 7, 2007)

Yep.. and a simple maintained on / off is really all you would want. If you look at the cover door for his contactor you will see the provision for an on / off on the left of the cover. In the center is the reset for the overload contact and to the right is the provision for a 3 wire control momentary start / stop. This is standard for this starter. In order to get the 3 wire control to work in an air compressor application is to add a relay. 3 wire control has a lot of advantages but I would say in a residential garage for a home owner it would not be what you would want...too hard to troubleshoot for someone not familiar with how the circuit is built. In the OP's case as I said earlier I want a way to stop the compressor located at the compressor. Rob gave the simple solution early on in this thread. Me .. I would get the optional maintained on /off control buttons and install it in the cover of the motor starter.


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## J. V. (Jun 1, 2007)

nap said:


> include a maintained on/off switch (toggle would be fine) rather than the momentary stop switch and that will work. That is what some/many/most (take your pick 'cuz I didn't keep track) have suggested. That is s simple 2 wire control and is fine.
> 
> 
> Not like mine will but it will work:wink:
> ...


Kudos to nap. That is *his* drawing that I edited. I can barely use Windows Paint. Nap also had a fine schematic that would have worked just as good. Please excuse the fine print. Like I said I am not very good with the drawing program. 
Thanks for the help with "Paint" nap


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## Stubbie (Jan 7, 2007)

I won't say a thing about your abilities with paint...a simple program to use..sorta on the level with solitaire.... My little 4 yr. old nephew is bored with it, my 6 year old cousin thinks it's stupid ..... when there is auto cad....:wink:


...as I was saying NAP and I are discussing a 3 wire control that will latch and hold the run circuit for an air compressor using a momentary start/stop station. The circuit must also allow the air pressure switch to cycle the motor/compressor and let an oil level shutdown kill power to the air compressor by breaking the latch circuit.

Anyway here is my diagram on how I think it could be done...... I would suspect there are several ways to accomplish this scheme.

*EDIT*: In the original drawing I had an error in that I had no L1 power source for the starter coil (wire on wrong terminal of relay). NAP caught this error and brought it to my attention ... soooo .... the drawing has been corrected. NAP suggested using a second contact in the relay where I am just jumping the relay from the run circuit to latch the relay coil.


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## Stubbie (Jan 7, 2007)

I wouldn't want to leave out JV's circuit ......


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## lash-1295 (Dec 7, 2009)

1. Do I have the heater in the proper place and right side up? Didn't come installed.

2. Do the pressure switch and the low oil cut off go in series on the dotted path with the on /off switch?


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## micromind (Mar 9, 2008)

That's exactly how the heater goes in. Just remove the two screws, drop it in place, and put the screws back in.

The pressure switch, low oil switch, and on-off switch are all wired in series where the dotted line is. It's not critical as to which ones goes where, but I'd connect the on-off to L1, then the others. Slightly safer that way. 

Wirenuts are OK to use inside the starter enclosure to connect the control switches. 

Rob


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## nap (Dec 4, 2007)

lash, what kind of switch do you have to turn this on and off? the drawing is showing a momentary contact switch, which is not going to work with the system you have.


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## lash-1295 (Dec 7, 2009)

I don't have a switch yet but my plan is to go with MM idea of a light switch. I understand it must be a two pole switch. correct? Would it be alright to add it inside the box and just cut out a hole for the switch lever?


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## Stubbie (Jan 7, 2007)

Hello Lash

Can you down size the image a tad ? 

You just need a single pole light switch. See drawing below. What we are doing here is is putting the oil switch, the air pressure switch and the 'off" switch in series with the control / run circuit that pulls the starter coil in ... closing the motor contacts and running the compressor. As long as the switch is 'on' the pressure switch will cycle. Open the switch and the coil drops out opening the motor contacts stopping the compressor motor. Or if the oil micro switch opens the starter coil drops out .. till you correct the oil level issue or if the pressure switch opens the starter coil drops out and stops the motor when it closes on low limit it starts the motor again. All of these devices are controlling the coil to pull in the contacts of the motor starter.

