# Wiring a 3 phase 208/230v A/C



## nap (Dec 4, 2007)

My first question is;

Is there 3 phase power at the house? While it is not impossible most residential services in the country are split single phase. 


So, before you get started trying to hook up a 3 phase unit, make sure there is 3 phase power there.


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## Daniel Holzman (Mar 10, 2009)

Judging from the post, the OPS is not in the US. It would greatly help if you identified where you live, and what type of electrical service you have.


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## zappa (Nov 25, 2011)

Foreclosures and vandalism, sounds like the good ole US of A to me. :jester:

You have a 3-phase unit but your home wiring appears to be single phase. Not going to work out. Can you take the unit back if in fact you have single phase?


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## supers05 (May 23, 2015)

Start by taking pictures of the panel. Find out if your house has 3 phase. This ac will not work if you don't have 3 phase in the house. If you do have 3 phase, it'll most likely be 4 wires coming into the main panel. 3 bus bars, a neutral bus and a ground terminal strip. If this is all there, you'll need 3 circuit breakers, or fuses. 
I have a feeling that you don't have the right ac.

Oh and take pictures of the ac, specifically the compressor


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## zappa (Nov 25, 2011)

Daniel Holzman said:


> Judging from the post, the OPS is not in the US. It would greatly help if you identified where you live, and what type of electrical service you have.


Yeah, the word "loom" made me wonder. But does a "get er done" cancel out a loom? :laughing:


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## zappa (Nov 25, 2011)

There are a few places in the US that have 3-phase to residential, like old sections of Phoenix. They run the house on two of the phases and only the A/C condenser uses all three phases.


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## supers05 (May 23, 2015)

zappa said:


> There are a few places in the US that have 3-phase to residential, like old sections of Phoenix. They run the house on two of the phases and only the A/C condenser uses all three phases.


Some types of compressors cannot run backwards, or you'll damage them. With some it'll only take a few rotations. (Fractions of a second for screw compressors. Luckily they are generally not found in residential.) Recip compressors don't care, and will work reguardless. While scroll compressors will die after a little while and won't cool at all. 
For split phase, it doesn't matter, but for poly phase it does.


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## roughneck (Nov 28, 2014)

3 phase is easy, providing you have 3 phase power supply in your home. 
Where did this used equipment come from, and is it properly sized for your ductwork and house?


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## Redcast (May 29, 2015)

All legitimate questions but step one is knowing if the home can be rewired to run the compressor. If not the rest is moot. The air handler is 110v and is matched to the compressor. The unit is a four ton and the home is a no attic modular 2000 sq. ft. house. in North Carolina. The air handler vent circumference is 1 inch larger than the old one. I know this is a generalization but the rest of the specks can be worked out with my HVAC guy. This unit is like new and was a storage auction steal...no returns. So is this doable or not that is the question and if so how. Thank you all for the feedback.​


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## supers05 (May 23, 2015)

3 phase wiring is very straight forward. 3 wires and a ground. (In Ontario, 3 phase stuff can use a ground 1 gauge lower then the current conductors.) 3 fuses(or breakers) across all 3 phase buses in the panel. Straight from the panel to your unit. (Also you need a disconnect next to the outdoor unit) During startup, your HVAC guy might have to swap 2 of the 3 wires. 
The indoor unit, would be across any 1 of the 3 phase buses and to neutral. (usually with a switch close to the unit, depending upon code)

It's not a matter of whether your house can be rewired, it already has to be supplied like that, or it's way too expensive, even if the utility will give it. (in residential areas, it'll be highly unlikely)


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## zappa (Nov 25, 2011)

Redcast said:


> So is this doable or not that is the question and if so how. Thank you all for the feedback.


99.99% sure that you don't have 3-phase to your home. To be sure you would have to do what *supers05* suggested and look inside of your panel for things he mentioned in post #5. If you have an overhead service feeding your home you could count the conductors. For 3-phase there would be 4 electrical conductors plus a smaller support cable. The electric meter could possibly say 3-phase on it also.

Technically you could use a single to three-phase electronic variable frequency drive but it wouldn't be worth the cost unless one of the proper size was included in the storage auction.


