Generac PP5000 generator output voltage

Old 12-10-15, 10:15 PM
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Generac PP5000 generator output voltage

I have a 19 YO Generac 5000 watt self-excited portable generator powered by a Tecumseh HM100-159436P. I've always run this generator at a no load speed of 3600 RPM but found that the RPM and voltage drooped considerably when under load.

I recently came across the spec sheet for the Tecumseh engine. According to the specs this engine should have a no load speed of 3750 RPM so I readjusted the no-load RPM to 3740 RPM and applied various loads, here are the results:

No load 3740 RPM 126.0 Volts @ 62.3Hz
1600 watt resistive load 3725 RPM 122.6 volts @ 62.0 Hz
3500 watt resistive load 3545 RPM 116.5 volts @ 59.0 Hz
5100 watt resistive load 3475 RPM 106.6 volts @ 57.9 Hz
Oil fired Furnace 3740 RPM 126.0 volts @ 62.3 Hz
1/2 HP Grundfos well pump 3735 RPM 122.9 volts @ 62.2 Hz

Weird thing about the furnace is when it kicked on I didn't really notice any voltage or RPM droop it pretty much stayed at the 126 volt 3740 RPM range?

Couldn't dial in the governor any better, if I adjusted the governor to give me 3600 RPM with a 3500 watt resistive load it would over shoot 3750 RPM when the load was removed. Considering the 3500-watt load is my water heater and a managed load I didn't want to push the RPM any further. The majority of the time the generator will be running lights, fridge, and furnace in the winter with the occasional well pump kicking in.

Does this sound about right? Your thoughts are welcome.
Old 12-11-15, 06:07 AM
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I would say it's doing quite well for a small portable generator.
Old 12-11-15, 06:19 AM
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That's similar to what I've seen with other old generators. Some have been better than others but they all seem to drop to some extent under load. I had a really old one that under heavy load the frequency would be so far off that the picture on a tv (old CRT style) would roll depending on the generators load.

I assume your furnace didn't have much affect is because it doesn't draw much power. Many furnaces operate off a 15 amp 120 volt circuit with room to spare. Your furnace might only be pulling 500 watts. A far lighter load than your 1'600 watt test load.

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