On 2017-04-27, Jim Wilkins wrote:
"DoN. Nichols" wrote in message
...
On 2017-04-26, Jim Wilkins wrote:
"mike" wrote in message
news On 4/26/2017 3:02 AM, unk wrote:
I want to cut AC power if the temperature drops below a
close-to-freezing
temp, and I want it to work even if there's no power (takes care
of
the
power fails first then system freezes then power is restored -
bang
goes
pump motor). This needs to be accurate to about 1-2 degrees.

[ ... ]

http://www.ebay.com/bhp/capillary-thermostat

Not the same, but it reminds me of something used for
temperature controlling a circulating water bath.


http://www.philadelphiainstrument.com/thermoregulators.asp

[ ... ]

These made accurate mechanical thermostats obsolete:
https://www.amazon.com/AGPtek-Digita.../dp/B00BVWYH5A
-jsw


Agreed! I have a nice one by Omega for my heat-tread oven which
can be turned on, set for 1800 F, and overshoot by only one degree F.
(It pauses about 3/4 of the way to temperature and stops heating for a
bit to calculate the overshoot and compensate for it.)

But he was looking for something mechanical -- or with a minimum
of electrical, so something like what I pointed to, with a couple of
relays, could do it -- with minimal battery backup. And the learning
curve, with all of the options which can be set in the controllers, may
be a problem.

Enjoy,
DoN.

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