12 volt thermostat idea's

[Gary_B]

 Well I have my solar kiln about complete, I decided to go with 12 volt auto cooling fans, I can purchase 3- 16 inch fans for 36.00, I figured they would be heat and moisture proof  and would push enough air. I am going to use a 12volt/110 converter, next thing I need is a thermostat that I can adjust to obtain proper temperatures for the fans to run on. Any ideas on a thermostat? I know I should use attic fans, but this is strickly experimental, and I am trying to keep the cost to a min. So far I have around 50.00 and that was for the waterproofing on the inside, all other items have been salvaged here and there. I will try and post some pictures soon.
                                                                          Ohio Gary

[WH_Conley]

I don't know about the heat, they are usually mounter in front of the radiator where it is cooler. If they survive it would be handy information to know. Keep us posted.

[Jason_WI]

If you can solder.....

http://www.uoguelph.ca/~antoon/circ/auto-fan.html



Jason

[Gary_B]

    Theres a few cars where the cooling fan is located in front of the radiator, one thing you have to be sure of , is whether it pushes or pulls air, most front mounted cooling fans pushes air which would be better, unless you use the other style and mount the fan on the outside of the baffle. This is all experimental, and I will keep everyone up dated.

[JimBuis]

Regarding your question about thermostats, the key question is what will be the temperature range that you are targeting.  Are you wanting the thermostat to be adjustable?  I assume so.  You could use a basic household thermostat, i.e. one without all the programming devices, but I don't think the temperature range will go high enough for what you need.  There are some thermostats designed to control attic fans that are probably in the range that you want.  Some of these will have contacts that are opened and closed via a bimetallic strip which reacts to the ambient temperature.  Such a thermostat would operate okay for low voltage as you are describing in your application.

You will also have to know how many amps those motors are going to be pulling.  Most likely the thermostat will have to operate a relay so the relay can handle the amps you're motors will be pulling.

Having run off at the mouth, what do I know about kilns?  Absolutely nuthin!!  ;D ;D ;D  I do know a thing or two about heating & A/C as well as electrical stuff.  Good luck.

Jim

[Don_Lewis]

Call any HVAC place and get a line voltage thermosat. Then use it on the 120v side of the converter.

[Gary_B]

  Thats sounds like a pretty good idea , I think that is my best route, and the most simpliest. I hope to have this kiln fired up this weekend, if everything goes well.

[JimBuis]

Gary, you may want to double check the total amperage of your three motors against the amp rating on the secondary side, the 12 volt side, of your transformer or convertor as you call it.  Make sure the transformer will put out enough amps.  It may be okay right now, but over time if you add more motors keep this topic in mind so you don't have the transformer burn out on you.  Likewise check the amp rating on the primary side, that is the line voltage or 110 VAC side, against the amp rating of the thermostat you get. ;)

I am making these amperage suggestions because this is the most easily overlooked area for the handyman. ;)

Jim

[Gary_B]

  Hey Jim,
  Thanks for the advice, for I need all I can get :D Ive got to check into these matters before persuing any further. I wish I could just go with 3 attic fans.....but at 50.00 a pop, I just cannot do that right now. The auto fans I want to use are 16 inch and out of a taurus, If I dont have any problems with the amps, they should really work fine....we will see.
                                                                     Gary

[Larry]

As Don suggested a standard line voltage thermostat will work sorta...it doesn't have a high enough range in the hot old summer nights.  I'm running one in my solar kiln but resort to manual control in the summer...not a problem as me and the boss are both retired.  Neighbor built a solar kiln two years ago...we decided a timer was the cheapest solution and better than the thermostat but some manual intervention is still required.

Here is a line voltage thermostat that works great with the widest range of any I have found.  Little pricey though.

https://forestryforum.com/board/index.php?topic=11490.0

[Gary_B]

Well I checked on the amount of amps a ford taurus cooling fan draws and its close to 130 amps start up then drops down to like 60 amps after running, well that scraps that idea. Most converters only produce like 3 amps, thanks for the advice before I went out and bought 3 cooling fans for nothing, never gave it a thought. Thats what I like about this forum, so many people willing to help others.
                                              Gary

[JimBuis]

Just so I don't get a reputation for being the guy who tells people their ideas won't work, here're a couple of ideas. ;)  You can take that old car alternator you have laying around, a good truck battery [Truck should be read as it is rated at 400 CCA (cold cranking amps or greater.), and that useable 110 Volt motor you've had sitting on the shelf for years and make yourself a 12 volt converter that MIGHT work. ???  Although I haven't checked, I doubt that your cooling fan motor would actually draw 60 amps after start up, 20 to 30 amps sounds more likely to me. :

