help with a 50amp breaker.

[wrooster]

Normal 50 amp service is 2 legs of same side of power source.

Using your volt meter measure the voltage to ground should be 110 +/_ voltage
Do same to 50 amp service still 110 volts to ground and across the lines same conductor so no voltage.

This is incorrect.

The 50A service is "split phase":

L1 -> N = 120Vac
L2 -> N = 120Vac
L1 -> L2 = 240Vac

The first clue that a receptacle or electrical system is split phase is that the neutral wire is the same gauge as the L1 and L2 hot wires. The nature of a split phase system (like a typical USA residential service) is that the neutral wire only has to carry the DIFFERENCE between the L1 and L2 currents. If L1 and L2 were not 180 degrees out of phase with each other, the neutral would have to carry the SUM of the L1 and L2 currents. Accordingly, this would require a heavier gauge neutral wire.

Hence, split phase power is employed in USA residential service applications such that it minimizes the amount of copper or aluminum needed.

Wrooster

 

[crazyal]

I think it should be a rule that if you are going to ask an electrical wiring question (which is fine) you need to take pictures and maybe even a diagram. There's just a lot of questions that have gotten different answers. It kind of sounds like the 50 amp GFI breaker is in a sub panel or maybe it's a panel that's attached to or an extension of the main panel.

My first question would be can a RV be powered by a GFI? Are the neutrals tied together with the grounds inside the RV? If they are I don't think a GFI will work.

 

[Bigkrank]

I just ordered a new enclosed trailer last winter and got 50 amp service. It is 125V, uses NEMA 5-50 plugs. I think the only place a 5-50 NEMA plug is used are on trailers/rvs like this.

This is 3 wire as shown in attached chart and only one line is "load". Don't believe some of the bull on some websites saying it is the same as split line residential, it most certainly is not, however on the newer very large rv's I know they use a 4 wire plug and I would certainly assume those are split line.

NEMA Plug & Receptacle Configurations Reference Chart (Straight Blade)

 

[beppington]

What I've learned from this interesting thread; I sure hope all of you know how to use a multimeter correctly & safely :thumbsup:

 

[cycle_gator]

I suppose you can getjust about anything, but I will offer that 50 amp single phase circuits in RV parks are very rare. Normally, the largest single pole circuits you find are 30 Amp.

Yes, the "standard" 50 amp RV plug is a 4 conductor, two phase circuit.

I to wish we could help the OP, but at this point, I think our best advice is to part with a couple hundred and have a professional electrician troubleshoot this. I have witnessed two people nearly electrocuted on the steel steps of their RV's because someone engaged in amateur FUBAR wiring.

 

[pat32rf]

My money's on Hosspuller. I bet the panel in the trailer has a grounded neutral, they must be isolated back to the GFI...same as our sub-panels. Up here we ONLY ground the neutral at the main panel, never in a sub-panel.

 

[Qapla]

...Up here we ONLY ground the neutral at the main panel, never in a sub-panel.

That is the code here. In fact, our code says that in the main panel, the neutral MUST be bonded and that in sub-panels, it MUST NOT be bonded.

Bonded = being connected to ground, the case/box and/or ground rod/wire.

 

[cycle_gator]

Actually single point ground/neutral bonding is true in any state that has adopted the 2008 NEC.

The bond is to occur at the first point possible after the service entrance and anything downline from there the neutral is to be isolated from ground. FYI this was "just" changed in the 2008 NEC, prior to that point the "grounding conductor" or neutral and the "Equipment ground" ground wire were bonded in every sub-panel. The issue with that was that it often crated parallel paths to ground in a fault situation and could electrify any equipment grounded surface along that path. So, the code was modified.

I suspect that either the wiring is not correct, or the distance invovled is causing a timing issue with the GFCI. These things are really touchy.

There also remains the very real possibility that there is an electrical leak in the RV. All it takes is a little water in the wrong place. I can't tell you how many times I have popped a GFCI in the rain becasue the end of an extension cord got a little wet. On one of my previous RV's the refrigerator would sometimes pop the GFCI when it was just starting up and then not have another problem after that.

I have also had the arc from plugging in the RV pop the GFCI.

That is why I still recommend finding a pro to have a look. In this case a dollar saved may be a life lost.

 

[JB4310]

So is it code or just good practice that the entire RV/ boat be GFI protected from the campground or dock?

I would think there would be so much that could cause nuisance trips that it would be difficult to keep the gfi closed.

JB

 

[cycle_gator]

I need to research that a bit. At one time, it was only 20 amp or smaller that required GFCI for exterior application. Now, either through the NEC or local code additions, it is all exterior outlets, even the big guys. However, I note that few equipment suppliers put 30 or 50 amp GFCI breakers into their RV panels as a standard, which makes me wonder.

While I think it is great practice to protect against faults that develop as a consequence of wiring installed in a moving, vibrating vehicle, it seems like the sensitivity of the fault detection is better suited to a bathroom than the typical exterior environment.

I am in process of installing four 20-30-50 amp RV power panels on my property and intend to experiment with one of these to see what issues I run into. However, the GFCI will be installed immediately next to the receptacle, as opposed to back in the service panel. It is possible that is the root of the OP's issue if it us a long run from subpanel to receptacle as it becomes a timing issue of sensing any differential in the neutrals as the line side has to run all the way back to the subpanel, first. Even an arc when connecting could cause the GFCI to pop.