HVAC automation


Staff member
I have a single zone HVAC setup, and my thermostat is located in a very open area. At night, I want my AC to run just long enough to cool down my bedroom (which takes minutes versus 10-20 minutes for my living room), so I am thinking about automating this.

If I replace the dumb thermostat with a nice HAI thermostat, connected to my Elk, which also will be connected to an Elk temp sensor in my bedroom, would this be a good setup? I am mostly concerned about being able to override the thermostat.

The setup should be fine....however, you will have to use different rules.

If you write a rule based ont he temp in the bedroom then how will you manage the temp in the big area. It gets further complicated if the bedroom is on a different floor. In my case my bedroom is upstairs and the temp is always different than my temp in the living room that is on the graound floor.

It will work but you will have to write rules based on what you are trying to accomplish and how it will effect when you don't want to run it by the bedroom scenario.

If you can get the thermostat and the temperature sensor connected directly to the Elk (which appears to be the case here), then it just becomes a question of writing the right rules. You would also need a way to activate this mode, which could be anything (Elk keypad, X10, etc.). The harder part is alternating between any "special" modes and the standard mode. Ideally you would store the current normal settings just before executing a special mode so that they can be restored later.

I'm also planning a few of these modes myself for my RCS stat and I'm planning to do it along the same lines. To start with I want to create modes to:

- On request, turn on cooling for (eg: an hour) to dehumidify, but then put regular settings back.

- On request. turn up heat by 1 degree for up to a certain amount of time.

- Lower cooling setpoint by 1 degree early in the morning in anticipation of a very hot day, going back to regular setpoint during the next night.
I have an RCS TR40 and associated add-ons, but I must admit I've been sorely tempted to use one of my older embedded controller boards to drive the system directly. The TR40 does exactly what it is supposed to do. Nice and boring and safe.

Of course, I'd probably blow something up with a home-brew HVAC controller, so I'd probably better stick to the TR40.

FWIW, I was toying with the idea of active registers or dampers and temp sensors in each room. (With a back pressure bypass of course!).

Nah, just not enough hours in the day.. Perhaps after they extend days to 48 hours...