The overload (O.L.) will also drop the starter coil out if the motor runs at too high amperage for too long.

I believe this is what Rob is wanting ... it is essentially the same circuit J.V. posted.


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## micromind (Mar 9, 2008)

Stubbies drawing above is exactly correct. 

The light switch will enable the compressor to run, when it's on, the compressor will cycle on and off with air usage. If the oil level gets too low, it won't run at all until the oil level switch is reset. When the light switch is off, the compressor won't run at all. 

Man, I wish I could draw like that!

Rob


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## lash-1295 (Dec 7, 2009)

Thanks for all the help. I believe I have it wired correctly. I will try in the morning. The drawings really helped. No one ever answered about the grease type for the motor. Will standard high temp grease work or does it need to be some special type? LOL it does take grease doesn't it. Those sure look like grease serts to me.

Thanks again for all the help I have learned alot more than I knew when I started. Alway a good thing!!


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## Stubbie (Jan 7, 2007)

HI Lash

You need air compressor oil which is usually a 30 wt. non detergent. Go to the big box then to the air compressor department should be on the shelf.

As for the switch I would mount a handy box at one of the knockouts on the compressor starter enclosure.

The grease fittings are for bearings high temp grease is fine.


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## lash-1295 (Dec 7, 2009)

Thanks stubbie. I have already drained and replaced the compressor oil. I plan to run it for a while and change it again because the oil I removed was a bit gummy. Would it be ok to mount the switch inside the box? There are a couple of knock outs on the front that look like they would fit it.


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## micromind (Mar 9, 2008)

Be careful when greasing an electric motor. Just about any kind of grease that's made for ball bearings will work, but stay away from synthetic. Even though it's actually a better lubricant, the bearings would have to be removed and cleaned of all mineral grease first. 

Don't use too much. Two full pumps would be about right for a motor this size. Using too much will force the grease through the seals, and it'll be flung onto the end turns of the windings. All oils and grease will attack the insulation of the windings. 

This usually isn't necessary, but to insure that no grease gets past the bearing seals, remove the drain plugs below the bearings first (if there are any). Then squirt the grease in. Then run the motor for 10 minutes or so. Then put the plugs back in. Usually, nothing comes out, but if it does, better here than on the windings. 

Once every 3 years is about right for your application. 

Rob


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## Stubbie (Jan 7, 2007)

lash-1295 said:


> Thanks stubbie. I have already drained and replaced the compressor oil. I plan to run it for a while and change it again because the oil I removed was a bit gummy. Would it be ok to mount the switch inside the box? There are a couple of knock outs on the front that look like they would fit it.


Yes there are switch knockouts on the cover. The one on the right side of the cover is where a momentary start/stop goes. You just might get a decora type switch to fit right in that knockout. Or make a nice little plate and mount behind the knockout hole with a regular toggle switch to the backside of the plate. But yes one of the cover knockouts would be an excellent place for the switch but I wouldn't mess up the cover unless I had a perfect fit or nowhere else to mount the switch on the unit.

I'm not sure what the factory on /off switch costs. This mounts on the left in the 2 small rectangular knockouts. Might be worth checking out. You could just wire in the single pole and if no other issues get the factory on/off...I'll try to price it sometime today or tomorrow.


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## Stubbie (Jan 7, 2007)

The two knockouts on the left side of the cover are not for an on/off switch. They are for indicating pilot lights to tell you the status of the starter. 

All switches go in the right hand knockout. the off/on is about 20 bucks through my supplier so you should be able to get similar pricing. It appears to be a selector type switch rather than a push button maintained.


