I need to know the wire gauge to run an above ground water pump. The voltage will be 220 volts. The pump states max. amps 26, and the length of wire run is 70 feet. Thank you. Matt

There is no longer a 220 VAC drop. It is now 240 VAC.

Assumptions:

Continuous load (Power on for more than 3 consecutive hours).
Copper conductors.
Temperature not to exceed 86 degrees (F).
Direct bury cable (UF 86 degrees (F)).

You will need a dual pole 30 AMP Circuit breaker.
70 ft. of #10/2 AWG UF (60 celsius) cable.

That will deliver 235.5 VAC @ 30 amps to your pump.

10/3 cable 30 amp breaker

Hank,

Thanks for the quick clarification. I corrected my typo.

A 26 amp load would require a 40A breaker and at least #8CU wire.

The max continuous load for a 30A circuit and #10 wire would be 24 amps.

Also, "3-wire" would be wasteful. There is NO need for a neutral run to this straight 240v load. 8/2 cable would be fine.

Stan,

Why? #8. A 30 amp breaker into a known 26 amp load is rated correctly.

Did you make the change because multiplying 26 amps by 1.25 (continuous on percentage) yields 32.5 amps? In which case, you would need to use #8/2 with a 40 amp breaker.

Odd, the wire size calculator I used did not pick up the continuous amperage change. Maybe I should go back to using pencil and paper.

I think Stan did it for the distance, and the Load. The motor will love it.

I did it for the continuous load as Don suggests. The OP simply says water pump.
This could be anything, so we assume continuous load.

26x125%=32.50A

I may not have given enough information. The water pump is 2 HP and feeds to a large pressure tank. The pump runs at the most for about 15 min.at a time to bring up the pressure. I am sorry I didn't give enough info in my question. Also, if I use 2 wires how do I ground the motor? Mabey a ground rod?

Is that 26 amps at 240v or 120v

10-2 means 2 conductors, the ground is not a conductor, therefore 10-2 will have 3 wires, 2 conductors and a ground wire.

You will need to pull a #10 for ground.

That is 26 amps at 249 volts

Quote:

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Originally Posted by grandma-tlc

That is 26 amps at 249 volts

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HUH??

Grandma, are you also shorey?

Yes I am using my wife's computer. I also missed a key. It's 240 Volts not 249. MY computer took a time out. Thanks.

240v makes sense.

Is there more info on the motor nameplate than you gave? Can the motor be run at either 120 or 240?

240V 26A for a 2hp motor just strikes me as odd. It seems like twice the current that it should be.

The nameplate shows amps as 26/13 so it can run at 120v or 240v.

Then that's 13 amps at 240 volts. At 125% for motor load you are back to the 10/2 cable.

430.6(A)(1) says that if a motor is marked with it's horsepower then Table 430.248 shall be used to determine ampacity instead of the nameplate. By the table you have 12A and at 125% of that you have 15A.

Since there is a condition that would allow this motor to run continuously the circuit needs to be sized to be loaded at no more than 80% so a 20 amp breaker is required. I'd probably still run the 10/2 cable though.

Stan,

My original error was caused by a loose nut on my keyboard. :)

This morning when I re-started the conductor size calculator instead of toggling the radio button for "Continuous Load", I placed 26 Amps into the Continuous Load block and out popped the size #8 AWG and a 40 Amp breaker.