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

Sam_Spade
Explorer
Nov 16, 2016
Campinfan wrote:
I like the idea of soldering the connections though.

You can NOT solder aluminum.
Dusty_R
Explorer
Nov 16, 2016
Campinfan wrote:
When you put copper and aluminum together, you should apply some anti-oxidation guard (ox-guard from Lowes) compound. It comes in a tube. I like the idea of soldering the connections though.

National Electrical Code does not allow copper/cu and aluminum/al wire/conductors to come in contact/touch each other.
One way to splice/join together is with a split bolt with a separation bar within it. The cu conductor is put on one side of the bar and the al on the other. Also the al conductor must have anti-oxidation paste put on it.

Dusty
Chris_Bryant
Explorer II
Nov 16, 2016
That is not aluminum wire, it is tinned copper. Regardless, it doesn't need to be soldered, and should not be, as you need to be able to disconnect it for various reasons.
TenOC
Nomad
Nov 16, 2016
Campinfan wrote:
When you put copper and aluminum together, you should apply some anti-oxidation guard (ox-guard from Lowes) compound. It comes in a tube. I like the idea of soldering the connections though.

I do not think you can solder Aluminum.
j-d
Explorer II
Nov 16, 2016
I tried to view the picture, and maybe get it linked in here so we all could look at it, but no joy for this Luddite.

It is NOT uncommon for high-amperage "Splices" in an RV to overheat and fail. Sad but true. Had a recent case where all 120VAC went out. Turned out to be that the spices (wire nuts, in a Box) overheated and burned out where the flexible shore tie cable met the Romex interior wiring. I was able to help the OP solve it over the phone. SHOUT OUT to Winnebago! The Wiring Diagram was on line and helped me ID the suspect spot. OP had an RV tech scheduled for a couple days later. Called to cancel and tech asked if he'd been using electric heaters. OP had been, and tech said they're a common problem source, at the splices. This OP was able to solder the connections, then wire nut and tape them

BUT BUT BUT, be sure you're going copper (one side silver tinned is OK) to copper. IF aluminum is involved, personally I'd look to replacing it, but if you want to connect, you'll need special connectors and an oxidation-preventing paste.
MEXICOWANDERER
Explorer
Nov 16, 2016
Houses are not subject to pavement joints and pot holes. Sometimes meeting NEC code is not enough and can cause fires and fatalities. NEC CODE IS NOT ENOUGH! When in doubt use YSC yacht safety council high voltage protocols. They are far stricter than stick and brick standards.
mrmomb
Explorer
Nov 16, 2016
Interesting that your transfer switch is wired shore power priority. Mine as factory wired is generator priority as stated in the OM. I did test to verify such.
Sam_Spade
Explorer
Nov 17, 2016
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 ???
Junior30
Explorer
Nov 17, 2016
Thanks for the instructions. Here is another attempt at the photos! hope this works.

Click For Full-Size Image.

Click For Full-Size Image.
Chris_Bryant
Explorer II
Nov 17, 2016
Everything did what it was supposed to do safety wise. Just cut back to good wire and reattach. Don't solder, just use a good mechanical connector.

FWFW, I dug out a length of Onan wire used on the output- this from a 7kw, but they use the same on the 4kw. The markings on the wire (other than CB1 CB2 Neutral and GND):

12 AWG (3.3mm2) E137925-L (UL) SIS 600V AND AWM 3173 600V OR 3237 1000V -- 156016 CSA CL 1251 125C 600V OR AWM I A/B 125C 600V FT2 -- MADE IN USA

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