Hello,
When I activate my HRV the furnace fan kicks in. Is it possible to have the HRV kick in when the furnace fan turns on?
Cheers :)
Do you want to activate the HRV anytime the furnace fan starts? If someone turns the thermostat to FAN ON this would cause the HRV to run 24/7.
What kind of HRV and furnace do you have? Is the furnace wired to W1 and W2?
You could use a DPST 24V relay. With Vanee/Venmar we need to close B and G to activate the HRV. So wire the HRV B and G terminals to the 24V coil of the relay. Then wire the furnace R terminal to the NO relay terminal. Wire the thermostat W wire to the NC relay terminal. Wire the C relay terminal to the W terminal on the furnace. This way the HRV will run anytime there is a call for heat.
If you have a two stage furnace using both W1 and W2 this would not work. You would have to use 2 relays.
If you want the HRV to run when the thermostat is set to FAN ON, use the wiring above but instead of using W, use G.
Wire the HRV B and G terminals to the 24V coil of the relay. Then wire the furnace R terminal to the NO relay terminal. Wire the thermostat G wire to the NC relay terminal. Wire the C relay terminal to the G terminal on the furnace. This way the HRV will run anytime the thermostat FAN ON is enabled.
I would just buy a smart thermostat like the Ecobee. Or upgrade the existing HRV controller to one that allows programming. This won't run the HRV anytime the fan runs but at least it lets you control the HRV. Likely you have a HRV control that is either on or off or at the most offers intermittent operation.
Thanks for responding. ;D
I have a Venmar Constructo model # 43110 with a wall control model # 40350. Interlock relay # 90-294Q SPDT 120v.
Lennox furnace model # EL296UHE
Wire the HRV B and G terminals to the 24V coil of the relay. Then wire the furnace R terminal to the NO relay terminal. Wire the thermostat G wire to the NC relay terminal. Wire the C relay terminal to the G terminal on the furnace. This way the HRV will run anytime the thermostat FAN ON is enabled. Just eliminate the existing interlock wiring if you add this relay as you no longer want the furnace fan to start when the HRV starts.
This relay would work for you,
https://www.amazon.ca/Emerson-90-293Q-Enclosed-Fan-Relay/dp/B000H5Y1SA/ref=asc_df_B000H5Y1SA/?tag=googleshopc0c-20&linkCode=df0&hvadid=360115781192&hvpos=1o5&hvnetw=g&hvrand=15717040749204475665&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9061309&hvtargid=pla-307234734456&psc=1
Since you're eliminating the existing interlock wiring you can likely just use that interlock relay to do the same thing.
It may be much easier to just upgrade the HRV control to the lite touch control,
https://www.venmar.ca/220-accessories-lite-touch-constructo-wall-control.html
At least it offers intermittent operation 20 min per hour. I don't think your HRV is compatible with the Platinum Wall control which allows programming
I have an Ecobee 3 Lite and it reads 30%humidity.
I have the constructo wall control # 40350 which I set the dehumidistat control to the outside temp. but it never seems to click off.
I turn it counter clockwise and hear a click, making the hrv run on low. I turn it clockwise past the click making the hrv run on high.
Is my wall control deffective?
No, those controls run 24/7 or off.
The dehumidistat just cycles between low and high speed.
The dehumidistat never reaches the setting I choose.
Well when you turn the dial clockwise, above the click, it enables low speed but the HRV will always run 24/7 if that control is in any position but off.
That why I mentioned the lite touch control. It offers intermittent operation.
Thank you. You have been very helpful.
Here is my wall control. Can it be calibrated?
There is nothing to calibrate. Replace that control with something else.
Min = low speed 24/7
Max = high speed 24/7
The dial is only used when set to Min. If it drops below the humidity setting it will engage the high speed fan.
That control runs the HRV 24/7 in any position but off.
Ideally I would like the furnace fan to come on only when either the main wall control is set to max or the lite touch control in the bathroom is activated.
Here is my hook up diagram.
Originally you only wanted the HRV to run whenever the furnace fan is running. Now you only want the furnace fan to come on when the HRV is set to max or when the bath timer is turned on. That's not how the interlock works. The furnace fan will come on anytime the HRV is turned on.
Can the furnace fan be energized when the HRV is set to MAX only?
No, the HRV interlock wiring starts the furnace fan anytime any speed is activated.
Upgrade your Ecobee to one that controls an HRV. Then you will only be using one HRV fan speed and can set intermittent operation. You can also eliminate the interlock wiring as the Ecobee will start the furnace fan when the HRV runs.
The furnace fans comes on when the HRV is set to MAX only.
Here's what I did. I also was able to calibrate the Venmar main wall control # 40350.