Free cooling plus two stage cooling

Not sure if this should go here or in Customization…

I’m trying to better manage a setup for a small computer room and think I might could make the HestiaPi work with some coding work, which I can probably figure out. I’ve never used openHAB though but the coding doesn’t look too bad.

I just wanted to see if I’m crazy or if this sounded feasible. I see the version on the crowd funded page has four relays. I would like to use one for dehumidify (a standard feature it looks like), one for free cooling, and the other two for two stages of cooling.

I don’t see anything for “free cooling” and about the only commercial thermostat I’ve seen with this is some from Venstar. It wouldn’t have to be a “stage” in my case, but essentially monitor the outside temperature, and it’s below the room temperature by a few degrees, activate the free cooling damper/fan. I know I’d need to interface an outside temp probe but that looks fairly easy to do. The main thing would be the coding but it’s pretty simple logic.

For the two stages of cooling, I don’t see why the heating stages can’t be “inverted” so to speak to work for the cooling instead.

Does this sound like a doable project?

Once you give openHAB the outside temp, “swapping” heating with cooling would be very easy. Checkout the rules/default.rules file inside the openHAB dir in our ONE branch on GitHub. I think the rule is called checkcurrtemp or similar.

What are the criteria for each cooling stage?

Cool idea :wink:

Thanks for the reply!

I went ahead and manually installed HestiaPi on a Pi 2B I had laying around so I could use it somewhat, although of course with no relays or sensors and only remote control.

I looked at the code and saw the Heating2Timer and Heating2Delta and how they handle the second stage. I think this would work well.

The more I thought about it though, I think it really needs to have 3 stages instead of just 2. This looks like it wouldn’t be too hard to implement, another timer and delta along with the logic of a total of 3 pins and another routine.

In my case for stage 1, which looks to be handled by the “checkcurrtemp” a call could be made to get the outside temp. If it’s, say 3 degrees below the temp setpoint, then CoolingPin could turned on, otherwise just max out the Cooling2Timer and change Cooling2Delta to 0 so stage 2 will come on.

Stage 2 and 3 would work just the same as Heating and Heating2 do now, you would have a threshold and a set time before the stages were activated, the only thing would be to activate stage 2 right away if the stage 1 “free cooling” wasn’t available, which I think just forcing the timer and delta settings would do that.

The “checkcurrtemp” could be modified to check for a setting such as “free cooling” and then adjust the timers/delta accordingly if it’s actually available or not, assuming “free cooling” was enabled.

Sorry if I’ve rambled on here, but hopefully this makes some sense.

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