Smart Frost and Humidity Thermostat

This is not a project, yet. I’m just noodling the concept and would appreciate feedback before I go further.

I want to control the environment in a cabinet in a remote location. It has power and electronic equipment that is only on some of the time - so the dynamic heat generation changes over time. (For interest, I’m a radio ham and it’s my remote shack).

Currently I have two generic thermostats: one to control a heater if the temp drops too low; and another to control a fan if the temp gets too high. I use two, because the dead band is so wide (currently 4C to 30C).

Temperature regulation has been working fine over the past year. The issue is condensation.

Occasionally, the temp may be slightly above 4C but because the radio hasn’t been on for a few days, the humidity can get to the point where condensation starts to form on metal surfaces. The cabinet is not insulated and this is the UK, so humidity in winter can often be high. I can remove the problem by leaving base power on (e.g. the main PSU) to raise the temperature above the dew point, but I don’t want to do this as I am paying for the electricity.

What I’m considering is adding a humidity sensor input to the Low thermostat that dynamically adjusts the set point so that humidity stays below a defined level. Basically, a generic thermostat with two control loops: one for temperature and the other for humidity.

Has anybody been down this path before? Any thoughts or ideas?

Humidity is very local, so using a sensor to find the dew point will be near impossible.
The winter actually means that there will be less water in the air, also in the UK, but the air can not contain that much water at lower temperatures.
This means to get rid of the dew you will have to raise the temperature to get the air to contain more humidity and then use the fan to blow that air out and suck some new in.
The new air will then be cold and when you warm it up it will again suck up humidity.

The trick here is to get the airflow correct.
Suck cold air in from the bottom and blow hot air out in the top, but not in a higher speed than what you heating can manage, when it have to heat it up.

Maybe you could use one of the custom components below to calculate the dew point,add 1C, then use this as the target temperature for your heater thermostat.

I have commissioned several outdoor equipment cabinets in the UK with anti-condensation heaters but I can’t remember what we used to set the stat’s to.

Thanks, @WallyR. There is passive airflow but the current fan is on/off with no proportional control. I’ll have to noodle a bit more.

Thanks. I think the combination of this with @WallyR’s ideas may be the way to go.