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## Stubbie (Jan 7, 2007)

Lash

Just wanted to point one thing out. On the front of the starter you will see a small rectangular black button. This is the indicator that pulls in when the coil energizes closing the motor contacts. It is spring loaded to the coil solenoid. If you manually push it in the motor will run regardless of the on/off switch being in the off position. What you are doing is hand closing the motor contacts by overriding the control circuit. So be aware that if you push that button in and hold it in the motor will run regardless of the oil pressure switch, on/off switch or air pressure switch position. Once you release it the button will pop back up (spring ) and the motor will stop. It has a few useful purposes when trouble shooting or if you want to jog the motor a bit. Otherwise just be aware and keep your hands and clothing clear of moving parts if you push that button in.


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## spark plug (May 5, 2009)

Stubbie said:


> Lash
> 
> Just wanted to point one thing out. On the front of the starter you will see a small rectangular black button. This is the indicator that pulls in when the coil energizes closing the motor contacts. It is spring loaded to the coil solenoid. If you manually push it in the motor will run regardless of the on/off switch being in the off position. What you are doing is hand closing the motor contacts by overriding the control circuit. So be aware that if you push that button in and hold it in the motor will run regardless of the oil pressure switch, on/off switch or air pressure switch position. Once you release it the button will pop back up (spring ) and the motor will stop. It has a few useful purposes when trouble shooting or if you want to jog the motor a bit. Otherwise just be aware and keep your hands and clothing clear of moving parts if you push that button in.


Glad you pointed out that fact. (about the override switch. All of the above is provided the magnetic starter is wired correctly). As I said in the beginning of this journey. (The present thread.) Because if it's miswired all bets are off. As I encountered in my capacity as part of a maintenance crew in an HRF. (Health related facility) It seems that the Construction electricians (it was a brand new building) made a ton of mistakes in the wiring. For example, some of the "Mushroom" exhaust fans on the roof (those that ran on 3 Phase) had their motors burned out due to the fact that the installers never checked the direction of rotation. A lot of them spun the wrong way, burning out the motors!


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## electures (Dec 22, 2009)

lash-1295 said:


> Was told it was a 5 hp single phase so what I am missing is the full load amps. Any idea how to determine that? The only labels I can find at all are on the low oil cutoff and I think on the pressure switch itself.
> 
> Thanks


The procedure below is based on the requirements of the 2008 NEC.

*430.6(A) 1* states;
*(1) Table Values. **Other than for motors built for low speeds (less than 1200 RPM) or high torques, and for multispeed motors, the values given in Table 430.247, Table 430.248, Table 430.249, and Table 430.250 shall be used to determine the ampacity of conductors or ampere ratings of switches, branch-circuit short-circuit and ground-fault protection, instead of the actual current rating marked on the motor nameplate*. Where a motor is marked in amperes, but not horsepower, the horsepower rating shall be assumed to be that corresponding to the value given in Table 430.247, Table 430.248, Table 430.249, and Table 430.250, interpolated if necessary. Motors built for low speeds (less than 1200 RPM) or high torques may have higher full-load currents, and multispeed motors will have full-load current varying with speed, in which case the nameplate current ratings shall be used.

Table 430.248 indicates 28 amps for a 230V 5HP single phase motor.

*430.22(A) General* states;

*(A) General. *Conductors that supply a single motor used in a continuous duty application shall have an ampacity of
not less than *125 percent of the motor’s full-load current rating as determined by 430.6(A)(1).*

28A x 125% = 35A

Table 310.16 indicates #8AWG is rate for 40A.

Next we look at sizing the ground fault, short circuit, overcurrent protective device.

430.52 states;

*430.52 Rating or Setting for Individual Motor Circuit.*
*(A) General. *The motor branch-circuit short-circuit and ground-fault protective device shall comply with 430.52(B) and either 430.52(C) or (D), as applicable.

*(C) Rating or Setting.*
*(1) In Accordance with Table 430.52. *A protective device that has a rating or setting not exceeding the value calculated according to the values given in Table 430.52 shall be used. (Also read the exception.)

Table 430.52 states that for an inverse time circuit breaker (ITCB) protecting a single phase motor it is to be sized at 250% of the FLA as stated in Table 430.248.

28A x 250% = 70A

Based on the above calculation a 70A ITCB is correct.

