Exercising your generator with a load

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Hey Mike, about this tip…

Don’t just exercise the pooch, exercise the generator, too. Fire it up and run it at half-load (or more) for two hours each month.

I just read this Quick Tip in the RV Daily Tips Newsletter, but I wonder just how to run a generator at half-load? And why do I have to run it for two hours? That’s a lot of gasoline and gas costs money. Can’t I just run it for 5 or 10 minutes every month to make sure it’s working? –Joey D.

Hey Joey,
Let’s cover this as a two-part answer. So how and why do you load a generator at 50% power? It’s difficult to turn on enough LED lights to load even half of what a small Honda EU2000 generator can produce, and if you have a 3kW to 6kW genny that’s even more difficult to get enough load.

What we need is something that draws continuous power, can be adjusted to between 750 and 1,500 watts, and doesn’t break the bank. Lucky for us that exactly describes a portable electric space heater you can purchase anywhere for $25 to $40. Here’s a link to a good one on Amazon. I like the ceramic space heaters a lot since they’re compact and have a tip-over safety switch. And many of them have dual-heat settings for 750 or 1,500 watts, which is just perfect for a 1kW, 2kW or even 3kW generator. This one on the left is a 750/1,500-watt version.

So if you have a little 1kW generator like I use for just charging batteries and running my electric hedge trimmer out in the woods, select the 750-watt setting. If you have a 2kW genny, then the 1,500-watt setting would be fine since that would be a 75% load. If you have a 3kW genney, then the 1,500-watt setting on the heater would provide a 50% load. And if you have a 6kW generator with 240-volt output (actually 120/120-volts), then buy a second 1,500-watt space heater and load each 3,000-watt side of the generator to 1,500 watts. Pretty easy, really…

So why is a load really needed and how long do we need to run the generator? Well, what we’re trying to do is get the generator up to full operating temp in order to burn off any water vapor and the resultant acids that build up in the oil. And to do that you need at least an hour of running with the generator producing enough current to make the engine work hard and produce heat. Just idling it doesn’t work really well since it probably won’t come up to full temperature. And the worse thing you can do is run it for 5 or 10 minutes and shut it off, which is just enough time to build up a bunch of corrosive acids in the engine which will eventually rot out the exhaust system and internal oil seals. Nope, if you’re going to start up an engine, then you really should run it for at least an hour. And while running it once a month is the gold standard, I admit to being a little lazy and maybe only starting and running them every couple of months over the summer. But pick your times and put it on your maintenance calendar. 

In any event, follow all safety precautions when running a generator. Don’t do it in an enclosed space to avoid carbon monoxide poisoning. Don’t place the space heater next to anything flammable since it’s surprisingly easy to set things on fire. And don’t run it unattended because if something does go wrong, you want to be close by to deal with it. Pull up a lawn chair with a good book (maybe my book RV Electrical Safetyshameless plug), start up the genny and turn on the heater load. And don’t forget to always check your generator’s engine oil first before ANY startup. Yes, I  know they have low-oil shutoff systems, but generators are expensive and you can keep them running for decades with just a little preventive maintenance. 

At the end of the camping season it’s really best to drain out all the gasoline you can, and run the fuel tank dry. This helps prevent varnish buildup in the carburetor or fuel injector. But if you’re full-timing or otherwise can’t guarantee your generator will be shut down for the entire winter, then add an appropriate amount of a fuel additive such as STA-BIL® Fuel Stabilizer. I’ve used this in my chainsaws and snow blowers for decades since I don’t want to drain out the chainsaw gas over the winter (I live in the woods), and I might not need to use my snow blower all winter after fueling it up in the fall (I live in Maryland). And I regularly use STA-BIL® Fuel Stabilizer in both my 1kW and 3kW Honda generators, which I generally don’t run dry unless they’re very close to empty. But I do run a space heater load on them a few times a year even if I don’t need generator power for anything in particular. That way if there’s a power outage or I need AC power in the woods I can guarantee a quick start … and that always works for me.

Let’s play safe out there….

 

Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

##RVT834

 

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Tom

My portable gensets are run on ‘real’ gasoline. All my small engines also. Unfortunately, cannot do that with the installed set in the RV.

Mike Sokol

Note that I said “gold standard” is a monthly run, which is what home backup generators are often set up to do. The key is that if you have a portable generator and it’s not run for a year or more, then the chances it will start when you need it goes down.

Steven Scheinin

Is the same true for propane powered generators?

Debby Clark

In a Class A motorhome with a 8KW generator, wouldn’t running both air conditioners while the generator was on create sufficient load, vs me going out and buying space heaters? I’m assuming that testing the generator each month for an hour at a time under load applies here also?

Barry

Additional, the windings inside the generator portion will develop rust over time. Running a generator until fully warmed with a 50% or greater load will assist in keeping the electrical windings free of moisture and therefore rust.

Frank

For full timers, who do not boondock, this monthly exercise regimen is not doable, as most campgrounds prohibit generator use.