What temperature to have electric fan turn on??

Started by tinkerer, February 28, 2013, 01:46:46 PM

Previous topic - Next topic

tinkerer

Hello! I've finally got back to working on my Yanmar generator project. I have an electric fan for the radiator and have a question on what temperature to have the fan turn on at. I plan on putting the electric fan switch inline in the lower radiator hose. I think my thermostat is 190 degrees, "don't quote me on that because I'm not at the shop right now." I was thinking that the fan should switch on at a lower temp than the thremostat as the sensor is in the lower radiator hose. How much lower should it be set at?

Thanks!
Ben

Henry W

The way to set it up is if you have a 180 deg. F. engine thermostat than the cooling fan thermostat should be higher. I would think 10 deg. higher.

Henry

Henry W

If your engine has a 190 deg F. thermostat try a 195 deg F. fan thermostat. A 190 engine thermostat starts opening at 190 and is probably fully open near 195.

Henry

Henry W

Make sure you use a 50 - 50 mix of coolent and mineral free water like distilled water. Distilled water is very corrosive by it self but after adding 50 % coolent it becomes non corrosive.

Henry

Carlb

I would put the sensor in the top hose not the bottom hose and go with an on temp of 195 to 200.  the off temp on most snap switches is about 20 degrees then the on temp.

Carl
My Projects
Metro 6/1  Diesel / Natural Gas, Backup Generator  
22kw Solar in three arrays 
2.5kw 3.7 meter wind turbine
2 Solar Air heaters  Totaling 150 Sq/Ft
1969 Camaro 560hp 4 speed automatic with overdrive
2005 Infiniti G35 coupe 6 speed manual transmission

Ronmar

I agree sensor at the top would be better for this application, and set to pick up just before the thermostat fully opens.  I can see some issues with this in a stationary installation such as a generator.  In a auto, there is usually continous airflow, and the thermostat regulates engine temp using this flow and the fan never runs.  The fan is for when the vehicle stops and looses it's normal airflow, it kicks in and runs untill the vehicle is in motion, and the coolant temp at the rad outlet drops enough to indicate this.  Since the fan is the only airflow in the stationary install, it will either thermally cycle and cycle the fan, or the fan will always run. If you are planning on using a automotive electric cooling fan, Most of those DC cooling fans were designed for auto operation, and were not designed for continous duty. The one in my truck goes for months and months without running, only in the summer in traffic is it needed to maintain temp.  A typical auto fan also pulls a LOT of DC current... 

IMO, you should attempt to replicate the automotive application.  I would use 2(or more) fans...  The regular large electric in a shroud behind the rad(pulls air thru the entire radiator surface when running) to kick on when the temp peaks above the thermostat maximum, and one or two(or more) small computer fans across the front(along the top where coolant is the hottest), that run all the time.  The goal is to match the steady state airflow to the average load keeping the engine temp near the top of the thermostats control range, but the large electric never runs.  Then if the load rises, or something happens to one or more of the computer fans, the large fan will start to cycle to maintain temp.  Computer fans are cheap, available everywhere, rated for continous operation and use very little energy...

My .02
Ron
"It ain't broke till I Can't make parts for it"

Horsepoor

#6
I also use two fans on my radiator. Because I work 12 to 14 hours before, during, and after hurricane impacts, I need to ensure redundant / failsafe cooling. I use one 12 VDC automotive radiator type fan in the pusher mode, and a second 12VDC in the puller mode. One 12 VDC has a temperature switch to engage at 200F and the other runs continiously. Power supplies for each fan are seperate and on seperate circuits. If a failure to one occurs (blow fuse or other), I still have the other.

My 20/2 is in the hot Florida summer running under moderate loads (5K to 7K watt) which requires only one fan. Anymore load requires two fans up to the maximum output of 11K. Additionally, I installed a Home Depot exhasust fan just in front of the radiator and the two 12 VDC fans. The exhaust fan ducks all out going air through the radiator first. Again, only one fan is required for cooling under moderate load. But the exhaust fan works very well and when I am home, I use it as the primary cooling fan. If a failure to the exhaust fan occurs, such as a termal shutdown trip, which has never happened, then the 12 VDC fan would engage at 200F and cool the radiator, cycling on and off.

When I am away from home, I engaged the exhaust fan, engage the 12 VDC fan, with the third fan (12 VDC) ready to engage at 200F. Additionally, I have an emergency shut down system that shut down the engine at loss of AC power which feeds the 12 VDC transformers or 220F which means I have a cooling system failure. I feel pretty comfortable leaving for 14 hrs at a time, wife can not trouble shoot system while I am gone. I know it is inefficient to run two fans (one 120 VAC and one 12 VDC) continiously while I am gone, but there is something to be said for piece of mind.

I echo the multiple fan methodology in the other posts.

BruceM

#7
My "fan" is powered by the engine exhaust; induced draft cooling ala the Rumely Oil Pull tractor.  No worries about breakdown or backups.  Old farm tech is impressive.

Thanks for the correction guys, I had a memory lapse and gave credit to Gravely instead of Rumely.

vdubnut62

#8

That's a heck of a foolproof way to assure air flow too, I plan to use the  old Rumely method in my installation.

Ron
When governments fear the people, there is liberty. When the people fear the government, there is tyranny -- Thomas Jefferson

"Remember, every time a child is responsibly introduced to the best tools for the protection of freedoms, a liberal weeps for the safety of a criminal." Anonymous

Ronmar

Yea, I would probably employ the Rumley method on mine if it had a radiator:)
Ron
"It ain't broke till I Can't make parts for it"

squarebob

GM90 6/1, 7.5 ST head, 150 Amp 24V Leece Neville, Delco 10si
Petter AA1 3.5 HP, 75 Amp 24V Leece Neville
2012 VW Sportwagen TDI, Average 39.1 MPG

BruceM

#11
Thanks SquareBob!  It's good to know it was Charles Hart who invented the induced draft radiator around 1907, along with the almost overhead cam.  So often the real inventors get forgotten.  

Given that my radiator and coolant lines are over-sized, maybe I should follow Charles's lead and use oil as coolant.  Then I'd just need to find a 250F thermostat and see if my fuel efficiency improved.    :)


vdubnut62

I have often sat here and pondered the problem of a high temp thermostat. Although I was looking to go about 210-220 and use commercial waterless coolant, propylene glycol based
IIRC.  Ideas anyone?
Ron.
When governments fear the people, there is liberty. When the people fear the government, there is tyranny -- Thomas Jefferson

"Remember, every time a child is responsibly introduced to the best tools for the protection of freedoms, a liberal weeps for the safety of a criminal." Anonymous

mike90045

What temp is the O-ring at the bottom of the cylinder good for & will it deal with hot oil ?

Ronmar

Well with oil's viscosity, I don't think you would need a thermostat as it might be a little sluggish to thermosiphon anyway:)  ON the bright side, if the O rings failed, oil in the sump would not be too much of a problem...
Ron
"It ain't broke till I Can't make parts for it"