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Electric fan control

I have a link here to a part i like a lot and they take tons of abuse everytime you use your dryer.

its called a thermal disc and im thinking why not use this disc to control my fan.

these thermal switches used in a dryer are normally closed contacts but upon reaching thier calibrated rated temp , they open up and remove the high amperage going to the heating elements in the dryer.  when they cool down, the contacts close and allow power to return to the heating elements.

These switches can be had in normally open as well.  This is what i think would be needed along with a calibrated temp rating of say 200.  When the temp of the engine reaches 200 there abouts,, the switch will be installed in line with the fan ground with a hot wire supplied when the key is on.  upon reaching 200 deg, the fan comes on,, runs till the thermal disc cools off then the disc opens the ground shutting the fan off.

sound good?

I just dont see why i really have to use a relay,, thats all.

here is a pic of what im talking about but its the same thing we have all probably replaced on a dryer once or twice in our lives.
http://www.appliancepartspros.com/modelsearch_model.aspx?part_id=3094244&model_id=302485&pkw_=thermal

this site is wayyyy over priced for these parts as these temp switches can be had for less than 2 bux.

Electric fan control

Reply #2 –
My buddy at AutoZone is getting me an electric fan installation kit.Wiring,relay,everything in one kit.I'm more comfortable that way.
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Electric fan control

Reply #3 –
That sounds good. I would think you would want the relay in there so it carries the load not the switch. I say this because is it better to replace the switch or the relay. I would think the relay. I put to after market fans and put them on my car. I even got he fan controller from the same company. I didn't put the added relays like on the instruction sheet. About 3mos later the controller went out. Luckily my buddy worked at the parts store. So we warrantied it out. Then I put it in with the 2 relays and now it has been in there for 3+ years and no problems.
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Electric fan control

Reply #4 –
Scott, I think I'd still rather use a relay. The reason why is this:

You might think I'm crazy, but the cooling fans in your car likely draw MORE amperage than the dryer in your house. You only need look as far as your fuse panel for proof - you'll probably find a 30 amp breaker for your dryer plug (I'm pretty sure that's what's in my breaker panel, anyway). An electric cooling fan in a car, however, can easily melt a standard 30 amp relay.

The reason your small 12V electric motor draws more current than your huge 220V dryer is the voltages themselves. The dryer might use 5,000 watts, but at 220V that 5,000 watts will only pull 22 amps.

The electric fan motor, on the other hand, only has 12 volts to work with. It might only use 400 or so watts, but requires around 35 amps to do so at 12volts.

Switch and relay contacts usually have ratings for amperage and voltage, but the amperage ratings usually stay the same regardless of voltage - the relays I used to use in my sequencers had contacts rated at 10 amps for 12VDC, 120VAC, or 240VAC. In other words the relays could carry up to 2400 watts (240 volts X 10 amps) or as little as 120 (12 volts X 10 amps) as the maximum.

It's all in the current. Higher voltages use less current to get the same work done (wattage). Look at the wiring in your house. Most standard household circuits use 14 gauge wiring and are fused at 15 amps. 15 amps @ 120V would give you a maximum capacity of 1800 watts on the entire circuit. That would be the equivalent of 32 55-watt headlight bulbs all pulling their current through a skinny little 14-gauge wire.

Now try connecting those 32 55-watt headlight bulbs to a 14 gauge wire on a 12 volt battery. The wire would melt in a stunning display of sparks and smoke. Why? Because to pull that same 1800 watts out of a 12 volt battery you would need to draw 150 amps - nearly 10 times what a 14 gauge wire is rated to carry. Indeed, four 55-watt headlight (or fog light) bulbs are about the most you'd ever want to put on a 14-gauge wire circuit, and I'd only ever put half that many due to voltage drop concerns.

In other words, this was a very roundabout way of saying that the dryer switch would probably not last long running an automotive fan (or in the case of Turbo Coupes, two automotive fans).
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Electric fan control

Reply #5 –
Quote from: jcassity;165418
I have a link here to a part i like a lot and they take tons of abuse everytime you use your dryer.

its called a thermal disc and im thinking why not use this disc to control my fan.



sound good?

