grsthegreat

I was called to 3 residences. 2 of the units were less than 4 years old and one was a 2013 model. All 3 were continuing to operate but hunting or surging constantly after about 2 to 3 minutes of normal running. Would continue to surge even with gen main breaker open. I used a monometer on 2 of them and the problem was before the generator. All regulators were free of snow, but temps were about 0F wind chills. Blowing snow and 20 mph winds. I figured the problem was primary tank regulators. All 3 tanks had at least 70% fill. I tried warming up regulators and it helped a bit, but did not end problem. 


here’s the kicker. By turning the fuel selector knob about 1/6 to 1/4th the way towards natural gas side the unit ran great. 60 HZ, 240 V output and averaged 3600 rpm under load.

if I tried to turn it back to full propane...it surged.

im at a loss. I left the settings to allow operation throughout outage... figured it can’t hurt. But I’ve never seen this before.

any ideas

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Cobranut
grsthegreat wrote:

I was called to 3 residences. 2 of the units were less than 4 years old and one was a 2013 model. All 3 were continuing to operate but hunting or surging constantly after about 2 to 3 minutes of normal running. Would continue to surge even with gen main breaker open. I used a monometer on 2 of them and the problem was before the generator. All regulators were free of snow, but temps were about 0F wind chills. Blowing snow and 20 mph winds. I figured the problem was primary tank regulators. All 3 tanks had at least 70% fill. I tried warming up regulators and it helped a bit, but did not end problem. 


here’s the kicker. By turning the fuel selector knob about 1/6 to 1/4th the way towards natural gas side the unit ran great. 60 HZ, 240 V output and averaged 3600 rpm under load.

if I tried to turn it back to full propane...it surged.

im at a loss. I left the settings to allow operation throughout outage... figured it can’t hurt. But I’ve never seen this before.

any ideas



The fact that it's happening on three different units suggests something environmental or fuel related, especially with the fuel selector making that difference.
Is it possible all three had tank fills from the same fuel supplier?
Perhaps another gas like butane was blended into the LPG.  Butane has a lower vapor pressure than LPG and can be an issue at cold temps.

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78buckshot
Hi grsthegreat, by chance are the generators 20-22kw? Those are the models that I have the most issues with in terms of surging. We have very few LP generators in our customer base but I have adjusted the fuel pin on natural gas units with the same results as you have noted.
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Peddler
Are the generator regulators vented by a pipe or tube that goes underground back away from the regulator.  Many times I have seen any vent with a trap in the vent line get water in that line and it starts moving back and forth causing a fuel surge,  If you have a piped vent try just loosening the cap on the regulator which will allow it to breath at the regulator.
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grsthegreat
I never thought to ask who supplied fuel, but since all are within 15 min drive from each other it’s possibly same supplier. The vents were not piped away from the regulators at all. Regulators were 5 feet from units. The 2 newer units were 22 and the older unit was a 14 kw.

ill be interested to see if issues resolve themselves when it warms up next week.  Then I have to figure out whether or not to reset the fuel pin to fill propane or leave them alone.
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restosud
did you try to open the airbox partially? usually smooths out the 20/22kw.

Have a 20kw on natural gas that does this all the time.throttling the gas valve cures it.
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78buckshot
Did you happen to notice any frost forming on the regulators, propane makes a good refrigerant and will evaporate below 32 degrees and create ice. If the regulators or the LP has any water in them it will freeze and restrict the flow.
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grsthegreat
restosud wrote:
did you try to open the airbox partially? usually smooths out the 20/22kw.

Have a 20kw on natural gas that does this all the time.throttling the gas valve cures it.
Yes, the air box removal did not help. the only thing that worked was moving the fuel selector pin.
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