Help! Are we getting the run-around?

17 years ago

I posted a question earlier about a poorly functioning Generac standby home generator. Normally, I'd just continue my original thread, but I wanted to be sure to catch your attention again. We just got a call from our electrician with an update. Here's what he said:

1. The presently installed 13 KW Generac generator will only put out 60 HZ when MORE THAN half of the generator's capacity is used. We would never reach that requirement unless our water heater was running. So, during the test run, the generator was only able to put out 57 HZ and that's what caused one of my husband's computers to blow out, the other one to not run at all (just click), and the ceiling fan to buzz loudly.

2. The electricians have installed three similar generators this year, but all installations were for people with wells. The wells use a lot of power & run almost all the time, so those customers were able to meet the half capacity requirement and received 60 HZ power.

3. Generac is coming out with a new model sometime in the next month or so that will kick out 60 HZ whether or not the generator is run at more than half capacity.

Does any of this make sense? The electrician said he's still communicating with Generac and will call us tomorrow with more info. He's suggesting that we send back the present 13KW and install the newer model. We are understandably very wary. Any thoughts, insight, or suggestions are appreciated.

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Comments (2)

billhart
17 years ago
I would expect a generator to be set slightly high in frequency at no load, and slow down a little under load. It might be set for 60.0 Hz at half load, and then at full rated load it would be a little less than 60 Hz. Not the other way around.

My recently acquired 5 kW portable unit goes from about 65 Hz at no load to 55 at full load. I haven't used it enough to have a lot of experience, and have not run anything sensitive on it. Most devices will be ok at 65 Hz. I would start being cautions about the full load condition and 55 Hz.

A ceiling fan should start and run on 57 Hz, probably even 55 Hz, and not buzz grossly more than normal. As I said, my computer is specified to run all the way down to 50 Hz. Frequency changes may trip a UPS into and out of battery mode, but that is supposed to be safe for the computer.

The pump argument is bogus. A well pump, even if it runs a lot, is an intermittent load. Almost no one would use so much water that the pump runs continuously. It will not keep the load continuously above half rating, or any other value. As it turns on and off, it will cause fluctuation in the load and as a result, small fluctuations in frequency.
wayne440
17 years ago
It sounds as if your "electrician" would be well advised to call on someone more familiar with standby generators, and to ask them to properly set the speed of this unit.

The link points to Generac manuals, you will not find any reference to the need for a well pump in any of them...

Here is a link that might be useful: Generac manuals on line
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