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

[2.7ecoboostFordBronco]

Hello, I have a 2013 Kohler 38RCL 38 kW standby generator. It contains a GM 4.3L 6 cylinder "VORTEC" engine, similar to one that came in GM Vans/Light trucks around 2013. It came with a house that I bought and runs on natural gas. My electric bills were $600 USD/mo when I moved in, which I was in part able to track down to the generator's engine block heater. It was plugged all the time and using 20 kWh per day, or about $150/mo in electric bills. The generator starts itself once a week for 20 minutes for maintenance. I've since purchased a smart plug and programmed the block heater to come on 2 hours before the scheduled weekly start, then to shut down after it starts. It also has a battery maintainer but I will keep that on all the time

My questions:

Considering I average ~10F temperatures at noon (when it starts) in the winter, is 2 hours of preheat time sufficient for the block heating? At 60F average in the summer, is there any benefit to the block heater or should I just unplug it in say, May, then plug it back in around September? I know this amount of preheating would not really be necessary on a modern car engine (upon which my generator is based), but I wasn't sure how the natural gas aspect of this motor could affect the need for preheat.

Since the generator does start up and rapidly apply throttle during a power outage, am I risking generator damage by not keeping the block heater on all the time in winter for unexpected power outages? Of course if there is an impending wind or ice event I could pre-emptively turn the pre-heater on to keep it ready, then put it back on the normal schedule when conditions subside. I am using a 0W-30 oil to cope with the cold temps (this is in south central Alaska).

Lastly, since this is natural gas, what maintenance considerations are there beyond what I'm familiar with on a car engine? Do spark plugs really need changing every year? What about the air intake filters? I will change the oil and oil filter every year regardless of how much it was used. Using HPL PP PCMO 0W-30 and a premium guard XL cartridge filter.

Thanks in advance!

 

[walterjay]

How many RPM does the gen run at?

 

[2.7ecoboostFordBronco]

How many RPM does the gen run at?

1800 RPM according to the spec sheet.

Here's details of how it does the weekly exercise (which is actually only 20 minutes, apparently)

Kohler 38RCL manual

 

[dnewton3]

The easiest way to know how well the 2 hours of preheat is working is to get an inexpensive thermal gun and take a few temps around the block when it's cold, and then see how much it warms up as the block-heater warms it.

As for the spark plugs, pull them and give them a good look over. Anyone who can change their own oil should also know what decent plugs look like.

The air filter is likely fine unless you're in a very dusty area. Get an air-intake gauge and install it. Change by the gauge and not hours.

 

[hemitom]

Summer no need to plug in at 60f. Actually I would not use the block heater until temps got down to around 0f
2 hours of block heater time should be sufficient .
Can you program the maintenance run time ? every second week should be sufficient .

 

[twX]

The main reason that industrial standby generators have some pretty powerful block heaters that are always powered on is to ensure that the engine can make sufficient power almost immediately after starting up, which a cold engine may not be capable of. The engine also needs to be able to start reliably, but the heaters are usually a lot more powerful than necessary for this.

For a residential application with an oversized generator an no big motor starting loads, you really just need to keep the engine warm enough for reliable starting, but a bit of extra heating will be better for the engine. With that 800W heater, 2 hours should be enough heating time in the winter.

For random starts due to power outages in the winter, you might consider running the heater continuously, but at a lower power level. A timer set to run the heater for ~15 minutes every hour should keep the engine warm enough to start reliably without using too much power. You could wire this up in parallel with the timer you use for exercising, so that you still get full heating before a scheduled start. If the engine starts reliably with no preheating at 10F, maybe you don't need to worry about this. A heated battery blanket will only use 50 to 80 watts and might help with starting.

 

[ElectroMechanoMan]

There are some good solutions for this problem. First, I would try to start the unit at cold temperatures without heat. If it does, you may not need heat. You could go to a lower wattage heater. If you run synthetic oil, 30-40 degrees should be warm enough. Another idea was installing a thermostat that would only turn on heat below a certain temperature. We do this at the mill on outdoor gear boxes that require the oil to be warm, plus we use low wattage heaters that remain on all winter, but they are only 100w heating 30 gal of oil. Warm enough to run, cool enough to keep the oil from coking on the heater she’ll.

 

[Kurtatron]

Seems so counterintuitive to “exercise” a machine every week. I’d think that causes more engine wear than just keeping it off. Machines are not muscles. They don’t atrophy sitting around, they just get brittle and leak. If it were mine, I’d let it sit until the time comes for an outtage. Maybe exercise it every month? Seems so strange to me.

