Running home generators under load

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goldstar

goldstar

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Electrical Contractor
This is somewhat related but I didn't want to pirate this thread away from the OP because it looked like the conversation was going in another direction:

Running Generator Under Loaded

Does anyone know if there is any negative outcome in running reciprocating natural gas generators under loaded? I know diesel units will wet stack and fail very premature however I can't find anything regarding natural gas units.
forums.mikeholt.com

In Nov of 2018, I serviced a 22KW Generac generator at a customer's house. When I drained the oil it came out looking like chocolate milk. I checked with my service station mechanic and he advised me to flush the engine and install new oil, so I did. When I went back this past November to do the service and drained the oil it again came out the same way. I checked with a Generac dealer who told me that if the unit only runs for 10 minutes a week and never under load that moisture can build up in the oil pan. The unit has to run under load occasionally to prevent this.

Has anyone else run into this situation ?
 
goldstar said:
This is somewhat related but I didn't want to pirate this thread away from the OP because it looked like the conversation was going in another direction:

Running Generator Under Loaded

Does anyone know if there is any negative outcome in running reciprocating natural gas generators under loaded? I know diesel units will wet stack and fail very premature however I can't find anything regarding natural gas units.
forums.mikeholt.com

In Nov of 2018, I serviced a 22KW Generac generator at a customer's house. When I drained the oil it came out looking like chocolate milk. I checked with my service station mechanic and he advised me to flush the engine and install new oil, so I did. When I went back this past November to do the service and drained the oil it again came out the same way. I checked with a Generac dealer who told me that if the unit only runs for 10 minutes a week and never under load that moisture can build up in the oil pan. The unit has to run under load occasionally to prevent this.

Has anyone else run into this situation ?
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He's correct, also moisture (condensation) enter crank from air filter through the crankcase vent. This is a known issue that in cold climates actually will ice up to the point that generator will stop working or may not start. Here Generac encourages installation of air intake heater as well as crankcase and battery heater. Mostly is about ease of starting, but may help with regards to moisture buildup.
 
I’ve heard of this happening (engine is never run up to normal operating temperature and get condensation in the crankcase), but have never seen it personally.
I would inspect the coolant level just make sure there isn’t a leaking head gasket.
 
This is an air-cooled unit on the north side of the house where it's very shaded. Also, I forgot to mention that the unit keeps shutting down due to low oil pressure. I went back to check the oil level and it was OK and clean. I'm guessing that the oil pressure switch may be defective. I thought it might be due to the moisture but that wouldn't make sense after only two weeks of operation with new oil.
 
goldstar said:
... I'm guessing that the oil pressure switch may be defective. I thought it might be due to the moisture but that wouldn't make sense after only two weeks of operation with new oil.
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It might not be defective, per se, but it might be fouled with your water-oil emulsion. Don't guess; check it with a well-calibrated pressure gauge.

New Jersey is a cold and humid climate, for sure, but that's not a sufficient explanation. Other engines in this same climate don't have this problem. Being on the north side of the house and shaded is irrelevant; every other similar engine is shaded by virtue of being in a cabinet.

Ten minutes might not be enough time to raise the oil temperature and drive off accumulated moisture, and might even be making matters worse. Combustion gasses contain H₂0, some of which blows by the piston rings and ends up in the crankcase. Does this engine have a simple crankcase vent or positive crankcase ventilation? It's not likely that a significant amount of moisture is getting into the crankcase via the crankcase vent when the engine's not running; there's very little pressure differential available to move air in or out.

My suggestions:
Check the compression and oil pressures. It might be just a worn-out engine.
Check the oil temperature after five, and after ten minutes of exercising without a load, to confirm that ten minutes isn't adequate.
Change the exercise schedule so it runs longer and less frequently. Schedule it at daybreak, when there's the least amount of water vapor in the air.
 
The owner can do a manual start, say monthly, and run it for, say, 30 minutes.

Or, trip the ATS main and run the generator loaded for the same half hour or so.
 
drcampbell said:
It might not be defective, per se, but it might be fouled with your water-oil emulsion. Don't guess; check it with a well-calibrated pressure gauge.

New Jersey is a cold and humid climate, for sure, but that's not a sufficient explanation. Other engines in this same climate don't have this problem. Being on the north side of the house and shaded is irrelevant; every other similar engine is shaded by virtue of being in a cabinet.

