# 20 Amp breaker keeps tripping on 7" grinder startup



## jggramlich (Jul 11, 2013)

We are running a steel fabrication shop and have an issue with 20 amp breakers tripping when using our 7" grinders. The grinders are Metabo 24-180 in case anyone cares.

The grinders are rated for 15A, but usually several times a day our fabricators trip the 20A breaker while using these tools. Each grinder is on its own circuit but the breakers are still tripping. The tripping usually occurs on start, but can happen if the grinders are heavily loaded.

We've got maybe 50' of wire run (I think it's 14ga, I have to go check) and another 50' of heavy duty extension cord they're using for the grinders.

I've changed both 20A breakers out with new and the problem has not disappeared. The grinders are about 2 years old and are pretty much used every day.

I am hesitant to up to 25A breakers. I shouldn't have to cut the factory-end off of a power tool to get it to operate properly (25A breaker would mean receptacle and wire and plug change).

I don't have problems replacing the wiring or any of that rot were it to help. I intend on checking the current draw of the tools on monday...must go tool shopping first. There is potential that both 7" grinders have gone bad, but I doubt it.

Assuming I keep the circuit at 20A, would upsizing the circuit wiring and downsizing the extension cord make a significant difference in breaker tripping?


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## seabee41 (Dec 21, 2010)

Your local electrical contractor can answer that for you.


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## MechanicalDVR (Dec 29, 2007)

You obviously can't read or you wouldn't be on here.


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## seabee41 (Dec 21, 2010)

My bad


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## ponyboy (Nov 18, 2012)

Call an electrician. Or hire one full time for your facility, sounds like he'd stay busy


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## denny3992 (Jul 12, 2010)

seabee41 said:


> My bad


Dont think that was directed at u seAbee....


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## J C (Jul 11, 2013)

The grinders will surge momentarily. This is normal. The CB's are prolly getting warm with them running on and off all day.

How old are the circuit breakers? Tried a new one?

Does it happen on various circuits?

You could try testing them by plugging into a 20amp receptacle nearest the panel and see if it holds. If so, maybe replace the circuits in question with #10 wire and heavy duty cords #12ga min.


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## micromind (Aug 11, 2007)

Depending on the brand of breaker, you might be able to get 'high magnetic' breakers. These are designed to not trip on high inrush from motors starting.


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## Spark Master (Jul 3, 2012)

I like the 20 amp breaker on 14 ga wire. And another 50' extension cord. :thumbsup:
All with a 15 amp machine. 

I bet your at 100 volts under load.


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## BostonSparky (Jan 12, 2012)

jggramlich said:


> We are running a steel fabrication shop and have an issue with 20 amp breakers tripping when using our 7" grinders. The grinders are Metabo 24-180 in case anyone cares.
> 
> The grinders are rated for 15A, but usually several times a day our fabricators trip the 20A breaker while using these tools. Each grinder is on its own circuit but the breakers are still tripping. The tripping usually occurs on start, but can happen if the grinders are heavily loaded.
> 
> ...


You should have 911 on speed dial.


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## Jlarson (Jun 28, 2009)

This is what happens when welders wire things.


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## sparky970 (Mar 19, 2008)

Spark Master said:


> I like the 20 amp breaker on 14 ga wire. And another 50' extension cord. :thumbsup:
> All with a 15 amp machine.
> 
> I bet your at 100 volts under load.



Your voltage drop would be under 10 volts


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## Loose Neutral (Jun 3, 2009)

My friend has a metal shop and his electrical work is hideous. Romex everywhere. He even used his torch to blow thru some girts and just ran the romex thru there. SEU cable everywhere. Stupid ass iron worker. They all think it's just black to black and white to white.


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## Southeast Power (Jan 18, 2009)

jggramlich said:


> We are running a steel fabrication shop and have an issue with 20 amp breakers tripping when using our 7" grinders. The grinders are Metabo 24-180 in case anyone cares.
> 
> The grinders are rated for 15A, but usually several times a day our fabricators trip the 20A breaker while using these tools. Each grinder is on its own circuit but the breakers are still tripping. The tripping usually occurs on start, but can happen if the grinders are heavily loaded.
> 
> ...


Low voltage on an inductive load. What happens to amperage?


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## Speedy Petey (Jan 10, 2007)

I'm not even putting the DIY disclaimer on thie one. 

Please call an electrician.


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