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Onan Generators

Onan Gen Shutdown


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  #1  
Old 02-11-2014, 12:25:14 AM
mech1369dlw mech1369dlw is offline
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Default Onan Gen Shutdown

I have read a few times about not letting the generator shut down while under load by running out of gas. Why? What happens that is so bad about this happening? just curious. Thanx
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Old 02-11-2014, 12:34:53 AM
Jim Marcozzi Jim Marcozzi is offline
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Default Re: Onan Gen Shutdown

Quote:
Originally Posted by mech1369dlw View Post
I have read a few times about not letting the generator shut down while under load by running out of gas. Why? What happens that is so bad about this happening? just curious. Thanx

It can:

Kill the residual magnetism that's required to start generation
Overload the regulator since it will go full field to try to compensate for low output
Damage the load due to spikes, low voltage or incorrect frequency

I'm sure others will add
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Old 02-11-2014, 08:36:25 AM
Wayne 440 Wayne 440 is offline
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Default Re: Onan Gen Shutdown

In addition to the possibilities Jim mentions, add "considerably lighten one's wallet".
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Old 02-11-2014, 10:06:19 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan Gen Shutdown

The older ones with out regulators are not effected as much as the ones with them. It doesn't always damage them. But you want to avoid a loaded shut down as much as you can. Don't need to see the magic smoke come out.
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Old 02-11-2014, 10:34:48 AM
Leon N. Leon N. is offline
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Default Re: Onan Gen Shutdown

Shutting down a Magneciter designed generator under load will not damage this style generator but it may do harm to the connected loads. Just not a good idea to abuse your refrigerator compressor or even the TV. As mentioned already, it may damage the later designed Onan voltage regulator controlled generators.

Nevertheless, back in 1970 I designed and successfully installed my own version of a generator shunt trip device for the very reasons mentioned above. There are all kinds of so called shunt trip devices. However, mine monitors the generators frequency. When the frequency is within spec limit, + or - 3 hertz, a contactor closes there by making the 120/240 output available. The circuit is also damped to prevent nuisance tripping.

Leon
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Old 02-11-2014, 10:42:15 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan Gen Shutdown

They call that roll off protection now of days Leon. Sure saves some money
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Old 02-11-2014, 04:27:10 PM
Isaac-1 Isaac-1 is offline
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Default Re: Onan Gen Shutdown

Thanks for bringing up this topic, it reminded me that I had a 200 amp shunt trip molded case breaker laying around, maybe I will use it to build a safety out of range (high / low voltage or frequency) trip for my MEP-003a since they tend to go high voltage on AVR failure.
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Old 02-11-2014, 05:04:51 PM
scoops scoops is offline
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Default Re: Onan Gen Shutdown

Quote:
Originally Posted by Leon N. View Post
Shutting down a Magneciter designed generator under load will not damage this style generator but it may do harm to the connected loads. Just not a good idea to abuse your refrigerator compressor or even the TV. As mentioned already, it may damage the later designed Onan voltage regulator controlled generators.

Nevertheless, back in 1970 I designed and successfully installed my own version of a generator shunt trip device for the very reasons mentioned above. There are all kinds of so called shunt trip devices. However, mine monitors the generators frequency. When the frequency is within spec limit, + or - 3 hertz, a contactor closes there by making the 120/240 output available. The circuit is also damped to prevent nuisance tripping.

Leon
I'd be more interested in what you built Leon.
Care to share how it was constructed?
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Old 02-11-2014, 05:13:57 PM
Leon N. Leon N. is offline
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Default Re: Onan Gen Shutdown

Scoops, yes think I can assemble some information. I am not a computer wiz, but I will see what I can do.
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Old 02-11-2014, 05:32:27 PM
grif grif is offline
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Default Re: Onan Gen Shutdown

Quote:
Originally Posted by Leon N. View Post
Scoops, yes think I can assemble some information. I am not a computer wiz, but I will see what I can do.
Is that schematic from the Radio Amature Handbook for a voltage controlled trip using a GFI still floating around here?
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