Electric Cooling Fan, Where does the Thermostat

[dickfoster]

In my way of thinking, monitoring rad temperature would make more sense. When shut off, that fan would continue to run as long as that engine is hot, long after the fan has cooled the rad down.

View attachment 489408


A slightly better view of the blower. I have never seen this before.

Another point, be sure that whatever you do to be sure to fully shroud the fan so it covers the entire cooling surface of the radiator or you cooling efforts will be negatively impacted. A good fan shroud is as important as the fan itself.

 

[BukitCase]

I'm sorry Industrial, but your last statement ("When shut off, that fan would continue to run as long as that engine is hot, long after the fan has cooled the rad down") makes NO SENSE AT ALL - I've worked industrial automation control for 35 years, and no matter WHAT you're trying to control, you want the SENSOR located ON the object that NEEDS the control - in this case, that means ON the ENGINE, typically somewhere in the water jacket.

If you have the sensor in the RADIATOR, as soon as the RADIATOR gets cool the fan will SHUT OFF. Then, IF enough latent heat from the ENGINE warms the RADIATOR enough the fan will turn back on. In a way, thermostats are just switches - they will operate for a given number of times depending on how well they're made, then they will FAIL.

So placing the thermostat in the RADIATOR will not only be less efficient at keeping the ENGINE cool, it will cause the thermostat to FAIL sooner due to switching on/off more times.

BTW, that's a nice lookin' "CAT" diesel ...Steve

 

[Industrial Toys]

I don't quite know which purrs nicer. That is a really sweet running Isuzu. Just a bigger and more expensive project, given the cooling requirements, than I had figured on.

That is the kind of input I value. But with sensor on block, on start up, engine gets warm, fan comes on, but rad is still cold, really doing nothing useful. Or is this timing issue so minor, that it doesn't matter?

I saw many Rad/Electric fan combos on E-Bay where the fan did not fully cover the rad and had no shroud. The Yanmar Radiator Shroud Electric Fan Combo I bought for $180.00 US is nicely configured.

 

[dickfoster]

I'm sorry, but your last statement makes NO SENSE AT ALL - I've worked industrial automation control for 35 years, and no matter WHAT you're trying to control, you want the SENSOR located ON the object that NEEDS the control - in this case, that means ON the ENGINE, typically somewhere in the water jacket.

If you have the sensor in the RADIATOR, as soon as the RADIATOR gets cool the fan will SHUT OFF. Then, IF enough latent heat from the ENGINE warms the RADIATOR enough the fan will turn back on. In a way, thermostats are just switches - they will operate for a given number of times depending on how well they're made, then they will FAIL.

So placing the thermostat in the RADIATOR will not only be less efficient at keeping the ENGINE cool, it will cause the thermostat to FAIL sooner due to switching on/off more times.

BTW, that's a nice lookin' "CAT" diesel ...Steve

Sure it makes sense. The thermostat is actually what controls the engine coolant temperature thus the engine temp on a liquid cooled engine. The job of the radiator and fan is to supply coolant sufficiently cool enough and of sufficient volume to allow the thermostat to do it's job. The engine thermostat sets engine temp and it is not always fully open and only part of the time fully closed like when you first start the engine. It's more like a valve than a switch. They typically start to open about 3 degrees below the temperature rating and aren't fully open until the coolant is about 20 degrees above the rated temperature. BTW you don't want ice cold coolant rushing into a hot engine either or you run the risk of thermal cracking parts of the engine. The thermostatic switch that controls an electric cooling fan is a switch, either on or off but you can have some hysteresis built into it i.e. on at a higher temperature than it shuts off at. What were you doing for those 35 years?

 

[BukitCase]

Dick, first of all I agree with everything you just posted - my problem was that NOWHERE before this did ANYONE mention that there even WAS a "normal" engine thermostat, so I took it to mean that the fan "thermoSWITCH", was the ONLY control in play.

Assuming that is NOT the case, and there's an ENGINE thermostat AND a fan switch (the sensible way to do it) then I retract my concerns (and apologise to Industrial Toys for any confusion).

