Wire guage too small -- what are the ramifications?

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tkeoki

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My pump is installed 358' down + 15' of wire to the well house, so roughly 375'. I just noticed that they installed 12awg wire. 10awg was what was payed for.

My voltage at the controller box is 244, i've never measured it at anything less than 240 -- the last time I measured current from the pump it was 11.9 amps, so assuming I'm not completely messing up my calculations, that would mean I'd have a 7.4% voltage drop and the voltage at the motor would be about 222v. So the motor voltage would still be within spec.

But are there any other concerns with having that high a percentage drop from the controller to the motor?

My pump was replaced 3 1/2 years ago, it was a crazy time and I wasn't able to check out the installation process as much as I usually would. (I did catch them installing a completely different no-name 1 1/2 hp pump instead of the Grundfos 2HP that was supposed to be installed.)

Part of the problem was that I wasn't the one being billed. It was through a 3rd party insurance company, which took me out of the loop a little bit.
 

Craigpump

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1.5 hp on #12 is good for 310' + 10% so theoretically it's good for 341'.

The motor might run a bit hotter which could lead to a shorter life.
 

DonL

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Kind of late to do much.

You should be OK.

The price to change the wire would exceed the benefit.
 

tkeoki

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It's a 2hp pump so at least according to franklin manual is good for 250', right? And yeah, I'm not looking to replace the wire. Just wondering if there are any issues I need to be aware of.
 

Valveman

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Here is a quote from Franklin about the use of soft start equipment.

"Reduced-voltage starters may not be required if the maximum recommended cable length is used. With maximum recommended cable length there is a 5% voltage drop in the cable at running amps, resulting in about 20% reduction in starting current, and about 36% reduction in starting torque compared to having rated voltage at the motor. This may be enough reduction in starting current so that reduced-voltage starters are not required."

Reducing the wire size will not only save money on installation cost but, can also function as a soft starter. So there should be no problem. I hope you didn't pay for a 2HP, because 11.9 is maximum amps for a 1.5 HP motor.
 

DonL

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It's a 2hp pump so at least according to franklin manual is good for 250', right? And yeah, I'm not looking to replace the wire. Just wondering if there are any issues I need to be aware of.


Like Craig was saying, the motor may run a bit warmer or hot if the voltage is real low.

If it trips the internal motor protector, then you should worry and fix it.

Are you having problems with it ? Or just pissed because you got screwed ?
 

Valveman

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Volts X Amps = Watts

The lower the voltage the higher the amperage. Amps make heat, not the voltage. So as long as the amperage is below Service Factor Amps you are still good. If you had low voltage in your area to start with, the amperage might exceed SFA.
 

tkeoki

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Not having any problems, and not even mad--just making sure there's not anything that would be cause of concern or anything I needed to do to correct any issues.

If anything, I'm a little upset at myself for not checking at install time and not noticing till now.

I guess I'm a touch confused on the amps. The 2hp motor is listed as 10 amps at Full Load and 13.2 at Service Factor Load. What should my amp reading be typically? Does it depend on where I'm at on the pump curve? I think my average pumping head is around 380 ft, which according to grundfos data equates to P2 as 2.54hp. I'm not sure what the P2 value means, though.
 

Valveman

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You could be back on the pump curve a little and get 11.9 amps. I would run the pump wide open with no pressure (all the faucets you have on). Then if it pulls higher than 11.9 amps you have a 2 HP. If it stays at 11.9 you have a 1.5HP. It is even possible to put a 2HP motor on a 1.5 HP pump. Then even though you have a 2 HP motor it will only pump 1.5 HP water and pull 1.5 HP amps.
 
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