# Low coolant temp alarm



## zz28zz (Nov 24, 2021)

New member here. Got a 55kw diesel, towable Kohler genset. It is set up as a Standby generator. When set to Auto, it alarms for coolant temp any time the temps drop below 60 degs F.
Per the Decision Maker 550 manual, this 60 degs setpoint is not user programmable. Genset has a coolant heater but I don't want it running all the time during the fall/winter months (in central Texas).

From what I have gathered so far, the coolant heater is not needed unless the temp is below freezing.
If I connect the coolant heater, it heats the eng to ~ 100 degs or so and keeps it there.

Is there a way to over ride the low coolant temp setpoint? I.E. some way to enter/modify the factory settings??
Does this genset need the coolant heater when temps are between freezing and 60 deg F?

Thx!


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## iowagold (Jan 22, 2020)

yup
use a thermo block.
let me know if you need links for those.
i run heaters on the diesel units at 45-55 deg f or below.

here is the rub.
this helps keep the oil warm as well as the head temps for a better start and run.
and helps with startup wear.

i also like a battery charger with desulfate and a battery blanket heater to keep the battery warm and up to full charge.


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## drmerdp (Apr 10, 2018)

iowagold said:


> yup
> use a thermo block.
> let me know if you need links for those.
> i run heaters on the diesel units at 45-55 deg f or below.
> ...


I’m curious, what do you mean by thermo block?



zz28zz said:


> New member here. Got a 55kw diesel, towable Kohler genset. It is set up as a Standby generator. When set to Auto, it alarms for coolant temp any time the temps drop below 60 degs F.
> Per the Decision Maker 555 manual, this 60 degs setpoint is not user programmable. Genset has a coolant heater but I don't want it running all the time during the fall/winter months (in central Texas).
> 
> From what I have gathered so far, the coolant heater is not needed unless the temp is below freezing.
> ...


Is the generator connected to your home via an automatic transfer switch?

Block heaters can really effect your energy bill. Diesel block heaters at least on trucks draw about 10amps. If the block heater was active 24/7 for a month... That’s over a hundred bucks a month. If the heater is thermostatically controlled then it won’t need to run constantly, that might validate just keeping it connected and keeping generator ready to go.


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## zz28zz (Nov 24, 2021)

Yes, the genset is connected thru an ATS. My current block heater has a thermostat so once the coolant reaches ~110 degs F it will cycle on and off so it wouldn't run 24/7. However I'd like to save energy and wear & tear on the heater when it's not really needed. 

I could add a thermostatic switch inline with the power cord for the heater and have it come on when it gets close to freezing, however the low coolant temp alarm will still be going off once coolant temp drops below 60 degs F. 

One idea I had was to add a custom selected resistor across the coolant temp sensor to offset the indicated coolant temp. For example when coolant drops to 40 degs F, the controller would see that as 70 degs F. Taking this idea one step further, the resistor could be connected across the temp sensor thru a normally closed relay. When eng starts, the relay would energize, opening the circuit (taking the resistor out of the circuit) and coolant temp would read correctly again. 

Being able to adjust the factory setting for the "coolant temp low" set-point would be the ideal method but no clue if that can easily be done or not.


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## OrlyP (Oct 19, 2021)

The manual says it's a fixed value.









You can use an external programmable thermostat to control the coolant heater, assuming it runs off 120V directly. Some wiring modifications are necessary.

With this, you can set the high and low temperature window at which the heater should operate.

Something like this:








bayite Temperature Controller 1650W 15A BTC211 Dual Digital Outlet Thermostat Plug, Pre-Wired, 2 Stage Heating and Cooling Mode, 110V - 240V, Fermentation BBQ Reptile Aquarium: Amazon.com: Industrial & Scientific


bayite Temperature Controller 1650W 15A BTC211 Dual Digital Outlet Thermostat Plug, Pre-Wired, 2 Stage Heating and Cooling Mode, 110V - 240V, Fermentation BBQ Reptile Aquarium: Amazon.com: Industrial & Scientific



www.amazon.com





If you just need dry contacts to interrupt the heater circuit while retaining most of the factory wiring, use something like this:








Inkbird F and C Display PID Temperature Controller Thermostat ITC-106RH Relay Output AC 100 to 240V : Industrial & Scientific


Buy Inkbird F and C Display PID Temperature Controller Thermostat ITC-106RH Relay Output AC 100 to 240V: Temperature Controllers - Amazon.com ✓ FREE DELIVERY possible on eligible purchases



www.amazon.com





Both have external temperature sensors that you can mount near the factory coolant temp sensor. You may need to experiment a bit in sensor placement and calibration. There will be at least a few degrees difference between what the factory sensor is seeing vs the external sensor.


