With the expected arrival of Hurricane Earl tomorrow, last night I fired up the generator and made sure everything was working properly. Oil’s good, plenty of propane, all is well. It’s hooked to the house through a code-installed and inspected transfer switch, so the wiring isn’t of concern to me, it’s more of what’s going on inside the generator.
Reading the label on the side of the generator (I’ve used it for years, perhaps now is a good time to read the directions…), the words “floating neutral” caught my attention. I understand the concept of a grounded neutral versus a floating neutral, but I get confused when they are being tied together. Does the floating neutral become a grounded neutral when the generator is tied in to my grounded panel? If not, does my house then become floating neutral instead of grounded? Or is something else going on here that I’m just not getting?
The floating neutral label indicates that the neutral of the generator is not bonded to its frame. If you are using the generator stand-alone in a remote location, this is actually safer then having a bonded neutral. In your house though, you definitely want the generator neutral bonded to ground. This will maintain the safety action of GFCI breakers and outlets.
Typically, at your main breaker panel in the house, the neutral buss bar is bonded to the service ground bar. Unless you have some kind of very wacky wiring, when the transfer switch is flipped to “Generator”, the neutral will be bonded to your house ground. That will still leave the actual generator frame ungrounded, but that isn’t necessarily a problem.
GFCIs work by measuring the current through the hot and the neutral, and trip if they aren’t equal. GFCIs will still work properly even if the neutral isn’t grounded. The idea is that if the current going out doesn’t match the current coming back then at least part of the current has found an alternate path, which usually means going through ground somehow.
If this is a permanent installation (which it sounds like it is, since you’ve got the transfer switch and all of that) then you should ground the frame of the generator. Otherwise, if there is ever a fault the frame could become “hot” which would be a potential hazard.
Thanks for the response - that makes sense, given the setup of the generator.
The generator itself isn’t permanent, it’s a portable generator that plugs into the household system via a 4-conductor cable. I have to wheel it out when I need it to hook it into the house (Something I need to do before I leave for work Saturday morning, so the wife can still have power should it be out).
True, but without the neutral bonded to ground, there can be no alternate return path, so the currents must be balanced at all times and a GFCI won’t trip.