marinas

[paul renshaw]

Is there any code article that prohibits more than four conductors in a raceway on a dock in a marina? And I mean other than normal fill percentages, etc. Someone asked me this today and said their electrician told them this. I did not see anything in the article pertaining to marinas and have never heard this before. Thanks, Paul

 

[earlydean]

Re: marinas

none that I'm aware of

 

[charlie b]

Re: marinas

No such rule exists. You might ask "someone" to have the electrician cite the source.

 

[paul renshaw]

Re: marinas

The guy who asked me this is a power engineer, and that is kind of what I told him..ask for a code reference. This may be another case of the good old answer "because it's code" to satisfy a customer that does not know any different.
Charlie, I get the impression you do not believe that "someone" else asked me this. If I have a question myself, I am not shy about asking it. If I do not know the answer, it's not a stupid question. Thanks for the replies, Paul

 

[bennie]

Re: marinas

Hello Paul: It's been a long time.

Calculating circuits, and associated wire size, for a marina, is a new ball game.

The engineer is correct about the number of conductors in one conduit. There is no specific words to the effect of not permitting more than four, but when you examine the entire design issue you will see why four wires, with a neutral that excludes applying the 80% adjustment factor is an economical procedure.

The problem that soon becomes an expensive issue is the load for each receptacle, the demand factors, plus voltage drop, will make an elephant out of a mouse, very quick.

Calculate the wire size for four 30 amp receptacles on a 300 foot run. This will soon show how careful the engineering must be. You don't want to apply the 80% factor.

 

[paul renshaw]

Re: marinas

Hey Bennie, good to hear from you, it has been a long time. That makes good sense, and is probably the reason behind his statement. Thanks again, Paul

 

[charlie b]

Re: marinas

Originally posted by paul renshaw: Charlie, I get the impression you do not believe that "someone" else asked me this.

Not my intent at all, and I apologize if it came across to you in that manner. If you had said that ?John? had told you this, I would have said to ask ?John? to ask the electrician for a code reference. But as you named no names, I was merely suggesting that you trace the rumor back to its source, starting with the person who told you the story.

So let me try again: You might ask the ?someone? who told you this story to have the electrician who told them the story cite the source.

 

[steve66]

Re: marinas

Bennie:

You have lost me on your reasoning. A 30A receptacle circuit requires #10 wire. However, at 90C, #10 is good for 40A. If you derate it to 80%, you get 32A. The result is that you can still use #10 wire with more than 4 conductor's for 30A receptacle circuits.

You also mentioned voltage drop. Trying to compensate for voltage drop would require larger wires. This would make derating even less of an issue because the wires are already sized larger than necessary to carry the rated current.

Am I missing something here?

Steve

 

[bennie]

Re: marinas

First of all, I am assuming the wiring is on floating docks with boat slips, in a marina.

A 100 slip dock will be approximately 600 feet in total length. Allowing 12 feet per slip width, 50 slips on each side.

The service will be on the shore. 100 slips will require a minimum of 100, 30 ampere circuits.

The end of dock, 30 amp receptacles will require #2 cu. for voltage drop, and No.#3 with the 80% adjustment factor.

Install marine power panels for 6 slips per panel will take 17 circuits from the service equipment. The wire size will vary according to the length. The panel load is 162 amps, requiring from 2/0 to 350 kcmil cable.

Design is a real issue, and done wrong it will bite you in the pocket book. It has been a long time since I worked on floating docks, so check out my calculations.