Major short in generator wiring - Pictures

[Junior30]

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.

[tmartin000]

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.

[DrewE]

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.)

[Chris_Bryant]

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

[Junior30]

Thanks for the instructions. Here is another attempt at the photos! hope this works.


Click For Full-Size Image.




Click For Full-Size Image.

[Sam_Spade]

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 ???

[mrmomb]

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.

[MEXICOWANDERER]

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.

[j-d]

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.

[TenOC]

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.

[Chris_Bryant]

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.

[Dusty_R]

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

[Sam_Spade]

Campinfan wrote:
I like the idea of soldering the connections though.

You can NOT solder aluminum.

[96Bounder30E]

Moved from General RVing

[Campinfan]

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.