Author Topic: nest and hrv  (Read 2523 times)

Offline godfather55v

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nest and hrv
« on: November 30, 2016, 09:30:37 AM »
so I broke down and got a NEST thermostat!  Got it installed, works great w/ my carrier system including 2 stage furnace, 1 stage air condition, and humidifier.  However i have this HRV staring at me.  My local installer said to just put it on a timer to run 15/hour.

I have two questions,
1. would i be better getting a fantech controller that would be more proactive about monitoring usage?
2. not understanding the furnace interlock, i would think i would want this to run when the furnace/aircon isn't running.  It does have a fan of it's own.  There was no interlock setup w/ it originally, but then again it was all ran though a carrier thermostat. 

a little background, i live in iowa, HRV model hrvxxlhb1150, furnace 59tp5a

Many Thanks!

Offline Admin

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Re: nest and hrv
« Reply #1 on: November 30, 2016, 10:18:56 AM »
The NEST can control a dehumidifier or humidifier but not both.  I don't think it will control an HRV.  The Ecobee3 has dry contacts you can use to control the HRV.  I would leave the NEST controlling the humidifier.  Make sure to set the NEST to control the humidifier with heat only.

The Carrier HRV is really a Venmar/Vanee HRV rebranded.  You can use the lite touch control and wire it to B, G and Y.  It offers intermittent operation.  The HRV should be interlocked with the furnace so that the furnace fan runs anytime the HRV starts.  The HRV motors are only designed to exhaust stale air and bring in fresh air.  You need the furnace fan to distribute the fresh air throughout the house.  Make sure to use the 3 wire interlock and wire the NO, NC and C terminals on the HRV.  The HRV should not be used during the summer months and can be turned off..

Offline godfather55v

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Re: nest and hrv
« Reply #2 on: November 30, 2016, 03:10:10 PM »
w/ the interlock, does the furnace blower run on high or low, or what ever speed the hrv is operating?

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Re: nest and hrv
« Reply #3 on: November 30, 2016, 03:14:19 PM »
The HRV interlock ties into the furnace G wire and powers the continuous fan.  When you turn the thermostat fan to ON, that furnace fan speed will be the same speed used when the HRV is turned on, once interlocked.  The furnace fan has no idea if the HRV is running in low or high speed.