# Table saw tripping breaker - please advise



## Yooperman906 (Dec 17, 2010)

I am having trouble with my table saw continually tripping the breaker in my panel. I can't figure out what could be going wrong to do this, but I'm hoping somebody out there has run into this before and can suggest a solution.

I've been working on a project, making my own shiplap out of 1" cedar. The saw was working well at first, but has since started tripping the circuit breaker. My family is home now, and that circuit has other loads on it. 


Firstly, about the tablesaw:

Craftsman Model#: 315228590
Motor: 120 Volts/ 13 Amps 

Now about the circuit supplying the table saw from the main panel in my house (100 AMP):


20 Amp, Square D breaker in the panel
12/2 W Ground to the outlet (~25 ft)
Outlet: 20 Amp GFCI (which is not tripping)
Extension cord: 10/3 (50 ft)
Table saw is plugged into the extension cord

I moved the extension cord to the dedicated circuit (as described above) and thought my problems were over. Much to my surprise, the saw is still tripping the breaker on this dedicated 20A circuit. :surprise:

All I can imagine is that the blade is getting dull, and that this could strain the motor and somehow cause it to draw more "juice" (forgive my ignorance if this is a foolish suggestion), hence tripping the breaker.

To test this theory, I powered up the saw with no board or any other impediment to the blade spinning freely. It started spinning, seemingly reaching full speed and then the breaker tripped shortly thereafter (but not "immediately"). This leads me to think my former theory about a dull blade being the cause is debunked.:vs_worry:

The owner's manual suggests that using a 12 AWG extension cord up to 100' is acceptable, so I can't imagine that my wires are an issue.

I'm far beyond the end of my wits here, and I really need to get that saw humming again tomorrow to make some headway. Any insights would be most appreciated.

Thanks much!
Jake aka Yooperman

p.s. The motor is thermally protected, but the overload protector has not tripped to my knowledge (at least, I have not pressed the reset button).


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## dmxtothemax (Oct 26, 2010)

First of all, is the stated current of 13 A
Is this the running current ?
or the FLA current ?

You are not taking into account the "STARTING CURRENT"
the starting current of an electric motor will be many times
it's normal running current, so tripping a 15 or a 20 no probs.

You need a different type of circuit breaker,
one designed for electric motors they have 
a slower trip curve, these will allow for the 
very breif but large start up surge.

Over here we call them "slow blow".

I think you guys call them "type two".


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## Jim Port (Sep 21, 2007)

If the breaker is tripping on overload from long periods of use age the thermal components will need to cool down. Otherwise it will trip quickly again, even if not under load.


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## joed (Mar 13, 2005)

Could be an issue with the motor. The start switch switch could be stuck and not disengaging. Do you here the click when the motor spins up and slows down?


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## Bria Johnn (Feb 18, 2009)

This is a thermal magnetic circuit breaker.

Does it trip on start up or after running for a while

So several items will result in an operation of the CB.



1. Defective CB (DUH! as the kids say)
2. Loose connection at the CB line or load or in the CB interior results in 
excessive heat, and trips the CB on thermal
3. Overload, if you are edge ripping a deep cut, this will over load the CB.
if you are cutting for long periods this can result in heating 
of the CB and tripping
4. Inrush, motor starting load as noted there is a high current draw on 
start up.


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## Yooperman906 (Dec 17, 2010)

joed said:


> Could be an issue with the motor. The start switch switch could be stuck and not disengaging. Do you here the click when the motor spins up and slows down?


I do not here any clicks, but thanks!


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## Yooperman906 (Dec 17, 2010)

dmxtothemax said:


> First of all, is the stated current of 13 A
> Is this the running current ?
> or the FLA current ?
> 
> ...


Thanks, and yes, I am aware of start-up surge. Since it was working well before though (I cut many boards successfully before I had the problem) I don't think it's an issue with surge. It could be that I should be using a different type of breaker, I will ask some folks with shops around here.


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## Bria Johnn (Feb 18, 2009)

Yooperman906 said:


> Thanks, and yes, I am aware of start-up surge. Since it was working well before though (I cut many boards successfully before I had the problem) I don't think it's an issue with surge. It could be that I should be using a different type of breaker, I will ask some folks with shops around here.


Depends on how you are cutting the boards and type of wood as I mentioned in my post.

I have a Delta Cabinet Grade saw, 220 VAC 16 amps, I can use the saw all day long, with no issue, but if I make a rip cut on edge red oak, the CB will trip.


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## Yooperman906 (Dec 17, 2010)

Thanks to all for the replies. I think that maybe Jim and Bria are describing the likeliest of issues - overload resulting from a long period of use. I will add, however, that I was not able to cut even one board once I moved over to the dedicated circuit. This new circuit was , of course, on a different breaker and conductors than the other one, so if it was an issue with the breaker, I'd think that I would have been able to get a similar amount of work done as I had before I started having problems.

