As in my previous post the thermostat inside our 4 year old Hotpoint freezer has failed and isn't replaceable due to being buried in the foam lining of the casing.
Ive bought this Inkbird temp controller
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happily turns the power to the freezer off at -18 degrees and on again at -16.
However when the temp controller restores power at -16 the freezer doesn't restart! Yet it did restart whilst using the temporary plug in timer set to off/on every 30 minutes.
If the lamp doesn't work, try setting it up in reverse as a thermostat for heating, by connecting a heater to the "heating" socket rather than using it a freezer stat and plugging in to the "cooling" socket. If heating works, it would suggest that the cooling side is faulty in some way.
"[Heating Cooling Dual Output & Delay Protection] Dual relay output to connect in a position with refrigeration and heating systems at the same time. Heating / Cooling differential function can be set to protect separately for cooling and heating for temperature control of violent change.
Also, compressor delay protection for compressor control." <=== what does this mean ???
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Refrigerant compressors come in two types. Some compressors can tolerate a "slug of liquid" on the suction side. Other compressors might be damaged by the ingestion of liquid (such as a piston compressor). We use a lot of scroll compressors instead, because a scroll compressor can tolerate a small amount of liquid in the line.
If you delay the switch-on of a compressor, right after it switches off, this gives time for liquid in the suction side to boil and turn back into a gas. Reducing the chance that an "intolerant" compressor will be presented with that slug of liquid.
So even when the temperature criterion is met, the unit may delay turn-on, for the number of minutes you programmed it for.
That's answered a question I've had for a few days. I have just started using a portable air conditioner, and they tell you not to turn it on for three minutes after turning it off (in fact, it has a timer circuit to prevent that).
Historesis in the thermostat? Most thermostats have a different on and off value depending on whether the temp is falling or rising, otherwise it would be cycling on and off very fast. You can show this on a fan heater quite clearly, as the knob has to be turned back further to make it come on, than it does for it to go off. Brian
Are you sure its actually turning it on though? Also of course there could well be another thermostat somewhere else. It hold work though I think expecting it to be as accurate as 2 degrees is a bit too much. Brian
Are you just testing by, say, putting the probe inside the freezer to see at what temperature the compressor goes off and then removing the probe to raise the temperature quickly to see when it comes on again or are you running it as you would normally? The instructions indicate that there is a compressor delay of up to 10 minutes if you try and cycle between the temperatures too fast. The timer (up to 10 minutes) is initialised when cooling stops.
It has provision for a startup delay, I had that set to two minutes, Ive increased it to four and its now working fine, currently set to switch off at -18c then on again after a drop of 2.5c.
I'm now playing around with different positions with the sensor for best overall control.
The measured temperature rising from -18 to -16 in less than 4 minutes suggests it was measuring the temperature of free air. FWIW one sensor position known to avoid that is inside a bag of petit pois.
Isn't free air what you want? The bag of petit pois is likely to stay cold for a lot longer, by which time the croissant on the next shelf has already gone soft. In other words, when you open the door and let warm air in, you want the freezer to fire up to cool the air, you don't want the air to be cooled by warming up items in the freezer.
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