I have this controller. It's designed to monitor the ambient temperature. When it drops below a set point, I believe that point is adjustable from 0 to 61 degrees F, it turns on whatever is plugged into it. You set the time and it will come on two hours prior to that time. It's intended purpose is to power an engine block heater, mostly for Diesel engines. Well, I have two of them. They CAN be used on gasoline engines as well. All you need is an engine block warmer of some sort and it will switch it on.

Inside is a small relay, SPDT type. The NC portion is not used. When commanded, the relay closes the NO contacts and turns on a small heater, 1800 watts. It's 120VAC powered and when the heater comes on power is conducted through this device.

As mentioned, there's a relay with an unused NC terminal. I tested it. It's closed when the system is not powered. So I could conceivably rewire it to shut something OFF at a given temperature. Unfortunately the temperature range is only adjustable between 0 & 61˚F. Thought I might use it in the reverse mode, where I use it to turn OFF a device when a drop in temperature reaches a preset point. IF (big IF there) IF I can change the setting range to run anytime temperature is above - oh, say 100˚F then I would have a use for it. Not the design intended use, but a bastardized method. As I said, I can rewire the relay (cut a trace - add a jumper) and make it turn something OFF (instead of ON) when temperature drops below a set point. Unfortunately I can't think of something I'd want OFF when temp drops below set point.

Any ideas or suggestions? I DO have a fish pond and don't want the pump running when temperature drops freezing so I COULD conceivably use it there; but as I said - I don't have a ready purpose for it.

Whatcha think?

 

Hi. Try operating a fan that pulls warm air from attic space into dwelling when temperatures deserve the action. Or / and reverse, at hours the attic air is cold and dwelling is warm. Or venting the dwelling into attic if attic is too hot. Or sucking outside air into whatever benefits from it, avoiding cooling/heating equipment operation when possible. It takes a convoluted logic, timing, idling, hysteresis, sensors at exterior, interior, attic, to save energy.

 

Hi. Try operating a fan that pulls warm air from attic space into dwelling when temperatures deserve the action. Or / and reverse, at hours the attic air is cold and dwelling is warm. Or venting the dwelling into attic if attic is too hot. Or sucking outside air into whatever benefits from it, avoiding cooling/heating equipment operation when possible. It takes a convoluted logic, timing, idling, hysteresis, sensors at exterior, interior, attic, to save energy.

The problem is the available adjustment for temperature range. IF I modify the unit to switch OFF when temperature drops below the set point I could be making living spaces just flat out too cold.

I have been toying with the idea of making an insulated cabinet for my paints and stains. IF the temperature drops below the set point the heat comes on and keeps the inside of the cabinet from getting too cold, or freezing.

 

I have been toying with the idea of making an insulated cabinet for my paints and stains. IF the temperature drops below the set point the heat comes on and keeps the inside of the cabinet from getting too cold, or freezing.

If this is the project you have in mind I wonder if using the controllers you have is the simplest and best solution. How about a mains driven thermostat (usually used for central heating control) to turn on/off at the set temperature (with suitable hysteresis) controlling an incandescent light bulb and fan if necessary to distribute heat. If the cabinet is well insulated you may not need much power to keep it warm.

If you want to keep it low voltage, there are low voltage thermostats, fans and automotive bulbs which would do the trick and maybe give tighter control with less built in hysteresis.

 

If this is the project you have in mind I wonder if using the controllers you have is the simplest and best solution. How about a mains driven thermostat (usually used for central heating control) to turn on/off at the set temperature (with suitable hysteresis) controlling an incandescent light bulb and fan if necessary to distribute heat. If the cabinet is well insulated you may not need much power to keep it warm.

Most thermostats don't go much below 60˚F. I wouldn't want to be keeping paint that warm if not necessary. These silly controllers can be set for temperatures of 0˚F to 61˚F. Far lower than what a conventional TC would do.

If you want to keep it low voltage, there are low voltage thermostats, fans and automotive bulbs which would do the trick and maybe give tighter control with less built in hysteresis.

Had in mind something like a heating pad set on low. If temperature drops below a set point, in this case 40˚F then the pad comes on. It doesn't have to be in direct contact with paint cans, just somewhere at the bottom so its warmth can rise.

We'll see. Willing to consider other suggestions as well. Also keep in mind I can modify this to switch OFF at or below set point. Meaning it could be used as a ventilation controller. But the problem with that is the temperature range.

 

Good point about thermostats, although how about a froststat? Quick search showed one that can be set between -5C and 15C.

Heating pad sounds good, placed at the bottom of the cabinet it’d probably heat evenly enough with natural convection without needing a fan.