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. ^_^
On Dec 3, 2:40 am, The Daring Dufas <the-daring-du...@stinky-
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:
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.
On 12/3/2012 6:54 AM, email@example.com wrote:
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. ^_^
That's what the span adjustment is for. You set a thermostat for say
35Â°F with a span of 3Â°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 35Â°F "cut-out" and 32Â°F "cut-in". This
will preventing the heater from going on and off and on and off. The
heat will turn on at 32Â° and off at 35Â° but there will be some overshoot
with the temperature where it may hit 37Â° 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
On 12/2/2012 3:52 PM, firstname.lastname@example.org 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. ^_^
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.
This is a semi-underground uninsulated concrete "bunker" under a 3 season
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
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.
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.
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
So that's why I intend to keep the room above freezing
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.
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
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
It would work fine but there are off the shelf products to do the
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