10 A Shunt Trip - Electrician Talk - Professional Electrical Contractors Forum

InPhase277 · 07-12-2009, 12:41 AM

An electrician buddy of mine called tonight, said he had an emergency call to a gas station to go on in the morning. Seems that, from the customer's description, a breaker that controls 6 pumps is tripping. He described it as a double pole Square D QO 10 A shunt trip. And really that's all that is known at this point. My buddy asked me if I had one of those breakers so he would have one with him just in case it turns out that is the problem. Of course, 10 A is not something I use alot of. I do, however have a 20 A shunt trip in that config. If that is the problem, that will at least get them up and running until he can find a supplier for the correct breaker on Monday.

My question is: Is this a branch breaker or a control circuit? The only 10 A circuits I have installed are almost all control circuits or specialized motor circuits. I have also never done any work in a gas station except lighting upgrades and remodels, never touching the pump controls. When he said this breaker killed 6 pumps, the first thing that popped into my mind was that it must actually control some contactors that in turn control the pumps. He didn't have an answer either. Any theories or experience?

**frenchelectrican** · 07-12-2009, 04:04 AM

Quote:

Originally Posted by InPhase277

My question is: Is this a branch breaker or a control circuit? The only 10 A circuits I have installed are almost all control circuits or specialized motor circuits. I have also never done any work in a gas station except lighting upgrades and remodels, never touching the pump controls. When he said this breaker killed 6 pumps, the first thing that popped into my mind was that it must actually control some contactors that in turn control the pumps. He didn't have an answer either. Any theories or experience?

InPhase277.,

To answer your question yes the control circuit is a " Master " for gaz pumps and IIRC majorty of the gas station I ran into they will have a gas pump subpanel with a master contrator or shunt trip breakers { if the local code require it } so that breaker will handle Emergcy pump shut off circuit so the control do feed from that to the E stop switch { useally you will see at least two E stop button one outside and one inside }IIRC they are wired either 24 volt or 120 volt so if one of the conductor shorted out it will trip the breaker plus they have NC concats on E stop circuits once you past that there are few contractors for the pumps.

Oh yeah majorty of gas station the pump will be located in the underground tank except like racing gaz or Kenorse fuel it will be either way depending on what they do with smaller tanks it can be underground or above ground tank.
For above ground tank the fuel pump motour will be at the fuel dispinser unit.

Yeah you may want to check the Expolison proof stand off Y fitting to make sure they are not damaged.

I hope it will help you with this question and I know few other guys here may know little more they can chime in with more details.

Merci,Marc

**MDShunk** · 07-12-2009, 08:55 PM

10 amp circuits seem to be a regular feature in gas station breaker panels for pump islands, but I'm not even sure that squares with the NEC. Seems like they should be in the pump control panel and not in the breaker panel.

Toronto Sparky · 07-13-2009, 09:42 AM

I've seen a shunt breaker used to power the coil in a contactor that kills the power to the panel feeding pumps and lighting in the gas bay.