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## drmerdp (Apr 10, 2018)

zz28zz said:


> Yes, the genset is connected thru an ATS. My current block heater has a thermostat so once the coolant reaches ~110 degs F it will cycle on and off so it wouldn't run 24/7. However I'd like to save energy and wear & tear on the heater when it's not really needed.
> 
> I could add a thermostatic switch inline with the power cord for the heater and have it come on when it gets close to freezing, however the low coolant temp alarm will still be going off once coolant temp drops below 60 degs F.
> 
> ...


How well does the generator start in cold temps? The whole point of the block heater is to have a reliable start. If the unit fires up in cold temps without throwing a failure to start code in automatic mode then faking the temp signal through a relay and resistor is a feasible idea.

Seams like the better plan would be separate controller for the block heater with a lower set point. The factory 110degree setpoint is probably Ideal for starting but definitely a drain on the wallet in electricity.


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## iowagold (Jan 22, 2020)

yea this new EPA thing is part of the warm engine deal...
they like a pre warmed engine for a clean run on start up.


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## zz28zz (Nov 24, 2021)

OrlyP>> I saw the same thing in the manual. I've worked with various controllers for many years. Many have a "secret" factory service mode that allows for some additional tweaking. Others have the s/w parameters (limits) burned into an EPROM and they are much more difficult to change. I suspect the latter, but it would be nice if there was a easy way to access it.

I found a basic analog style "heat only" thermostat rated at 22 amps. Requires hard-wiring but I think I would be able to easily connect it so it controls the existing 120V outlet the block heater plugs into. This would provide a cleaner/more OEM appearance IMHO.
TPI KT110 Industrial Series Thermostat, SPST Heat Only, Wire Leads: Amazon.com: Tools & Home Improvement

The "block heater" is technically a "coolant pre-heater". It's supposed to regulate coolant temp in the block to 100-120 degs F. all by itself but not sure exactly how it does that. Suspect the "brains" are within the sealed heater unit.. Probably wouldn't be able to change the 100-120 deg range it regulates itself to.

Weird thing about the Kohler site is they recommend a block heater if temps approach 0 degs at one place, then say 50 degs F at another place.


https://kohlerpower.com/en/generators/industrial/product/block-heaters




https://resources.kohler.com/power/kohler/industrial/pdf/g6175.pdf



Not sure if I really need a remote temp sensor on the proposed new temp controller. I was envisioning just using the ambient temp within the enclosure to trigger the block heater. 

drmerdp>> So far, the coldest temp I've started it at was 57 degs F. Fired right up at that temp. I have some experimentation ahead of me. 
At the moment, I don't hear the alarm unless I open the enclosure, but I have a remote annunciator panel (yet to be installed) that will alarm inside the house and needlessly irritate the family. 


Iowagold>> Gotta love the EPA!!

Another concern is that I have no idea how reliable these coolant per-heaters are. They don't appear to have any moving parts but if the heater element fails, I'm SOL. Was thinking abt picking up a spare. Any thoughts/experiences on reliability??


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## OrlyP (Oct 19, 2021)

Unless you can find a detailed datasheet of the heater core, we can't for certain determine how it self-regulates the temp. Very likely just a mechanical thermostat but I can't be certain.

You'd want the external temperature probe for the controller to get its reading from the block itself so it knows when to power down the heater once the upper limit is reached.

If you just leave it to measure ambient, you can have a situation in which the ambient is 60 or lower but the block is still being maintained at a balmy 100-120 (factory preset), which I believe was the original problem. With a proper feedback, you can set the heater to run only if the block goes down to 60 and shuts off the heater when it reaches 85, for example, well ahead of the OEM 100-120 preset.


