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Old 10-09-2014, 19:27   #1
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Boat: Tayana 58 DS
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Generator Voltage Monitoring Relay Needed?

I recently had the voltage monitoring relay control fail. It monitors the output of the generator (Fisher-Panda 11kw) and only allows it to connect to the boat's AC system if it is 230V +/-. If the voltage varies above or below a certain point (30%?) the control is supposed to shut off the relay that connects the genset. It failed, and the monitor was flipping in and out, even though the voltage varied by 1% or so.

It got me to thinking... how important is this voltage monitor? It seems to have a fairly wide operating range (when it works) -- maybe 30% or so. I don't see much variation at all in the generator output. I suppose it could cause a problem with the appliances if they were under/over voltage, but I've never had a problem with that and there is a voltage gauge.

Do others have a over/under-voltage monitoring control on their genset? If so, or if not, have you needed it? Ever hear of a genset running wild and ruining appliances (watermaker, washer/dryer, A/C, dishwasher, battery charger, ...)?

Thanks in advance.
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Old 10-09-2014, 19:41   #2
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Re: Generator Voltage Monitoring Relay Needed?

According to a F-P brochure, the base units have a tolerance of +/- 8% of nominal output voltage, and the deluxe ones have the 'VCS' regulation which holds the voltage to +/- 3v (!!) of nominal.

So, is it a protection relay control, or this more elaborate regulator that has failed?

Given the price of the generator, and the value of your AC loads, it's probably wisest to simply get the genny repaired back to factory spec. If you run without the relay functioning, and it goes wild and fries a bunch of AC gear, your insurance company may not take kindly the fact that you bypassed the relay
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Old 10-09-2014, 19:55   #3
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Re: Generator Voltage Monitoring Relay Needed?

Quote:
Originally Posted by Lake-Effect View Post
According to a F-P brochure, the base units have a tolerance of +/- 8% of nominal output voltage, and the deluxe ones have the 'VCS' regulation which holds the voltage to +/- 3v (!!) of nominal.

So, is it a protection relay control, or this more elaborate regulator that has failed?

Given the price of the generator, and the value of your AC loads, it's probably wisest to simply get the genny repaired back to factory spec. If you run without the relay functioning, and it goes wild and fries a bunch of AC gear, your insurance company may not take kindly the fact that you bypassed the relay
Thanks for your quick response. I probably didn't explain the situation well enough.

The voltage monitoring relay that failed isn't part of the generator -- it is part of the boat's electrical system. After the generator there is a circuit breaker (50A/240V), then a selector (generator/off/shore power), then this monitor, which energizes a momentary switch, which, if flipped, energizes a relay, which enables the AC system to be powered by the generator.

If the generator is already regulated to +/-8%, why add an external +/-30% guard on it -- especially since the guard is so prone to fail?
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