240v Shore Power Connection

[DotDun]

Let's try this:

US Marina 50A 240VAC is Split Phase.

4 wires, hot, hot, neutral, ground

It's called split phase as each hot is 120v off neutral and 180 degrees off each other. Hence, you get 240v between the 2 hot and 120v between either hot and neutral.

[Dockhead]

[QUOTE=Dennis.G;1688124]

Originally Posted by Dockhead

Yes, badly mistaken.

Generally 240 VAC marina power is single phase 240 hot to hot and 120 hot to neutral. The four wires hot, hot, neutral, and ground. Ground and neutral are bonded together somewhere (e.g., panel feeding dock) and should be very close or at same potential as each other. Note that some docks will provide 240 single phase with 3 wire outlets (no ground, just grounded neutral) while other with 4 wire outlets (separate neutral and ground). In USA the 3-wire outlets no longer meets electrical code requirements so only seen in older marinas.

There is 3-phase at some marinas for mega yachts, but usually 480.

The above are USA/Canada/Mexico electrical outlets I have seen.

I will defer to superior electrical knowledge!

I've never heard of four-wire single-phase power, and can't find any reference to it, but that don't mean it ain't so, and I don't claim to be an electrical expert. In Europe, where I live, household 400v is definitely three phase, and there is no higher voltage single phase. The U.S. is, as in all things, different I guess.

Electrical Service Types and Voltages | Continental Control Systems

Single Phase Three Wire
Single Phase Three Wire Electrical Service
Also known as an Edison system, split-phase or center-tapped neutral. This is the most common residential service in North America. Line 1 to neutral and Line 2 to neutral are used to power 120 volt lighting and plug loads. Line 1 to Line 2 is used to power 240 volt single phase loads such as a water heater, electric range, or air conditioner.



Three Phase Four Wire Wye
Three Phase Four Wire Wye Electrical Service
The most common commercial building electric service in North America is 120/208 volt wye, which is used to power 120 volt plug loads, lighting, and smaller HVAC systems. In larger facilities the voltage is 277/480 volt and used to power single phase 277 volt lighting and larger HVAC loads. In western Canada 347/600V is common.




Four-wire, single-phase? Can't seem to find any reference to that anywhere, but will be grateful to be enlightened.

[Dockhead]

Originally Posted by DotDun

Let's try this:

US Marina 50A 240VAC is Split Phase.

4 wires, hot, hot, neutral, ground

It's called split phase as each hot is 120v off neutral and 180 degrees off each other. Hence, you get 240v between the 2 hot and 120v between either hot and neutral.

Ah! :lightbulb:

Now I get it.

I apologize for all the misinformation! :sheepishgrin:

Split-phase electric power - Wikipedia, the free encyclopedia

[Dennis.G]

This is outlet type I am referring to.

This is a 30A version. Also common in a 50A version.

[DotDun]

Originally Posted by Dockhead

Ah! :lightbulb:

Now I get it.

I apologize for all the misinformation! :sheepishgrin:

Split-phase electric power - Wikipedia, the free encyclopedia

Yes! As the diagram you posted shows, all that happens is the center tap on the secondary winding is called neutral (and connected to ground). This creates (2) 120v taps, each one 180 degrees out of phase (120 + 120 = 240).

FWIW, these are isolation transformers, not autotransformers (otherwise it wouldn't work bonding the neutral/ground of the primary with the center tap of the secondary).

[sailcrazy]

So, to Dockhead.....looking at your drawing, it would seem that my initial "guess" at wiring my connection, with 2 of my 3 wires to the 2 "hot" leads, and the 3rd to ground, would give my the 240vAC to the boat, ala European and Asian power poles, still provide the ground, should be correct. The "neutral" wire in your drawing is not used, unless a 110v power source is wanted. And all is well? Am I missing something? I know I still have the 50cps vs the 60cps issue, but the power would be proper and safe?

[DotDun]

Originally Posted by Dennis.G

This is outlet type I am referring to.

This is a 30A version. Also common in a 50A version.

NO!