Hence, I'm back downstream to the saw motor. Perhaps I'm just overworking it and it needs rest. I will describe my work further in my reply to Bria's post.


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## Yooperman906 (Dec 17, 2010)

Bria Johnn said:


> Depends on how you are cutting the boards and type of wood as I mentioned in my post.
> 
> I have a Delta Cabinet Grade saw, 220 VAC 16 amps, I can use the saw all day long, with no issue, but if I make a rip cut on edge red oak, the CB will trip.


Thanks, Bria - very useful to have these woodworking examples. And, yes I'm sure that what I'm doing is a high-strain task:

Cutting 3/4" lap joint (1/2" deep) on the edge of 1" rough cedar (dry) to make shiplap. Making matters "worse", I'm using a wobble dado instead of a stack.

The motor is convertible, i.e. I could rewire it to run on 240V @ 6.5A, but I'd have to run a new circuit for that. Based on your setup, it sounds like I might still run into trouble with the work I'm doing. What do you think?

Furthermore, if I am doing this "the hard way", I'm very open to recommendations on how I should be making shiplap - but perhaps I need to move things to the woodworking forum if we go that route.

Thanks again!


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## joed (Mar 13, 2005)

Yooperman906 said:


> I do not here any clicks, but thanks!


Then the start switch is stuck and you are running on start windings. This will overheat the motor and overload the circuit.


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## SeniorSitizen (Sep 10, 2012)

There are very few table saw motors that wouldn't benefit from a good cleaning. About the only example I can think of at the moment is a saw that's still in its shipping crate. :smile:

Pictured is the actual motor that was on one of my pre-owned saws I bought at auction. Thought I'd mention that so you don't cut me down too bad.

Dirt/saw dust may not be the problem at all but consider taking a look to see if that little fan blade can pump the required air.


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## Yooperman906 (Dec 17, 2010)

joed said:


> Then the start switch is stuck and you are running on start windings. This will overheat the motor and overload the circuit.


Wait, so I should expect to hear clicks on normal operation? I guess I'll have to listen more closely to evaluate this particular aspect of the situation.

What am I listening for, brushes? I will try and listen more, but I'm pretty sure it's just getting hot from overwork. I just did another dozen boards without incident, then it tripped the breaker for the first time today after I started the saw back up.

The way I'm doing this is slow going, I run each board through twice to make the lap joint on both sides. Before I make the first pass through, I set the fence (boards are varying widths) and only then do I turn the motor on. After each pass through the saw, I turn off the motor, walk to the other side of the saw and pull my board through the anti-kickback teeth (I have sawhorses supporting the boards as the come off the table [and onto the table as well]). Then I slide the board back, walk back around the saw, position the board, power up the saw, and make the second cut. Then I turn the saw off, go pull the board thru, put it onto a stack, and grab the next board...

I'm going to move on to another task while I wait for the motor to cool down.

If you think I should do more listening, I'd be happy to, but not quite sure what to listen for. I can give it a go if, after reading the above, you still think it might be the windings issue.

Thanks!


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## Yooperman906 (Dec 17, 2010)

SeniorSitizen said:


> There are very few table saw motors that wouldn't benefit from a good cleaning. About the only example I can think of at the moment is a saw that's still in its shipping crate. :smile:
> 
> Pictured is the actual motor that was on one of my pre-owned saws I bought at auction. Thought I'd mention that so you don't cut me down too bad.
> 
> Dirt/saw dust may not be the problem at all but consider taking a look to see if that little fan blade can pump the required air.


Good thing to check for sure. I've been cleaning regularly as I work with the shop vac to keep things clear - including the motor housing. It looks clear, but I'm sure there is some fine dust in there. A good reminder to clean it out when I'm done with this project.


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## joed (Mar 13, 2005)

Here is a video of a an AC motor. If you go to about 3:25 in the video you will see and hear the start switch clicking in and out as the motor is starting and stopping. Your motor should be doing something similar even though it is probably more enclosed.


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## Yooperman906 (Dec 17, 2010)

I had to put my head close to the motor to hear the clicking, but I could definitely hear it click, especially after turning the motor off, it's easy to hear a distinct click. I didn't know about these centrifugal switches, thanks for the info!


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## joed (Mar 13, 2005)

You need a clamp on ammeter to check the current when the motor is running and no wood is being sawed.


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## mpoulton (Jul 23, 2009)

You've mentioned that the breaker will trip even when you're not cutting, but not instantly on startup. This is not normal and should not be possible even if the breaker is hot from lengthy use under load. The fact is that a 20A breaker will not trip quickly even with moderate overloads. At 30A it should take 1-7 minutes based on a typical trip curve for a 20A breaker. If your saw trips the breaker while running without cutting, there's something wrong. Need to measure current to see what's going on.


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## joed (Mar 13, 2005)

It is possible the switch is clicking but the points are welded and the start winding is still not disengaging. Current measurement will confirm this.


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## Yooperman906 (Dec 17, 2010)

I will update this once I've been able to measure the amperage. Back to my "day job" tomorrow.