Anyway, after all of this stuff that you would have to scrounge up, it might be easier to come up with some used attic fans.  Some guy who does a lot of home remodelling might come across some fans over time that are being removed and aren't worth much to anyone else.  Just an idea that like my other writings ain't worth much. ;D ;D

Jim

[Randy]

Gary, I am sure you need to recheck your amp draw on those fans, I have several 12 volt fans with 14" blades that draw in the 5 to 8 amp range---running. But to run 3-------you will need a fairly large Power supply, or if the fans are going to be cycling on and off  you could us a good battery with a decent automatic charger hooked to it. For a thermostat, keep in mind that you can use a high voltage like a attic fan thermostat to control a 120 volt relay, that can breaks the lower voltage to the fans. Good luck. Randy

[Gary_B]

  Randy thanks for the advice, what are you using to run your 14 inch fans? I hope I can work something out, due to the amount of air a cooling fan moves, Ive thought about using a 12 volt rv battery with a charger hooked to it. just and idea. Any advice is appreciated.
                                Gary

[Randy]

Gary
To be truthful--------I didn't measure my fans last night, but I was close-------they are 13" across the blades. I don't have a Kiln, but maybe oneday I might decide to build one. I am just a Tinkerer-----I live Off-Grid,  And I like building "things". 12volt is my life------I have 30 golfcart type batteries with a fair amount of solar panels(1560 watts). I do have 120 volts through a inverter. Now my computer is in my Business-workshop on grid. I have never tried the attic fan thermostat on just 12 volts dc-----it might work, but if it will not------them I would hook it to 120 volts then use a good--size relay----or even 3 relays if I needed one for each fan(because of amp draw)--------Let the thermostat cut the relays on and off-----------break one leg to the 12 volt fans with the relay-----Should work good. I would put the relay's outside the kiln, because of moisture inside. Hey--I think it would work, but if it will not------Back to the drawing board---LOL. I will come up with something. Some times it IS BEST to go with "things" that are designed for the purpose(factory built). Good Luck.  Randy

[scottr]

JimBuis , there are 15 amp bimetal thermostats available from the attic fan manufacturers . The question is whether they will hold up under the acidic conditions of drying oak . Something to consider is if you have an older attic fan with the old bimetal thermostat is that they did not have a firestat (thermal fuse) that would turn off the fan in the event of a over temperature condition like a fire .        Scott

[KnotBB]

40 amps is a lot at 12 vdc.  You can almost weld sheet metal with that current/voltage.

Most auto cooling fans I've seen are hooked up with 18 guage wire (down wind in Chrysler products) which will not support 40 amp continues draw.  The wire would become a fuse and blow.  Strange thing about fans is if they can't move air (vacuume?) or the air flow in is restricted, the current draw goes down.  That's why your home vacumme speeds up when the intake gets plugged.  No load on the motor. 
On your converter (I'd call it a 12 volt power supply) be sure you're not confusing it's current draw when in use verses it's available out.  In general current X voltage = power;  power in = power out (not current) So if you had 120 volts in at 1 amp you could have 12 volts out at 10 amps (120v X 1a = 120 watts  and 12v X 10a = 120 watts).  Nothing is 100% efficient so you wont have 120 watts out.  Some of the power gets used as heat.(12 volts X 30 amps = 360 watts)

I saw something like what you said on the Internet and wondered about it.  I've got 25 years as an electronic tech and it just didn't ring right.  I'd get an amp meter and check it myself.

Steve 

[Kcwoodbutcher]

You can get an adjustable thermostat from Penn or Johnson controls. I have one that runs the over temp fan on my kiln. The temp range is 70 to 140. The contact are controlled by a remote bulb so wood acidity is not a problem. The on/off swing is 3 degrees. I think the amp rating is 25 at 120V. These sell for close to 80 bucks new but there are usually several on e-bay. I bought mine for less than twenty. If you interested I'll look up the model#. By the way the switch is dual throw so in addition to turning on the fan at over temp it can turn on a heater at under temp. It allows me to run my DH kiln as a conventional kiln if need be.

[treenail]

Have been using a snap disc bi-metalic thermostat for years in a fan assisted thermal air siphon solar panel that I installed for house heating , way back in 1982. Very dependable. Will turn the fans on at 110degrees F and shut them off if the temp drops below 90F. Pretty simple. Also have a variable greenhouse thermostat that is mositure shielded for a bowl kiln, but that isn't low priced. Works great, but it is only a year old, and I can't review how it will stand up in the long run, as it is in the acidic/wet environment of wood drying.