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## beenthere (Oct 11, 2008)

Redcast said:


> All legitimate questions but step one is knowing if the home can be rewired to run the compressor. If not the rest is moot. The air handler is 110v and is matched to the compressor. The unit is a four ton and the home is a no attic modular 2000 sq. ft. house. in North Carolina. The air handler vent circumference is 1 inch larger than the old one. I know this is a generalization but the rest of the specks can be worked out with my HVAC guy. This unit is like new and was a storage auction steal...no returns. So is this doable or not that is the question and if so how. Thank you all for the feedback.​



Since you probably don't have a 3 phase service. You would need a transformer/inverter to convert to 3 phase for the condenser. 

http://www.zoro.com/phase-a-matic-p...3fKuB3K3wmiXgos3d8srQaAr4P8P8HAQ&gclsrc=aw.ds


That one may or may not be enough to start the condenser. As it only goes up to 5 HP.


Next question. Does your house need 4 tons? Is the duct system big enough for a 4 ton unit?


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## zappa (Nov 25, 2011)

beenthere said:


> Since you probably don't have a 3 phase service. You would need a transformer/inverter to convert to 3 phase for the condenser.
> 
> http://www.zoro.com/phase-a-matic-p...3fKuB3K3wmiXgos3d8srQaAr4P8P8HAQ&gclsrc=aw.ds
> 
> ...


Those static converters are not recommended to run refrigeration compressors no matter how oversized the converter is. They manufacture the third phase with a capacitor. Sorta the reverse of a split phase motor.

Good question about the 4 ton and duct work.


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## roughneck (Nov 28, 2014)

If your home doesn't have 3 phase, you'll have more money tied up into electrical modifications then you'd have just buying the correct equipment. 
We have no idea if you have 3 phase in your house. But you can't just hook a 3 phase unit into a single phase system. It physically will not run.


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## yuri (Nov 29, 2008)

zappa said:


> There are a few places in the US that have 3-phase to residential, like old sections of Phoenix. They run the house on two of the phases and only the A/C condenser uses all three phases.



Not wanting to diverge but am curious why would they use 3 phase at all in Resi. Only reason I could see would be for AC but the units cost more so what would be the point.


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## zappa (Nov 25, 2011)

yuri said:


> Not wanting to diverge but am curious why would they use 3 phase at all in Resi. Only reason I could see would be for AC but the units cost more so what would be the point.


I heard this from a couple of pro electricians who work in Phoenix but I can't remember the history or reason behind it, if it was even mentioned. I'm guessing 3-phase was originally in the area and then residences started being built. Could have been a power company decision to better manage the loads? You could PM micromind and ask if he still visits this forum.


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## beenthere (Oct 11, 2008)

The A/C can be metered separately. And include power factor charges.


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## yuri (Nov 29, 2008)

Phoenix, I thought they used Swamp coolers and not AC?

Maybe the rich folks had AC and the others used the "coolers".

Max no difference, just trivia.:laughing:


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## supers05 (May 23, 2015)

yuri said:


> Not wanting to diverge but am curious why would they use 3 phase at all in Resi. Only reason I could see would be for AC but the units cost more so what would be the point.


Some jurisdictions use 3-phase to domestic use. (houses) Europe does this often. You can still use single phase motors just fine on 3 phase. 3 phase motors have superior starting torque and efficiency over single phase motors.

https://en.wikipedia.org/wiki/Electric_power_distribution


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## Redcast (May 29, 2015)

*Wiring a 3 phase 208/230 A/C*

So after selling some of the storage stuff the HVAC unit cost me Nothing. The cost of adapting it to fit my needs has got to dwarf the cost of a new ( correct unit). This unit has never even been hooked up there isn't even solder on the Freon copper tubes where they connect.. Without a professional HVAC guy sizing it to fit my application I can only refer to rudimentary ballpark figures. The compressor puts out 37,000 btuh the math I used requires 20 btu's per square ft. my home is approx.1918 square ft =38,360 btu,s. That puts me close to what I need. I know this isn't precise but finding out how to power the compressor is the only way to calculate the cost of a retrofit. That compressor is under 5 horsepower which should make the phase converter idea plausible. Over the 5 HP might be where the use of them becomes problematic and earns the phase converter in general a false rep. Rough rule of thumb is 12,000 btu's per horsepower but new compressor designs muddy the reliability of that data. The whole thing is a guessing game anyway with windows, climate ,insulation, roofing, attic, no attic, vent size etc. all part of the equation. If someone can lay out a simple electrical diagram with or without a Phase converter that would be great. Thanks again to all.


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## nap (Dec 4, 2007)

Redcast said:


> All legitimate questions but step one is knowing if the home can be rewired to run the compressor. If not the rest is moot.​



your ac guy is not going to handle anything unless you have 3 phase power to the home so, either you do or you don't. If you don't, the rest is moot.

while it can be done if you do not have 3 phase, talking about what to do until you answer the question is an effort in the hypothetical. The wiring in whole is going to be very different if you have 3 phase power than if you don't.


