Exploring options to interlock and control Venmar HRV

[cmihai]

Hello everyone,

I just installed a Venmar A160H75RT HRV (via simplified installation, or T-4, which requires furnace interlocking). I also have an existing Ecobee 3 Lite with PEK (Power Extender Kit). This is my first HRV and I have so many questions on the wiring front. Hopefully someone faced those challenges and can share some insights.

In terms of interlocking I am extremely confused, as there is little similarity between their wiring diagrams (attached, chapter 3.3.2 and 3.3.3 at the bottom of the page) and the "3 wire interlock method" that I have read about on this forum. In their wiring diagrams I'm not sure whether to connect the HRV wires before the PEK or after the PEK (I'd assume it would be after the PEK since PEK was installed long ago because there was no C wire at the thermostat).

Is it still valid to use the "3 wire interlock method" that I have seen on this forum, such as:
a) connect HRV R (I have no HRV NO, I'd assume NO is the R port on my HRV) to R on furnace board
b) connect HRV C to G on furnace board
c) marette HRV G wire (I have both G and Gf ports on my HRV, I'd assume HRV NC is the G port) to the G wire coming from PEK

The other questions are about how to control the HRV. I realized the built-in control on the unit only offers  MIN and MAX operating modes, other than STB (standby). Kind of disappointing. As per the installation manual (same attachment, chapter 3.3.1), the HRV can be controller via a thermostat and it gives access to AUTO mode (HRV operating according to outdoor temperature). AUTO mode seems optimal.
Is there a way to have my thermostat (Ecobee 3 Lite) control the HRV?
If the answer is no (Ecobee 3 Lite cannot control my HRV), is it better to find a compatible thermostat or buy a Venmar wall control? Do people usually let their HRV run continuously on MIN setting during winter?

Thank you so much for any insights

[Admin]

Have a look at this wiring diagram using a 4 wire interlock.

The Ecobee Lite can't control the HRV but the Ecobee 3 or above can.  You would connect the Ecobee ACC terminal to the HRV Vent terminal, and that would provide intermittent HRV operation of usually 15 minutes per hour, depending on how you setup the Ecobee ventilation settings.

With the Ecobee 3 or above you won't need interlock wiring as the Ecobee will control the furnace fan.

[cmihai]

Amazing, Admin, your diagram matches theirs! Over the last couple of days I have called Venmar and Ecobee technical support numerous times and I can say Venmar support is absolutely clueless (they can read the installation page to you but nothing more), while Ecobee support is much more professional and willing to help, however there's a limit to what help they can extend (e.g. they don't understand their internal PEK wiring).

For the G connection from HRV to PEK I have 2 possible options and I wanted to ensure I select the correct one:
- option 1: connect HRV G terminal to G input port on the PEK (that connects upstream to thermostat)
- option 2: connect HRV G terminal to G output port on the PEK (that connects downstream to furnace)
I am assuming I need to follow option 2, essentially taking the PEK G connection FROM G terminal on furnace TO G terminal on HRV. Would you be so kind to confirm?

In the meantime I have ordered a Venmar wall control to give me better options to control the HRV, but I appreciate you offering the option with the Ecobee ACC terminal. In my case, it would require a 5th wire at the thermostat which I don't have.

Finally, Venmar recommends connections on their Y and W terminals (to the same terminals on furnace) to detect and learn when the furnace runs (cooling or heating) and run at the same time to avoid extra runs. Do you have any experience with these optional connections?

Thank you so much.

[Admin]

I have noticed depending on the version of Ecobee the PEK wiring is different.  But for the Ecobee 3 Lite the Ecobee C wire goes to the PEK G terminal upstream to thermostat.  So you would connect HRV G wire to PEK G terminal downstream to furnace.  Yes to option 2.

I've never used the optional W and Y connections but it says,

The Virtuo technology allows synchronizing the unit operation with the furnace/AHU operating time. It prevents unnecessary AHU operating time while providing a better air distribution.

I'm not 100% sure it works with the Vanee main control.  They also sell an Advanced Touchscreen model.  I assume it just delays the ventilation until there is a call for heating or cooling so that the HRV runs with them when needed.