Had a major short and near fire due to the wiring from my generator this past weekend. While on the road we had the gen running with the a/c going. The wife went to use the microwave and when she did everything shorted out. We have used all appliances while on generator power before with no issues. Upon arriving back home I traced back the problem to a junction box in a compartment just after the generator. I found evidence of a major short in the wires. It appear as though the wires may have come loose and separated slightly causing the short. One concern I have is the wires from the generator are some type of stranded aluminum wiring and the wires running from there to my transfer switch are solid copper. Could the dissimilar metals be an issue? Should I, Can I replace the wires coming from generator?Judging from the photos this could have been worse especially if the wires had not been inside of a junction box.

Just for the record, every electrical fault is not a SHORT.Your problem is a bad connection causing heat due to the high resistance at the connection point.And yes, the proper way to connect Al wire to copper is NOT to just twist them together and put on a wire nut. Alas, I do not remember the proper way.Are you sure that the shiny ones are not tinned copper ?

It appears to be arching that probably occurred over a period of time due to a lose connection.

Play it safe. Pigtail them together, solder them, proper size wire nut on top of that, then electrical tape over all. In residential construction you'd never get away with having a connection of two Romex runs like this outside of a junction box. Why they do/did it in MH construction is beyond me.

Cannot see the pictures, but if it's an Onan, that is tinned copper, not aluminum. It is high quality wire.

Rovin' Bones wrote:Play it safe. Pigtail them together, solder them, proper size wire nut on top of that, then electrical tape over all. In residential construction you'd never get away with having a connection of two Romex runs like this outside of a junction box. Why they do/did it in MH construction is beyond me.The connection that the OP posted was in a junction box, and a weather tight one at that. They were simply hypothesizing that it would be worse if it were not in a box, and that's true, which is partly why code requires junctions to be in boxes for both residences and RVs (for all ordinary circumstances).It does look as though the nut on the strain relief grommet thingy (whose proper name escapes me at the moment) for the lead from the generator needs to be tightened down a good bit, besides the connection repairs.

Major short in generator wiring - Pictures | Good Sam Community

DrewE
Explorer II
Nov 17, 2016
Sam Spade wrote:
mrmomb wrote:
Interesting that your transfer switch is wired shore power priority.

Seems totally logical to me.

IF you have shore power available and connected, why would you want to get power from the generator ?

Indeed, why would the gen even be running ???

Generator priority over shore power is the most common arrangement with an automatic transfer switch. The main reason, I believe, is that there is a time delay for switching to the priority input and that is generally needed or at least wanted for a generator to let it get up to speed and have its output stable before switching over the load. In particular, it's not at all nice to try to start it under load, and if it were the non-priority power source it would always be starting under load unless shore power were not available.

There are times when one may wish to use generator power even though shore power is available, too. The shore power may be glitchy or unreliable. The voltage may be low (but not so low that the transfer switch fails to register). The generator may be being exercised. Yes, in all these cases one could disconnect from shore power, but if that's needed why bother with having an automatic transfer switch at all? (And, of course, not a few RVs do work fine without one, relying on manually plugging in the supply lead to generator power.)
tmartin000
Explorer II
Nov 17, 2016
Ive seen this a ton of times on boats. This was due to a loose connection that over time will build up resistance and eventually begin to arc, which leads to fires.

Plain and simple, it was not a solid connection to begin with.

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