If the motor fails to start and run then 430.52(C) (1) Exception No. 2(c) can be applied which states;

_(c) The rating of an inverse time circuit breaker shall be permitted to be increased *but shall in no case exceed 400 percent for full-load currents of 100 amperes or less* or 300 percent for full-load currents greater than 100 amperes._

_28A x 400% = 112A_

_Since we can’t exceed 400% of the motor FLA we round down to a 110A ITCB on a piece of #8 AWG conductor._

:thumbsup:


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## lash-1295 (Dec 7, 2009)

Stubbie, thanks for pointing out the momentary switch. I was wondering what that was. 

Hopefully this thread will help someone else with a simular problem. I didn't have any luck googling it when I started this project. There are alot of smart guys on here. Thanks for the help.

I do have a few more questions though. Right now I am using the plug which came with the compressor. I cut the end off and used a universal plug that will fit into the dryer outlet. I want to run an outlet to garage. I want to be able to plug in a 220 welder as well. So here are the questions.

Most plugs I have seen have a three prong configuration. Should I wire it with a ground if I use one of those?
What type of plug would be best?
What type (gauge/size)wire would I need to run from the main panel to the outlet?
I have space in the box for breakers so no problem there.
It would be alot easier if I could run the wire inside the attic and drop it down both walls. Any code problems with doing that? (Texas)


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## spark plug (May 5, 2009)

lash-1295 said:


> Stubbie, thanks for pointing out the momentary switch. I was wondering what that was. Hopefully this thread will help someone else with a simular problem. I didn't have any luck googling it when I started this project. There are alot of smart guys on here. Thanks for the help.
> 
> I do have a few more questions though. Right now I am using the plug which came with the compressor. I cut the end off and used a universal plug that will fit into the dryer outlet. I want to run an outlet to garage. I want to be able to plug in a 220 welder as well. So here are the questions.
> 
> ...


I'll just address your question about the Momentary Switch. That's a switch that makes contact only while you hold it (or press it, in our case.) The purpose of it is to power the "Latching circuit". Meaning. the loop that energizes the coil and keeps it pulled in, closing the contacts of the Motor. That could run continuously until the contact is broken by pressing the OFF button, which breaks the "Latching circuit" (loop), releasing the coil and the contact points are opened, stopping the motor. (Oversimplified).


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## micromind (Mar 9, 2008)

If you're going to install an outlet to run the compressor or welder, I'd use a 50 amp 250 volt one. The NEMA number is 6-50. It looks a lot like a standard outlet, except it's about 3X larger. 

If you're using NM cable (Romex), it'll need to be 6/2 with ground. If it's conduit, #8s will be OK. Use a 50 amp 2 pole breaker. 

These outlets and plugs are readily available. The welder might come with one from the factory. 

On another note, the post above that quotes the code is exactly accurate, but I'd like to add one thing. 110.14 (1) (a) (4) states that motors can use the 75C column in table 310.16 This does not apply to type NM cable though. 334.80 says you have to use the 60C column. 

Unfortunately, to get down to the nitty-gritty of connecting a motor, you have to look at several different articles in the code. Too bad it wasn't just one that'd cover it all. 

To sum up; if the wire is in conduit, use the 75C column. If it's NM, use 60C. 

Rob


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## Stubbie (Jan 7, 2007)

lash-1295 said:


> Stubbie, thanks for pointing out the momentary switch. I was wondering what that was. Hopefully this thread will help someone else with a simular problem. I didn't have any luck googling it when I started this project. There are alot of smart guys on here. Thanks for the help.
> 
> I do have a few more questions though. Right now I am using the plug which came with the compressor. I cut the end off and used a universal plug that will fit into the dryer outlet. I want to run an outlet to garage. I want to be able to plug in a 220 welder as well. So here are the questions.
> 
> ...


Rob has it correct. If your wanting to run both a welder and this compressor out of the same receptacle you need a 2 pole 3 wire grounding type. Meaning 2 hots and a ground in the plug. No neutral is required for 240 volts. The compressor needs a 40 amp branch circuit if it is a actual 5 hp motor. Seems we determined that it was a 5 hp.

