I want to turn the fan-only mode on for my HVAC if the temperature of the top floor is 3 degrees hotter than my basement.
I have a temperature sensor on both floors, but I can’t seem to find the appropriate WHEN card to say “When the temperature of the top floor minus the temperature of the bottom floor is greather than 3”.
Any suggestions?
WHEN
temperature basement has changed
or
Temperature top floor has changed
THEN
calculate number-variable ‘temp-difference’ is {{temp-top-floor - temp-basement}}
WHEN
‘Temp-difference’ has changed
AND
‘temp-difference’ is greater then 3 and fan is off
THEN
turn on fan
In addition to the suggestion of @Wim_Post: both suggested flows can be combined into one, by using the following logic card that you can use to check whether the difference between two temperatures is more than 3 degrees:
This eliminates the use of a separate variable.
I don’t see that logic card. This is what i see for a when card:
I can see what @Wim_Post is saying and would go that way.
It turns out that the ecobee app doesn’t expose the controls that I need this for unfortunately.
It’s an AND card. It’s a condition you want to check (hence AND) not a trigger.
The flow would then be:
WHEN
Temperature basement has changed
or
Temperature top floor has changed
AND
{{temp-top-floor - temp-basement}} is more than 3 is true
THEN
Turn on fan
You are correct, the only controls ecobee allows are setting system mode (automatic/heat/cool/off). Independent fan settings aren’t there. You can set a specific temp, and “return to program” so you can do a temporary temp override and then cancel it. Not sure why they didn’t expose the fan and dehumidifier (which is what I wanted) in the app.
One thing to be careful of if you use logic that depends on the “Temp has changed” scenario. The temp on those ecobee sensors is very slow to update, so it’s far from realtime, and ecobee’s app appears to be even slower updating. So where your temp sensor data in your ecobee app on your phone updates every 5 minutes (I think), my experience is that the Homey app updates far less reliably. Particularly the motion sensor data. I tried using the ecobee sensors for motion sensor triggering of flows, and it’s useless. The sensors don’t update regularly enough. It’s a battery management strategy in the design of the sensors.
The other problem with that logic scenario is that temps fluctuate all the time, so that logic would be triggering virtually constantly. You’d have to put in logic to mitigate that, such as "when temp differential is more 3 degrees.
A much simpler solution is to just set your ecobee fan to run a minimum of 30 minutes every hour. Unless you have airflow balancing issues, that should keep your spaces within a reasonable tolerance. If you have a three-story structure on a single system, it is incredibly hard to keep the temp stable across all three floors. The loads vary too much. If it’s just a single floor plus a basement, you at least have a chance, but it’s still an airflow balancing problem.
