Running a switched and always on circuit to outbuilding

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Old 02-25-15, 12:45 PM
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Running a switched and always on circuit to outbuilding

I have a pump house with a 1HP pump in it located about 700' away from my house. This was built in the '50s and is in serious need of updating. Currently, there is a contactor at the house (controlled by a switch in the basement) which energizes 2 hot lines that power the 240V motor in the pump house. The wires are up in the air on old poles. I will be trenching in a PVC conduit and pulling new THWN (sized appropriately for the voltage drop on such a long run).

While I'm doing this, though, I'd like to add a 120V circuit for lighting and maybe some low wattage heat tape to keep the pipes and pump from freezing in the winter.

I need this 120V circuit to be always powered, but the 240V circuit to the pump itself to be switched from the house.

I was originally thinking I could run 2 hots for the pump, a hot and a neutral for the 120V circuit, and a ground. However, I think this will run afowl of NEC 225.30 which limits the number of circuits running to an outbuilding to one.

Next I thought I could run 2 hots 1 neutral and a ground to the pump house, install a subpanel, and use the contactor at the house to switch one of the hots. The other hot would always be on and would serve the 120V circuit. However, I'm pretty sure switching one pole is a code violation, too, even though I'm not sure what section applies.

Another idea is to install the sub panel in the pump house and move the contactor to the pump house. I would have to run 2 more wires from the house to energize the coil of the contactor. I don't know if it's okay to have the contactor switch a circuit on the subpanel in the pump house and energize the coil of the contactor with a circuit from the main panel in the house. In any case, I think this violates 225.30 again, because now I have both a feeder to the subpanel and a branch circuit to the contactor coil going to the pump house.

Last idea is the same as above but to use a low voltage (24v?) coil on the contactor in the pump house. I'm assuming the low voltage control would not count as a circuit under 225.30. Can I run these wires in the same conduit? Do I need a disconnecting means for them? Is this the right way to do it?

Any other ways to go about solving this problem? I don't want to do wireless control due to difficulty of getting it right (sloping terrain and large trees in the way) and reliability concerns.
 
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Old 02-25-15, 12:58 PM
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Welcome to the forums.

I would definitely set a sub panel and remote contactor in the pump house.

You could pull in a few extra #12 THHN's as a control line from the pump house. The power for the controls would be generated from the pumphouse. Stay with a 120v coil. The distance is too long for 24vac.
 
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Old 02-25-15, 03:30 PM
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Pete's definitely got the right idea. You wouldn't even need to do a subpanel as this could just be considered a multiwire branch circuit given that the pump is only 1HP so your breaker would not exceed 20A. It doesn't change the details of the installation that much either way.

I'll also recommend you consider using #2 or #4 XHHW (aluminum) wires instead of THWN (copper) for the subpanel feeder just due to cost.
 
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Old 02-26-15, 07:33 AM
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"You could pull in a few extra #12 THHN's as a control line from the pump house. The power for the controls would be generated from the pumphouse. Stay with a 120v coil. The distance is too long for 24vac."

You will need three of these smaller wires, raw hot from the shed, switched hot back to the contactor at the shed, and neutral accompanying the raw hot in case the next homeowner wants to have a pilot light at the switch in the main house to indicate convenience receptacle power on at the shed.

The latest NEC requires the neutral at outlet boxes serving switch loops.
 
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Old 02-26-15, 02:00 PM
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The two #12 wires I'm recommending will go straight to the pressure switch. There is no neutral required in this setup as it is not considered a lighting switch loop.
 
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