I retired 4 years ago, but the 35 years I referred to were spent in 2 different rare metals plants producing Titanium, Zirconium, Niobium, Hafnium and several by-products of those processes - Each process is different, and depending on the process we needed to control temperature, pressure, flow, SpG, pH, level, AC and DC current and voltage (as in vacuum arc melting furnaces), vacuum systems (a LOT of the processes do NOT like AIR)

Prior to that I built a few engines for other hotrodders in the early '60's, taught electronics in the military, worked on videotape recorders for Memorex, finally got sick of California traffic and moved back to Oregon. Been here ever since... Steve

 

[franklin2]

Get serious, they slip through one hole through the fins in the core. About equal to one bugs worth of blockage. I would rather do that than introduce a coolant leak. I probably would have gooped it with some RTV if I had done it that way.
BTW I was born right down the road in Waynesboro, a long long time ago.

I just followed the instructions. I had another one I installed, and what I did with that one is installed a 1/2" pipe tee in one of the heater core hoses. A couple of hose barbs threaded in the tee hooked the hose back up to the core, and a fitting with a 1/4 brass compression fitting sealed the probe. That methods worked ok also, but more involved to install. Here's a picture.

 

[Raspy]

It seems to me the best place for the sensor is on the radiator. That is where the fan is blowing and that is the temperature of the water going to the engine, as it's thermostat allows. With the sensor in the engine outlet water hose, the fan will run continuously whenever the engine is up to temp, regardless of radiator temp. The radiator only needs the fan running if it is too hot to cool the engine. And it's better if the radiator stays warm. With the fan always running the radiator will always be cold unless the engine is under full load.

 

[franklin2]

It seems to me the best place for the sensor is on the radiator. That is where the fan is blowing and that is the temperature of the water going to the engine, as it's thermostat allows. With the sensor in the engine outlet water hose, the fan will run continuously whenever the engine is up to temp, regardless of radiator temp. The radiator only needs the fan running if it is too hot to cool the engine. And it's better if the radiator stays warm. With the fan always running the radiator will always be cold unless the engine is under full load.

Not true if the sensor temp is set correctly, which it is supposed to be. For example, the engine thermostat let's say is 190F. The fan thermostat can be set at 220F. The engine will warm up to 190F, the thermostat will open, and water will flow through the radiator. Depending on conditions, the radiator starts doing it's job and the fan may not come on at all. If there is a large load or it's a very hot day, the radiator and the coolant will get to 220F and that will kick the fan on. On this unit, the fan will most likely stay on till 205 to 210 when it will cut off.

What this equates to in the real world in a vehicle? The fan really never comes on going down the highway. Only if you are in town sitting at stoplights or pulling a hill on a hot day. It all depends on the vehicle also, different sized engines, different sized radiators, different weight vehicles, different grille areas, etc.

P.S. I think this thread started with reference to a diesel engine. It's very important that diesel engine warm up and that it runs warm for good efficient combustion. A cool running diesel will be smokey and not fuel efficient and be down on power.

 

[Industrial Toys]

Well, I guess it's best if the sensor goes on the rad. Maybe I will get lucky and there will be a pipe thread location for it. Won't know til I get it.

Just curious. Does fluid go in the bottom of a rad to follow convection?

Thanks

 

[dickfoster]

Dick, first of all I agree with everything you just posted - my problem was that NOWHERE before this did ANYONE mention that there even WAS a "normal" engine thermostat, so I took it to mean that the fan "thermoSWITCH", was the ONLY control in play.

Assuming that is NOT the case, and there's an ENGINE thermostat AND a fan switch (the sensible way to do it) then I retract my concerns (and apologise to Industrial Toys for any confusion).

I retired 4 years ago, but the 35 years I referred to were spent in 2 different rare metals plants producing Titanium, Zirconium, Niobium, Hafnium and several by-products of those processes - Each process is different, and depending on the process we needed to control temperature, pressure, flow, SpG, pH, level, AC and DC current and voltage (as in vacuum arc melting furnaces), vacuum systems (a LOT of the processes do NOT like AIR)

Prior to that I built a few engines for other hotrodders in the early '60's, taught electronics in the military, worked on videotape recorders for Memorex, finally got sick of California traffic and moved back to Oregon. Been here ever since... Steve

Well since it's a water cooled engine the odds are pretty high that it has a thermostat in it somewhere.