Then, to get things rolling; what size is your service?

what is the voltage requirement for the AC unit?

what are the current draw ratings on the equipment?

what is the actual HP rating of the compressor and fan of the condenser unit?​


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## beenthere (Oct 11, 2008)

That compressor may only be rated at 37,000 BTUH at a 130°F condensing temp. But the condenser it is in, is rated far higher, and designed for a 105°F condensing temp.

Load calcs are less guess work then you think. And over sized unit will leave the houe with high humidity. And if the duct work is too small. You may not be able to run the A/C until its 85 outside.


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## roughneck (Nov 28, 2014)

Do you have 3 phase power in the structure?


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## nap (Dec 4, 2007)

zappa said:


> You could PM micromind and ask if he still visits this forum.


yes he does and has been here recently. 

in fact he was on here today


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## nap (Dec 4, 2007)

yuri said:


> Not wanting to diverge but am curious why would they use 3 phase at all in Resi. Only reason I could see would be for AC but the units cost more so what would be the point.


an off topic question that you might be able to answer:


would there be an advantage to altering the speed of the compressor? You folks have spoken of multi-stage units but what would happen if you simply took a typical unit and slowed the motor. Would it provide a variable output without damaging anything?


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## yuri (Nov 29, 2008)

The typical scroll or recip compressor uses a PSC motor same as the condensor fan so no it cannot be slowed down. Not practically anyway. Would damage the compressor from poor oil return. The VFD scroll is designed for oil return at different speeds.

Altering the speed of the compressor with a VFD drive alllows them to use digital control. Allows them to use sensors/thermistors on the indoor and outdoor coil and vary the fan and compressor speed proportionally to the load. The very high end Lennox,Trane etc also have communicating digital tstats so you can see where digital proportional control comes in. Also can control the indoor blower speed for humidity removal yadayadyada.

Your basic capacity control on a scroll is a solenoid operated bypass valve in the scrolls. All or nothing and can only reduce it 1/3. Some Trane use 2 compressors for multistage but that is 2X the compressors to break down + cost.

VFD is the future and as the cost comes down and the gov't require higher SEER units it does the job very well.


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## yuri (Nov 29, 2008)

Redcast said:


> So after selling some of the storage stuff the HVAC unit cost me Nothing. The cost of adapting it to fit my needs has got to dwarf the cost of a new ( correct unit). This unit has never even been hooked up there isn't even solder on the Freon copper tubes where they connect.. Without a professional HVAC guy sizing it to fit my application I can only refer to rudimentary ballpark figures. The compressor puts out 37,000 btuh the math I used requires 20 btu's per square ft. my home is approx.1918 square ft =38,360 btu,s. That puts me close to what I need. I know this isn't precise but finding out how to power the compressor is the only way to calculate the cost of a retrofit. That compressor is under 5 horsepower which should make the phase converter idea plausible. Over the 5 HP might be where the use of them becomes problematic and earns the phase converter in general a false rep. Rough rule of thumb is 12,000 btu's per horsepower but new compressor designs muddy the reliability of that data. The whole thing is a guessing game anyway with windows, climate ,insulation, roofing, attic, no attic, vent size etc. all part of the equation. If someone can lay out a simple electrical diagram with or without a Phase converter that would be great. Thanks again to all.


I would not waste my time with this project. If you use a convertor and you get a brown out or any low voltage it may blow or get damaged or damage the compressor.

You can buy Goodman units DIY at Alpine Air. 

Sell this one on Flea Bay and use the $$ to buy a single phase Goodman.


http://www.alpinehomeair.com/


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## supers05 (May 23, 2015)

It might just be cheaper to sell that unit on 3bay and buy a new unit that suites your needs.


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## nap (Dec 4, 2007)

yuri said:


> The typical scroll or recip compressor uses a PSC motor same as the condensor fan so no it cannot be slowed down. Not practically anyway. Would damage the compressor from poor oil return. The VFD scroll is designed for oil return at different speeds.
> 
> Altering the speed of the compressor with a VFD drive alllows them to use digital control. Allows them to use sensors/thermistors on the indoor and outdoor coil and vary the fan and compressor speed proportionally to the load. The very high end Lennox,Trane etc also have communicating digital tstats so you can see where digital proportional control comes in. Also can control the indoor blower speed for humidity removal yadayadyada.
> .


thanks..



now, back to the case at hand:

a VFD is a box full of magic. It can be used for so many purposes it is nothing less than magical. In this situation, the OP can probably use a VFD as an inverter to supply the 3 phase power to the unit. The biggest problem is anything within the unit that is single phase power. The VFD can be programmed to run full speed only (or as a soft start if desired ramping to full speed). It can take single phase input and provide 3 phase output. It can even increase voltage. It's magic.

and they are not very expensive anymore. $200-$300 would likely get a VFD capable of doing what the OP needs. 

so, if the OP wants to provide some information rather than arguing, he might get a solution.


