marina bid

[mkgrady]

I'm preparing a bid to disconnect and reconnect a bunch of docks at a marina in Massachusetts. The marina is going to be dredged and the floats are in the way. Three 270' docks (A,B & C) will be seperated at some of the existing float joints at the closest junction box. I see what looks like problems on some of the docks' existing wiring and I could use advice.

Dock A feeds 8 old hubbell pedestals with double 20 amp receptacles in each. Doesn't the code require 30 amp for boats? Are in-use covers required?

I think I have to rewire the dock when it gets put back together because the feeder that runs down the dock (above the flotation blocks and under the deck boards) is 1/0 thhn/thwn in PVC but it goes to open wire at the float joints so the dock can flex. Open wire with some kind of fabric for protection seems like a code violation??? The PVC runs to a PVC junction box under the deck boards where each pedestal is tapped in with a smaller cable in a smaller PVC conduit. Doesn't the code prohibit a splice under the deck? If allowed, is a JB under the wooden deck boards considered accessable?

I'm concerned that if I have to run all new cable I will have to upgrade the pedestals too.

Dock B has similar problems except the pedestals have 30 amp receptacles. But here they didn't use any conduit or junction boxes at all, just open wire and open splices inder the deck?

Dock C seems to be newer and better. Type W multi cable as the main with smaller cable to the peds but the splices are still under the deck of the floats. Is this OK???

I'd really appreciate any input. I've wired shipyards that were already designed but I haven't wired a marina in over 20 years

Thanks, Mike

 

[jimwalker]

Re: marina bid

What you have seems like a never was to code install.So i would be prepaired to bring it to code.Had everything been to code at time built i think it might been grandfathered in and you could remove for repairs and reinstall.Talk to the local ahj as he will be headed that way anyways .A marina is not a place for open wiring

 

[mkgrady]

Re: marina bid

Thank you Jim for that response. Good advice. Can anybody address any of the other (other than open wiring) questions? My biggest concern is the splice boxes under the decking (above the flotation blocks) of the float. Does the code require splices above the datum plane?

 

[hardworkingstiff]

Re: marina bid

You need to read NEC 555.

I used to think NEC 555.9 would prohibit the use of junction boxes below the deck boards. But now I wonder if it is referencing the electrical connections for the boat to shore power, not electrical connections in a junction box.

The standard 120V-30A twist lock receptacle is what is used for shore power for smaller boats. The 240/120-50A twist lock receptacle is what is used for shore power for a little larger boats. The the next size is (2) 120/240-50A receptacles or (1) 120/240-100A receptacle. After that they are asking for 3-phase 480V.

The very smallest boats may not require power except for a battery charger (120V-20A receptacle). I would say in use covers are required).

The open wiring (IMO) is wrong! The type W is ok (but the splice boxes are in question).

I would let the property owner/rep know that I was going to "chat" with the AHJ about these issues, then go talk with him/her.

If they are dredging, I wonder if they are going after larger boats. If so, I doubt your wiring is adequate.

You really need to read 555 (a couple of times).

Other than that, GO FOR IT. Marinas are FUN. The voltage drop issues are a pain though. If you size everything to meet the "recommended" voltage drop, I don't think you will get the job. I always try to get my customer to a minimum calculation of 220V with a 2% voltage drop from the power company (235.2V delivered) and an 80% usage at the outlets for the boats (30's and 50's, not the 20's).

Good luck.
HWS

 

[augie47]

Re: marina bid

I used to think NEC 555.9 would prohibit the use of junction boxes below the deck boards. But now I wonder if it is referencing the electrical connections for the boat to shore power, not electrical connections in a junction box.

I've sure been wrong before, but I see no cause to "wonder" here:
"555.9 Electrical Connections
ALL electrical connections shall be located at least 305 mm (12 in.) above the deck of a floating pier. All electrical connections shall be located at least 305 mm (12 in.) above the deck of a fixed pier but not below the electrical datum plane."

As a rule , we avoid the splices by "looping" the cables thru the pedestals (the ones we use are designed for that). When movement is a problem, Type W cable seems to be the solution.

A lot of un-inspected dock wiring is a true disaster, but it appears this one might be an award winner. IMHO, definitely a time to get the local AHJ involved.

As HWS said, it can be fun. Taking everything into account (NEC, voltage drop, flexibility, pvc expansion (if applicaple) etc.) they can be a challange and offer a sense of accomplishmnet when completed and accepted.

 

[hardworkingstiff]

Re: marina bid

augie,

Since you have installed marina wiring before, what is you approach to dealing with the long distances and voltage drop? Are you able to get the customer to spend the money to keep in within 5%? It gets tough on those 400' runs.

What current draw to you use with the boats? 100%? 80%?.... ?

 

[augie47]

Re: marina bid

most times we "loop" our pedestals on a 200 amp run...4/0 normally
unless our calculator is off, that keeps us to under 5% on a 200 amp run..
we usually figure 100% of receptacle rating, and apply 555-5 when applicaple. the AHJ has agreed to let us go 1 outlet over with no complaint.

