Thread: Power back on
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Old 10-19-2019, 09:51 PM   #25
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The National Electric Code requires a fused (or circuit breaker) disconnect where the service first enters the building (with a few exceptions which wouldn't apply to a private home.) This would have to be ahead of any automatic transfer switch. The generator output also has to have a disconnect and protection, but that is likely part of the generator.

Without the utility protection, you would have a serious fire and shock hazard in the transfer switch. The utility feed in many cases can provide far more current than the wiring to the transfer switch can carry, if there is no protection.

It is possible that for residential transfer switches, that the disconnect and protection is attached to the transfer switch.

You would be wise to get an electrician to spend a little time with you to determine and explain what does what in your system. And then make labels (actually required by the code) for each disconnect or circuit breaker.

While you want to "exercise" your generator weekly for 20 minutes or so, that is typically with no load, which will not disclose many generator problems. (and you also need to look at the hours indicator on the generator fairly often and log it, so that you know that it actually ran for the test if you weren't there.)

As others have said, the only true test is to pull the utility disconnect simulating a power failure, and verify that the genset picks up the load. Let it run for a half hour or so, then turn the utility disconnect back on. The power should switch back in a few seconds, and the generator should run for 10 or 20 minutes unloaded before shutting off. Make sure it shuts off, another well known issue.

The issues with genset failures are fairly often transfer switch issues, not genset issues. The transfer switch is exposed to power surges from the utility, like lightning, and they all have solid state sensors in them. You may have to install a good sized surge protector to attempt to protect the transfer switch from being zapped. The transfer switch, if outdoors also has to be protected from water infiltration.

Also, the generator engine has a battery to start it, and that battery must remained charged. If the weekly exercise doesn't run it enough to keep the battery charged, the installation will need a trickle charger, and then the danger becomes overcharging. Kind of like your boat engine if you don't run it that much.

I work part time as Chief Engineer of a couple of radio stations, and I can tell you that gensets and transfer switches, while very necessary in that business, can be a real PITA to keep maintained.

I'd also suggest at least two PM visits by a qualified service contractor, one in summer, one in winter.
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