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## yuri (Nov 29, 2008)

I don't think he is arguing but after many years of reading posts "some" people like to dream up "low cost" solutions which don't really end up being "practical" or even work. The process of inventing a no cost solution is the journey though not always based in reality.:yes:

Some people only want to hear what they want not provide info or communicate back and forth. Just the nature of mankind and the net.


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## nap (Dec 4, 2007)

yuri said:


> I don't think he is arguing but after many years of reading posts "some" people like to dream up "low cost" solutions which don't really end up being "practical" or even work. The process of inventing a no cost solution is the journey though not always based in reality.:yes:
> 
> Some people only want to hear what they want not provide info or communicate back and forth. Just the nature of mankind and the net.


maybe not arguing but failing in aiding in his own journey. He wants answers but so far has been reluctant to provide much information one could use to provide such answers. 

Heck, he still has not confirmed he has only single phase power other than by saying a phase converter might be a solution if...well, I tend to forget what the rest was since it really didn't matter in attempting to provide him with an answer.


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## Redcast (May 29, 2015)

Nap, I like your perspective what specifically can I contribute to make this happen. If I have to have a professional come over to the house to get specific questions answered that might take a day or two. If I have to take measurements or make detailed descriptions I can do that. I am learning a lot here and you have focused on a possible solution.


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## Redcast (May 29, 2015)

*Wiring a 3 phase208/230v A/C*

I have single phase.


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## nap (Dec 4, 2007)

right now you really don't need a pro. You are in the investigative phase and much of what is needed can be discovered by you.

You need to look at the equipment. There should be a data tag on it. On that tag it will give you a wealth of information including the required voltage and the resulting amperage for any given voltage. There may be a tag giving a max OCPD, maybe not. 

list any other info on the equipment either on that tag or any other label you might run across. 



then, you need to look at your electrical service to find out what your service size is. There is likely a main breaker in the panel. It will have a number on it; what is it?


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## roughneck (Nov 28, 2014)

If you have single phase power get single phase equipment. You might sink a ton of money into this and it would end up not working. 
Buy what you need. Don't try to force something to work. You'll pay a high price in the end


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## Redcast (May 29, 2015)

*Wiring a 3 phase208/230v A/C*

Main breaker 8j2200b
type bj
10,000 a
120/240 vac
cu al
type 1 enclosure
max main breaker 200a
120/240 
1 ph 3 wire
120/208v 3 wire when used in a 3 ph 4 wire network suitable for service equipment as per 354 of the national equipment code
short circuit 10,000 rms 22,000 rms

compressor
unit supply 208-230v 3 ph 60 hz
compressor 208-230v 3 ph 11.2 rla 88 lra
fan motor 208-230v 1 ph 60 hz
1.5 fla 1/4 hp
min circuit ampacity 15.5
max fuse or max circuit breaker (hacr type per nec) -25factory charge 4 lbs 90z r-410a

there is a schematic showing the fan motor and compressor hookups if needed

air handler
unit power supply 208-230v 1 ph 6o hz
motor 5.2 fla 1 hp 3 ph 60 hz
max outlet air temp 200 deg f 
multi-source power installation of the following with accessory numbers listed

there is a reference to a heat pump 612t with heater voltage 208/240 and accessory numbers following that reference with system pressure @ 500 psig and the same test pressure


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## roughneck (Nov 28, 2014)

If you want to keep this equipment why not rip out the 3 phase parts and install single phase equivalents. Should only be $1,000-$2,000 tops to do that depending on compressor cost.


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## WyrTwister (Jul 22, 2013)

Please forgive me if this has been asked and answered .

How old and what SEER rating is the 3 phase condenser you have ?

Are you planning on living in the house or planning on " flipping " it ?

God bless
Wyr


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## Redcast (May 29, 2015)

*Wiring a 3 phase208/230v A/C*

Nap wasn't sure if model numbers are helpful here I can supply them if needed. When I looked up the compressor part number it was for a York. 2009 model.


