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Need a thermostat, on 32F
By nothing to lose, Section Controls Posted on Sat Dec 09, 2006 at 05:30:09 AM MST
Any idea where to get something ready made and cheap?

I would like to find a thermostat or such that will turn on at around 32F.
This is for a well pumphouse. Since it takes awhile at below 32F for water to freeze and bust a PVC line then somewhere around 32F-35F is near where I want the setting to be to turn on the heat, prefferably back off again around 40F.
120V line. Heat source is just a 100 watt light bulb. Right now if I think I need it I turn it on for the night. So far only one night I used it, was supposed to get to 8F but I think we had around 15F for a low.
I would rather have it turn on off as needed and maybe put 2 100watt bulbs in instead of one. One works unless it blows! So 2 would run half the time using the same power and if one blows the other would just run longer, still the same power for same heat.
Most the stuff I look at turns on about 58F and I never need heat at 58F for a well!

Need a thermostat, on 32F | 9 comments (9 topical)

Re: Need a thermostat, on 32F (3.00 / 0) (#1)
by TomW on Fri Dec 08, 2006 at 11:12:50 PM MST

NTL;

I have a thing that plugs into an outlet and has an adjustable on temp. It is for household AC and is called a "winter Watchman" can't remember the manufacturer but will look tomorrow. It would be perfect for your needs I think. I have had it for decades and bought it to use in my well pit to ensure it couldn't freeze the lines.

In fact I just googled it up and this is the unit only a bit more modern looking :

http://electrical.hardwarestore.com/15-59-misc-alarms/winter-watchman-219899.aspx

For $23 it could save hundreds in repairs.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

Re: Need a thermostat, on 32F (3.00 / 0) (#2)
by Gordy on Sat Dec 09, 2006 at 07:30:53 AM MST

That will work for a 100w light bulb. I can't quite make it out but in the lower left corner it looks like it's rated 100w. The local hardware store has them, they also have (over by the heat tapes) a couple of unit's that at first glance looks like a outlet multiplier but with 1 or 2 outlets on it. These have a higher wattage rating, and are what I chose for my well house. As I didn't want to have to open it up all the time to check the light bulbs, I went with a Wal-Mart $9.99 electric heater set on low. The switch in it is preset on @ 35 & off @ 40 If I remember right. And I think was in the $15 to $20 range.

If I was to use light bulbs I think I would use multible smaller bulbs (40w) as they tipicaly have longer lives and as redundancy if 1 or 2 do fail.

Gordy

[ Parent ]

Re: Need a thermostat, on 32F (3.00 / 0) (#3)
by fungus on Sat Dec 09, 2006 at 07:50:41 AM MST

Also you could get two higher wattage bulbs and put them in series. Thius will halve the power of an individual bulb but will almost never need replacing.

'Two things are infinite: the universe and human stupidity; and I'm not sure about the universe.'-Albert Einstein
Fungus - www.reenergy.co.uk

Re: Need a thermostat, on 32F (3.00 / 0) (#4)
by stephent on Sat Dec 09, 2006 at 09:07:06 AM MST

Insulate the heck out of the whole thing....very well if using light bulbs, etc.
Light bulbs burn OUT often....the little ceramic heaters will too but hopefully less often. It's the humidity changes that will get to most stuff you can readily adapt to that environment.
The humidity will get to just plain old thermostats.
Read a bit here http://www.chromalox.com/products/prodinfo/en/srl.html or google search for "heat trace" + "self regulating".
This is the stuff I routinely install for commercial or even residential water line freeze proofing....it lasts and lasts--it should see the energizer bunny into the grave even. No contacts, no t-stats, just use a plain old light switch to turn it off during warm or hot weather to save even a few more dollars cuz it does run slightly during hotter temps--just a little, but not much currant draw.
Most are designed more/less to be fully conducting around 37 to 38 deg F.
They are rated from around 3 watts per foot and up--I would say use the smallest one and not wrap it on pipes less then 1 1/2"--just tape it straight onto pipes in straight line--bigger stuff, wrap it one turn every 8" to 1' or so--follow manufacture's instructions in any case. Then insulate.
This stuff sits doing it's job outside in -20F (and way lower) weather with 4" of insulation on water/chemical pipes for decades.
But it's a bit pricey--but worth the $$.
Just a suggestion for lower maintaince/problems.

Re: Need a thermostat, on 32F (3.00 / 0) (#5)
by pyrocasto on Sat Dec 09, 2006 at 11:39:08 AM MST

I'd do s search for disk type thermistor/thermistats. $10 and I bought 2 that turn on at 110, and off at 90F. They come in different ranges of temperatures, I just got mine for a solar heater.

Re: Need a thermostat, on 32F (3.00 / 0) (#6)
by bilbo7500 on Sat Dec 09, 2006 at 02:08:05 PM MST

If you can find an old pool timer (it turns the pump on and off to filter the water), some of them have a "freeze guard" on 'em. This you can set at 32 - 34 whatever and it circomvents all other controls and turns the pump on until the temp goes above whatever you've set for it.

Re: Need a thermostat, on 32F (3.00 / 0) (#7)
by elt on Sat Dec 09, 2006 at 09:27:23 PM MST

Hi,

I have a Hunter brand freeze sensor (for irrigation systems) on my shop alarm system so I know if the furnace stops working. I got mine on sale for $8 but I think the a good shop around price is more like $20. It opens at 37 degrees which is okay for an alarm system but you'd need another relay to make it close and handle the amp/volts for your lights.

I have a Reddy Heater thermostat plug-thing for my kerosene torpedo heater. I did a quick google for them and I don't believe I paid the $40 to $50 that I see online. It shows 40 degrees as the lowest temp. Northern Tool and Ebay have one that goes down to 30 degrees for about $40 but, jeez, for half that price I wonder if you couldn't modify the thermostat on a cheap electric heater and wire in your light bulbs instead of the nichrome wire...

- Ed.

Re: Need a thermostat, on 32F (3.00 / 0) (#8)
by nothing to lose on Sun Dec 10, 2006 at 07:07:51 AM MST

Thanks guys, several good ideas there.

.
nothing to lose

Spelin and tpying are my strong points, not electronics.

Re: Need a thermostat, on 32F (3.00 / 0) (#9)
by mrpackethead on Thu Dec 28, 2006 at 05:55:29 PM MST

Not quite what you are asking for, but i built something very similar using a PICmicro controller, a temp sensor, a triac and a optoisolator, total cost about $12. If its any use to you, I can post the circuit details
Everything should be as simple as possible. not simpler.

Need a thermostat, on 32F | 9 comments (9 topical)

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