50 Amp split to 30 amp legs

[S/V Adeline]

Originally Posted by BruceS

Only place there are "2 legs" down under is mostly in factories or other bigger users.
Work it backwards in watts?
110V X 50A = 5500w
240v X 25A = 6000w
Our marina only has 15A receptacles but in reality they have 32A breakers. Many big houseboats have normal house sized kitchens plus a couple of reverse cycle air conditioners.
I'm not an electrician so I'm not going to be going into more detail other than what I see...

The reason I followed this thread is we just parked our motorhome (30amp) in a park with only 50amp service, and i just custom made my own 50amp to 30amp adapter. Everything I know about land based electricity with be useless once we set sail to foreign lands :'(

[Frankly]

The physical laws governing electrical current and voltage are universal. Their application can vary from country to country, marina to marina.


Frankly

[ForeverDes]

Originally Posted by zboss

I need a gut check on something because I think the answer is obvious but I'd rather ask...

We have two 30 amps inlets on our boat. When in many marinas, we need to use a 50 amp splitter. I assume that when we use that splitter one hot goes to one 30 amp and the other hot goes to the other 30 amp.

But how does this actually translate to power delivery? Is the power evenly distributed 25/25 or is it more like a demand where the total of both legs can't be more than 50 amps?

Disclaimer: My electrical experience is from residential wiring.
Amps aren't really "provided" by anything. Fuses and breakers limit the amps that can be pulled on a circuit, either by an appliance or because of a short. If a appliance is rated at say, 1200 watts, that means it pulls 10 amps on a 120v circuit and 5 amps on a 240 volts circuit. In American wiring, 240v is provided across 2 hot "legs", or 120v is provided by using 1 hot leg and the neutral leg, if there is a neutral leg. (some applications don't require a neutral, and some that should have neutral don't and use ground as neutral instead. don't.)

Originally Posted by rslifkin

If it's using a 50A 125/250V connection and splitting that to 2x 30A 125V, then it's taking each hot and feeding it to one of the output. You can draw 30A on each output with no issues. The 50A 125/250 outlet can supply 50A on each of the 125V legs or 50A at 240V (using both legs and not the neutral).

I agree with the above. If you pull more than 30 amps on either side, your breaker in the boat should trip. If you pull more than 50 amps total, the shore power breaker should trip.



Basically, the splitter doesn't distribute amps, its distributes voltages by splitting the 2 hot legs.

[zboss]

Originally Posted by boat driver

I think you have a typo- 50 amps will come down each leg, thereby giving the potential of a 50 amp draw on the 30 amp cord.

Not really a typo... just saying that each leg COULD provide 50 Amps. We are just drawing 30 on each.

[smac999]

Assuming you are plugging into 50a 240v. (I have never seen 50a 120, though it existed many years ago).

It has two 50a 120 lines inside. So you can pull 30a from each. (you can pull 50a from each if your 30a breakers were not working). Making splitting 2 30.’s from a 50 slightly unsafe for this reason

[smac999]

Originally Posted by BruceS

I often wonder why it's so hard to include "USA" in some of these electrical posts?
Nothing like "2 legs" in my marina............... or even 120V ....

50 and 30a = USA.

Europe is 16a and 32a

The issue is when people say 230v because that could either way. As people wrongly call us 240v 230v

[BruceS]

For many years in Australia it was 240V but now it's officially 230V. (nom)
Using '2 legs' here is called 3 phase or 480V. (or probably 460V now?)

[ForeverDes]

Originally Posted by BruceS

For many years in Australia it was 240V but now it's officially 230V. (nom)
Using '2 legs' here is called 3 phase or 480V. (or probably 460V now?)

In the US, 120v uses 1 hot leg and one neutral, 240v uses 2 hot legs, and both 120v and 240v are considered single phase.
3 phase uses 3 hot legs and varies in voltage, but 480v is common. 2 hot legs from 3 phase is typically 277 v. Most industrial lighting is rated for 277v.

[rslifkin]

3 phase in the US is typically either 120/208 or 277/480 (phase to neutral is the lower voltage, phase to phase is the higher). House service is typically 120/240 split phase (120 hot to neutral, 240 hot 1 to hot 2).

[Frankly]

If the 50 amp shore power connector/ adaptor is 4 wire then most likely you have 120/ 240 volt with each 30 amp 120 V leg on a separate phase. If the 50 amp connector has only 3 wires then most likely you have a 50 amp 120 V feed split into two 30 amp 120 V feeds.

Other variations but these are most common.

For the rest of the world YMMV, but the line to neutral is often 230 volts vs 120 volts typical in the US.


Frankly