I'm having a new house wired, including a backup generator wired to selected circuits. My electrician said that if my 'selected circuits' include some with GFI protection (ie. In the kitchen) then the GFI outlets would not work when running under generator power. I do not understand why this would be. I asked him if he meant that the outlet would work but with no GFI protection, and he said the outlet would not work.

The generator will be a typical 18KW propane unit (e.g. Generac) with automatic transfer switch wired to a separate subpanel.

Why would GFI outlets not work normally when running under generator power?

I never heard of this. If the genset, transfer switch, and GFI devices are all wired properly, all should work just fine.

There are large installations, such as hospitals, for example, where nearly everything is on back-up generator, and there is no problem with GFI devices.

Ask him to show documentation that GFI devices will not even deliver power when connected to a generator.

If he cannot prove this, I would question how he does the connections of the genset and transfer switch.

To test him, ask if your generator will be considered as a Separately Derived System, or a Non-Separately Derived System, and why. If he stutters or is unsure, or porduces some nonsense answer, then he is not the one to be wiring this generator.

Great answer. For what one person's experience is worth, my shop light on a GFI outlet worked with my generator. The furnace worked too, unlike many reports. Both my furnace and when hooked up, my generator are connected to the equipment ground in the main box. I strongly suspect many of these ''won't work on the generator'' reports involve cutting corners on grounding.

Thanks for the quick replies and great advice. My intuition is that my electrician may not have much experience with generators, and I have not confronted him with these questions. I will go ahead with my plan for circuit selection and I'll find out for myself. The transfer switch will go in with the roughin, but I plan to bring the generator in several months later. Might have another electrician by then.