Gen and shore power

[kuzined]

Never did it but was told that if the generator is started when you are plugged into shorepower, a lot of damage would happen. Just wondered if that is true.

[rgatijnet1]

On my Monaco coach, if the generator is started when hooked up to shore power, the transfer switch will shift to generator power as soon as the generator gets up to speed. No damage done at all.
During hot weather where I am running the AC with the generator while going down the highway, I can keep it running while I hook up to shore power, and then shut the generator down. A very short delay and then it switches to shore power.
I also have the Energy Management System that prevents electrical problems that others may have with their generator/shore power.

[jbrad13]

My coaches owner's manual states that running the generator while connected to shore power will cause significant damage and void any/all warranties

[tropical36]

kuzined wrote:
Never did it but was told that if the generator is started when you are plugged into shorepower, a lot of damage would happen. Just wondered if that is true.

Not true. Either with a transfer sw. or a separate genset outlet, you can only be receiving one source at a time unless there was some kind of a rare quirk that shorted the transfer sw. across and something that I've never heard of.

[naturist]

It is not SUPPOSED to be possible.

It is true that if your generator output gets hooked to the mains, you generator will be toast. But there is supposed to be either a cutover switch or a need to unplug the rig from the mains in order to plug it into the generator so that that is not possible for even an idiot to arrange.

That said, all kinds of things happen because somebody did something stupid, if you get my drift. It's a little like firearms: until you have personally checked to make sure there is NO ammunition in the chamber, or the magazine, you need to treat every gun as if loaded and ready to fire. In this case, unless you have personally checked the wiring and switches, every electrical setup should be assumed to be arranged by an idiot and ready to explode in a shower of sparks. Just my tip for safe running.

You never know when the rig manufacturer will have put the new kid on the job, and HE wired up a death trap. So depends on how rich you'd like to make your heir's lawyers.

[jplante4]

Only if the transfer switch doesn't do what it's supposed to. This switch is supposed to cut out gen power when the shore power comes on.

The "damage" would most likely be limited to the generator with the shore power trying to drive the generator as a motor while the motor is trying to drive it as a generator. It would probably break a shaft or a shear pin if so equipped. Of course there's always a chance that the gen will come on line in phase with the shore power, if which case you're feeding the grid but nothing bad happens.

[bsinmich]

Theoretically it should not happen if you have an automatic transfer switch. If you have a manual transfer by plugging in thee coach cord to the gen. outlet you can't possibly do that. You would be putting power into the grid and most likely not on the same phase. If power is out and you are using a generator at home you could very well electrocute a lineman working on what he thinks is a dead wire. A good system would be to unplug the generator if that would happen to you in a CG.

[AndyW]

Depends on the motorhome? On mine it wouldn't be possible - I have to plug the shore power cord into a socket that runs to the generator to run off generator power. So if I was plugged into shore power and started the generator, it would just run with no load.

[pointrow]

I don't know what MH you have but mine comes on when power cuts off and shuts down when power comes back on automatically depending on load. I believe most all have that feature in one form or another whether auto or manual.