Location is Portland, OR.
I have a small (6x10) greenhouse on the west side of my yard. In the winter, the outside temps can go below freezing, but even on days when the overnight temp is below 32, the afternoon temp _in the greenhouse_ can get up into the high 90s due to the sun. I set up an inexpensive 2-stage temperature controller (Bayite BTC211) to power a heater below 38 degrees. Since this controller has both heating and cooling functions I thought I could use it to power both a heater for low temps and an exhaust fan for the sunny winter days when the temp can get quite high.
Unfortunately, all the temp controllers I've been able to find operate with a single set point and "cooling differential"/"heating differential". So for my application I tried using a set point of 60 with cooling differential=25 and heating differential of 20. This works, the heat turns on at 40 (60 minus 20) and the exhaust fan turns on at 85 (60 plus 25). The problem is that once heating or cooling is triggered, it won't stop until the set point is reached.
For example, if the temperature starts out at 50 and drops below 40 the heat kicks on but won't turn off until it reaches 60. Same with cooling. If the temp goes above 85 the exhaust fan starts but won't turn off until the temp drops below 60. This is OK in winter, but in summer it means the exhaust fan is running much longer than it needs to.
What I really want is a simple controller that behaves like a home thermostat, with TWO set points, one for heat and one for cooling. For example I'd set the heating temp to 40 and the cooling temp to 80. As long as the temperature stayed between 40 and 80 neither the heater nor the exhaust fan would run.
I've spent a couple of hours online and have been unable to find anything that works this way, in a form factor similiar to the Bayite BTC211.
Anyone have any suggestions on where to find such an item? I guess one solution is to use 2 separate controllers, one for heating and one for the fan, but that seems a bit much
