Block heater for a Natural Gas Standby Generator (38 kW Kohler)

[Number_35]

Starting at least 15 years ago, GM's block heaters (sold here) have had a thermostat in the cord that does not enable current flow to the heater until the ambient temperature is -18°C (0°F) or colder, so you might want to limit your block heater use accordingly.

As far as how long to run a block heater, it's a case of diminishing returns. Much of the increase in coolant temperature is realized in the first hour (approximately 50%), around 75% after two hours, and 90% after three hours.

There's no gain after four hours.

Is there any way you could monitor coolant temperature on cold days, and experiment with different block heater run times to see how long it takes to get the coolant temperature up to 0°F?

When I park outside at -30°C (-22°F) and use the block heater, the coolant temperature maxes out at about 21°C (70°F), much warmer than GM thinks is necessary. That's a rise of 51°C (124° F) in four hours, so one hour (with an estimated coolant temperature increase of 25°C (77°F) would have been quite adequate.

Your results will differ, of course, depending on the wattage of your block heater, coolant capacity, engine architecture, etc.

 

[2.7ecoboostFordBronco]

I can certainly experiment! even though I’m in Alaska the winter temps where I live are pretty mild, (avg January low is ~10F). I’m inclined just to leave it off unless it gets below 0. The generator does have a control panel where I can see oil temp,etc.

The electrical contractor I had come out to service the generator recommended that the block heater stay on below 30F. I didn’t want to argue but that just seemed a little warm for it to me and I wasn’t sure it would be worth $1000/year to do that (that’s how much grid electric it would cost, to run the block heater for half the year, approximately).


BTW, this is the plug the block heater is attached to, is this a thermostat controlled extension cord? There are almost no labels on it the cord, and if it is thermostat controlled it must be set to something around 40F or higher because it has transmitted power continuously for the last 6 months. I guess I could bring it inside and test.

 

[tcp71]

I doubt that has any thermometer functions. It's just an extension cord with 3 outlets.

 

[dnewton3]

I am interested in all this in part because there is an impending volcanic eruption where I live and I want this thing in good working order, and am trying to source a stockpile of air filters. Kohler only seems to sell these in a kit that comes with their branded oil, oil filter, and spark plugs, so I'm going to have to back-source a filter of this size; took it to Napa and they were able to back source it as a 253107.

This is an interesting problem most of us don't consider; volcanic ash in the air. Should this happen, I should think that traditional filter-media filters would be nearly worthless, as they would clog quickly in times of very high airborne debris (ash; dust; etc).

I would think that maybe a better set-up would be some kind of very high-end cyclonic filter system. Ones that essentially spin the incoming air and use centrifugal force to push the debris to the outsides of the housing. There were some (very few) automotive applications like this. One that comes to mind is the air filter for the Ford Focus of the early 2000s. It was a lifetime filter; non-serviceable. Very elaborate intake tract. Or, there are some made for off-road equipment (dozers; excavators; etc). Or agricultural tractors. These are made to operate in very high dust conditions.

One thing's for sure ... if a volcano goes active in your area, that expensive generator is likely to screech to a halt quickly if it doesn't have a very, very good air filter system. The massive amount of silica and ash would just ravage those cylinders with no hesitation whatsoever.

 

[2.7ecoboostFordBronco]

I called Kohler and they had no recommendations for ash. They did explain that the block heater is set to operate automatically when the coolant temp falls below 80F and shuts off when the coolant gets to 100F. Apparently at outside air temps of ~45F or less this means it will be on almost all the time, at least for my installation.

Mechanics around here swear by panty hose as ash pre filters. Maybe I could somehow tape some panty hose material to the air intake vents as a pre-pre filter, or at least around the air filter housing.

Or, might be best just to shut it down unless the cold from lack of furnace heat gets unbearable in a power outage. I hope that the power grid won’t go down and it wouldn’t be an issue, but I’m not going to count on that.

 

[road_rascal]

Goodness… the fuel burn on these must be incredible??? Who manufactured the engines? Twin turbo V12?

Power Solutions International. This generator is one of our main backups in case the grid goes down.

 

[2.7ecoboostFordBronco]

It was only 25 F outside so I figured I’d let it start cold as a test during its scheduled exercise. As expected, no issues. Oil pressure was 60 after start up and dropped to 50 psi at the end 20 minute bi-monthly exercise. Coolant temp started at 25 and was 160F at the end.

 

[YB1111]

Two hours of preheating in winter should be enough, especially since you’re using 0W-30 oil—it flows better in the cold. For summer, I don’t think you need to keep the block heater plugged in at all. My habit is to unplug it from May to September. Saves power and keeps things simple