2 30 vs 1 50 power cord

[GordMay]

Originally Posted by Chief Engineer

... 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...

As Yogi Berra said: “I always thought that record would stand until it was broken."

[Goldie]

Originally Posted by GordMay

As Yogi Berra said: “I always thought that record would stand until it was broken."

You don't have much of a life, do ya?

[GordMay]

Originally Posted by Goldie

You don't have much of a life, do ya?

"If my doctor told me I had only six minutes to live, I wouldn't brood. I'd type a little faster." ~ I. Asimov

I still find each day too short for all the thoughts I want to think, all the walks I want to take, all the books I want to read, and all the friends I want to see.

[Chief Engineer]

To paraphrase President Reagan

"Mr. Gorbachev, LOCK DOWN THIS THREAD"

[Doghouse]

Thank you everyone. Not only has this thread provided me with the original information, but also brought my attention to the very interesting problems associated with these configurations.

I will spend some time over the next couple of days and see if I can work out a "safe" 50 to 30 splitter.

[Auspicious]

Originally Posted by btrayfors

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).

At the risk of being pedantic, I believe there are three 120V "hots" and *three* 208V "hots."

If the three phases are called A, B, and C and the neutral is called N then the 208V "hots" are between A-B, B-C, and A-C. The 120V "hots" are between A-N, B-N, and C-N.

[ssullivan]

Originally Posted by GordMay

I still find each day too short for all the thoughts I want to think, all the walks I want to take, all the books I want to read, and all the friends I want to see.

Man, isn't that the truth?...................

So little time in a day.

[Goldie]

"The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts."
~Bertand Russell

[btrayfors]

Auspicious,

Yes, of course...there are three each 208v and 120v "hots" in a 4-wire 208/120V Wye transformer system.

As I said, it was a long day :-)

Thanks for the catch. You can be pedantic all you want!

Bill

[GordMay]

I doubt that many Marinas wire their Shore Power pedestals with 208/120V 3∅ “Y” systems.

If the distribution system is 208V, they’d likely use 208-240V transformers.
Most larger boats, requiring more than 120V service, are wired for 240V.

Applying a 208V supply to a 240V load results in only about 75% of the nominal power. This is not good for motors, the most common 240V load.


The Codes & Standards applicable to Shore Power Systems (North America) are:

ABYC Standard E-11 - “AC & DC Systems onjBoats”

NFPA Standard 70 - “National Electrical Code” (NEC), Article 555
which now includes the requirements of:
NFPA Standard 303 - “Fire Protection Standard for Marinas and Boatyards”

NFPA Standard 302 - “Fire Protection Standard for Pleasure and Commercial Motor Craft”

[Eleven]

Insurance and such to one side, overload deivices can only protect downstream. If the cable gets damaged the overload trip will only trip at 50Amps plus. A thirty amp cable will burn out and may start a fire in/on your boat. A pair of thirty amp cables don't do any better if one is damaged and shorts out. Circuit protection has to be at the start of each cable and sized to that cable or less.
Apologies to those that know and practice these things.

[Joli]

All I know is the 50 amp cords are heavy! We only charge batteries aboard so tend to step down from 50 to a single 30 cord for daily use. If we were to run AC we would go back to the 50's.

[btrayfors]

Gord,

"I doubt that many Marinas wire their Shore Power pedestals with 208/120V 3∅ “Y” systems. "

Actually, it's quite common. The following post is from busnut:

Quote
Posted on Saturday, September 11, 2004 - 8:37 am: Gary, most high rise office buildings are wired for 208/120 due to the proliferation of PC loads. In the earlier years, all the large mainframe computers were 208/120 volt three phase also.

There are many instances where the main power feed into a building is 460 volt, three phase or higher, up to 4400 volts and maybe even 7200 volts, with step down distribution transformers installed on each floor to step the voltage down to 208/120.

I have worked at literally hundreds of marinas throughout the world and I do not recall any that did not have three phase power, however it was not generally apparent. Typical wiring was to bring two phases to a power pedestal, for example phases A and B. The next pedestal would have phases B and C and the next pedestal would have phases C and A. This way the distribution would generally be fairly evenly loaded. For the yachts that needed three phase power we generally had to run a shore cord to two different power pedestals.

The newer marinas that cater to yachts over 80-100 feet all have three phase power at each pedestal. Below is a link to some of the equipment I developed and manufactured for many years.

http://www.shorpower.com/products/tecpower/index.shtml

Richard

Unquote

Additionally, many of the larger boats "process" their power onboard. They use automated transformers to convert 208V to 240V....or to do whatever other conversion is required. Also, the 100A feeds for larger boats on the powerposts can be three-phase or single-phase. At our marina, feeds for the megayachts are both, side-by-side -- which sometimes results in interesting results if a boat tries to use both :-)

You're right, of course, about the losses involved in using 240V equipment on 208 lines. However, a lot of equipment is also available in 208V configuration, and it's best to use this if your marina only provides 208V.

It would be very interesting to do a thorough survey (who'd pay for it??) to know what the actual wiring and power availability is at each slip in a large sampling of marinas!

Bottom line: mariner beware :-)

Bill

[GordMay]

Originally Posted by btrayfors

... It would be very interesting to ... know what the actual wiring and power availability is at each slip in a large sampling of marinas!
Bottom line: mariner beware :-)
Bill

Originally Posted by Joli

All I know is ...

I’ve never (knowingly) encountered a 208V 1∅ 3W marina shore power outlet; which is not to say they don’t exist, or are even common.

Unfortunately, many of us just “plug in” , without knowing to what we are connecting. This is particularly egregious when utilizing a “go-around” adapter.

BTW: I couldn’t get your link to work.

208V supplies to 240V equipment may be more than merely inefficient, it can be damaging to motors (in particular).
Lighting (except ballasted types) and resistance heating will work fine (tho’ at lower output); but motors can also suffer from over-heating and permanent damage, as well as reduced outputs.

[btrayfors]

Gord,

Sorry about the link. Try this one: http://www.shorpower.com/

Here are just a few of the many hundreds of marinas which have 208/120 dockside power availability:

Mississippi: Coastal Marinas: Harrison County, Mississippi

Fort Lauderdale: Fort Lauderdale Grande Hotel & Yacht Club in Florida, United States. Buy high quality framed images, prints, t-shirts. Up to date marine weather, services information, and photos

British Columbia: Van Isle Marina, Boating British Columbia

Trinidad: Crews Inn Hotel and Yachting Centre

Bahamas: Bahamas.com \ Sampson Cay Marina Vendor Detail

Bahamas: Bahamas.com \ Sampson Cay Marina Vendor Detail

Washington, DC (my marina): Capital Yacht Club Facilities

Bill