Nest (gen2) + HE265 + Lennox gas furnace)

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Old 02-14-16, 10:09 PM
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Nest (gen2) + HE265 + Lennox gas furnace)

Hi,

I've searched through the forum to try and figure it myself, but the other posts don't use the same equipment or I didn't understand the answer. Here is my question:

I have a gas furnace (Lennox C33-25B-2-3), hooked up to a humidifier (Honeywell HE265) + Humidistat (Honneywell H8908), an air exchanger (Lifebreath 155MAX), an air conditionning (Hiseer?) and a Nest Thermostat (Gen 2).

At the moment, the Nest only controls the heat, cold and fan (with wires Y1-cool, G-fan, W1-heat, Rh-power).

I live in Canada, where we have 4 seasons and during winter I often see ice in my windows (despite my home being less than 10 years old). Looking at the humidistat, it seems I should adjust the humidity % depending on the outside temperature, but I only think about making the adjustment about twice per winter. This is why I would like to have it hooked to the Nest, in the hopes of reducing ice in the windows.

Looking at the Nest Pro manual, I'm trying to figure out if I have a 1 wire or a 2 wire Humidifier, to determine if I need a White Rogers 90-290Q 24VAC HVAC Relay.

Attached is a crude diagram of my wiring (not shown: Wiring of the air exchanger, the A/C nor from the Nest to the HVAC - I can post pictures if needed).

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Do I need a relay? How should I make the connections?

Thanks

PS: I've been hesitating for a long time over weather I should hook the humidifier or deshumidifier/air exchanger to my Nest, since I must choose one of the two. I opted for the humidifier since this is the one that needs "regular" adjusting (during winter) depending on outside temperature, whereas the air exchanger only needs to be "adjusted" during season changes (if at all... I never change its setting actually). Is this the right decision?
 
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Old 02-15-16, 12:18 AM
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Connecting the humidifier to the nest is a good idea. The wiring is fairly basic. The colors or polarity to the humidifier is not important as it is AC. You will need an additional wire from the nest to the humidifier location for the * control.

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Old 02-15-16, 08:38 AM
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Thank you so much PJmax. I did the wiring, it was fairly easy since I have extra strands in the wire going from the furnace to the Nest.

As per your drawing, I've completely taken out the H8908 humidistat from the circuit. Should I leave it attached to my furnace to keep shut the gapping hole in the duct, or remove it and "seal" the square hole with thin aluminium tape?

Regarding the Nest settings, I selected:
*:
Type: Humidifier
Activate: Hum only
Fan: Activate


W1:
Source: Gas
Delivery: Forced air
Fan: Activate

I am unsure about the 3 items in bold above... Is this ok? Or should the humidifier work with the heat? What about the fan? When they say "fan", do they mean the fan from my air exchanger (because I just realized that it isn't hooked up to anything - not the furnace nor the thermostat) or is there a fan in the furnace?

Finally, how should I test that the humidifier is working properly? Nest does offer the "test" option but how to I confirm the humidifier is "on"?

Thanks
 
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Old 02-15-16, 09:36 AM
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You can leave the h'stat in case it's needed in the future or blank it over. Your choice.

I only set up my humidifier installations to humidify with heat. I've found that having the thermostat turn the fan and humidifier on without heat to be ineffective and a waste of energy. Based on your location.... that may be different.

There is a fan/blower inside of your air handler. That's the fan that moves air thru the house.

You can stand near the humidifier.... you should hear the water flowing if it's active.
 
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Old 02-15-16, 10:30 AM
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Thank you so much. This forum - and its users and moderators - are so invaluable. Thank you.
 
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