I just dont see why i really have to use a relay,, thats all.


this site is wayyyy over priced for these parts as these temp switches can be had for less than 2 bux.


Sounds great!

 Would like to use something of that nature on a Taurus fan conversion possibly switching on between 170-180 on a 160 thermostat. Keeping the engine around that temp should help power.  If the eec runs a little rich, it shouldn't be a problem if all else is tuned well.
 No relay=less parts to break  ;)
[SIGPIC][/SIGPIC]88 t-bird: 5.0ho, gt40y, crane 2031, fms 1.7, paxton@5#, aod wide ratio, tci stall, performer rpm upper, 70mm bbk, pro m 60, 42#s, 3.73 7.5" posi, jba shorties, borla, upr x. 13.4 @ 104mph. cbaza, moates, tuned by decipha

Electric fan control

Reply #6 –
Carmen, thats a great comparison... Really nothing I could add to it...

Electric fan control

Reply #7 –
If it works great, if it doesn't that's ok too. Figuire it's worth a try at least. Imho it was a good idea if it wasn't for the amperage issue and also learned something new today. I wouldn't have bet that 12 volt dc electric fans pull more current than an ac dryer element.
One more question to ask if one you would answer please:
The fans pull more current at startup than full speed.
Would the dryer element be the exact opposite?

Thanks,
 Mike
[SIGPIC][/SIGPIC]88 t-bird: 5.0ho, gt40y, crane 2031, fms 1.7, paxton@5#, aod wide ratio, tci stall, performer rpm upper, 70mm bbk, pro m 60, 42#s, 3.73 7.5" posi, jba shorties, borla, upr x. 13.4 @ 104mph. cbaza, moates, tuned by decipha

Electric fan control

Reply #8 –
Quote from: t.birdsc;165915
If it works great, if it doesn't that's ok too. Figuire it's worth a try at least. Imho it was a good idea if it wasn't for the amperage issue and also learned something new today. I wouldn't have bet that 12 volt dc electric fans pull more current than an ac dryer element.
One more question to ask if one you would answer please:
The fans pull more current at startup than full speed.
Would the dryer element be the exact opposite?

Thanks,
 Mike

The dryer element would be the same - more current at startup. Not by much though - resistance goes up as temperature increases, and as resistance goes up current goes down (with voltage staying the same), so once the element got hot it would draw less current. Again, though: Not by much, because the difference in resistance would not be enough to make a significant difference.
2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

1988 5.0 Thunderbird :birdsmily: SOLD SEPT 11 2010: TC front clip/hood ♣ Body & paint completed Oct 2007 ♣ 3.55 TC rear end and front brakes ♣ TC interior ♣ CHE rear control arms (adjustable lowers) ♣ 2001 Bullitt springs ♣ Energy suspension poly busings ♣ Kenne Brown subframe connectors ♣ CWE engine mounts ♣ Thundercat sequential turn signals ♣ Explorer overhead console (temp/compass display) ♣ 2.25" off-road dual exhaust ♣ T-5 transmission swap completed Jan 2009 ♣

Electric fan control

Reply #9 –
Quote from: Thunder Chicken;165962
The dryer element would be the same - more current at startup. Not by much though - resistance goes up as temperature increases, and as resistance goes up current goes down (with voltage staying the same), so once the element got hot it would draw less current. Again, though: Not by much, because the difference in resistance would not be enough to make a significant difference.


Then it would be the inverse of a thermistor? Would a capacitor help it work?
 When your learning it seems like it's never the last question.
Also, I didn't mean to steal the thread.

 Mike
[SIGPIC][/SIGPIC]88 t-bird: 5.0ho, gt40y, crane 2031, fms 1.7, paxton@5#, aod wide ratio, tci stall, performer rpm upper, 70mm bbk, pro m 60, 42#s, 3.73 7.5" posi, jba shorties, borla, upr x. 13.4 @ 104mph. cbaza, moates, tuned by decipha

Electric fan control

Reply #10 –
thank for the replies,
i was just thinking and comparing the enclosed and enviromental exposure the thermo switch has to put up with being bolted to a device in a dryer that gets as hot as it does.

