Lake De-icer

[kortelectric]

I need to provide power for a boat dock: De-icer (aerator) and boat lift. I plan to run power to a disconnect (20 amp, 120/240v) at the shoreline and then branch circuits to the de-icer and boat lift (20 amps each). There is a 300ft boardwalk (all new permanent pilings and treated lumber construction) from the high water mark that goes over a bog leading to the dock. I will need to bury a cable from the high water mark to the main distribution panel of the house about 100ft. I am also considering using a junction box every 100ft of the boardwalk (4) for use as a pull box, splice box and to tap for 120v receptacles for low voltage lights. Its about 400ft from the power source to the dock. What suggestions would you have?

 

[JFletcher]

I would upsize the wire and conduit for voltage drop and also for future use. #6 may sound like overkill now, but next year they'll put in a jet ski lift or lighting or want a dedicated 20A receptacle. Upsell it, let them know that it'll be less expensive in the long run. Working off a jon boat is kinda slow going and impossible at high tide on most docks I've seen. Check the tides before scheduling the work.

Welcome to the forum!

 

[luckylerado]

I need to provide power for a boat dock: De-icer (aerator) and boat lift. I plan to run power to a disconnect (20 amp, 120/240v) at the shoreline and then branch circuits to the de-icer and boat lift (20 amps each). There is a 300ft boardwalk (all new permanent pilings and treated lumber construction) from the high water mark that goes over a bog leading to the dock. I will need to bury a cable from the high water mark to the main distribution panel of the house about 100ft. I am also considering using a junction box every 100ft of the boardwalk (4) for use as a pull box, splice box and to tap for 120v receptacles for low voltage lights. Its about 400ft from the power source to the dock. What suggestions would you have?

It won't hurt to follow Art. 553 even though it is not floating and I recommend reading Art. 682 as well.

At a minimum, GFCI protect the circuits, I suggest at the breaker, and sufficiently ground all metal parts especially any swim ladders and hand rails.

 

[kortelectric]

Lake De-icer

The calculation I came up with was a #2 copper for 400ft with resulting in under 3%. Does a 120/240volt circuit reduce my voltage drop? So I can have 2- 20 amp circuits? also can I tap into that for outlets along the boardwalk for low voltage lighting transformers? and Thank You.

 

[JFletcher]

The calculation I came up with was a #2 copper for 400ft with resulting in under 3%. Does a 120/240volt circuit reduce my voltage drop? So I can have 2- 20 amp circuits? also can I tap into that for outlets along the boardwalk for low voltage lighting transformers? and Thank You.

<3% VD while great is kind of overkill imo. What are the actual amps of the lift and de-icer? If they are 120V loads then 240V does nothing to reduce VD*. ofc you can tap into that along the boardwalk; if you go with j-boxes every 100', leave a loop of wire in them to break and make up any future connections.

I did a Southwire VD calc:

1 conductors per phase utilizing a #6 Copper conductor will limit the voltage drop to 5.90% or less when supplying 20.0 amps for 400 feet on a 120 volt system.
For Engineering Information Only:
55.0 Amps Rated ampacity of selected conductor
0.4662 Ohms Resistance (Ohms per 1000 feet)
0.051 Ohms Reactance (Ohms per 1000 feet)
8.4 volts maximum allowable voltage drop at 7%
7.069. Actual voltage drop loss at 5.90% for the circuit

*Aside from one load (lift) is one one leg and the de-icer on the other

 

[kortelectric]

De-icer

De-icer

5 amps, 1/2 HP motor for the de-icer. Not sure on the boat lift but I think probably similar to the De-icer.

 

[JFletcher]

5 amps, 1/2 HP motor for the de-icer. Not sure on the boat lift but I think probably similar to the De-icer.

The lifts I have seen have 2 motors, one fore, one aft, to lower a boat. Even at that, running the de-icer (5A) and lift (15A) simultaneously would only be 15A on a 240V service, unless the de-icer is 240V, then it's still 20A max. #6 is good for that for 400', and more provided the extras arent heavy draw or run at the same time as the lift and de-icer.

 

[mgookin]

5 amps, 1/2 HP motor for the de-icer. Not sure on the boat lift but I think probably similar to the De-icer.

The permit for the biggest life I ever sold was a 50 ton lift. I'm not saying your customer is going to need that but the advice is to check with your customer. If he tells you what he wants and that changes later, it's on him.