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Old 01-23-2016, 09:06 PM   #1
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Exercising the generator

Good article by a man who knows generators.

Key points: minimum 2 hrs./month (good to remember even when always or generally plugged in...and in the winter even if batteries out); and minimum 1/2 load.

RV DIY Article – Why & How To Exercise RV Generators | RV DIY® Channel with Mark Polk

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Old 01-23-2016, 09:24 PM   #2
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I have a Guardian house generator that exercises every week on the time and day that I set it and it runs for twelve minutes not under load and that's the way It's set up at the factory.I run my rv gen about once a month for about 20 minutes, sometimes under load and sometimes not. I keep my MH in a storage yard and I'm not going to sit there for 2 hours, seems like a waste of time and gas.

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Old 01-23-2016, 11:14 PM   #3
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I agree, 2 hours a month is a waste of time, fuel and engine. Overkill.
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Old 01-24-2016, 02:00 AM   #4
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That is a bit overkill. I fire mine up for about 30 minutes every 2 months under a small load.

I don't worry about bad fuel. A double dose of Stabil is all it needs to be ok for a year. I have 10 month old fuel in my snowmobiles and they ran just fine last weekend on our first trip out.

The reaal reason to run a generator is to avoid losing the "field" My parents learned this the hard way during a bad storm when their backup generator started, ran fine, but didn't generate any electricity. Good thing dad was sharp enough and knew how to flash the field using a cordless drill attached a corded drill that was plugged into the generator 120v outlet.

I do not know if loss of field excitation is an issue with inverter generators...not sure I'm not smart enough to know.

Regardless 30 minutes every couple of months is all that I ever do and I never had had a generator problem yet.
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Old 01-24-2016, 02:22 AM   #5
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yes, loss of the field coil magnet's magnetism is a big issue, but so is general corrosion of the entire armature if it sits in a high moisture area for extended periods. the engine itself isnt going to fair too bad if its got stabilizer in the fuel.

just running the generator from time to time is better than nothing, but it is always best to run it under at least 50% load to allow the engine and the armature to achieve operating temperatures.

The old trick of backfeeding power into the genset (usually via driving an electric motor with another power source) is only viable on most conventional generators. this wouldnt work on an inverter generator, but that being said inverter generators arent as susceptible to losing magnetism as a conventional generator. on the old engine driven welders that sat for a while we used to have to pull out the booster cables and give the field coil a zap to get it going lol

Either way, i would recommend running a genset AT LEAST every 6 months (in a moderate climate, more often in a humid environment) or any other engine for that matter.... Engines and attachments were designed to be used, let them sit and gaskets, seals, and bearings will all suffer.
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Old 01-24-2016, 04:08 PM   #6
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Exercising the generator

Obviously people will do whatever they want. But here it is directly from Cummins Onan:


Exercising Your Generator

It may seem surprising that “not” using a machine could cause performance problems, but with RV generators that’s exactly the case. Regular “exercise” is an important part of keeping your generator healthy. Lack of exercise can cause moisture build-up and fuel system degradation that make it run poorly. In fact, in as little as 30 days, the fuel in gasoline-powered generators can begin to gum and varnish the fuel system. Fuel varnishing results in hard starting and surging. (A surging generator never settles at a stable operating speed.)

To prevent such problems, it is recommended to run gasoline generators at a minimum of 50 percent capacity (2000-watts, or one air conditioner for a 4000-watt set) for two hours once every four weeks. This is necessary to help keep moving parts lubricated, expel moisture and control fuel varnishing in the carburetor. A long two-hour exercise period is preferable to several short periods. While traveling, this can be accomplished by running the air conditioning. If you own a diesel generator, regular exercising can help reduce internal condensation and helps keep seals lubricated.


The cost for a 3.6K LPG unit for 2 hrs. @ 1/2 load is about 1.2 gal. @ $2.85 or about $3.40. For a 4K gas unit, 2 hrs. @ 1/2 load takes 1 gal. @ $1.65. Based on Cummins Onan average consumption figures and current local prices.

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Old 01-29-2016, 07:15 AM   #7
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In commercial applications such as phone companiy facilities and water authorities they automatically exercise their generators under full load weekly or bi-weekly. The reason: They require reliability.

Some of those Onan carbs can't be rebuilt so I figure I can burn a lot of gas before I match the price of a new carb.
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Old 01-29-2016, 07:37 AM   #8
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I run mine about 30 mins per month. It's very cold in Michigan so the only thing I can think of loading it with is a space heater although I haven't done that yet. It's stored in the driveway until spring.
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Old 01-29-2016, 07:39 AM   #9
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I drain the carb of gas in my 3 gennys after I fog them. I haven't had a problem yet,(knocking on my head). I have an Onan and 2 hondas.
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Old 01-29-2016, 08:04 AM   #10
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I had my carb modified to run on propane as well as gas. Runs much better, spark plug lasts forever, oil does not get as dirty and no bad gas to deal with. One 20 lb propane tank is roughly equal to 5 gallons of gas.

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