 

[jimwalker]

Re: marina bid

The last marina job i did was about 9 years ago.It was one of the few jobs that i must say was fun.If it wasn't for traveling i would have stayed with them.Was right next to a state park and got to see plenty of nice things leaving the park on jet ski's

 

[hardworkingstiff]

Re: marina bid

Originally posted by augie47:
most times we "loop" our pedestals on a 200 amp run...4/0 normally
unless our calculator is off, that keeps us to under 5% on a 200 amp run..
we usually figure 100% of receptacle rating, and apply 555-5 when applicaple. the AHJ has agreed to let us go 1 outlet over with no complaint.

Are you using type W or conduit and building wire? Are these floaters or fixed piers?

I mostly am wiring floaters. W makes it so much easier, but materials are a lot more.

Who's power center do you use the most. I personally like the "Lighthouse" from Marina Power and Light.

 

[iwire]

Re: marina bid

Originally posted by augie47:
most times we "loop" our pedestals on a 200 amp run

What do you mean by loop?

Are you leaving the breaker making a loop and returning to the breaker?

 

[mkgrady]

Re: marina bid

Thanks for all the replys. I spoke with the AHJ (and I'm meeting him at the site tomorrow). He will not grandfather anything. He says once it is worked on (disconnected to move the floats and reconnected) he will make an inspection. At that time everything must meet code. To me that means the two docks with the open or semi-open wiring will have to be totally rewired including updated pedestals with in-use covers- 30 amp minimum. I would go with type W multi cable the way the third dock is wired. Its wiring (type W) is fairly new and everything seems OK except the cable taps to the peds are made in boxes under the deck and not 12" above as seems to be code. The marina owner will go nuts if this recent wiring has to be re-done. I'm also not sure about how the taps from the peds to the larger circuit wires meet code. Maybe this is the 10'tap rule but some are longer than 10'. This could be eliminated by using the broad based (no conduit) peds that extend to the deck where the circuit cables connect to bus. I think this is what is meant by looping.

 

[hardworkingstiff]

Re: marina bid

Loop feeding is where you run from one pedestal to the next to the next, the same way you would wire receptacles in a house. With loop feeding, you quickly run out of ampacity. I've wired pedestals that had four 50-amp receptacles on them, loop feeding those is impossible because you have to run a 200-amp cable to each pedestal (or a 400-amp cable to loop feed 2 pedestals).

In my estimates, loop feeding drives up the cost of cabling. The actual wire cost more to loop feed than it does to home run each pedestal. I think it has to do with not having amperage ratings going up linear with copper content, therefore it costs more per amp for copper for larger cables.

Labor savings become questionable. Pulling a #4 W cable can easily be done by hand. Pulling a 1/0 - 4/0 type W cable is a machine operation, plus it is much more difficult to handle.

Loop feeding can help with actual voltage drop since you have a larger cable and more receptacles, it takes much more usage to get the amps up enough to cause a voltage drop issue.

Boats do not always draw a lot of current. I often think about it this way, you build a house to withstand 140 MPH winds on the coast, but how often do you actually need that? Is the cost necessary? With the house, it is. With wiring for boats........... maybe.

Wish me luck today, I take my GC exam in NC.

 

[augie47]

Re: marina bid

hws:
I agree with your commnts on "loop" vs individual pulls. I should have detailed that the latest docks I have encountered have been "floating concrete" docks with pvc piping factory installed in the concrete with pull boxes at the pedestals. Individual runs on these were not practical as the conduit fill and derating made it impossible, hence the looping.
I would tend to agree that if you are installing cables, individual pulls to each pedestal very well might be the best way to go. I bow to your experience there because I have not calculated the
costs of the methods on a particular dock as the construction has fairly well dictated the wiring method. I especially appreciate your comment on the peds with (4) 50 amp receptacles. From what I've seen, I wonder how often those are actually supplied with a 200 amp circuit as it sees so many of these installations go uninspected. Every time I see them wired properly I do wonder what actual load is encountered.
Heres this boat tied up to the dock with as much available "service" as a 300 sq ft house.

 

[charlie b]

Re: marina bid

I once did a cost study for replacing the floating docks at a marina. The question was whether it was more economical to transform down to 120/240 at the head of the dock, or to bring 480V onto the dock and have step down transformers at strategic locations. The answer was that the 480V option was much cheaper.

The process was a bit tricky, though. I used what I think is being described here as a "loop feed," for the cabling between the transformer and each of several panels along the dock. (Each panel would power a number of pedestals.) But as you go from the first panel to the next, two things happened. One is that you have fewer pedestals being fed by the conductors, which brought down the calculated load for the remainder of the run. The other is that the demand factor had to be based on fewer pedestals, which tended to bring up the calculated load. I used a spreadsheet to figure out the conductor sizes between any two points, and to calculate the voltage drop along the total path.

 

[hardworkingstiff]

Re: marina bid

charlie,

I have performed those same calculation and came up with a different answer. By the time you figured in the service disconnects and panel on the dock, the prices were similar. Then you had the additional cost of maintaining transformers and panels over the water.

I sure would love to see those calculations though.