Adding an HRV Controller

[YYC_duel_fuel]

Hello,

I was hoping for a bit of input on adding an HRV controller to an existing system.

My current wiring setup is shown in the first image below. Our HRV unit is wired with a simple switch and is interlocked to the furnace blower on "HI". As a side note: looking at the lifebreath info, it looks like my interlock is a bit different - running only through the COM and NO connections. It seems to function fine (flipping the HRV switch turns the HRV and furnace blower on), just wondering why it was done this way?
Is it that this setup allows for the HRV switch to activate the blower when turned on, but my thermostat can also activate the blower to recirculate air in "fan only mode" if I want to (i.e. no HRV)?

Anyway, more to the point, if I opt for a Lifebreath controller (as shown in the second image), it looks like a simple 3-wire install on the HRV terminals (RED, YEL, GRN). Would I also simply remove the 2-wire plus jumper setup I currently have for the switch (HI, ON and RED)?

Would installing this controller have any impact on the interlock with the furnace? Basically, I'm just looking to have a bit more control on when the HRV comes on (time per hour, humidity, etc.) vs. a simple on/off switch.

Thanks in advance for any feedback!

[Admin]

What you did should work perfectly.  The only issue I see is the interlock is backwards.  COM should go to furnace G and NO should go to furnace R.

The reason the NC and 3 wire method is used on the interlock is because on some systems, using the 2 wire method, can cause the AC to run.  To use the 3 wire method you would connect COM directly to the furnace G terminal.  Then marrette the thermostat G wire, you removed, to the NC wire.

[YYC_duel_fuel]

Thanks very much for the feedback - not sure why the interlock was done this way in the first place, but like anything, there seems to be a whole range of HVAC installers out there. The heat pump is a new addition to the system by a different contractor, so maybe the original installer figured it wouldn't be an issue (assuming this is analogous to your AC comment).

At the very least I will flip the COM and NO wires. To add a 3rd wire I would need to run an additional wire, so that might be what I do at some point. But in the meantime, while I haven't seen an impact on the heat pump (AC) being turned on, I'll keep an eye out for it.