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## Dutchy491 (Sep 18, 2019)

My question to all involved… Is there any concern about internal condensation with a block heater running as much as this one is? That was always a concern with small aircraft, thus only turned on several hours prior to use…


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## zz28zz (Nov 24, 2021)

Dutchy491 said:


> My question to all involved… Is there any concern about internal condensation with a block heater running as much as this one is? That was always a concern with small aircraft, thus only turned on several hours prior to use…


This is a concern for me also. Sorta like have a car that only gets driven a couple of blocks each day. The condensation builds up from the thermal cycling but never gets hot enough to evaporate out the moisture.





OrlyP said:


> Unless you can find a detailed datasheet of the heater core, we can't for certain determine how it self-regulates the temp. Very likely just a mechanical thermostat but I can't be certain.
> 
> You'd want the external temperature probe for the controller to get its reading from the block itself so it knows when to power down the heater once the upper limit is reached.
> 
> If you just leave it to measure ambient, you can have a situation in which the ambient is 60 or lower but the block is still being maintained at a balmy 100-120 (factory preset), which I believe was the original problem. With a proper feedback, you can set the heater to run only if the block goes down to 60 and shuts off the heater when it reaches 85, for example, well ahead of the OEM 100-120 preset.



The heater uses "thermosiphoning" to move the coolant (no actual pump) so I envisioned just a thermal switch inside the heater to maintain the coolant temp. Once the heater element shuts-off, the flow stops.

Sounds like this method of remote temp sensing would necessitate some type of sensor that screws into the block somewhere and had the same temp/resistance curve as the sensor that comes with the temp controller. That might be a challenge, not sure. One thing for sure is that I'll need to experiment with starting the gen at gradually decreasing temps to find where it's no longer happy starting up. In most situations I'd be concerned abt starting and applying a heavy load immediately to a cold eng, however since we use propane for heat, there wouldn't be much of an electrical load, in the winter anyway.


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## iowagold (Jan 22, 2020)

i bet the 0 deg f is for the gasoline version.
as this is a back up power diesel gen set so they like to keep it warm and ready to run all of the time...

this also brings up the question of fuel heater on the fuel filter.
as long as you drain the water out of the fuel filter you should be ok.

we had this last week when the temps dropped to 15 deg f a water separator burst on a new clients unit.
we have it marked in the check list for daily drain....
the operator did not even check the oil or the coolant as instructed... but just signed off the check sheet.
yup does not work for them any more....
i did add a fuel and oil filter blanket heater they work well for the super cold days.
and tank heaters for the metal hyd and fuel tanks.
I have a feeling it will be a coollllddd jan and feb in Iowa.


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## Dutchy491 (Sep 18, 2019)

If you run a good synthetic small engine oil that will be a great help in cold weather starts. The Amsoil Synthetic Small Engine Oil 10w30 has a pour point close to -50c I believe. It’s diesel rated too. That means in any temperature warmer than that the oil will flow throughout the engine instantly at startup. Very important for sure… There’s currently a promo for free shipping. Pm for a link.


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## iowagold (Jan 22, 2020)

it is all about the warm temps for the clean start up burn and parts fit as well.

just like in F1 cars the tight fitting parts you need the engine warm before you fire it up on these units.


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## OrlyP (Oct 19, 2021)

How long does the block heater has to work, say, to bring up the temp from below 40 up to 100?


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## iowagold (Jan 22, 2020)

a long time as the mass is large


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## OrlyP (Oct 19, 2021)

zz28zz said:


> Sounds like this method of remote temp sensing would necessitate some type of sensor that screws into the block somewhere and had the same temp/resistance curve as the sensor that comes with the temp controller. That might be a challenge, not sure. One thing for sure is that I'll need to experiment with starting the gen at gradually decreasing temps to find where it's no longer happy starting up. In most situations I'd be concerned abt starting and applying a heavy load immediately to a cold eng, however since we use propane for heat, there wouldn't be much of an electrical load, in the winter anyway.


That's true. I mentioned before that some experimentation is necessary. Getting unstuck between a rock and a hard place is never easy. 

Now, you have to decide:
1. Best for the engine.... keep the heater running, leaving it to its own devices and let it use up as much energy it needs to get the job done.
2. A little compromise... find a sweet spot where the heater operates within a smaller temperature window relative to the OEM, just enough to not trigger the low coolant temp alarm. It shouldn't draw as much power over a 24h period.
3. Sever all diplomacy.... leave the heater unplugged from power and put a switch on the alarm to mute it.

Personally, I'd choose #2 every time.


