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BlueBSH 03-16-2011 10:34 AM

Sump pump large draw of power
I have an electic monitor on my house to watch the current wattage used in the system, put a new sump pump in last month worked fine, used about 300 watts when it ran.. ran about once every 20 minutes (yes we have a lot of water in the ground here...) but I noticed this past week an odd trend... my electic bill went up drastically because usage went up almost 200 KW, which makes no sense, as this pump is lower wattage then the one it replaced... then I noticed on my usage monitors website peaks every 15 minutes for about a few minutes at 1.9KW, normal background wattage is 400 watts when everything is sitting idle in the house... thought ok just a lot of water to pump, didnt hit me the wattage was so high... well it somehow how is at 2.5KW with the same pattern spaced out perfectly, turned the breaker for the pump outside off wattage never spiked in the house, so it definatly was teh pump... went out last night to look at the sump pit outside (it goes down 10 ft from the ground level... and it had about 2 ft of water in it, which isn't good if there is a pump in there...

well checked the GFIC breaker it wasn't tripped... unplugged the pump, and plugged it back in noticed a faint hummmmm, unplugged it now silence so I wasn't just hearing something, there was a humming noise from inside the pit.... decoupled the discharge pipe and pulled the pump up...

looking at the pump saw nothing wrong by just looking, plugged the pump motor straight into the outlet, and hummmmmm, it appears the motor seized up... no idea why, haven't had that happen before especially on a 1 month old pump...

but my real question is why did it use so much electic up? and why did how much it use increase over time? as of last night it was using up about 2KW itself! at 110 volt that is 18 Amps! and the circuit is only a 20 amp line but has 15 amp outlets and the motor is only rated for 15 amps (the cord and plug on it)

McSteve 03-16-2011 10:51 AM

A stalled or seized motor will draw a ton of current until either the breaker trips or the windings burn out.

Motors have something called LRA or Locked Rotor Amps as part of their nameplate rating. This is how much current the motor draws if the shaft is prevented from turning.

Apparently yours has an LRA below the level required to trip the breaker.

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