# See if yall can answer this ?



## ashveal (Aug 8, 2010)

I have a circuit that is tripping

To start with its a single phase 120/240 225 A QO panel connected to a 20A breaker then wires runs approx 1.5 ft hooks to a 20A p&s GFI recep this same circuit goes down and hits 3 more gfi receps ran from line side to line side.
well the problem is when the customer STARTS their chop saw straight to the 1st gfi no drop cord 50% of time it trips breaker you can add a drop cord or move down to the next recep on same circuit and will not trip or move to another circuit same length from breaker and will not trip

things i have tried 
change breaker 
changed gfi
check neutral and hot wire for good connection changed hot wire out with longer wire by rapping around in the panel and it helped but still had issue

then changed hot wire out from #12 stranded to #10 stranded 
same problem 

the only thing im changing is length of wire that is solving issue 

specs of CHOP SAW 15a pull but i have notice it pull close to 50a on this circuit when starting just for like half second but on another it pulls 40 ish amps i have changed phases still no avail 

my thinking when using drop cord the length is giving the amps time spread out over 25ft but when straight to recep and it own cord all those amps are hitting that breaker at same tim which in turn trips breaker


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## MDShunk (Jan 7, 2007)

What are your megohm readings on the saw, and does the extension cord have a continuous ground path?


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## ashveal (Aug 8, 2010)

havent checked ohms but yes drop cord has ground


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## Big John (May 23, 2010)

Ashveal,

I think you've got the right idea: I think making the circuit longer increases it's impedance, and reduces the starting current the chop saw will draw by just enough to keep the breaker from tripping.

Other than wrapping a wire around the inside of the panel 30 times, I would install a 30A fused disconnect on a 30A breaker, and then I'd put 20A time-delay fuses in it and run my receptacle off of that. I'm thinking that would do the trick. 

I'm not sure how else to legally solve it.

-John


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## micromind (Aug 11, 2007)

The easiest solution is to get a 'high magnetic' breaker. 

In this case it would be a QO120HM. 

The inrush current of the chop saw is high enough that the breaker is seeing it as a fault. The 1-cycle (1/60 sec.) trip rating of a QO120 is about 250 amps. The rating of a QO120HM is about 800 amps, the same as a two or 3 pole unit. 

Smaller or longer wire will cut this inrush considerably, but I'd simply install the HM breaker.

Rob


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## Introyble (Jul 10, 2010)

ashveal said:


> I have a circuit that is tripping
> 
> To start with its a single phase 120/240 225 A QO panel connected to a 20A breaker then wires runs approx 1.5 ft hooks to a 20A p&s GFI recep this same circuit goes down and hits 3 more gfi receps ran from line side to line side.
> well the problem is when the customer STARTS their chop saw straight to the 1st gfi no drop cord 50% of time it trips breaker you can add a drop cord or move down to the next recep on same circuit and will not trip or move to another circuit same length from breaker and will not trip
> ...


Guess I'm confused as to why 3 additional GFCI's are wired in a single circuit.
I always thought a single gfci would protect all the non gfci's when wired as you described. Honestly, you don't need 4 gfci's on that circuit, get rid of them.

Not to be a wise ass, but they are meant to protect a single location and that many gfci's is bound to be a headache.

Most GFCI's are designed to trip with as little as 5 milliamp current fluctuation. We all know what happens when an electrical motor first starts up ~ potential current spike up to 10 times its rated FLA's.

Rid yourself of the additional series GFCI recepts, since the one will protect the other three you mentioned. See if your problem goes away then.


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## WIREDOG (May 27, 2007)

Try a different saw and see what the result is


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## ashveal (Aug 8, 2010)

I dont see why that would help i can move down one and it works fine and its under a huge barn open sides and we all know what will happen if you feed 3 receps out of 1 gfi. they'll be running saws ,grinders ,drills compressor etc. and i dont think that would work very good it would be fine in a office or house but i dont like running them like that
and the gfi wasnt tripping the breakers were 
any way i fixed it and we got paid customer happy


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## oldtimer (Jun 10, 2010)

ashveal said:


> I dont see why that would help i can move down one and it works fine and its under a huge barn open sides and we all know what will happen if you feed 3 receps out of 1 gfi. they'll be running saws ,grinders ,drills compressor etc. and i dont think that would work very good it would be fine in a office or house but i dont like running them like that
> and the gfi wasnt tripping the breakers were
> any way i fixed it and we got paid customer happy


 SO !!!!! How did you fix it?????


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## nitro71 (Sep 17, 2009)

He had it screwed up and now he doesn't want to tell us about it!


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## JohnR (Apr 12, 2010)

Because I had the same problem with my chop saw before I sold it, I can guess that he found out that if you plug the thing into an extension cord it no longer will trip the ckt.


Was that your fix?
My miter saw was drawing 15A FLA and on startup would bump over the 20A the breaker was rated at. didn't matter if it was a QO or a generous electric. But as soon as a Ex cord was introduced even a 12Ga cord it wouldn't.


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