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## roughneck (Nov 28, 2014)

So how are you going to connect this unit to your existing electrical service that will make keeping this equipment cost effective?


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## nap (Dec 4, 2007)

roughneck said:


> So how are you going to connect this unit to your existing electrical service that will make keeping this equipment cost effective?


I don't have the time to get too involved at the moment but:


first, I would suggest changing the air handler motor to single phase. It will simplify things and it would avoid a possible problem. granted it is a cost but it is probably cheaper to change the motor than than the preferred other method of using a second vfd to run the air handler. 


then, you need to run a seperate power for the condenser fan (which is already single phase) and the control circuitry (one circuit can handle both just as it is now). The VFD should be used to power only 3 phase devices. Using a leg or two of the vfd would cause the load to be unequal. That could throw the vfd into a fault. You could theoretically use the same circuit to power the fan/control as the vfd. I would prefer to run a separate circuit if possible but you wouldn't have to. 
that's about all I can toss out there is short order and without researching a vfd for the purpose. 


I won't be back on this today though. other things to do.


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## beenthere (Oct 11, 2008)

Pretty sure he already said the air handler is 120 volt.


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## roughneck (Nov 28, 2014)

Thougt he said the air handler had a 3 phase blower motor?


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## roughneck (Nov 28, 2014)

I think the OP has a DIY project in mind, but this goes way past that sort of work. This isn't anything you'll be able to run down and purchase at the hardware store. At a minimum he will need an electrician.


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## nap (Dec 4, 2007)

roughneck said:


> Thougt he said the air handler had a 3 phase blower motor?



yep, he did but...



> air handler
> unit power supply 208-230v 1 ph 6o hz
> motor 5.2 fla 1 hp 3 ph 60 hz
> max outlet air temp 200 deg f
> multi-source power installation of the following with accessory numbers listed


but in that same statement he did say it requires a single phase power supply BUT it also says: multi source power installation but that says with acccessory numbers listed. I wouldn't think a blower motor be considered an optional accessory.


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## beenthere (Oct 11, 2008)

roughneck said:


> Thougt he said the air handler had a 3 phase blower motor?


He said its 110 volt. 



Redcast said:


> All legitimate questions but step one is knowing if the home can be rewired to run the compressor. If not the rest is moot. *The air handler is 110v and is matched to the compressor.* The unit is a four ton and the home is a no attic modular 2000 sq. ft. house. in North Carolina. The air handler vent circumference is 1 inch larger than the old one. I know this is a generalization but the rest of the specks can be worked out with my HVAC guy. This unit is like new and was a storage auction steal...no returns. So is this doable or not that is the question and if so how. Thank you all for the feedback.​


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## nap (Dec 4, 2007)

beenthere said:


> He said its 110 volt.


he also said it is 208-230 volt 3 phase as well but the air handler only required a 208-230 volt single phase supply


Houston, we have a problem.


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## beenthere (Oct 11, 2008)

Would help to have the model numbers of both the indoor and outdoor unit.


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## WyrTwister (Jul 22, 2013)

Three phase equipment on a single phase service ? He needs a magician , not an electrician . And probably a banker , also .

Do I hear the Mission Impossible theme playing in the background ?

This whole discussion is a waste of electrons / bandwidth .

God bless
Wyr


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## Redcast (May 29, 2015)

Obviously I made some earlier mistakes on the specs but I thought the most recent post cleared that up. I copied word for word the information on all the tags, the fuse box, compressor and air handler. The only omissions were model numbers and several non descript lists of accessory model numbers ON THE AIR HANDLER referring to the heater. I was hoping since the main breaker box listed the use of 3 phase in a 4 wire network suitable for service that that was a viable option. Why would that be mentioned if it wasn't? The model numbers are as follows;

Compressor model#TCGD48S43S1A SERIAL#W0L9297876 (I believe the 2ND DIGIT IS A ZERO for both units serial#'s) 
AIR HANDLER MODEL#MA20DN21H SERIAL# WOD9711028
UNITARY PRODUCTS GROUP


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## WyrTwister (Jul 22, 2013)

The AHU has electric resistance heat ?

That could be re-wired for single phase . Whether you could afford the electric bill or not is another matter .

How many KU of heat ?

God bless
Wyr


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## WyrTwister (Jul 22, 2013)

http://r.search.yahoo.com/_ylt=A0LE...0909.pdf/RK=0/RS=dbei2EXTK_M91XwCWiZuB1Wf7ms-

For the condenser .

