I need to hook up the outbuilding to the main power pole. It was hooked up before and we moved, moving the outbuilding. I have 10/2 WG UFB wire. the photo shows main power pole.

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What size amp do I need to put in it? then run the wire to outbuilding where second photo shows the subpanel inside. there are 4 15 amps and one 30. Not all are being used. When I hooked it up only the top two 15 amp seem to work, the bottom 15 amps do not. My son said it might be because the breaker in the main pole is only a 20 amp breaker. Is he correct? Or do I need better wire? it runs about 90 feet. enter image description here

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    I think we need a wider shot of that subpanel. I want to know why there are 2 black wires on the 2 breaker feeds, but only one black wire in 10/2. – Harper - Reinstate Monica Jul 24 '19 at 0:11
  • How big is this outbuilding, and what loads are in there? – ThreePhaseEel Jul 24 '19 at 0:28
  • outlets, window ac. lighting – Carol Anderson Jul 24 '19 at 0:35
  • 6 outlets, window ac. overhead lighting, water heater. but i never run water heater and window ac at same time. 12 X 24 building. The subpanel was hooked up by an electrician. the wires run outside to a small connector box. that connector/junction box is where I tied in the 10 /2 the exact same way he had it before we moved. I think I need to elimanate the connector box and pull the 10/2 stright up though the floor to the subpanel and hook up. I took new photos but can figure out how to upload – Carol Anderson Jul 24 '19 at 1:07
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    I don't see a supply neutral. Is the supply individual wires in conduit, or a cable with 2 black wires? – Harper - Reinstate Monica Jul 24 '19 at 12:57

You're probably only getting half your circuits because you're missing a service leg. You said it is connected to a 20 amp breaker with 10/2. That really sounds like you're running 120V when it should be 240V.

Your 10/2 can handle a maximum of 30A. The bare minimum change you need to make is to take out the 20A breaker you're connected to and put in a 30A single pole breaker. You will get a voltage drop of around 5% with that length of 120. Pull out the 30A breaker in your sub panel and move the 15A breakers down one row. Only one bus is probably live in the panel right now. Put a 30A single pole breaker on the water heater circuit. (Skip another row in the sub panel for the same reason. ) ONLY DO THIS IF the heater can be set or wired for 120V. Your heater will heat much more slowly if you don't use 240V. This should be functional, but you will very likely trip your breaker if you're doing anything at all when the water heater comes on, depending on the actual current draw of the heater. The supply is definitely inadequate, and you will be relying on the circuit breaker to not let your house burn down. This is also 100% not to code.

If you can upgrade the wiring to the trailer, get a 50A two pole breaker, two 4 AWG conductors and a neutral, and run it through conduit. I will cost a few hundred dollars in materials, but it won't be a fire hazard.

  • I only want 120 volts. nothing requires 220. the ac is 8000, the waterheater is a tank unit. the ac is only run for the hotest month, then it is shut off. I only run the waterheater when ac unit is not running. So i need a two pole breaker, two 4 awg conductors, neutral and conduit, but what wire would be best. – Carol Anderson Jul 24 '19 at 11:56
  • Is the 30A breaker connected to the water heater? Are there two wires coming out of it? If so, you need 220 to the trailer. Also, 4 awg is the wire size. If they make direct burial 4/3, it would be a beast to handle. – Valkor Jul 24 '19 at 14:24
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    A water heater can be run on 120v but the recovery time will be ~4x longer than if run on 240. – Ed Beal Jul 24 '19 at 16:34
  • @Ed Beal Cool, thanks for the info. I will edit my answer to include that. – Valkor Jul 24 '19 at 18:55

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