Automating HRV (Venmar)

[tomatopi]

I searched the web for HRV control and didn't come up with much, so here are my findings so far.

I have a Venmar HRV with a C4 controller. It's a basic unit with Off, On, Boost, and Recircuilate mode. There are 4 wires to the controller.

Green and Black seem to be the main control wires. If they are disconnected, the main switch on the HRV unit takes control and it defaults to "On". The other settings are controlled with various resistance loads between these wires.

44k = Off
22k = On
11k = Boost
6.5k = Recirculate (*see below)
3.6k (momentary) = Reset Filter Indicator

There are also Red and Yellow wires. If I remember correctly, the Yellow is just for a Change Filter LED. The Red and Black wires seem to be shorted with the Recircuilate mode is on. I never went so far as to determine if this is actually affecting the recircuilate damper or just the "Fresh Air" LED bypass on the panel. I only use On and Boost so didn't explore it any more. Ceiling fans tend to use less power for air circulation so I just ignored recircuilate.

I wired these to an HAI relay board using two relays. I put two 22k resistors in series for the default "Off" position with one resistor between the NO and C of the first relay and the other between the C of the first relay and the C of the second relay. I put a third resistor between the NO of the first relay and the NO of the second relay. The green from the HRV was on the first relay NO and the black was on the second relay C. In this configuration, there is 44k resistance when both relays are off. When Relay 1 is tripped, it bypasses the resistor between NO and C giving 22k resistance - On. When Relay 1 AND Relay 2 are tripped, it puts the resistor between the two NO's in parallel with the resistor between the two C's giving 11k resistance for boost. The only thing to remember is to have Relay 1 (On) on or both Relay 1 (On) and 2 (Boost) on at the same time, not just 2 (Boost only). There probably is a more elegant way, but this setup used 3 resistors of the same value to make things easy. Programming can easily bind the relays so I considered it a non-issue.

Hope that helps somebody else out there.

Peter

f

 

[drozwood90]

Which unit did you get? I've been looking, and the Honeywells are the ones that come up the most.

--Dan

I searched the web for HRV control and didn't come up with much, so here are my findings so far.

I have a Venmar HRV with a C4 controller. It's a basic unit with Off, On, Boost, and Recircuilate mode. There are 4 wires to the controller.

Green and Black seem to be the main control wires. If they are disconnected, the main switch on the HRV unit takes control and it defaults to "On". The other settings are controlled with various resistance loads between these wires.

44k = Off
22k = On
11k = Boost
6.5k = Recirculate (*see below)
3.6k (momentary) = Reset Filter Indicator

There are also Red and Yellow wires. If I remember correctly, the Yellow is just for a Change Filter LED. The Red and Black wires seem to be shorted with the Recircuilate mode is on. I never went so far as to determine if this is actually affecting the recircuilate damper or just the "Fresh Air" LED bypass on the panel. I only use On and Boost so didn't explore it any more. Ceiling fans tend to use less power for air circulation so I just ignored recircuilate.

I wired these to an HAI relay board using two relays. I put two 22k resistors in series for the default "Off" position with one resistor between the NO and C of the first relay and the other between the C of the first relay and the C of the second relay. I put a third resistor between the NO of the first relay and the NO of the second relay. The green from the HRV was on the first relay NO and the black was on the second relay C. In this configuration, there is 44k resistance when both relays are off. When Relay 1 is tripped, it bypasses the resistor between NO and C giving 22k resistance - On. When Relay 1 AND Relay 2 are tripped, it puts the resistor between the two NO's in parallel with the resistor between the two C's giving 11k resistance for boost. The only thing to remember is to have Relay 1 (On) on or both Relay 1 (On) and 2 (Boost) on at the same time, not just 2 (Boost only). There probably is a more elegant way, but this setup used 3 resistors of the same value to make things easy. Programming can easily bind the relays so I considered it a non-issue.

Hope that helps somebody else out there.

Peter

f

 

[tomatopi]

I can't remember the model of Venmar HRV exactly. They use a couple standard controllers for thier HRV's out there. C34 is one of them (made by Venmar). If your Venmar uses the C34 controller, this should work.

I just noticed, I typoed the original instructions and said C4 not C34. The C34 is on the bottom right of the remote.

Peter

Which unit did you get? I've been looking, and the Honeywells are the ones that come up the most.

--Dan

I searched the web for HRV control and didn't come up with much, so here are my findings so far.

I have a Venmar HRV with a C4 controller. It's a basic unit with Off, On, Boost, and Recircuilate mode. There are 4 wires to the controller.

 

[drozwood90]

I actually meant which HRV unit...not the controller.

Thanks!

--Dan

 

[tomatopi]

I think it was HRV2500 or something. It was a cheapie model to satisfy building codes only. It works. No balancing or anything. I think they're sold under another brand name as well, but can't remember.

Peter