Author Topic: HRV with Nest  (Read 140 times)

Offline sandlerdmitri

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HRV with Nest
« on: April 20, 2017, 01:48:04 PM »
Hello,
I have Venmar HRV unit with 4 wires coming out (Black, Red, Yellow and Green).
Cannot make it run using nest thermostat.
Please, help.
Thanks

Offline Admin

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Re: HRV with Nest
« Reply #1 on: April 20, 2017, 02:34:52 PM »
The NEST can control a dehumidifier or humidifier, not an HRV.  The NEST * terminal is powered with 24V and you need 2 dry contacts.

The Ecobee3 smart thermostat does have dry contacts and will control the HRV.

You only need 2 wires to turn the HRV on and off.  The only downside to using a Ecobee3 smart stat to control the HRV is that you will only be able to control 1 speed not both.  Your HRV is probably wired to Y, R, G and B.  You only need to use G and B wires when using the Ecobee3.  Twisting those 2 wires together should start the HRV on high speed.  The Ecobee3 will have a setting to turn the ACC+ and ACC- terminals to dry contacts.  Connect the G and B wires to those terminals.