Wiring problems

[BB_TX]

Originally Posted by bcrvman

Electrician here. I know of no way to get 240V on any appliance in an RV without connecting the appliance to the 2 hot legs. A neutral (white wire) breaking off will cause 0 Volts on that entire circuit.

Actually being a 120/240 split phase power system, it depends on where the neutral was broken, and whether two devices were each connected to a different hot, and on whether those two devices were both turned on.

Looking at the pictures, if one of the neutral wires on the left side of the neutral buss lost continuity with the buss bar, then there would be zero volts on the device(s) connected to it. But if the neutral wire on the right side of the buss bar (the source neutral) were broken, and the neutrals on the left still intact, and there were two devices with each one connected to a different hot, and both were turned on, then there would be 240 vac across those two devices since they would effectively be connected in series to the two hots. The neutral buss bar would be floating. The actual voltage applied to each individual device would be dependent on the impedance of each, not 240 vac to each.

[laverdur]

I recommend an electrician who will have the test equipment to measure current on the ground and neutral wires. Overheated neutral wires can indicate improper phase balancing but if your rig started out with only 30 amp service, then there is only one leg of power. That would seem to rule out phase balancing but not excessive current from using too many items at once.

[beekeeper.va]

I am also an electrician. Concur with all that said unplug and get some help. Another issue I saw is that the ground and neutral land on the same bus bar. This is not in accordance with code. The only place that is to happen is the source panel and that is the campground's service. Our RVs are to be treated like a big appliance or a subpanel. Grounds and neutral are to remain on their own bus bar and not connected.

[BB_TX]

Originally Posted by beekeeper.va

I am also an electrician. Concur with all that said unplug and get some help. Another issue I saw is that the ground and neutral land on the same bus bar. This is not in accordance with code. The only place that is to happen is the source panel and that is the campground's service. Our RVs are to be treated like a big appliance or a subpanel. Grounds and neutral are to remain on their own bus bar and not connected.

I wondered about that also. But it appears in the picture that the green wires go down behind the neutral bar. My guess is there is a ground bus bar behind the neutral bar that you can not see due to the angle. Note that there are no screws in the neutral bar tightened down except where there are white wires.

[Ml barber]

Most rv 30 amp breakers are 120
Same as 20 amp. Looks like half the box is 30 the other 20. 50 amp rv is a 240 that needs both legs

[McRod]

Originally Posted by mhs4771

A few things: A 20 amp and 30 amp breaker does not make for a 50 amp service. A 50 amp service box has TWO 50 amp breakers.
Sounds like your unit might have been originally a 30 amp service that someone modified without really knowing what they were doing. The overheated wires are probably a result of running to many higher power appliances at the same time.
I think it's time to call in the Heavy Guns and get an Electrician to see exactly has been done.

My public math education said 20 + 30 = 50. So it "could" be a single leg 50 amp service. You can run up to 50 amps on a single leg of service.

50 amp service today is generally two legs of 50 amp service, which can support 100amps.

[McRod]

Originally Posted by dallasrules

I hope these are the right pictures

Dallas,

Those look like two circuits. Or maybe a service feed and one circuit. Hard to tell from the pics. The black, white and green/copper wires will go to the same circuit.
Looks like they have been overloaded, which will cause them to burn.

I would trace them to see where they go. That will also help you determine if it's two circuits or 1 and a service feed. They should be replaced anyhow. You can look up some charts online to help you properly size the replacement 8/10/12 gauge wire. Size them to the 20 amp or 30 amp breakers accordingly.

To trace a wire you can physically follow it from end to end, or you can use a voltmeter to check continuity or just flip switches/breakers until you can see what turns on/off.

The hots (black wire) will go through each breaker. The neutral (white wire) will go to the buss bar and the grounds ( green/copper) will go to a ground bar.

Typically, your service feed will come into the box and wire to each of those bars and the hot will go to your main breaker (30 amp). Everything feeds from there.

Get yourself a voltmeter so you can check continuity and power.

[McRod]

Looking further at pics, looks like your service feed (50 amp) is coming in from the right side. The 50 amp service leg has two hots (black and red). Typically 6 gauge wire. I can't tell from the photo where they go. Do they go to another box?

[BB_TX]

Y’all are ignoring the fact the OP said he has a 50 amp power cord. And his picture shows a power cord coming in with 4 wires; black, red, white, and green. And Carl, who has been a MOC member for 15 years, said some of the early Montanas had that arrangement with one hot leg of the 50 amp power cord going to a 30 amp breaker and the second hot leg going to a 20 amp breaker. And it appears that is what the OP has, even if it is someone’s modification rather than OEM. That would give a total of 50 amps available to the RV. Yes, it is only half what the true 50 amp source can supply, but still 50 amps. And it would have 240 vac across the two hots.

[BB_TX]

Originally Posted by McRod

Looking further at pics, looks like your service feed (50 amp) is coming in from the right side. The 50 amp service leg has two hots (black and red). Typically 6 gauge wire. I can't tell from the photo where they go. Do they go to another box?

