Neautral wire overheating

Hard to guess at answers, but a couple of comments;

-don't assume the bus bar, or terminal block is aluminum. Most these days aren't, but are alloy or plated copper.
-clean the block, but don't get aggressive. You don't want to damage plating or create ridges
-it is hard to get good connections on wire or blocks that have overheated, because of material characteristic change. Generally recommend replacing the overheated parts.
-is your system 50 A or 30 A? If it is 50 A and the surge protector is connected incorrectly, the neutral could be carrying more current than the phase.
-I would be surprised if this problem is caused by long extension cord. That causes voltage drop and can cause connection to overheat. You may just have bad luck, but I am surprised to see two neutral connections that overheated, and no overheating in the phase.
-is there evidence of overheating in the distribution panel, or just in the surge protector?

From the pictures, it appears the phase and neutral connections are made the same way so it is surprising to see the issue only in the neutral. Is there anything else connected to the circuit and have you checked all of the incoming wiring. As I said, one bad connection I can see understand, but two on the same wire indicates higher current than expected (but doesn't negate bad workmanship).

Finally, some loads can result in harmonics that will overheat the neutral, but this occurs usually in 110/220 circuit.

Good luck

Hi,

What is the voltage at the shore power outlet? What is the voltage at the RV?

That's the contractor, not a buss. Looks to me like a simple case of carboned up and consequently overheated contacts internally. I doubt this has anything to do with the lugs themselves.

KcBorne wrote:
I guess i can try these 2:colloidal copper compound and reaming the bus bar. The screws are snug and the wires appear clean. My surge protector is shot from these 3 meltdowns. Thank God for the lifetime warranty! Hopefully progressive don't try to weasel out of it. I've had that experience with warranties before.

That thing is shot. I wouldn't waste my time or safety with that. That big black device is a contactor. you could have some oxidation on the neutral line contact causing high resistance which is causing the heat.

I'll point out that basic electrical theory states that the current will be the same at all points in a circuit like that- the hot is carrying the same current as the neutral, and the current is the same at the plug, outlet, cord, etc. It is just a bad connection at the point of failure, and once it has overheated, you need to replace everything that got hot. The only thing a longer cord would do is drop the voltage a bit, causing just the air conditioner to draw more current, but it will not draw enough to burn up the wire- a breaker would trip far before that happened due to an over current situation.

I think it started out as a bad connection on the white wire side of the contactor. See how the lug is twisted left. In tighting the temrinal it should be twisted right at least. Righty tighty remember. loose lug or loose wire in lug started it. Send it back to Progressive and maybe they can rebuild it for you. I always use an anti oxident on all wires and I take the lug screws out and give them a little too. In AC current the load shows up equally on both wires. There is no plus or minus. This trouble was because of a loose connection somewhere right at the contactor. wire in, wire out, contacts themselves?

The problem started with the first failure, which was most likely a loose connection. No matter how hard you tried to clean up the connection, once a terminal is overheated, no matter how tight you make the connection, it will fail in the future. The contractor needs to be replaced. Since the failure was due to a loose connection, I would be surprised if Progressive repairs it under warranty, but it is worth a try.

Since most overheating is caused by loose connections, and a RV gets lots of vibration compared to a house, it is worth taking the time at least once a year to power down the RV & checking & retightening all the electrical connections including both 120V & 12V in your converter.

Chris Bryant wrote:
I'll point out that basic electrical theory states that the current will be the same at all points in a circuit like that- the hot is carrying the same current as the neutral, and the current is the same at the plug, outlet, cord, etc. It is just a bad connection at the point of failure, and once it has overheated, you need to replace everything that got hot. The only thing a longer cord would do is drop the voltage a bit, causing just the air conditioner to draw more current, but it will not draw enough to burn up the wire- a breaker would trip far before that happened due to an over current situation.

Absolutely true-- for 30 amp service which is what the OP has.

But, with properly wired 50 amp service, the neutral carries only the DIFFERENCE between amps on L1 and L2. So there can be a very large difference in current, if for example both roof A/C's are running.

enblethen wrote:
You buss work appears to be extruded aluminum. You need to be using a good de-oxidation compound. Colloid copper may not be enough. Read label closely before applying to aluminum busss work.
The connectors for the cable entering your surge protector do not prevent the intrusion of moisture. You or manufactuer should seal to prevent moisture if used outdoors.

This is why I gave this advice above in this thread. In order. Cleaning the bore on the aluminum bus until it gleams is for people with a little patience. But conductivity is far higher than just squirting in a spritz of aluminum deoxidation compound. The synthetic oils in a good colloidal copper compound prevent the aluminum from oxidizing. I used this protocol on 3 phase 100 amp 254 volt services, located 200' from crashing tropical Pacific Ocean waves. Using an aluminum deoxidation liquid followed by colloidal copper is NOT recommended. Colloidal copper also has lasted ten years bonding a copper ground wire to a copper plated steel ground rod without corroding, next to the ocean. The colloidal copper compound is excellent for it's intended purpose...

Here is what I had written above...

"Disconnect from shore power and inverter, remove one wire at a time and ream the hole with the wire brush until it gleams."