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I am running 10 gauge wire to my dock which will be about 100 ft from the disconnect box on the house to the dock. I will be providing electricity to a 1/2 hp hoist, which runs on 110, that will only run a few minutes at a time, a 75 watt light bulb, and a ceiling fan to be used occasionally. What size breaker do I need to use? I was told I could run 220 to the dock. If I do that will I have to have a breaker box on the dock to split into two separate 110 circuits? Florida location.

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It doesn't sound like you need 220, 110V should be fine for your purposes as you've described them. – Aaron Jan 26 '13 at 2:13
Don't forget the overload protection for the motor. – Tester101 Feb 20 '13 at 16:22

30 amp breaker. Full load current on the motor is about 10 amps, plus a couple more amps for the other stuff gives you a voltage drop of 2%, less than the allowed 3%, so you're OK. You can run 220 as 2 branch circuits with a shared neutral. It's not really 220 because you can't power 220v equipment, but the voltage between the hot legs of each circuit is indeed 220v. You don't need breakers at the dock for this configuration, but you will need 3 conductors plus ground and a handle tied tandem breaker at the house panel.

Every thing will run fine on one circuit, so there is no advantage except you get 2 circuits. The voltage to ground is the same either way, so there is no added efficiency for the extra voltage.

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As long as you're running the conductors for 220V, install a small subpanel at the dock. The additional cost is minimal, and it opens up future expansion options. Increase to 50A and you'll have a lot of headroom for whatever you come up with later. And your motor will last longer, with reduced voltage drop. – Jay Bazuzi Jan 26 '13 at 4:58
If you run a multiwire branch circuit ("2 branch circuits with a shared neutral."), you can indeed have 220V equipment wired up. Also, you'll use either two separate consecutive breakers handle tied together, or a single double pole breaker. Not a tandem breaker. – Tester101 Jan 26 '13 at 13:09
The ceiling fan and 75 watt bulb together are probably barely an amp. 20A seems like it would be plenty; dual 20A circuits would allow for a convenience outlet on the second side (perhaps for a power washer, vacuum, etc.). I may be wrong, but I don't think you could/should connect an standard outlet to a circuit rated for 30A. Voltage drop is driven by the conductor size, not the breaker rating. – TomG Jan 26 '13 at 15:14
Re: TomG's comment. The breaker needs to be at least 25 amp to accommodate motor start up current or there will be nuisance tripping. So we still need 10 ga wire, so may as well use it's full capacity of 30A. @Jay & Tester, thanks for your comments. – bcworkz Jan 26 '13 at 20:41

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