Generator question

Capt Storm is correct if:
The transfer switch has isolated the gens output from the shore power plug. There is no issue there and in a home system with a stand by generator (which uses the same transfer switch technology), this is exactly how it works. You don't have to unplug the "house" and there is no NEC code that says you have to as long as you have an approved automatic or manual XFER switch.

If your not using a XFER switch then unplug and stop using whatever cludge was used to connect the genny.

Capt.Storm wrote:
Good thought but yep,you're fine doing that.

NO! Wrong answer!!

YOU MUST UNPLUG THE CAMPER FROM THE HOUSE WIRING WHEN THE GENERATOR IS RUNNING. It is required by law, as well as common sense safety considerations. Somebody could get killed!

REALLY.

Here's the thing, power goes out at your house. Maybe it is because a tree fell on the lines. So what happens when the lineman goes to repair that line, grabs the end that goes to your house (after all, it is the load end, no power there, right) and instead finds a hot wire being charged by your generator?

Yeah, he gets electrocuted. And since it is illegal everyplace I know of to hook up a generator to the house wiring without provision for and actual disconnection from the mains, the authorities will track you down and charge YOU with the criminal offense.

SO, FOR GOD'S SAKE (not to mention your own and that lineman), __NEVER__ __EVER__ UNDER ANY CIRCUMSTANCES, __EVER__ FIRE UP THE GENERATOR IN YOUR RV WHILE LEAVING IT PLUGGED INTO SHORE POWER.

Beyond that, even if no lineman gets electrocuted, what happens to your generator when the power does come back on? Odds are good that your generator will be out of sync with the power plant, and you will have instant short circuit, with the little on at your house trying to overpower the big one down at the power station. If you are lucky, circuit breakers will blow before any damage is done. If not so lucky, your generator explodes in flames.

(Yeah, yeah, I know, if the HOUSE transfer switch is thrown, and the house disconnected from the mains, all is well. Similarly, if the OP's motorhome has a transfer switch, he's golden. But the original post showed no evidence of the sophistication of having such a setup. And sure-as-the-lord-made-the-little-green-apples, there will be people reading this thread who AREN'T sophisticated enough to have such a setup and use it.)

With all of the above being very accurate they DO NOT RECOMMEND starting the gen while the shore power is energized. If you are goint to exercise the gen as recommended unplug the shore power first.

Probably about as safe as a flight aboard a 777. No MH or ATS manufacturer warns about, or protects against, the Shore Tie cable going "hot" when the genny is running. I suppose some kind of catastrophic failure could let that happen, but like I said, no warnings or provision against it.
Just NEVER NEVER "back feed" the house by making up a double-male cord and connecting a coach outlet to a house outlet. OK to use the RV to keep your home fridge cold, simply run an extension cord inside and plug direct to it.

Relax, and enjoy the A/C.

Yes the transfer switch is designed to keep everyone safe. You have two inputs and only one output. The generator power can NOT be connected to the shore power - ever.

Once the power comes back on, the transfer switch will stay in generator run position. After you shut off the generator, then power is dropped from the relay, and then it can transfer back to shore power.

Your neighbors might want to plug into the RV. You can plug in your refrigerator, but not to many. Depends on how big the generator is. 4,000 watts will run one A/C at 1,400 watts, perhaps two. Each refrigerator or freezer is about 850 watts with about 500 more watts required to start the compressor. The A/C compressor takes about another 1,000 watts to start it. So if you plug in 2 refrigerators, and your A/C shuts off, it might not have enough power to restart it while the other refrigerators are plugged in.

With a 5,500 watt generator, then you can run 2 A/C units and 2 refrigerators, with enough reserve to start one of the A/C units at a time whenever that is required.

Fred.

Fred.

Good thought but yep,you're fine doing that.

The Logans wrote:
Well, the power was out, so we (DW and 5 dogs) moved out to the 2015 Jayco Redhawk, and I cranked up the generator. It was all good, and the AC was humming along.

Then I began to worry... the MH was connected to the 30 amp house power, and the generator was running. What would happen when the power came back on? Would the shore power back-feed into the 4KW Onan and blow the diodes, or is there some sort of protection against that?

Any advice would be greatly appreciated!

Unless you have tampered with your electrical system, that should not be a problem. If the cable it still plugged into the house and you are powering everything with the generator it means that you have an auto transfer switch. Don't worry, be happy.