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Unless there's an issue with the relay in the HRV or the interlock wiring, the 3 wire interlock method you described in your first post should work.  The HRV interlock gets 24V from the furnace R terminal to its NO terminal.  When the HRV starts it then sends 24V back to the furnace G terminal.  The thermostat is not involved.

If you had an Ecobee Premium I would suggest switching your humidifier to the 1 wire PEK connection and control the HRV using the 2 wire ACC connections.  You would just fish two of the wires from your HRV control into the thermostat and then set up the HRV for mechanical timer wiring.  You could then eliminate the interlock wiring because the Ecobee would automatically start the furnace anytime the HRV ran.

https://www.hvactechgroup.com/hvacforum/index.php?topic=4532.0

Thanks a lot for your reply! Unfortunately, my HVAC technician ended up removing the interlock wiring from the furnace control board, as he didn't want any potential issues, since we have a new furnace.

Here is the picture of the current furnace board without the HRV interlock. The furnace has a humidifier added as well, connected to my ecobee as a 1-wire accessory (1 wire to ACC+ on ecobee, and another to C terminal on furnace), and a condensate pump connected as well.

Furnace Control Board

Without the HRV interlock, I am able to turn the furnace blower on / off, or in continuous fan mode from my ecobee. When the HRV was interlocked, the ecobee wasn't able to turn the fan on the furnace on. My HVAC technician said something to the effect of furnace board not getting the signal from the thermostat to turn the fan on, via the HRV (not exactly sure what he meant).

Try posting a pic of the furnace terminals and the wire marretted to thermostat G.

If you click USER ACTIONS above you can reply that way and will be able to add pictures.

Does the existing thermostat start the furnace fan if you set it from AUTO to ON?

Here is another pic of the HRV Terminal Block - HRV Terminal Block

MY HVAC Technician connected the Green wire from COM terminal to the G Terminal on furnace board, Red wire from NO was connected to R terminal on furnace board, and the blue wire from NC terminal was connected to the G wire coming from the thermostat, using a wire nut. I think he got the wiring right, so we are unable to understand why the interlock isn't working like its supposed to.

Here are the pictures I wanted to post, but was unable to in the original post.

HRV Controller

HRV Terminal Block

HRV Wiring Diagram from Manual

Hi all,

I am hoping somebody here can help me out, as I haven't been able to find someone locally in last 2 years who could help me understand how my HRV works, or is supposed to. After not being able to find anyone, I read thru the manuals and figured out that the ductwork was connected wrong, and the HRV wasn't interlocked to the furnace. I had my HVAC guy fix all the ductwork, move the controller where my thermostat is. However, when he tried to interlock the furnace as per the Lifebreath manual, it doesn't seem to work.

Here is a picture of my thermostat and HRV controller. As you can see, HRV controller seems to be connected to the HRV properly, using the R, G and Y wired coming from the HRV.



Here is the picture of the terminal block on the HRV showing the R, G and Y wire from the controller, connected to the R, G, and Y on the terminal block.



The problem we have is with interlocking the HRV to the furnace. Here is the wiring diagram in the manual -


As per the wiring diagram, Terminal 8 (NO) is connected to R terminal on furnace, Terminal 7 (COM) is connected to G, and terminal 9 (NC) is connected to the G wire coming from the thermostat using a wire nut.

Unfortunately this doesn't seem to work. If I put my furnace is "continuous fan" mode, the fan blower doesn't turn on at all. Even when the HRV is on, it doesn't turn the fan blower on the furnace on. My HVAC installer was puzzled and said he will try to call Lifebreath to see if they can help out. When he did, they pointed him to the same wiring diagram as above. I was wondering if anyone here can help as well. My assumption is that with this setup, the fan blower should turn on when HRV is on. And I should be able to turn the furnace fan on for some time or in continuous fan mode regardless of whether the HRV is running or not. Is my understanding right? Can anyone advise what might be causing this setup to not work?

Appreciation any advice!

I would recommend visiting all the local HVAC wholesalers.  There is usually a bulletin board listing all the recent job opportunities.

Hi everyone, I recently graduated from the HVAC program in August and received my G2 license at the end of October. I've been actively looking for entry-level HVAC opportunities and have visited over 20 shops in person, but so far I've only had two interviews. I'd really appreciate any advice on finding HVAC jobs or if anyone knows of companies currently hiring in Ottawa. Thanks so much!

Yes, your first step is doing what rmuntz says.  Find an employer to sponsor you and sign you up as an apprentice.  If you have a licensed friend they can just submit their name as the business and act like a sole proprietor.  They will just need to register a sponsor account with their individual account on the STO website.  It's a 1:1 ratio, so a licensed person could only have 1 apprentice. This is all free.

Then you go through the Trade Equivalency Assessment process and the licensed person will sign off on the competency analysis training.  That costs $235 with the STO.  Then you use that to challenge the STO exam for $150.  And they will require the letter you mentioned but it is to prove the hours you have worked. (4500 hrs).

I think the idea is, your employer has to have someone who's licensed on staff. Could be him, could be another employee. Without that, who would you have been training under?