Amperage Issues with Jet Pump

Old 11-10-04, 10:56 AM
frank 409
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Amperage Issues with Jet Pump

I have a 1/3 hp jet pump which in the past ran on a 15 amp household circuit.
However, now if I plug it into a 15 amp circuit the fuse blows. But, if I plug it into a 20 amp circuit it runs fine.
Any ideas?
Old 11-21-04, 08:38 PM
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Sounds like a lot of amps for a small motor. I don't recall any 1/3 pumps that take more than 8-9 amps. If possible try measuring the actual amps consumed by the motor, using a clamp-on ammeter at the pressure switch.
Old 11-22-04, 06:15 AM
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Is this a 120V circuit?

I agree with seems like a lot of amps. I installed a 1/2 HP jet pump on 120V. It drew 9.4 amps. I later converted it to 240V (it's a dual voltage pump) and it now draws 4.7V.

Perhaps a loose connection?

Please explain the reference to "plugging in" the pump. Is it hardwired to the circuit?

It sounds like there are other things on the circuit which may draw enough amps to trip the breaker. Generally water pumps should have dedicated circuits.
Old 11-22-04, 09:54 AM
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If it is a 120v circuit, a 1/3 HP motor draws 7.2 full-load amps (FLA). But NEC Article 430, Motors, requires that you multiply the FLA times 2.5 to size your breaker, or 1.75 times if you have fuses.

Hence, a breaker would have to be 20 amps, a fuse would have to be 15 amps. (7.2 amps * 1.75 = 12.6, so you'd go up to the next standard size fuse, or 15 amps.) In an ideal world, that fuse should not be blowing if only the motor is connected to that circuit.

My guess is either something else is on that circuit, or perhaps you have some wiring anomalies (loose connection, short circuit, etc.), or there is a problem with the pump.

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