If you zoom in on the picture you can see that the incoming black wire curls back to a lug just above the 30 amp breaker and the incoming red wire curls back to a lug just below the 20 amp breaker. The incoming white wire goes to the neutral bus. And the incoming ground wire drops behind the neutral bus, presumably a ground bar.

[Mark7]

I enjoy reading these electrical threads... Everyone is an expert, and some are electricians! You don't have to read too far into a post to see who knows what they are talking about.

No matter how anyone replies, there are going to be arguments... That is why I refrain!

Anyone want to talk about tires?

[McRod]

Originally Posted by Mark7

I enjoy reading these electrical threads... Everyone is an expert, and some are electricians! You don't have to read too far into a post to see who knows what they are talking about.

No matter how anyone replies, there are going to be arguments... That is why I refrain!

Anyone want to talk about tires?

I am neither an expert nor an electrician, but I can definitely hook + to + and - to -; and follow a single color wire. I didn't read everyone's post, but I didn't see any arguing.

Firestone tires are THE only tire you need for EVERYTHING. After that last lawsuit they really got their act together!

[BB_TX]

Originally Posted by Mark7

I enjoy reading these electrical threads... Everyone is an expert, and some are electricians! You don't have to read too far into a post to see who knows what they are talking about.

No matter how anyone replies, there are going to be arguments... That is why I refrain!

Anyone want to talk about tires?

Your scorecard should make interesting reading.

[firestation12]

On a 50 amp cord, red and black wires are connected to opposite phases. The white wire only has to carry the amperage difference between the red and black wires. Example, if the black wire is carrying 40 amps and the red wire is also carrying 40 amps, then the white wire is at 0 amps. But if the red and black wires were connected to the SAME phase, the the white wire would carry the aggregate of the red + black. Using the previous example, the white wire would now be carrying 80 amps. If you were to measure the voltage between the red and black wires, the reading should approximately 240 volts. If it’s zero or near zero, then this would cause the white wire to severely overloaded when the electrical system is in full use.

[Drifty1]

On our 2002 3295RK we have a 30 and 20 amp breaker installed in the main breaker box. This main box feeds the sub panel built into the converter/distribution panel. The 20amp breaker feeds the A/C unit and the 30 amp feeds the rest of the circuits that feed the microwave,water heater ect. Our unit has a 50 Amp connection on the rear of the trailer and it came with a 50amp power cable. On our unit the factory installed a pin through the 30and 20 amp breakers in a similar way you would tie a 240v breaker together. I think this way the way the factory thought 50amp service worked in these early models.
I do believe that they changed this arrangement in the 2004 models but don’t quote me on that. When I installed my solar system on my trailer I installed a wire size to support 50amp power for about 50’ as I was going to run cable from the rear of our trailer to the front compartment and back to the main breaker box. What I did find out was that the factory wire was a least one wire size under of what I thought it should be for 50amp.
As for the burnt wire I think this was most likely caused by a loose connection on the breaker or lug. I would hope that the breaker would of tripped if it had to much of a load on it. These are my options as I have a vintage Montana without this new fangled 100 amp service. I would do extensive research online about RV wiring and then track down where all the connections should located.
Great post.

[firestation12]

One burnt neutral wire might indicate a loose connection. 2 burnt neutrals would be more indicative of overloading.

[dallasrules]

Apparently, the 20 amp/30 amp setup is how these trailers were wired back in 2003.

[DebNJim B]

This is a very interesting discussion. Some very good analysis of this odd wiring in an older RV, both from electricians and others that are obviously knowledgeable of how electricity works. I put myself in the latter group. Don't discount us, just because someone is not an electrician doesn't mean they know nothing. Remember many good electricians have hooked up 30A outlets for people at 240V because it looked like a dryer plug. My only comment would be that the white wires do not look burnt to me. The insulation on those wires may have overheated, however I have seen that same discoloration just from age. The only wire discoloration I see is the green copper ground wires which also seems to be from age as well.
If it were mine I would likely do some rewiring but as long as all connections are tight I think the OP could stay with what he has. It seems all systems are working as they should be.

[GBliss]

I ran into a similar situation with the discolored wires. 2006 RL3400, Air conditioner quit. Checking voltages, I found goofy voltages all over the place. I checked the breaker panel and found charred ground wires per picture 1. Screws on the ground buss were loose from the factory. I dressed the wires, reattached, tightened everything securely and replaced the A/C startup capacitor. Picture 2. The RV dealer I bought the capacitor from said they had run into this problem a lot. I have had no further problems with my electrical.

[BB_TX]

That’s actually the neutral buss bar with the discolored wires. But yeah, that has been a common problem and something every owner should check. Checked mine shortly after buying and found multiple wires not tightened down properly on the circuit breakers, neutral bar, ground bar, and 12 volt fuse panel also. Caught mine before they overheated.