God bless
Wyr


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## WyrTwister (Jul 22, 2013)

http://www.master.ca/documents/1air_handler_YORK_ANG.pdf

AHU 

God bless
Wyr


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## nap (Dec 4, 2007)

WyrTwister said:


> Three phase equipment on a single phase service ? He needs a magician , not an electrician . And probably a banker , also .
> 
> Do I hear the Mission Impossible theme playing in the background ?
> 
> ...


a vfd will fix everything.

http://www.teco.com.au/1ph-input-3ph-output


and needing a banker? Starting at the low low bargain price of $139.99. (plus shipping and handling) (didn't check the specs but the op has a small motor so it is not going to take a large VFD
http://www.wolfautomation.com/products/33819/compact-variable-frequency-drivebr14-to-3-hp-single-phase-inputbrweg-cfw10?gclid=CP_akN6j7cUCFYMCaQodDaAAbw




> In addition to a very small, easily mounted package, simplified keypad and bright LED readout, complete diagnostics and fully programmable I / O, the CFW-10 controls three phase AC motors with a single phase 120V AC input voltage will produce three phase 230V to drive motors up to 1HD and single phase 230V AC will produce three phase 230V to drive motors up to 3 HP.


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## roughneck (Nov 28, 2014)

5 tons for 2000 sq ft in hot and humid North Carolina?
Please......get a load calc and buy the proper equipment!!!
Bigger isn't better!


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## nap (Dec 4, 2007)

roughneck said:


> 5 tons for 2000 sq ft in hot and humid North Carolina?
> Please......get a load calc and buy the proper equipment!!!
> Bigger isn't better!



he said it was 4 ton. Do the model numbers provide for a different rating?


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## beenthere (Oct 11, 2008)

nap said:


> a vfd will fix everything.
> 
> http://www.teco.com.au/1ph-input-3ph-output
> 
> ...



He'll need one good for 4 horse power.


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## nap (Dec 4, 2007)

beenthere said:


> He'll need one good for 4 horse power.


http://www.ebay.com/itm/5HP-4KW-220...t-Motor-Ratting-Closed-Loop-New-/201205561368


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## WyrTwister (Jul 22, 2013)

And I am just guessing , but he may be able to buy a condenser for what a 4 hp VFD will cost ?

The VFD's I have wired were 3 phase in - 3 phase out . They were rated in amps at the required voltage . Not hp .

But I am not saying the responder is incorrect .

Often theorized that single phaser could be used for the input power for a VFD , since it gets rectified to DC .

God bless
Wyr


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## WyrTwister (Jul 22, 2013)

Wow ! $ 200 , I stand corrected ! They have really dropped in price !

Could have knocked me over with a feather .

God bless
Wyr


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## nap (Dec 4, 2007)

WyrTwister said:


> And I am just guessing , but he may be able to buy a condenser for what a 4 hp VFD will cost ?
> 
> The VFD's I have wired were 3 phase in - 3 phase out . They were rated in amps at the required voltage . Not hp .
> 
> ...


you can buy a 4 ton compressor for a couple hundred bucks? and have it installed?



> The VFD's I have wired were 3 phase in - 3 phase out . They were rated in amps at the required voltage . Not hp .


and that means what?

I linked vfd's that not only accept single phase in put and provide 3 phase output, some of them even will take 12o volt input and run it up to 240 output. 

I'm telling ya; they are boxes of magic.


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## Redcast (May 29, 2015)

Wow...a box of magic...just one small question. Will a power outage become a concern or maybe that's a question for the manufacturer. Thanks to all I Would have given up on me several pages ago. 
Anybody want to tackle how to figure out the right vent size?


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## beenthere (Oct 11, 2008)

Power outage is not really a concern. Will return to normal operation once power is restored.


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## roughneck (Nov 28, 2014)

What do you mean by "vent size"?


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## Redcast (May 29, 2015)

*Wiring a 3 phase 208/230 A/C*

Not being a HVAC person I suppose the terms I use are not the typical ways to describe whats needed. The size of the ductwork I guess is important for the proper airflow of the system which I think I should try to learn something about. Others have mentioned airflow as a contributing factor. I can see where vent size really isn't too accurate.


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## roughneck (Nov 28, 2014)

This is where manual j and manual s come into play. You don't guess at sizing. HVAC is a scientific trade, not a guessing game


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## Redcast (May 29, 2015)

Is that a DIY project or does it require sophisticated equipment?


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