Using this in an engine bay perhaps mounted to the radiator would put it in a cooler situation i thought.  I have seen some peoples posts on electric fan controls and notice there seems to be a thermal activated switch of some sorts but there always seems to be a relay.  Im sure those thermals are in line with the relay coil and the relay contact is taking the brunt of the first time contant on initial startup.

Ive seen these switches in line with HUGE / Large / small devises from industrial overhead double gurder crane systems , large and small 3phase to single phase applications on down to just around the house stuff like blower motors on a fire place to dryers.

I was just thinking that the aperage rating in them was sufficient to supply the ground side of a fan control.

My thoughts were to supply power to the fan via a wire that is hot with key on.  Next i would have mounted the thermal switch to an ideal area.  Next i would run the ground wire from the fan motor to one side of the thermal switch and a wire from the thermal switch to ground.

I thought the way i had it layed out,, most of the actual "power" would be used up by the fan.  Since the thermal switch should not have any resistance other than a direct short,, there wouldnt be and actual measureable load on the switch.
I was thinking the switch shouldnt really have a voltage drop cause its just a metal disc that snaps out to close contacts and retracts to open acting like a relay but with no resistance other than open or closed.

mounting it on the ground side made me think its worth trying and also thinking of how long these things last without breaking was a factor.

No thunderchicken,, i dont think your crazy,, your description was exactly what bugged me as you explained the difference in resistance.  the fan im sure has a much higher resistance than the simply arranged heating element of a dryer so the current proportions are obvious.  Eliminating that and considering the the universal applications of the switch makes me wonder why they rate these the way they do , its like they have this huge wide range of current applications,, thats all.  This like your home breaker you mentioned is a transiant application, not constant so that plus the 80 rule and the trip delay built into most square d breakers really make me wonder the actual current draw.,,,,,,,,,,,

im gonna measure what my current dryer draws....brb...........

Electric fan control

Reply #11 –
ok
actual current draw................with elements on.............

L1- 22A
L2- 24A

with elements off
L1- .25A
L2- 4.5A

Electric fan control

Reply #12 –
So i am cleaning out my fireplace blower motor assembly and notice this.  I didnt know adjustable thremal switches were available but apparently one of my old employers bought Therm-o-disc.

Here is a nice adjustable thermal switch.

like i mentioned above, The thermal disc would not be a load bearing device but become the path to ground for the fan.  No voltage drop, no current and vertually zero resistance, just a part of the conductor to ground.  I still dont understand why people think they need a relay for a fan.  ITs a pointless endevor when a control means added to the ground side of large load like a fan can be applied with less wiring and moving parts.

Here is what I found in my blower assembly,,,,, adjustable Normally open switch 110DegF to 250DegF.  I bench tested my blower control sw in series with an electric fan on a car battery and let it run for about an hour with jumper cables hooked up to the battery.  Nothing got hot on the switch.  I had to place the switch on my garage wood burner to keep the contacts closed though.
http://www.thermodisc.com/productdetail.asp?ProductID=83

Here is a dub'd automotive application thermal switch that just bolts down somewhere if you drill a hole and add a nut.
http://www.thermodisc.com/productdetail.asp?ProductID=89


Typical applications include:

• Control of electrically driven coolant fan motors found in most smaller cars which utilize front wheel drive, transverse mounted engines. The switch can carry the electrical load of the coolant fan directly, thus eliminating the need for a fan relay.

Electric fan control

Reply #13 –
Why not try it and see if it will hold up, sounds like it might.
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Electric fan control

Reply #14 –
Quote from: jcassity;165418
this site is wayyyy over priced for these parts as these temp switches can be had for less than 2 bux.


I would be surprised if they are over priced. Have you tried pricing this same part through your local appliance dealer?
My gas range quite working on Christmas Eve and I ordered three major parts for it from this place. Even with overnight shipping, it was cheaper than any of the quotes I got from local suppliers for just two of the three parts I needed.
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