Nest Install w/ Humidifier

Old 01-03-14, 07:22 PM
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Nest Install w/ Humidifier

Looks like I may have posted to wrong section...Can a mod please move to thermostat section? Thanks

Hi, I am going to install my new Nest thermostat in my home and just need some reassurance that I am on the right path.

I currently have a thermostat and a humidistat which are very old (35+). I would like to take out the humidistat and just use the Nest. I know I need to possibly use a relay, but just want to be sure everything looks like it will work. Attached are pictures of the Humidifier and Humidistat.


So as you can see or not (It's a mess of wires...), Two brown wires are attached to the solenoid and go into the humidifier, and a Red and Blue wire exit. The Blue wire from humidifier is connected to the White on humidistat, the Red from humidifier is connected to the C terminal on Furnace, and the Red from humidistat is connected to R on Furnace.

So is mine a powered or bypass humidifier?

THIS is the right relay to buy?

When Nest asks, “Does the unit require the heat to be on to function?” “Should the blower be on when the humidifier is on yes or no?” Do I answer YES to both?

Last edited by tameanaka; 01-03-14 at 07:45 PM. Reason: Wrong Section
Old 01-03-14, 10:16 PM
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Wrong forum.....maybe but no problem.

Your current humidifer is getting its power from the furnace on the R and C wires.

So basically you'd remove the two wires from your humidistat and wire nut them together.

The wire on C would stay right where it was.
You would remove the wire from the R terminal and it would go to the * terminal on the nest which means you'd need an additional wire from your furnace to the thermostat location.

Set your nest so that the humidifier only runs with heat. You don't want the thermostat turning the humidifier and blower on unless the heat is also running.
Old 01-04-14, 06:20 AM
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Excellent. So basically I'm wiring it like a Bypass pictured here.

Yeah I had planned on running a whole new thermostat cable as there are 2 2-wire cables now, and it's all kind of spliced together from whatever was laying around...

So when would a person need to use a relay? Just asking to learn more.

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