Looking for thermostat to operate at near 32F - 0C

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On 12-03-2012 21:31, grumpy wrote:

Like most thermostats, it is either on or off.
Swapping the two is trivial.
--
Wes Groleau

It seems a pity that psychology should have
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On 12/2/2012 11:49 PM, Wes Groleau wrote:

Sorry Wes, you're wrong. Thermostats have what's called a "set-point" and commercial thermostats on food service and industrial process control systems have adjustable "cut-in" and "cut-out" set-points for operation of heating or cooling. Even your digital wall thermostat for heating and cooling your home may have an adjustable span which is the temperature band where it will remain quiescent. The older traditional mechanical wall thermostats have an adjustable heat anticipator for that purpose. All control systems have hysteresis built in for them to operate properly. ^_^
TDD
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On Dec 3, 2:40 am, The Daring Dufas <the-daring-du...@stinky- finger.net> wrote:

OK, I see the point about refrigerator thermostats. The issue I overlooked was that they are obviously designed to close when the temp rises, which is the opposite of what is needed. Most probably can't be changed.
However, if you look at the rest of my suggestion, which was to go to Ebay and search for "refrigerator thermostat", it was spot on. Here, for example is a Honeywell refrigerator thermostat that has both NC and NO contacts that will work:
http://www.ebay.com/itm/NEW-HONEYWELL-REFRIGERATION-TEMPERATURE-CONTROLLER-T6031A-1029-SWITCHING-SPDT-/221160072188?pt=LH_DefaultDomain_0&hash=item337e2ae3fc
It's item 221160072188 if the above link doesn't work. Looking a few listings down, there is a pic of another thermostat that clearly has 3 terminals, suggesting it too, will support either heating or cooling.
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On 12/3/2012 6:54 AM, snipped-for-privacy@optonline.net wrote:

http://www.ebay.com/itm/NEW-HONEYWELL-REFRIGERATION-TEMPERATURE-CONTROLLER-T6031A-1029-SWITCHING-SPDT-/221160072188?pt=LH_DefaultDomain_0&hash=item337e2ae3fc
That's a mechanical version of the one in the link I posted elsewhere. I use thermostats of this type all the time because they are so versatile and easy to adjust via the keypad. ^_^
http://tinyurl.com/ccu2veo
TDD
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On 12-03-2012 02:40, The Daring Dufas wrote:

It's true that it would turn off too quickly, but if set properly, could still prevent freezing.
Would wear out more quickly as well.
--
Wes Groleau

You always have time for what you do first.
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On 12/3/2012 11:55 PM, Wes Groleau wrote:

That's what the span adjustment is for. You set a thermostat for say 35°F with a span of 3°F. Depending on whether you set it as "cut-in" or "cut-out" determines the behavior. If you have a heater you wish to control, the T-stat is set to 35°F "cut-out" and 32°F "cut-in". This will preventing the heater from going on and off and on and off. The heat will turn on at 32° and off at 35° but there will be some overshoot with the temperature where it may hit 37° after the heater is cut off. That's why the thermostats have adjustable spans so you can find a setting that will give you the average temperature you want. In food service, I have to fiddle with the T-stat settings to keep a proper temperature range where coolers may be opened and closed constantly by the kitchen staff. O_o
TDD
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On 12/2/2012 3:52 PM, snipped-for-privacy@optonline.net wrote:

Most household thermostats I've seen go down to 40-45°F which I suppose is warm enough to keep a whole dwelling above freezing. My digital goes down to 45°F. Here's a link to a digital thermostat of the type I use on walk in coolers for food service and it has a very flexible set-point which makes it very useful for many applications. The type by different manufacturers is available at any refrigeration/HVAC or any industrial supplier. ^_^
http://www.etcsupply.com/ranco-etc111000000-digital-temperature-controller-p-86.html?gclid=CPL9pPSX_bMCFQY5nAodyzgAYA
http://tinyurl.com/ccu2veo
TDD
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Thanks I'll do that.
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On Sun, 2 Dec 2012 13:58:58 -0600, " Attila Iskander"

Never saw one. Most have a minimum of 40. I maintain a large building that is mostly unoccupied but has water for sprinklers and bathrooms and use 40 to 45 as the minimum. That gives me a little margin if the heating systems fail.
Remember, their is also some stratification and cold spots along the wall and windows. There can be some variance side to side depending on solar load, air circulation, etc. If freezing is a danger, you want more than 34 degrees at the thermostat.
Depending on how often the room is checked and what happens below freezing, you may want to kick up the temperature to give even more time, say 12 to 24 hours of no heat before there is damage.
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wrote:

This is a semi-underground uninsulated concrete "bunker" under a 3 season porch. It's primary intent is tornado shelter, but it serves as a cold storage room for freezer, spare fridge, and other food items. Temperature never goes above 40F in summer, even with freezer and fridge in it.
Because in winter, temperatures can fall way below freezing outside, the temperature inside follows along.
The intent is to block it from going below freezing. so that stuff like spare milk and canned/preserved foods don't freeze.
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Attila Iskander Wrote: >

>

Two things:
A fridge or freezer thermostat wouldn't work because a fridge or freezer thermostat makes an electrical contact on a RISE in temperature. So, it would work backward to what you want. It would turn the heater on as the room warmed up rather than turning it on as the room cooled down.
Contrary to popular belief, you can freeze milk. I still remember watching newsreels in school that showed people buying frozen milk by the pound in Churchill, Manitoba. They would take it home, put it in a pail, let it melt and drink it.
--
nestork


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Had not intention of salvaging a thermostat from a fridge or freezer Nor do I intend to do anything that requires fiddling
I'm looking for and off the shelf, plug and play solution. (And a couple have already been shown)

Been there done that. I like having liquid milk when one of the kids goes down to get the next bottle So that's why I intend to keep the room above freezing
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wrote:

Look at my recent post near the top of the thread. There are refrigerator thermostats that have both sets of contacts, can be used for heating or cooling.

What exactly does that mean? You haven't specified if the thermostat you need is even 24V or 120V?
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Attila Iskander wrote:

Once again the answer is http://mcmaster.com just search on thermostat and you will find plenty of choices from ordinary ones that go down to 40F, to "freeze protection" ones that go down to 14F. I see some with a range of -30F to +130F.
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On Mon, 3 Dec 2012 06:08:17 +0000, nestork

Very simple. Use a NC relay and control it with the refrig t/stat
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Can that be translated into plain English ?
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Made perfect sense, to me. Use the Tstat, to signal the relay primary. When the refrig stat is calling, that will invert the binary output, so as to make a NC signal for the secondary, instead of the NO (close on rise) signal from the Tstat. Really very simple. Scooter, try to stay awake. This is on the test, and yes, I can see you in the back row.
Christopher A. Young Learn more about Jesus www.lds.org .

Can that be translated into plain English ?
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On Mon, 3 Dec 2012 20:34:25 -0600, " Attila Iskander"

Normally closed relay - then the thermostat energizes the coil and opens the contacts.
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Ok I get it now
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On 12/3/12 8:34 PM, Attila Iskander wrote:

NC is normally closed. The normal position of relay and switch contacts is their position when no outside force is acting on the device. The refrigerator thermostat normally kicks the fridge on when the temp gets too high by closing a set of contacts. The thermostat would energize your relay to open the relay contacts if the temp was above your set point. They, in turn, would shut your heater off. The thermostat's contacts would open if the temperature gets below your set point. That would denergize the relay. The normally closed contacts of the relay would close. That would allow power through them to your heater. It would work fine but there are off the shelf products to do the same thing.
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