If you know the electrical requirements of the welder that would help but in general stick welders like the ole lincoln 225 needs a 50 amp circuit on 6-2 with ground nm like Rob mentioned. If your doing car restoration I have a feeling your talking a wire welder so a 40 amp branch circuit using #8-2 with ground on a 50 amp breaker should be more than enough for the welder. You will still use a 250 volt rated nema 6-50 like these... left is the receptacle and right is the plug. The top upside down D is your ground terminal, the other two are your hots. It does not make any difference which hot goes to which terminal. You need a double pole breaker. I take it you have the compressor running??


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## electures (Dec 22, 2009)

micromind said:


> If you're going to install an outlet to run the compressor or welder, I'd use a 50 amp 250 volt one. The NEMA number is 6-50. It looks a lot like a standard outlet, except it's about 3X larger.
> 
> If you're using NM cable (Romex), it'll need to be 6/2 with ground. If it's conduit, #8s will be OK. Use a 50 amp 2 pole breaker.
> 
> ...


 
110.14(1)(a)(4) is not a code section. I believe you meant 110.14(C)(1)(a)(4) which only applies if the motor is marked with design letters B,C, or D. Otherwise 110.14 (C)(1)(a)(1) applies which requires the use of the 60 degree column. 

In my previous post I wrote out the procedure for sizing the conductors for this motor. #8/2 romex will work on a 70A breaker.

The welder is going to require a different size conductor and OC device.

Good luck!


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## Stubbie (Jan 7, 2007)

Hey lash

Check this out ... a 5 hp speedaire on ebay with your same manufacturer magnetic motor starter...

Also the blue button in the center of the cover is your overload contact reset in case the overload ever trips


http://cgi.ebay.com/SPEEDAIRE-BY-DA...emQQptZBI_Air_Compressors?hash=item4838c916d8


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## Stubbie (Jan 7, 2007)

electures said:


> 110.14(1)(a)(4) is not a code section. I believe you meant 110.14(C)(1)(a)(4) which only applies if the motor is marked with design letters B,C, or D. Otherwise 110.14 (C)(1)(a)(1) applies which requires the use of the 60 degree column.
> 
> In my previous post I wrote out the procedure for sizing the conductors for this motor. #8/2 romex will work on a 70A breaker.
> 
> ...


Design letters generally do not show up on anything but 3 phase motors. Nema requires that all three phase motors show the design letter on the nameplate ...this will be either B,C or D in the majority of cases. However this section of 110.114 is simply stating for those particular motors you are allowed to use 75 C ampacities. Other wise any motor showing terminations that may be 75 C can use the 75 C column unless limited by restrictions for certain cables like NM-b or SE. Almost all motors have that specification for terminals and nema requires that any motor leads when terminals are not used be 125C rated.

I agree that a welder may require a branch circuit different than the air compressor, however arc welders have a wide range of OCPD if using the NEC to calculate the branch circuit requirements. The manufacturer often states the OCPD and minimum conductor ampacity. Unless we know the welder he is getting we cannot state that it will be required to have a different branch circuit. It is unlikely that #8 is going to have any effect on whether or not he can use the welder. The limiting factor will be the OCPD for the air compressor and the power cord on his welder. In other words he cannot change the plug to a 6 -50 on a power cord with a 6 -20 or 6 -30 on it and he cannot use a breaker larger than what is specified by the manufacturer.

I would not install the maximum ocpd on this air compressor as calculated by the NEC. I would probably start with a 40 and see if it would hold. I would highly doubt that a 70 amp breaker would need to be required. 

I do agree with the information given that the conductor size should be #8 using 60C ampacities but could be #10 if thhn in conduit...however you would need defined information to use 75 C on this motor . You probably cannot get that unless you call baldor.


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## 3 legged dog (Dec 21, 2009)

Some pretty good info here. Did you get the compressor running?


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