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Old 26-07-2008, 14:23   #16
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Gord is very right about this point, and I'm a bit surprised that others haven't twigged to it.

Perhaps this is because it is common practice in many marinas to use a 50A splitter at the marina's power post, connected to two 30A cables running to the boat. This setup is most everywhere you look...."everyone does it".

However, it is a code violation and to my knowledge has yet to be tested in the insurance or legal arenas.

I suppose the defense would be, "Hey, why are they allowed to even manufacture and sell 50A splitters?". After all, if they cost so damned much, they've gotta be good, right?

They ARE handy, and afford a good measure of flexibility. But, there's also danger lurking for those who are unaware: the 30A cords are protected by a 50A breaker....this means that if you draw more than 30A thru them, the cords and connectors will heat up badly and the breaker won't pop until the cords are melted and a dead short occurs. And, hopefully, no fire occurs as well.

A related problem, mentioned elsewhere, is that the 30A connectors are pretty crummy, and these cords can't really carry a full 30A unless everything is spiffy: new, clean, tight connections with low ambient temperatures.

The flexibility of having two 30A cords, which can be strung together if needed for a particularly long run, or which can be plugged directly into 30A outlets when visiting other marinas...can't be denied.

HOWEVER, if you're gonna use a splitter you've got to be absolutely certain that:

(1) loads on each of the 30A lines never exceed 30A, and preferably stay well below 25A; and

(2) that all connections are as clean and tight and waterproof as you can make them.

Then, pray that you never have to get involved in an insurance battle or court case in the event of a mishap involving your power cord(s).

Bill
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Old 26-07-2008, 14:35   #17
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Originally Posted by GordMay View Post
Should you ever suffer a fire, you may find that you're insurance won't cover your loss; based upon that very clear code & good practice violation.
Connected to a 50A receptacle, your 30A cord(s) is/are seriously undersized.
Of course, adapting a 50A cord to a 30A inlet, at the load end, is also a violation; but slightly less egregious.
Good luck, and I hope you get another 10 years of safe service from your inadequate arrangement.
Geez, did I piss you off or something? I'm not an electrician but I don't think the outlet is 'putting out' 50 amps. The 50 amps is there to draw from. And I believe if you split that, then your two power cords can draw what is needed. Isn't there 2 legs of service in a 50 amp outlet, at least on a 50 amp/240 volt outlet? I don't think 50 amps is available to each cord. You shouldn't need to draw 50 amps through a 30 amp cord anyway. Maybe you can elaborate what code or good practice violation you're referring to. Can you give an example of what insurance companies consider this to be bad as well? I can't find anything in my policy. Why are these adapters even made if they're so bad? And why haven't you jumped all over Doghouse for asking such a question or anyone else who agrees with the splitter and 2 cord arrangement? Oh wait, I know why. It's because I didn't fully agree with your single cable is easier comment. Forgive me for not agreeing with you. I'll start flogging myself immediately. For everyone else, please disregard my above post, I've been told I'm wrong.
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Old 26-07-2008, 14:43   #18
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I read it so many times that cost out weighs benefit, but for me it's generally just the opposite. When I need a tool to do a job, I don't look at the price, I look at what the tool will do. If two tools will do the same job and one is cheaper, then I look at the quality of the two. Naturally I buy the best for the least, but price does not start my decision making...function does.
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Old 26-07-2008, 15:50   #19
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Originally Posted by Goldie View Post
... I'm not an electrician but I don't think the outlet is 'putting out' 50 amps...
I'll start flogging myself immediately. For everyone else, please disregard my above post, I've been told I'm wrong.
Right on all counts.
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Old 26-07-2008, 16:12   #20
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Right on all counts.
So are you going to address the good practice, code violation and insurance info you stated or do we just assume you're correct because you say so? Please give some examples. I'd really like to know if it is true or not. Maybe Bill can site the code violation. Or do you just want to be condescending? Funny how you didn't address anything else.
I'll await a decent reply.
Scott
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Old 27-07-2008, 06:10   #21
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It’s hard to know exactly where to start, without appearing to be “condescending” to someone (there will be a wide diversity of knowledge in such a large community as ours); and I don’t have the energy to write another* comprehensive textbook, or to cite every Code, Standard, and/or Engineering Principle relating to the issue(s).
Please don’t hesitate to ask any specific question that I leave unanswered.
* I will provide a short bibliography, to some excellent sources of information, at the end.

