Buying or building a snap disk

[pexring]

I'm looking for a snap disk to control the fans in my solar heating panels.  I'd like the fans to come on at about 85 degrees and shut off when the panel drops below that.  The snap disks I've found on the internet thus far seem to cost $24 on up!  A crazy price for such a simple device, I think.  

Does anyone have a source that's cheaper than $24?  

Or how about building my own.  Does anyone know where to buy bimetallic metal to make my own?  

Thanks,

Mark

[Ungrounded Lightning Rod]

Look for "thermal limit switch".

[nothing to lose]

Any suggestions how to limit the results to just the product "thermal limiting switch" and not get 1000 pages of products that use them like on demand hot water heaters! I also got mnay pages of other stuff like talking about them, but so for no one selling any.

[bob golding]

could try here. think they have a branch in the us.

rs components. type thermal switches in the search.

bob

[Volvo farmer]

You can get them for about $10 but I don't think they make them in temperatures as low as you are looking for. The lowest temperature one's I've seen cut in at 110F and out at 90F. They make an adjustable one which I think might cut in as low as 90F but those are about $30. These are commonly used on mobile home furnaces to turn the fan on, that's why the temperatures are generally higher than 90F. I think the standard differential on these things is about twenty degrees so if you're looking for something with a five-degree differential, I don't think a snap disk will work.

http://www.hvacoracle.com/parts/Controls/snapdisc.html

Volvo Farmer

[pexring]

The snap disks that operate attic fans seem to have the best temperature configuration -- on at 85 degrees, off at 77.  That would be perfect except for the price.  $10 would be a good price if I could find a couple for that.  

SO if I could find a source of bimetallic metal -- I'd try to make my own.

Mark

[debequechute]

If $24 is the the lowest you end up with, may as well go digital for fine tuning those on/off conditions:

http://froogle.google.com/froogle?scoring=p&q=%22digital+thermostat%22

[ghurd]

How about a regular old house thermostat?

With a mercury or contact switch to a relay for the fan?

They also have bimetallic springs in most of them.

I think the last one I bought to sacrifice was $8 at the big home improvement store.

[Norm]

  Quite easy to make your own, (if you're good at building your own ...which I'm not...but can see how it would work)  the bi-metalic coil from a thermometer, an optical system from a computer mouse plus a modified disk to replace the slotted one well any how you put special modified disk to replace the needle that was on the thermometer...I'm reambling but I hope you get the concept?    ( :>) Norm

[pexring]

I'm now using a regular house thermostat.  But you have to get one with an a/c control so it costs a little more.  I set the thermostat inside the solar heating panel -- but the high heat and direct sun really played havoc with the housing of the thermostat so that's why I want a simple ole snap button.  

Mark

[nothing to lose]

Yes those attic fan ventalator switches are very good! I'd like to find a cheap source for those too.

I bought a vent fan system cheap at an auction, about $2

I have been using the temp switch box from that for years above my wood stove.

 Used to be a light fixture in the ceiling there, so I go from wall switch to controll box mounted on ceiling above wood burner and back to a normall type wall outlet (specail mounted and orange so I remember what it is). Works great, when the burner is putting out alot of heat the box triggers and turns on the Box fans and moves the hot air. Turns off when the fire dies out so it doesn't blow cold air, and if I want the fans off because the house is getting too hot I just flip the wall switch to off and shut it all down.

I just looked at my ceiling

The box I have adjusts from 60f to 100f. That's the on temps, and I think it kicks out at 10f below the on temp. so if set to about 80, it kicks on at 80f and off at 70f. This is a 120v box, but should work fine for DC I would think unless arcing would welding the points, but I dought it would running low powered fans. Not like a high amp useage such as pumping water.

I'd like to get some of those button switches cheap like they use on electric clothes dryers to control the heating element. But lower temps probably. I have a few junk dryers I took some off of I will play with this winter, but I think the flip temp is too high for what I actually want them for.

[Volvo farmer]

I work on clothes dryers every day. Dryer thermostats are the open-on-rise type so would not be approriate for your needs, Some of them do have a 3rd terminal that will close on rise. However, the lowest temp you will find in there is 135F. Most limits have a number (stamped or printed) on them like L-135, that's the temperature they operate at.

Good luck,

VF

[nothing to lose]

Thanks about the number info, I'll have to look at mine see if/what they are stamped for.

Also I am actually thinking of something else to use those for and might have confused myself thinking 2 things at once? I want to open a circuit so it is off like for a blower when the temp is high enough, then when temps drop close the circuit and turn the blower on again. Sort of fan the flames/coals when adding fresh wood till it gets cooking good then shut of the blower. Then I also need a switch that only turns on at a low temp also, then if the fire totally dies out that switch shuts off the blower even though the other switch is closed to turn it on. With both inline the blower is off when no fire/no heat at all, but is on durring low heat to build more fire, off again when hot enough.

And of course a manual switch to turn it all off anytime I want it off regaurdless of temps.

[ghurd]

How about a used furnace fan control?

Temps are probably close to what you want?

Bimetallic. If nothing else.

If they get bent or old, they don't work right. 10' off is bad for a furnace.

Could twist or alter one for your use?

Ask nice, I bet the furnace guys change them everyday.

Still thinking.