This site seems to have a decent explanation:
Some portable generators are intended for use on jobsites, and therefore are subject to OSHA regulations for GFCI protection on all receptacles. These "contractor grade" generators have their neutral wire bonded to the ground wire to pass OSHA inspection on job sites. Since home and building main load centers also have the neutral bonded to ground, a loop is created, comprised of the neutral wire and the ground wire. A small amount of current is induced in this loop by the running generator. and since the neutral wire passes through the ground fault sensor, the GFCI senses this induced current and trips the main circuit breaker in the generator.
When using these neutral bonded generators to power a house or building through a transfer switch, the neutral bond wire on the generator must be removed, preferably by a dealer or a qualified electrician. NOTE: After this action, the generator will no longer pass OSHA inspection on job sites. Contact your dealer to determine if the neutral bond can be removed, and we recommend that a dealer perform this task. Honda dealers may refer to Honda Service Bulletin #20 for instructions on removing the neutral bond. Once this is done, no modifications to your transfer switch installation are needed.
If the neutral bond cannot be removed, you have two choices. The easiest solution is to lift the ground wire coming from the generator inside the transfer switch, and secure it with a wire nut, by itself. This eliminates the loop. Your other choice is to install a Switched Neutral Kit (SNK) accessory with your transfer switch, available thru our website.
Note that the generator is still grounded, it's just the neutral bond is gone. This means that the generator does not meet code for stand-alone operation anymore.
So your options are:
- Install a switched neutral kit
- Change to a neutral-switching transfer switch
- Remove the ground-neutral bond from your genset
Here's the instructions on how to do this for Honda generators: http://www.gen-tran.com/assets/pdfs/HondaGeneratorServiceBulletin20.pdf
Here's another good site that explains the issue and how to fix for several other generators: http://members.rennlist.org/warren/gt5000c.html
I will join longneck, you need to give to give this one to a pro.
If you do not understand about back-feeding a circuit, already, it is too easy to kill someone. I say this without exaggeration.
The biggest problem with running a generator with a transfer switch is that you have to wire it into your main panel.
For basic protection of life, (as well as the law,) it must NOT be possible to have your generator and the power to your house on the same wire, at the same time.
This is not a case of, just for a few seconds, or I would not do that, or I will triple check a written list.
It must not be possible under mechanically, electrically, on with quantum physics.
The reason is that if you put power on the 'dead' wires to your house, it is possible to kill someone a mile away, or more.
Emergency workers expect down lines to be dead. Yes, they do check first, but that does not mean that the situation can not change while they are working on them.
Transformers work backwards, low voltage at your generator (240) quickly becomes high voltage (thousands).
And sometimes people, and pets, or cars, just do not even see a fallen power line.
This is a case of some money to a pro vs life.
Best Answer
Yes
Sure, that ought to be possible. That looks like an automatic transfer switch. It was set up on only one of the two 200A feeds to your house. Presumably whoever wired your house was conscientious about putting important loads on that panel.
However, the switch is not hooked up. The wires bypass the switch. They left you some slack, but not enough slack to hook it up. Note that the wires you see go between the main panel (which is right there) and the house. One wiring run must be replaced with new wire. Obviously that should be the 3 foot run between transfer switch and panel. The installer will know this.
Knocking out a KO at the bottom of that panel and sticking a NEMA 14-50 inlet there won't be a problem. I would have the contractor do that, since it's cheap/easy work. If you want it somewhere else, you could DIY extend it to another location using Rigid conduit and #8 THHN wire. Rigid is hella expensive, but it only needs 6" burial cover so you can trench it with a garden trowel, which makes it very DIYable. No trencher rental.
The contractor will also need to add a manual "Util/Gen" button to the ATS, so you can throw it manually between Util and Gen. That will require understanding of the ATS, so hire someone who knows the system. This might bypass the electronic controller on the left wall, or use it. Don't be surprised if it also requires installing a battery.
I'm presuming you'll have a contractor do it. If you want to DIY this whole kaboodle, you'll really, really need to do the research on that ATS very thoroughly. Adding the switch button is non-trivial. I would mount the button outside the ATS rather than carving up the ATS case. If you need momentary pushbutton switches, a variety exist, including those made for the GE RR7 lighting system. Those fit in a standard form-factor and can take a weather in-use cover.
The future
Honestly, long-term... solutions like the Tesla PowerWall (well: better than the Tesla PowerWall) are coming up so very fast that installing a big 15+KW generator may not be the way to go by the time you're ready. Heck, even today, if you homebrew it, you can install an enormous battery+solar system for the price of the bigger generators.
Even if the solar is unavailable, just get a portable generator like that one. Such a system allows a small generator to punch way, way above its weight class. For an all-gas house like mine with light electrical loads, you get to run the generator an hour a day at the time of your choosing, just to top up batteries. For big loads, the battery starts and carries loads the generator couldn't possibly; the generator's only job is to keep the battery topped up, and it runs at full power/peak efficiency until that's done, then you shut it off until needed again.
It's a sweet combo, really. And most of the time the solar carries it anyway; and when power isn't down, you have the solar backfeed onto the grid via whatever arrangement your power company will accept. So you're making money on the deal too.
You have to look at the various systems available and how they install; many will want a setup like that ATS you have.