Scott is quite right that the (shore power) outlet is not 'putting out' 50 amps; however any number of abnormal overcurrent conditions, including overload, short circuit, & ground fault (anywhere downstream of the shore receptacle) can cause the boat’s electrical system to ‘draw‘ as much as 50 Amps (at which point the 50A shore power breaker should trip).

In such as case, a 30A cord(s) [or circuit] would not be protected by the shoreside breaker, as required by EVERY code & standard worldwide.

Any competent insurance adjuster would be tempted to deny coverage if such a violation were discovered, even if it wasn’t the proximate cause of an electrical fire.

As Bill notes, manufacturers do sell these devices - but are careful to note that “When using an adapter, total amperage drawn shall not exceed the amperage rating of the LOWEST rated component of the adapter”. Sounds like a “liability” dodge, to me (not a Lawyer).

A “code compliant” adapter would have 2 simultaneous tripping breakers, each rated 30A to protect the cords, inlet fitting, and boatside cable [inlet to main breaker(s) at panel(s)].
I know of no such device.
Even the very expensive Hubbel “Intelligent” adapters do NOT provide overcurrent protection.
http://www.hubbell-wiring.com/marine/pdf/YQAdapters.pdf

Further reading:

ABYC Standard E-11 ~ AC and DC ELECTRICAL SYSTEMS ON BOATS
https://www.abyc.com/committees/.%5CE-11.pdf

TP 1332E ~ Construction Standards for Small Vessels (2004)
Section 8.0 ~ Electrical Systems
Construction Standards for Small Vessels (2004) | TP 1332 | Marine Safety

Boatowner's Illustrated Electrical Handbook ~ By Charlie Wing
Boatowner's Illustrated Electrical ... - Google Book Search

Boater’s Guide to AC Electrical Systems ~ Marinco
http://www.ancorproducts.com/docs/guides/Boater'sGuidetoACElectrical.pdf

Hope this helps.
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Old 27-07-2008, 07:20   #22
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Will the 30 amp breaker in the boat suffice to protect such a cord meltdown?

So here is the big question. One has 2 30 amp inlets on the boat. The dock has a single 50amp outlet. What to do?
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Old 27-07-2008, 07:58   #23
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NO - the 30 amp breaker in the boat will not “suffice to protect such a cord meltdown” should the overcurrent occur between the shore power pedestal and the boat’s main breaker(s).
The 92) 30A pigtails, and cords will not be protected, nor will the boat cable from inlet to panel (up to 10' long).

If one has (2) 30 amp inlets on the boat, and the dock has a single 50amp outlet, you either re-wire the boat; or you violate codes and engineering practice in the least egregious manner practicable, by utilizing a single 50A cord connected to a reverse “Y” (50A to 2 x 30A) at the boat. This limits your exposure to the inlets & the boat cables to main breaker.

We seem to have come full circle.
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Old 27-07-2008, 10:21   #24
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How about this approach.

You fabricate a breaker box splitter. It has a 50amp coming in then splits with 2 25amp breakers connects to separate 30 amp connectors. The you plug your 2 separate shore power devices in this "breaker splitter devise". I don't know that it would be UL approved but the cables would be protected from over currents. I don't know the cost or what this "device" would look like, but conceptually it would seem to protect the cables, and deliver 2 separate 25 amp circuits.

I think I have has a 30 amp cable melt from some weirdness on a shore power. This is connection This is scary stuff and you need to get it right.
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Old 27-07-2008, 10:54   #25
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Originally Posted by defjef View Post
How about this approach.
You fabricate a breaker box splitter. It has a 50amp coming in then splits with 2 25amp breakers connects to separate 30 amp connectors...
... This is scary stuff and you need to get it right.
It could be made to work.
Maybe, if I get the energy, I'll think about a couple of options, and start a new thread with some proposed solutions. Maybe not...
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Old 27-07-2008, 19:05   #26
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Refer to pp. 146-147 of Calder's BM@EM

"In some US Situations, dockside power is available at a US 50 amp, 250 volt receptacle.....but the boat has 2 30 amp inlets..... It is a common prcatice to use a y adapter......It is an acceptable practice as long as the toatl amperage drawn with two inlets does not exceed the rating in the single 50 amp leg."

