Hubitat HVAC configuration assistance

[dmayo2]

Hubitat HVAC

I have six Keen vent zones. Each monitor a room sensor, and compare it to a virtual thermostat to determine if vent open/closed.

I have RM rules for each vent-zone. (let’s say cooling mode) So, if the room sensor says it’s too warm (comparing the setpoint of the virtual thermostat to the room sensor), turn on AC, and when it reaches set-point to turn the AC off. I have Ecobee4 integration.

I’ve tried numerous ways to configure the system but can’t quite come up with the ideal solution. I’ve tried using global vars, auto settings, etc. I can’t seem to wrap my head around the main Ecobee4’s role and how to control it.

If one zone needs the AC on, it’s easy to call the Ecobee4 and switch mode to cool, and Keen will keep all the vents in the zones that don’t need to cool down closed and open the zone that needs it. Easy peasy.

If a second zone needs the AC, it calls Ecobee4 and sets it to cool, but since it’s already on that mode, no issues, the AC just continues to cool, and Keen opens the vents to the second zone. Easy peasy.

I’m trying to figure out the best way to turn the AC off in different scenarios.

So, when one of the two cooling zones reaches the set-point, the KeenecticLite will tell the vents in that zone to close. Easy peasy. But what does that zone/virturalThermostat tell the real-life Ecobee4? If it changes the mode to off, then the AC turns off before the remaining zone is cool enough (hasn’t reached its set-point as determined by that zone’s virtual thermostat).

Does HE poll (or the virtual thermostat) poll the Ecobee4 (or vise versa) to see if any other virtual Therms are set to cool and adjust as necessary?

Do I set the Ecobee4 to auto from the first zone to reach temp? Will that allow the AC to remain on for the second zone that is not at setpoint yet?

Do I set the Ecobee4 heating set-point to, say 45F in the summer to make sure it never turns on, and let the virtual Thermostats turn “off” the AC by setting it to Auto? Do I set the heat and cooling set-points via the virtual thermostat?

And, finally, how do I control the Ecobee4 setpoint? If zone A (above example) wants to cool to 72F, and zone B to 70F? If zone A reaches first, what does it tell Ecobee4? Do I keep the Ecobee4 cooling set-point to something lower than the lowest zone set-point is configured? Or is everything dynamic?

Thanks.
cc: @reid.a.baldwin

[reid.a.baldwin]

There are a bunch of issues here.

I gather that you have an Ecobee in some central place in your home and have six Keen vents for six rooms. Are there places in the house that have normal (not Keen) vents? Is the Ecobee in one of those places?

One issue is that six zones probably means that at least a couple of those zones are relatively small compared to your air handler. Having only one zone open would likely create too much pressure in your duct system. If there are plenty of uncontrolled vents in the house that are always open, then this may be ok.

Also, switching your Ecobee to cool is not the same thing as turning your air conditioning on. When the Ecobee is in cool mode, it will turn the air conditioner on if the temperature it senses (wherever it is) is higher than its cooling setpoint. If you set the cooling setpoint very low, then it would do what you are thinking (but I am not so sure that is what you really want).

Doing what you are trying to do with RM would take some complicated rules. They would need to check all of the virtual thermostats and temperature sensors whenever a zone is satisfied. I don't encourage you to go to the work of implementing that because I don't think it would work well.

[arnb]

@dmayo2

I’m trying to figure out the best way to turn the AC off in different scenarios.

Create a simple RM rule
Trigger when any vent closes
Payload
if all vents are closed, AC off

This assumes the vent device has some sort of status attribute that can be checked. Otherwise you will need to create and manipulate some global variables reflecting the status for each vent.

The single point ecobee temperature reading may override your On/Off decisions. However, if you set the CoolSetPoint lower than you would normally want, your rule's On and Off commands should override that issue. It may also be necessary to adjust the ecobee's hysteresis setting.

Personally, I would set the Thermostat to Cooling mode for AC, and Heat when needed. I'm not a big fan of Auto.

And follow the advice of @reid.a.baldwin above regarding the mechanical system!

[dmayo2]

Thanks.
I was trying something along those lines in that I had each RM set a boolean global var if that zone needed AC or not. I just couldn't get the AC on/off Rule to work. The initial trigger is only available with OR, when I wanted if ALL vent-zones were 0/false, then turn AC off. There are sub conditions available, but I'm not sure how many subnested if/then statements I should do (or basically a switch statement that breaks out if any of the vent-zones are true, thus still needing AC.

Any suggestions on what to do with set-points? From each ventRule? or from the main Rule that checks if all vents closed/open?

[arnb]

A single rule should do. For example something like
if (device1(attribute) == closed && device2(attribute) == closed....ad infinitum)
thermostatdevice(off)

Should you be forced (hopefully not) to use globals, you will need to set the related trigger global off/false prior to testing. The device's "Current States' lists all available attributes.
(above is logic, likely not the RM structure )

Should you be forced to use a global...
Set up a single global numeric field initially at zero
Add 1 each time a vent opens
subtract 1 when a vent closes
Then the test would be
If (globalnumber < 1)
thermostat(off)

[dylan.c]

@reid.a.baldwin

One issue is that six zones probably means that at least a couple of those zones are relatively small compared to your air handler. Having only one zone open would likely create too much pressure in your duct system. If there are plenty of uncontrolled vents in the house that are always open, then this may be ok.

Another issue with small zones is a lack of airflow across your cooling system. Lower airflow means that the reduced amount of air is cooled to a lower temperature. If the airflow is too low, the temperature gets close to 32 degrees F., and the condensate on your coil freezes. This further restricts airflow, resulting in lower temperature, more ice, and the cycle continues until your AC kicks out on low or high pressure (I forget which). This may not hold true for systems with variable speed fans or AC compressors.

Did you ever get this to work? I just got an ecobee connected using the Universal Ecobee Suite.
I have a rule using Ecobee Stat reports equipmentOperatingState(idle) 'changed' as a trigger. I can see the state change in HE when the app polls the ecobee service, but the rule never runs. Just curious if you've tried something similar.

[reid.a.baldwin]

@dylan.c

Another issue with small zones is a lack of airflow across your cooling system.

We are actually referring to the same problem. Excessive pressure and low flow rate are closely related. Some blower types (ECM) work hard to maintain flow when there is increased resistance and use more power. Other blower types (PSC) produce less flow when resistance increases.