Thanks!
Jake


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## micromind (Mar 9, 2008)

If you have a dedicated circuit (straight shot from the breaker to the receptacle, no other loads) then it would be easy to make this circuit 240 volts. You'll need one spare space (2 is better) in the panel and you'll need to change the receptacle and cord plug to a 20 amp 250 volt type but the wire in the wall is ok with either 120 or 240. Just put some red tape on the white wire (a red sharpie will work too) and re-connect the motor.

If you do this, you'll notice the saw has considerably more power, laws of physics notwithstanding. 

Rob


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## Bria Johnn (Feb 18, 2009)

If you rule out all the other issues noted and the problem persist, try to make shallower cuts, making multiple passes to deepen the cut.


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## B-Nabs (Dec 18, 2014)

Just curious, is this circuit fed by an AFCI breaker?


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## jreagan (Feb 20, 2015)

micromind said:


> If you have a dedicated circuit (straight shot from the breaker to the receptacle, no other loads) then it would be easy to make this circuit 240 volts. You'll need one spare space (2 is better) in the panel and you'll need to change the receptacle and cord plug to a 20 amp 250 volt type but the wire in the wall is ok with either 120 or 240. Just put some red tape on the white wire (a red sharpie will work too) and re-connect the motor.
> 
> If you do this, you'll notice the saw has considerably more power, laws of physics notwithstanding.
> 
> Rob


I don't think that is true. The motor will generate the HP it is designed for. The only benefits from going to 240v is "smaller wires needed" and "lower voltage drop". You won't get more power from the motor.

http://www.thewoodnerd.com/articles/motorRewire.html


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## Yooperman906 (Dec 17, 2010)

No, I do not believe so. "Standard" square D breaker. It has no markings labeling it as AFCI.


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## joed (Mar 13, 2005)

jreagan said:


> I don't think that is true. The motor will generate the HP it is designed for. The only benefits from going to 240v is "smaller wires needed" and "lower voltage drop". You won't get more power from the motor.
> 
> http://www.thewoodnerd.com/articles/motorRewire.html


Moving to the higher voltage will lower the current draw.


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## joed (Mar 13, 2005)

What is the HP rating of the motor?


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## Yooperman906 (Dec 17, 2010)

joed said:


> What is the HP rating of the motor?


From the owner's manual:

...*

MOTOR (13/6.5 AMP) *- The powerful induction motor
is 3HP, with capacitor start and V-belt drive, and is
housed in a sturdy steel base.

...


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## joed (Mar 13, 2005)

The amp rating and HP don't jive. The amp rating is more in the 3/4 HP range.
A 3 HP should be more in the 34 amp range at 115 volts.
With belt off and no load there is no way a properly functioning motor should trip a breaker.
Are those same values stamped on the motor?


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## Bria Johnn (Feb 18, 2009)

joed said:


> The amp rating and HP don't jive. The amp rating is more in the 3/4 HP range.
> A 3 HP should be more in the 34 amp range at 115 volts.
> With belt off and not load there is no way a properly functioning motor should trip a breaker.


The 3HP rating is derived actually from PEAK HP or right at Lock Rotor Current. I do believe and the amperage is running current, a not so honest sales gimmick, IMO.


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## joed (Mar 13, 2005)

Sears got sued I think on that trick of peak HP for their compressor ratings a few years back.


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## SeniorSitizen (Sep 10, 2012)

I've found that a vid of my Kill-A-Watt meter does a descent job of recording the wattage draw at start up and during the many different operations power requirements.


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## jreagan (Feb 20, 2015)

joed said:


> Moving to the higher voltage will lower the current draw.


That's my "smaller wires" part. Yes, lower current. A little less heat. It won't make the motor more powerful. It won't save any money as the watts consumed is the same either way.


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## Knows a Little (Jul 7, 2016)

jreagan said:


> That's my "smaller wires" part. Yes, lower current. A little less heat. It won't make the motor more powerful. It won't save any money as the watts consumed is the same either way.


With lower amperage same conductor size MIGHT (?) help with inrush some.


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## micromind (Mar 9, 2008)

jreagan said:


> I don't think that is true. The motor will generate the HP it is designed for. The only benefits from going to 240v is "smaller wires needed" and "lower voltage drop". You won't get more power from the motor.
> 
> http://www.thewoodnerd.com/articles/motorRewire.html


When the motor is producing its rated HP, it doesn't matter if it's connected for 115 or 230. However when it's overloaded, it'll have higher breakdown torque when operated on 230 volts. 

Breakdown torque is the maximum it can produce during a gradually increasing load before a rapid loss of RPM. 

Something like a fan will never reach breakdown torque because the load is constant and controlled. Something like a tablesaw is regularly overloaded and can indeed see breakdown torque. Just about anyone who has had one connected for 115 volts then re-connected it for 230 will attest to the greater torque under heavy load. I've seen it myself as well.


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