My words...so you have to be judicious in the use of power....
You can't be running the stove, iron washer dryer and all your airconditioners and blowdryers at once

The worst case I saw was people that tried to plug in a plethora of ceramic heaters.......meltdown.....

Quote:
Originally Posted by jzk View Post
Will the 30 amp breaker in the boat suffice to protect such a cord meltdown?

So here is the big question. One has 2 30 amp inlets on the boat. The dock has a single 50amp outlet. What to do?
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Old 28-07-2008, 02:55   #27
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FWIW (and not overly important):
I believe, itís actually a "REVERSE Y" Adapter that adapts two (2) male 30 amp (125v) plugs (at shoreside outlet) to one (1) female 50 amp (125/250v) locking connector (inlet at boatside).
A "Y" Adapter connects 1 shore outlet to 2 boat inlets.
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Old 28-07-2008, 15:33   #28
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In the original post he staes he has a 50 amp shore power outlet and 2 30 amp inlets.

So he is utilizing a Y adapter
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Old 28-07-2008, 18:45   #29
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Like Gord, not sure that I have the energy to continue this discussion, wherein we've been beating the proverbial "dead horse".

No, Chief Engineer, it's not right that you're OK so long as the total load is less than 50 amps. The problem is that 50A receptacles on the docks are typically wired with not one, but TWO 50A breakers....a double breaker, if you will. The way they're wired, you could put, e.g., a 45A load on each of the two 30A/120V lines (for a total load of 90A) and the breaker(s) wouldn't trip.

It all has to do with the phases and the nature of the typical 208/120 Wye circuits found in most every marina and many commercial buildings. They bring four wires down the dock....three phases and one neutral. The potential between each phase wire and the neutral is 120VAC. The potential between the phases is 208VAC. Typically, the 50A receptacle on the dock will be wired with two "hot wires", representing two of the three available phases, plus a neutral or common wire. The third "hot" wire, representing the third phase, will typically go to the next power post, though in some marinas, like mine, it goes to a 30A receptacle on the same power post. Thus, in my marina, there's a 50A and a 30A receptacle on each power post.

Each of the three phases lags the other by exactly 120 degrees, the result on a 208V line is to provide three 120V "hots" plus two 208V "hots" (i.e., between any two phases).

Now, if all this sounds like jibberish....and it well might (it's been a long day)...please just take away these few thoughts:

1. If you're going to use a splitter, be very careful that the load on each 30A line never exceeds about 25A, except for momentary surges (like electric motor startup);

2. Be very sure that all connections are clean and tight; check them frequently, both by visual inspection and by putting your hand on the rubberized connectors to see if they're getting hot;

3. The REAL danger, which we've not talked about in this thread, is that of losing the neutral. If the neutral wire is compromised for any reason...dirty contacts, loose connection, surface corrosion, etc.....you could have anywhere from zero to 208 volts on either of the two 30A lines. How much voltage would be there depends on how the loads are distributed amongst the three phases (often, counting you and your neighbor on the next post). If the load isn't balanced, as it generally isn't, then high voltage will occur on one line while low will occur on another. This isn't fun...it could well destroy your equipment...and worse.

Just one further thought: don't assume that all the power posts in your marina are wired alike. In ours, for example, there are a couple of slips which are not wired this way, due to the historical wiring and rewiring and fixing and.....you name it. Beware!

Whew...didn't think I'd make it this far! Time to relax with a Mt. Gay :-)

Bill
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Old 28-07-2008, 20:53   #30
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As I sail off into the sunset......I will leave you to your labours........

This thread has deviated from the original request for information.....

I see this arrangement on many boats at my marina and others in the area....

Haven't had a boat burn up yet....did have one customer that tried to run too many ceramic heaters though...that caused some problems

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