Honeywell T10 vs Ecobee 4 for HRV Control

[Canadave]

Hi,

I am looking for a smart thermostat options that can control forced air gas furnace  + ac + HRV.   I would like the thermostat to run the HRV to optimize air quality and reduce / control humidity in the winter (eliminate condensation)  I would also like a manual HRV timed function.

I have narrowed my search down to the ecobee 4 / 5 or the honeywell T10. 

The two thermostats manage the HRV differently:

Ecobee
- has an option to use HRV to reduce humidity in the winter (I like this to protect against window condensation, though it's not clear how it decides to manage humidity and to what level or if I can set a target humidity, etc..)
- other than humidity control, basically runs the HRV x minutes per hour for when the house is occupied and unoccupied based on a setting

Honeywell T10
- runs HRV in an  ASHRAE mode based on input of home square footage, HRV CFM, number of bedrooms
- if not in ASHRAE mode, HRV runs based on a % of time
- has various lockouts that prevent HRV cycling (i.e., based on outside temperature)

I don't fully understand what ASHRAE mode is.  I think it just calculates the ideal air exchange for your house and based on CFM of the HRV, runs the HRV to ensure the ideal amount of air is exchanged regardless of indoor or outdoor humidity.   I was surprised at this and followed up with Honeywell who confirmed there isnt any specific humidity management with the HRV or ASHRAE mode. 

I like the idea of the ecobee humidity control for the winter and condensation,  but I'm unsure how well this even works with no configurability or settings. Will it also not run the HRV on humid summer days?   I also like the Honeywell T10 ASHRAE based ideal ventilation strategy, but wonder how this will work from a humidity standpoint (both in the winter if humidity gets too high causing condensation, or in the summer with too much ventilation causing damp air indoors).   Maye ASHRAE accounts for humidity somehow?

Interested in expert feedback on the these two HRV control approaches and which may be better and why.  Also, if there is another thermostat option with hrv control I may be overlooking. 


Thx.

[organometallics]

I cannot speak for those T-stats, but can speak of how a t-stat can control all those. I have a thermostat controlling my HRV (plus a/c, furnace and humidifier). I have it set to run at least 20 minutes every hour and to automatically run whenever the furnace fan runs (hot or cold). Also, when the HRV turns on (either from the 20 minute rule or from bathroom switch), it will also spin the furnace fan (regardless if its heating/cooling or just off). The HRV is connected to my Trane XL824 thermostat as an air purifier or "Air Cleaner mode".

In terms of how it controls humidity: you set your target level at the thermostat, say 35% when in heat mode and 50% when in cooling mode, in the summer, its dehumidifying with help from the a/c coils, while in winter, its both humidify (by humidifier) and dehumidify (by the HRV). They all work together to reach those target values. Yes, the HRV should/will run in the summer, its dehumidifying abilities are greatly reduced in the warm summer months, but will will still work to replace stale air with fresh air.

Also, the HRV I have (and probably other have this also) has a temperature sensor in the fresh-air intake. If it goes below a certain temperature, it will automatically defrost or circulate the air to prevent ice build-up in the core. This is completely controlled by the HRV and not the thermostat.

[ian905]

How you wired everything? I'm trying the set the same thing as you, but with the furnace interlock I can't manage to make it work.

[Admin]

I use the Honeywell Prestige but also have an Ecobee.  I prefer the Honeywell HRV operation to the Ecobee.  The Ecobee just seems to run the HRV every few minutes when you look at the logs.

Neither Honeywell or Ecobee require the HRV interlock wiring to the furnace.  Both thermostats should be able to activate the furnace fan when they turns on the HRV.

[ian905]

I've read multiple post after publishing the previous reply and correct me if I'm wrong, but it seem like I can't control the HRV if I have AC and Humidifier connect to my Ecobee 4. I've programmed my Ecobee to run the Fan "X time / Hour" and I would like my HRV to be following the same pattern but can't figure out a way.

[Admin]

The Ecobee can control the humidifier or HRV but not both.  If you wire the HRV to both ACC terminals you have to setup the Ecobee and it will automatically control the HRV and it should start the furnace fan when that happens.

The Ecobee fan programming has nothing to do with the HRV.