 

[mitsuman47]

Seems so counterintuitive to “exercise” a machine every week. I’d think that causes more engine wear than just keeping it off. Machines are not muscles. They don’t atrophy sitting around, they just get brittle and leak. If it were mine, I’d let it sit until the time comes for an outtage. Maybe exercise it every month? Seems so strange to me.

Agreed. Monthly seems much more reasonable.

 

[ElectroMechanoMan]

That is a self check to assure all systems are ready. We have a generator at the mill to provide backup power to the control system during an outage that does it. If it fails to start we get an alert and repair the problem.

 

[mk378]

Are natural gas engines hard to start in cold weather? I would think it isn't like gas or diesel since the fuel is already a vapor. It would be important to keep the battery warm.

 

[tcp71]

I wouldn't worry about block heaters unless it's below -30C, especially on a natural gas unit. It's not like you have to create an aerosol out of a liquid or have to worry about propane vapor condensing at -25C. Keep the battery up, use a 0w30 oil and fire it up when it's needed.

Block heater outlets at commercial sites here cycle on/off every 2 hours to reduce the load. Half the outlets in a parking lot run 2 hours, then the other half run 2 hours. That's enough to start cars in very cold temperatures.

Natural Gas:

 

[jjblbi]

You will want to check your recommended oil spec, some natural gas generators take special oil. Don't forget to exercise the transfer switch as well, a generator that runs but doesn't transfer the load is useless. You can probably extend the exercise schedule a bit, ask neighbors, co-workers, local mechanics what they are doing. Good luck.

 

[meep]

I mean I think @twX nailed it.

One thought I have is that if it requires a block heater to start in those temps, taking it out of the loop seems bad if you need it to start at a time when you haven’t had the heater running.

I’d be inclined to select a low-wattage heater and tie it into a thermostat, so that it only ran when temps were below some determined set point, maybe 0C or a few digits below that.

 

[Danno]

Question, if you had to choose between a block heater, which typically heats the water jacket of one side of a V engine, or an oil pan heater, what would be preferred?

 

[2.7ecoboostFordBronco]

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.

\Question, if you had to choose between a block heater, which typically heats the water jacket of one side of a V engine, or an oil pan heater, what would be preferred?

I would think a pan heater would be preferred, most folks claim the main benefit of a block heater is to get the heater for the cabin of a vehicle up to temp sooner, for comfort. I would think at least a little bit of the block heater heat does transfer to the oil to facilitate easier cold starting, though.

Ineterstingly the generator mechanic I had out to look at mine said the coolant was low because the block heater was "boiling the coolant off" from being on all the time. His words not mine. They had just replaced the water pump and coolant last year. I contacted the firm that did the water pump replacement and they said they thought the block heater was on a thermostat, but it certainly doesn't seem to be as it was 40F when I last checked it and it was still on, nor did I see any thermostat on the wiring circuit?

You will want to check your recommended oil spec, some natural gas generators take special oil. Don't forget to exercise the transfer switch as well, a generator that runs but doesn't transfer the load is useless. You can probably extend the exercise schedule a bit, ask neighbors, co-workers, local mechanics what they are doing. Good luck.

It currently has Kohler branded 5W-30 seen here:

Seems so counterintuitive to “exercise” a machine every week. I’d think that causes more engine wear than just keeping it off. Machines are not muscles. They don’t atrophy sitting around, they just get brittle and leak. If it were mine, I’d let it sit until the time comes for an outtage. Maybe exercise it every month? Seems so strange to me.

It is actually set to exercise every other week now that I checked the generator's digital control panel, despite the previous owner telling me every week.

 

[road_rascal]

We have 2 large backup generator sets at our plant (one 8.8L turbo V8 and one 39.2L twin turbo V12 on natural) that have block and coolant heaters on 24/7. We load test them every month for 2 hours.

 

[meep]

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

 

[Bailes1992]

Worth linking the block heater to an external thermostat so it only kicks in when the external temp drops below a certain threshold? I'd imagine M1 0w40 would be more than man for this and have no issues pumping well into minus figures.

 

[repairman54]

My homemade setup on my Generac used a battery heater pad and a stick on oil pan heater on the motor bottom plate. Both on a ThermoCube that was set to come on at 0f. With 0-30w M1 in it no issues starting at -30f.