So here is what I have. A 100 amp subpanel at the end of the pier fused at 50 amps from the house. I need to feed a boat lift that is 125' away at end of pier. The boat lift is rated for 120v @ 30 amps and 240 @ 20 amps. I was going to use it @ 120 v and ran a 10/3 down to it but forgot I need to de-rate the wire bc of the distance and should be 8/3. Now I'm ripping this wire out and going to run 240 instead . Now 8/3 would do the trick except I'm missing an insulated ground bc I'm running UF. My question is do they make 8/4 UF or what would be my best option as far as what wire to use. Trying to get away from running PVC. Also what can I use for disconnecting means at the motor? It has a cord now but when I switch to 240 I will wire from disconnect or whatever into it. What would you guys do?

 

You only need #12 for a 20 amp 240 volt feed. Is 20 amps the full load of the lift or the manufacturer's recommended circuit size? 125 feet may be border line at 125 feet but that depends on the lifts full load amps.

 

I'll presume what you are connecting is essentialy a "motor-type" Branch Circuit , a type of Branch-Circuit that does not require an insulated Equiptment Grounding Conductor.

The design of such a circuit is based on the motor circuit ratings as indicated on the name-plate . Essentialy , this is the horsepower and full-load current ratings which determine the ampacity of the conductors, the rating of the circuit-breaker , and the motor dis-connecting means..

 

20 amp for 240, 30 amp for 120v is the recommended breaker sizes. And in MD everything on pier has to have insulated ground. That's why I have to tape up the red leaving me without a neutral. And after 120' don't you have to de-rate the wire making this a #8 feed?

 

No if the voltage drop is in limits. That depends on the load. Example: If the FLA of the lift is 15 amps at 240 volts voltage drop would be 3% (232.9 volts) well within the ± 10% that is usually acceptable.

 

So your saying a #10 would be fine for 20 amp 240 v. Still have the problem with the uf and the non insulted ground!

 

So I'm going to run 4 # 10's THhn through 3/4 inch pipe. Once I get to boat lift what type of disconect should I use? The sub panel is 125' away so I'm sure u need one.

 

I hope by pipe you meant you'll be installing conduit and not water pipe. Why would you install 4 conductors? 3 is all that are needed for either a 120 volt circuit or a 240 volt circuit.

Since the lift has a cord, you could terminate your circuit in a Bell box with a 240 volt receptacle covered with an in-use weatherproof cover or you could buy and install a 30 amp non-fusible NEMA 3R safety switch and hardwire the cord into the switch. Another way to do it is to install sealtite flexible conduit from the safety switch to the lift.

 

Why 4 conductors? Isn't this a single-phase 240V load, with no neutral needed? Also, what type of pipe are you planning to run?

Any kind of disconnect you like, so long as it's in a NEMA-4 enclosure and rated for the load. It shouldn't need to be fused.