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## zz28zz (Nov 24, 2021)

While I was working on something else today, I plugged in the heater just to see how hot it would get before shutting off. Started at 60 degs and it had already shut off when I came back to check after abt 90 mins. Rough estimate would be ~0.5 degs/min for the eng heating rate . Thermal camera showed hottest part of block at 106 degs.. Hose leaving heater was at 119 degs so I don't think it had been shut off for very long. Will need to repeat test when I have more time to devote to it. Did notice the cyl wall of the eng was the warmest part. Bottom end of eng didn't appear to warm up much at all.

Also measured current at 12.5 amps (@120V) which matches wattage on data sticker of 1500W.
Referenced manual for part# on heater (326228) shows it to be ON at 120 degs, and OFF at 140 degs!! Also noticed* there is* a sensor for the heater that screws into block. Followed the wire from sensor and it goes into a small box that the 120V wiring for the heater passes thru. May be able to get a different sensor for it or maybe just connect a resistor across it??

Finding real data on eng wear vs eng temp at start-up would probably be very difficult to find and would be subject to various unknown variables. Finding the temp where eng has difficulty starting would be much more straight forward and will most likely be what I will use to judge the best compromise.


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## iowagold (Jan 22, 2020)

we do a head heater as well as an oil pan heater...
then use the thermal cut out.
and if the heaters are large enough 15 min before you start will help...

we use 200 on the head and 600 watt on the oil pan and 600 watt on the coolant.
and then a 100 watt on the fuel filter water separator.

if you are super cold like below -1 deg f use a 600 watt on the metal fuel tank.
and any hyd tanks as well. if it is like a skid loader etc.

for a gen set if you do a gen shack you can use a room heater or pex in floor radiant heat with oil as the solution for no freeze.
if you can keep the gen shack temp at 80deg f on a cold day that is all you need for a proper diesel start.
and you must use an heat ex-changer preheat for the air intake.


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## drmerdp (Apr 10, 2018)

iowagold said:


> a long time as the mass is large


So stoic…


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## drmerdp (Apr 10, 2018)

zz28zz said:


> While I was working on something else today, I plugged in the heater just to see how hot it would get before shutting off. Started at 60 degs and it had already shut off when I came back to check after abt 90 mins. Rough estimate would be ~0.5 degs/min for the eng heating rate . Thermal camera showed hottest part of block at 106 degs.. Hose leaving heater was at 119 degs so I don't think it had been shut off for very long. Will need to repeat test when I have more time to devote to it. Did notice the cyl wall of the eng was the warmest part. Bottom end of eng didn't appear to warm up much at all.
> 
> Also measured current at 12.5 amps (@120V) which matches wattage on data sticker of 1500W.
> Referenced manual for part# on heater (326228) shows it to be ON at 120 degs, and OFF at 140 degs!! Also noticed* there is* a sensor for the heater that screws into block. Followed the wire from sensor and it goes into a small box that the 120V wiring for the heater passes thru. May be able to get a different sensor for it or maybe just connect a resistor across it??
> ...


If it has a dedicated sensor then a resistor in series should be able to tweak the reading to lower the activation temp. Depends on the sensor, does resistance decrease or increase with temperature?


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## zz28zz (Nov 24, 2021)

Not positive yet but would assume it's like an automotive coolant sensor that has more resistance when cold. I have a temp/resistance chart for GM sensors. If my sensor measures close to what the chart says for that temp, I should be able to get pretty close on the resistor value needed to be installed in parallel with the sensor leads.


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## iowagold (Jan 22, 2020)

they use a cup of hot and cold water for testing sensors and a good fluke ohm meter on gm sensors.


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## zz28zz (Nov 24, 2021)

I had a couple of curve balls thrown at me today. Checked the coolant heater sensor and discovered the wires are molded into the sensor. No wiring is exposed at all. Appears a plug with a blind hole is installed into the block, then sensor goes inside the plug but never contacts liquid. Never seen one like this before.This project will wind up being more involved than I expected.

Moved on to the Gen controller coolant temp sensor. Found it's a 3-wire sensor plus a shield. Started with coolant temp indicting 62 degs. Sensor reads 30K ohms measuring across CTS Signal and CTS Supply wires. Connected 100k ohm across CTS Signal and CTS Supply. terminals, this made controller display 242 degs. Connected 200K ohms and temp read 150 degs. Connected 300k ohms got 114 degs. Connected 400K ohms, controller reads 95 degs. Ran out of 100K resistors.

