Marina Wiring

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megawatt

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Has anybody had an opportunity to work on a Marina ?
I'm currently working with an Engineer to correct some voltage problems on a large Marina, & wondered if anyone had some pearls of wisdom ?
The proposal I came up with was to convert part of the existing wiring to 480, & install a step down transformer much closer to the end of the Dock...seems the voltage drops to 90 volts during times of peak demand.
 
Re: Marina Wiring

To me this seems like a simple solution to this common type of problem (not just related to marinas), yet it does not seem to be something that is all that commonly done. It would seem like a very cost effective solution and I wonder why it is not done more often. are people afraid of running higher voltages or something?
 
Re: Marina Wiring

555.4 and 555.5 allow it, it does seem like it could be a cost effective answer.

Keep an eye out for the height of the transformer in relation to the "Electrical Datum Plane" 555.2 and 555.9
 
Re: Marina Wiring

The 2 that We plan to install will be 3R type & are going to mount about 12' off the dock, under the covered slips.
Have any of You had to purchase that cable that lays along the bottom of the lake ?
Sure would hate to deal with much of that stuff.
With the distance from the service disc to the far end of the Marina, being about 650 ft., this was the easiest method I could come up with without a major renovation project.
 
Re: Marina Wiring

Originally posted by megawatt:
Has anybody had an opportunity to work on a Marina ?
I'm currently working with an Engineer to correct some voltage problems on a large Marina, & wondered if anyone had some pearls of wisdom ?
The proposal I came up with was to convert part of the existing wiring to 480, & install a step down transformer much closer to the end of the Dock...seems the voltage drops to 90 volts during times of peak demand.
Click to expand...
This can be dynamic. Is the voltage drop due to the POCO transformer being sized too small? Is it because of the size of the feeders on the dock? Are the feeders feeding too many receptacles? Is it a combination of all?

While installing transformers on docks can help with voltage drop, I've found it is actually more cost effective to run larger cables (up to about 700') and put the service disconnecting means (MB panel w/breaker for the feeders) as close to the ramp to the dock as possible. The 2nd most cost effective means is to put a panel on the dock, that way you have larger conductors feeding the panel and they usually handle voltage drop better.

Please pay close attention to 555.5

Also be aware that a 3-phase distribution system starts with a voltage drop since boats are wired for 120/240 1-phase (unless you get into the mega-yachts).

Type "W" cable is rather expensive, but if the job can afford it, it is the way to go. If you use it, you need to use pin terminals at the breakers and lugs or pin terminals at the power centers.
 
Re: Marina Wiring

One more thing. I don't know what state you are working in, but I spoke with an inspector in Florida that told me they don't allow type W cable. I didn't get into it too deeply with him since I was only putting out a budget number, but you should check with the local authorities.
 
Re: Marina Wiring

Thanks for the advice "hardworkingstiff" this situation is a combination of problems.
It will be a single phase installation, & type "W" is allowed here.
The quickest, & most cost effective solution will be to use the cable that is already installed, and convert it to 480.
The initial design was pretty solid 25 years ago, but now these newer houseboats have 100, & 150 amp services.
The problem area is 20 slips fed from 2 200 amp disc, mounted on the hill above the Marina. The cable run, is roughly 600 ft.
I'm not sure how much cable is on the bottom of the Lake, but it's probably not enough to get any slack.
The rise, & fall of the Marina has slowly pulled the cables tighter, & I found 3 of the 6 disc had the cable pulled so tight that the knockouts were all broken out, with quite a bit of strain on the cable.
It will be an interesting project for sure !!
Still looks weird seeing 6 cables the size of Your wrist disappearing into the water.
 
Re: Marina Wiring

If you figure 10 slips at 100 amps each and 10 slips at 150 amps each you get 2500 amps. If you use the demand factors in 555.12, you get a 70% demand which puts your service at 1750 amps (in my mind in order to use this demand factor, this would have to be one service/panel).

If you split into multiple panels for your service disconnecting I believe you would need to use higher derating percentages. Lets say you wanted to split this into 2 panels with near equal loads. 5 boats at 100 amps and 5 boats at 150 amps in each panel for a load (at 100%) of 1250 amps. Using 555.12 (80%) demand factors you would need feeders (and panel) rated at 1000 amps and you would need 2 of them for the total loads.

If I understand you correctly, you have 2 200-amp 120/240 feeders to the dock. If you go to 480 that only gives you 800 amps of 120/240 power available. Using the NEC 555.12 as a design guide, I'd say you are still nearly 1000 amps short of the power required.
 
Re: Marina Wiring

Originally posted by megawatt:

Still looks weird seeing 6 cables the size of Your wrist disappearing into the water.
Click to expand...
megawatt,

Are these 6 cables multi-conductor? If so, 4-wire? What size? Is it type W or something else?

I would recommend someone perform an underwater inspection of these cables since they have been submerged for so long.

What state is this project in? (no, I have plenty to do and am not looking for more work :p )
 
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