I assume that you are aware that a 50A shore power connection is two legs at 50A each for a total of 100A. It is actually a 220v connection with two 110v legs that are out of phase.
Existing 30 amp main panel upgrade to 50 amp panel
- Thread starter Straycat22296
- Start date
Yes, but for those of us on 110V, we simply don't connect one of the legs. It isn't a 100A service when both legs are used for 220V, or when one is used for 110V. It is still 50A in all cases.
Mark
Mark
As far as I have ever seen, all 50A shore power plugs are 4-pin connectors.
If you are using a standard four pin shore power 50A supply, you have one leg that provides 50A @ 120v from the black wire and a second leg that also provides 50A @ 120v from the red wire. The voltage in the black wire is 180º out of phase from the red wire. If you use only 120v circuits, you will be able to use 50A from the black wire and another 50A from the red wire. On my motorhome, I have a 50A system and two of my air conditioners are on the black wire and one on the red because the three of them consume more than the 50A supplied on each leg. I have a 10kw generator. 10,000w is equal to 10,000w / 120v = 83.3A so I have just a little less power on generator than I do on shore power.
When you measure AC voltage, what is being measured it the max voltage measured from 0v where the voltage inverts to the peak of the sine-wave cycle. If you measure from either the black or red supply wire to the white common wire, it will show 120v [+120v - 0v = 120v]. At the moment in the cycle where the black wire is at +120v, the red wire will be at -120v. If you measure the voltage between the black and red wires, it will read 240v because what you are measuring is +120v - (-120v) = 240v
Here is a good video explaining how it works.
Here is a video from the same guy showing how the wiring works to get 240v from two 120v legs.
No one has suggested measuring the actual AC current with a clamp-on meter. The Power Energy Panel Meter that you have ordered will do this, but a clamp-on is easy and fast. You might find out that the main 30A breaker is tripping at a lower current than the spec. If that were the case, the breaker could be faulty. A simple replacement might just solve you power gobbling problem.
Sure, I understand all of this well. However, it is still true that those of us with single 50A circuits like the OP is asking about just connect one of the legs on our 4-pin connector - either in the plug (like mine) or in the socket (well, mine also by default of not needing a wire there).
Even in your case of bringing two 50A circuits on board, this is not 100A service, and the shore pedestal is not providing 100A service. That would require different size wiring and fusing. You are just bringing on board two separate 50A services, and they can never be combined.
Mark
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I think we are speaking in circles saying essentially the same thing. I never said that a 50A service is a 100A service. What I said is that with a 4-pin 50A service, you are bringing in two 50A 120v lines which gives you up to 100A of available power at 120v. This is over 3-times the power that you can get from a 3-wire 30A service.
Many people thing that if you are going from 30A to 50A that is [50/30 = 1.66 more power. It is actually 2x50/30 or 3.33 more power. My coach has no 240v devices, but it can use up to 100A at 120v. I assume that most pedestals are correctly wired so that I am bringing in 240V with the red and black wires on 180º opposite legs, but it would not really matter. Each leg can still supply up to 50A even if they are both on the same phase.
Not exactly..
30 amp 120 VAC is max 3600 watts (use only one phase)
30 amp 240 VAC is max 7200 watts (two phases wired as 240)
50 amp 120 VAC is max 6000 watts (one phase only)
50 amp 240 VAC is max 12000 watts (two phases wired as 240)
Using single phase, going from 30 to 50 amp gives you 6000/3600 = 1.66 times the power
Using both phases, going from 30 to 50 amp gives you 12000/7200 = 1.66 times the power
For either case, going from just one phase at 120 to using both phases at 240 doubles the power because voltage is doubled.
30 amp 120 VAC is max 3600 watts (use only one phase)
30 amp 240 VAC is max 7200 watts (two phases wired as 240)
50 amp 120 VAC is max 6000 watts (one phase only)
50 amp 240 VAC is max 12000 watts (two phases wired as 240)
Using single phase, going from 30 to 50 amp gives you 6000/3600 = 1.66 times the power
Using both phases, going from 30 to 50 amp gives you 12000/7200 = 1.66 times the power
For either case, going from just one phase at 120 to using both phases at 240 doubles the power because voltage is doubled.