Ten minutes might not be enough time to raise the oil temperature and drive off accumulated moisture, and might even be making matters worse. Combustion gasses contain H₂0, some of which blows by the piston rings and ends up in the crankcase. Does this engine have a simple crankcase vent or positive crankcase ventilation? It's not likely that a significant amount of moisture is getting into the crankcase via the crankcase vent when the engine's not running; there's very little pressure differential available to move air in or out.

My suggestions:
Check the compression and oil pressures. It might be just a worn-out engine.
Check the oil temperature after five, and after ten minutes of exercising without a load, to confirm that ten minutes isn't adequate.
Change the exercise schedule so it runs longer and less frequently. Schedule it at daybreak, when there's the least amount of water vapor in the air.
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Thank you. All great information and advice but far more time and investigation than I want to spend on this. I no longer install whole house generators (that's a long story for another time). I only do first echelon maintenance for my existing customers for whom I did whole house generator installations. That said, I'll pass this along to a maintenance company.

BTW, the engine shows as having only 39 hours on it. Unless it was a defect from the beginning the chances of the engine blowing are slim.

The unit is set to exercise at 3:00 PM every saturday. I'm thinking you would have to be an authorized dealer in order to change the length of exercise time.
 
Mine is a different brand (Honeywell) and it's set at 30 min every week. I live in north Idaho and near zero temps are normal in winter. No heaters. Always starts fine and the oil is clean when I do a tuneup. I'd say the run time long enough to get it hot is why.
 
LarryFine said:
The owner can do a manual start, say monthly, and run it for, say, 30 minutes.

Or, trip the ATS main and run the generator loaded for the same half hour or so.
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Thanks Larry, I'm sure she can do that but she's a single mom. Asking her to go outside when there's 2' of snow on the ground just to exercise the unit is a bit overkill, especially since she probably paid about $14K to get the unit installed. Kind of like asking someone to go out and start their brand new Cadillac because there's moisture in the oil and that's the only way they can think of clearing the problem.
 
A separate timer at the transferswitch could be installed, the thing with Generac though, is it will transfer the load too, but then she may recoup some of the loss on the power bill.
 
I know the OP stated it looked like chocolate milk. Not sure but don’t confuse this with what may just be the pre-lube (which in most cases is white) mixing with the oil. It does take a few oil changes to clear this up.
 
Is this a gasoline-fueled or propane? Oil dilution is far less of an issue with propane.
But yes, getting up to temp is an issue.

GA aircraft, air cooled, have this issue. You have to get the oil temp up to boil off the water that has been absorbed. You do that by leaning the mixture to raise the engine temp. They at least run under load.

Synthetic oil usually has fewer issues if approved.
 
This is a natural gas unit. The motor oil is 5W-30 synthetic. This is not pre-lube mixing in with the oil. This is the 2nd time this has happened in 2 years. I've referred the HO to call an authorized generator service co. to look into the problem. If I hear about the outcome I'll post it here.
 
10 minutes loaded or not is not long enough to boil off water that naturally ends up condensing there or blowing by the pistons and it keeps building up each time it only runs for this short time. If anything more frequent oil change might be necessary.
 
I am not an engine mechanic but it sounds like water in the oil. Since it is an air cooled unit, it seems likely the water is either a combustion product or coming from the air it is using. I can't think of any way short of running it long enough to get the oil warm and then running it until the moisture is gone that would solve such a problem, unless you could install an oil filter that removes moisture.
 
petersonra said:
I am not an engine mechanic but it sounds like water in the oil. Since it is an air cooled unit, it seems likely the water is either a combustion product or coming from the air it is using. I can't think of any way short of running it long enough to get the oil warm and then running it until the moisture is gone that would solve such a problem, unless you could install an oil filter that removes moisture.
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all internal combustion engines are subject to condensation inside. Short run times is going to make it worse, it never heats up enough to boil off water already in the oil, and more condensation can form when it cools back down. Do this every week for 5 minutes and not change the oil for two years - you possibly get a lot of water in the oil even though there isn't that much accumulated run time. Some locations will be worse than others just depends on conditions.

Even automobiles often is recommended to change oil every XXXX miles or three months whichever occurs first. This is the reason why the three months. Now if it isn't run at all and is stored in non condensing environment that maybe can change things.
 
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