The marine 50A 125v/250v plug is:

[DotDun]

Originally Posted by sailcrazy

So, to Dockhead.....looking at your drawing, it would seem that my initial "guess" at wiring my connection, with 2 of my 3 wires to the 2 "hot" leads, and the 3rd to ground, would give my the 240vAC to the boat, ala European and Asian power poles, still provide the ground, should be correct. The "neutral" wire in your drawing is not used, unless a 110v power source is wanted. And all is well? Am I missing something? I know I still have the 50cps vs the 60cps issue, but the power would be proper and safe?

The issue is you have no neutral. Neutral is normally very close to ground potential, and you've created a system where what is wired as neutral is now 120v off ground. In a perfect world, it shouldn't be a problem. Remember, don't touch the blue wire, it's now hot!!!

Do you have RCBO? (RCD/ELCI) If yes, that would be the first line of defense against someone getting hurt.

[Sand crab]

I screwed up that quote from Dockhead before mine(post #8). I meant to delete all but that one sentence from DH but deleted the quote at the end so it looks like I posted this. Only the last 2 sentences were mine which were these:


Nope. US is single phase but you are right about the mixing part. 3 phase is commercial or industrial applications.

I had 2 years electronics in high school and have done many electrical jobs including the complete wiring of 4 of my own new houses. Been there done that.

[Dennis.G]

Originally Posted by DotDun

NO!

The marine 50A 125v/250v plug is:

You are right for 50 AMP.

The 4-wire (125/250 single phase) version you will now find at many newer marinas is type CS6364 CS6365 and looks like attached photos.

I learned all about this outlet type at a marina in January. I had a 3-wire 125/250 conversion plug but could not hook up to marina's 4-wire single phase outlets.

[sailcrazy]

To DotDun...What is RCD/ELCI, and RCBO? I do have a Galvanic Isolator installed on the Green (Ground) line from the boat entry to the distribution panel, but I do not recognize the letter abbreviations you used.

[rwidman]

Originally Posted by sy_gilana

Use it as you have it and disconnect your reverse polarity light.............

The danger with seeking advice on web forums is that you will get some really bad advice. This suggestion is an example. Ignore it. Just because this person's boat hasn't caught fire or killed anyone (yet) doesn't mean yours won't.

[DotDun]

Originally Posted by sailcrazy

To DotDun...What is RCD/ELCI, and RCBO? I do have a Galvanic Isolator installed on the Green (Ground) line from the boat entry to the distribution panel, but I do not recognize the letter abbreviations you used.

Sorry, I'm referring to a ground fault breaker as the main disconnect on your distribution panel, the first thing in-line after the shore power inlet on the boat. I'm not sure what the EU is calling them, GFCI, RCBO, RCD, ELCI?? When used as the main disconnect they usually trip on 30ma of imbalance between hot and neutral.

[Sand crab]

Originally Posted by DotDun

Do you have RCBO? (RCD/ELCI) If yes, that would be the first line of defense against someone getting hurt.

RCBO Circuit Breaker, Single Pole RCBO Manufacturer and Supplier - Products & Services - GREEGOO Electric Co.,Ltd.

[Nicholson58]

Originally Posted by Scott Berg

Wow
A lot of bad info...

Standard US commercial power can be a lot of things
208/3 is quite common but in marinas 120/240 50a single phase is the norm

Large yachts use 100-200a 3 phase but not small ones

Hire a good marine electrician and this can be easy if not cheap

Yes, I do this for a living
No, I don't want to do yours, unless the job includes travel to the VI! <grin>



Sent from my iPhone using Cruisers Sailing Forum

So true on the bad info. The best information here is to find an electrician. Anyone who has a house in the US has 240 single phase consisting of two 120 volt single phase legs, neutral and ground. The two 120's feed opposite legs of the breaker box. Leg to leg is 240; leg to ground is 120. The only 3-phase you are likely to see here is in a factory where power to drive motors larger than say 5 HP is the norm. You will pay a premium to get three phase and it is not available except in areas zoned for industrial use. We sell & operate custom heavy equipment. Most 3 phase we deal with is 480 volts for 99% of the machinery. Our 5000 HP dynamometers are on special high voltage feeds under special arrangement with the local utility. Your marina power will almost certainly be single phase. If you don't know how to figure out what you are dealing with and how to handle it you shouldn't attempt to make the changes.