Water pump/electrical


Old 03-06-06, 10:50 AM
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Location: New Hampshire
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Water pump/electrical

Just had my (deep well) water pump replaced. The old one quit last night. I hardwired past the pressure switch to see if the switch was bad...still no pump. It was a 1/2 hp submersible. The pump guy put the tester on it and showed me where it was drawing 29 amps on each leg.

Any ideas why my breaker didn't trip? It's wired off a 20-amp double pole breaker with 12/2 romex.

Time to replace the breaker?

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Old 03-06-06, 11:29 AM
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Breakers have two trip mechanisms: one that trips on short circuits and one that trips on overloads. The short circuit mechanism will trip almost immediately on a short burst of 100s or 1000s of amps. The overload mechanism will trip on the heat caused by the overload. In your case, 29A on a 20A breaker is not a big overload so the thermal trip will be slow; it may take several hours for a 20A breaker to trip at 29A. Due to manufacturing tolerances, some 20A breakers may never trip at 29A.

You could try a new breaker, but yours doesn't seem necessarily bad.

EDIT: Please post the brand name of your breaker. There are some older brands which are known to not trip and are now considered unsafe. Federal Pacific (FPE) Stab-lock is one such brand.
Old 03-06-06, 11:40 AM
Join Date: Jan 2006
Posts: 131
at 240 volts fla is about 4.5. this sounds like locked rotor at 29 amps. is there a fla and lra rating on the nameplate. if the motor has an internal overload or a thermal cut out that will open from 29 amps if its rated at 20. a 20 amp breaker may not open from a 29 amp draw.
Old 03-06-06, 12:23 PM
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Thanks for the info.

No, no FPE panels here...ITE LoadCenter.


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