It hasen't been cold enough yet to find min temp for starting, but looks like I'll be close to 500k ohms for the resistor. Using an automotive type relay shouldn't be an issue but finding a 12V source to energize the relay when eng starts is proving to be a challenge.


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## iowagold (Jan 22, 2020)

zz28zz said:


> I had a couple of curve balls thrown at me today. Checked the coolant heater sensor and discovered the wires are molded into the sensor. No wiring is exposed at all. Appears a plug with a blind hole is installed into the block, then sensor goes inside the plug but never contacts liquid. Never seen one like this before.This project will wind up being more involved than I expected.
> 
> Moved on to the Gen controller coolant temp sensor. Found it's a 3-wire sensor plus a shield. Started with coolant temp indicting 62 degs. Sensor reads 30K ohms measuring across CTS Signal and CTS Supply wires. Connected 100k ohm across CTS Signal and CTS Supply. terminals, this made controller display 242 degs. Connected 200K ohms and temp read 150 degs. Connected 300k ohms got 114 degs. Connected 400K ohms, controller reads 95 degs. Ran out of 100K resistors.
> 
> It hasen't been cold enough yet to find min temp for starting, but looks like I'll be close to 500k ohms for the resistor. Using an automotive type relay shouldn't be an issue but finding a 12V source to energize the relay when eng starts is proving to be a challenge.


you might try heat conduction grease for the block adapter to the probe.
also check the depth on the probe to the bottom of the adapter hole.

you also might try a wire wound pot to dial in the exact range you need.


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## zz28zz (Nov 24, 2021)

Found out the dry adapter hole where the sensor for the coolant heater goes, is called a Thermowell. 

Picked up a 1650W Bayite temp controller mentioned prev. A few product reviews mentioned unit was not really suitable for high power for extended time periods. Plan is to have the temp controller operate a 120V relay. The relay will power the heater, so the temp controller should have very little load (~20mA). Still working on a method to connect the temp sensor to the eng. Got a couple of unused 3/8-16 holes on the end of the cyl head where I can attach the sensor. There's also a plug in the cyl head that appears to connect with coolant passage but thinking that sensing the actual cyl head temp may be a better way of measure eng temp since the coolant will get hot quickly and probably shut off the controller too soon. 

Temp sensor that came with temp controller is a "10K" type. Meaning the resistance is 10K ohms at 25 degs C. Appears this is a fairly common type of sensor but not the same as a GM coolant temp sensor. 

Still waiting for the 120V Omron relay to arrive. Plan is to mount the relay in a project box. Box will have two 120V outlets. One uncontrolled outlet to power the temp controller and the other outlet will come from relay to connect coolant heater. This way the heater and/or temp controller can easily be replaced if needed.


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## zz28zz (Nov 24, 2021)

Got the project box done late last night and installed it today. Went with a 30A relay for increased lifetime ((I hope). 10ga stranded wire for everything. Also wired into the back side of the generators 120V utility outlet (utility power) so to leave open a power plug for whatever. (Other outlet powers batt charger). Thermal camera shows nothing heating up inside the project box with heater on. Actually the plug that came with the heater got hotter than anything else so think I'm good.

Wound up using the temp sensor that came with controller. Hammered a piece of 3/4" copper tubing flat then folded it over a drill bit the same diameter as sensor. Drilled a hole thru it and mounted to a unused threaded hole on cyl head. Cal'ed cyl head temp sensor to coolant sensor when eng was cold. With coolant heater on, the cyl head temp follows coolant temp within abt 10 degs. Once heater shuts off the 2 sensor readings equalize fairly quickly. Got heater controller set to start-up heater at 65 degs and shut off at 85 degs. Seems to be working like a champ so far.


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## iowagold (Jan 22, 2020)

looks good!


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## OrlyP (Oct 19, 2021)

Glad you got that problem sorted out. You should see a significant reduction in your electrical usage.


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## zz28zz (Nov 24, 2021)

Definitely consider that project worthwhile. Difficult to determine the amount of power being saved but suspect it will be significant. Also should help extend the life of the coolant heater. Thx for pointing out the Bayite temp controller.Hopefully with it controlling just a relay, it will have a long happy life. On to the next project...


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