C-Wire Shared with Humidifier Control?

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Old 02-18-11, 06:56 PM
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C-Wire Shared with Humidifier Control?

Hi everyone,

I currently have a humidistat beside my programmable thermostat. I am investigating the possibility of replacing my thermostat with a wifi-enable thermostat.

The hiccup is that these wifi-enabled units require a c-wire power source, as opposed to the usual battery-only powered units.

Now I may be (or may not?) lucky in that, right next to my thermostat is my humidistat, which has the c-wire running to it (along with another wire, which I assume switches the whole-home humidifier on and off).

My question is: Am I able to simply pull off the thermostat and humidistat and tee in two connections off it, so that I have a C-wire lead to run to my thermostat and a C-wire to keep on the humidistat?

Thanks!

PS here's a picture of what I mean - I want to simply splice/tee the C-wire right in the wall behind these two so I have two C-wire leads to use:

 
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Old 02-18-11, 08:12 PM
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are you sure it is C and not 24v hot for the humidifier? The humidistat is only a switch and closes the circuit upon drop in humidity. You must ensure it is C before robbing the common for the humidistat. if you have checked this.... explain how, because you may be seeing c through the solenoid valve on the other side of the humidistat switch if not doing this properly.
 
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Old 02-18-11, 10:21 PM
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I am not 100% sure it is the C. I looked at the wire colour (a mauve-ish grey) and then went looked at the loom as it came from upstairs into my basement and into the furnace. I pulled the HE furnace cover and looked at where the loom was split back and the mauve-ish grey wire that was plugged into the clip labelled "C" on the humidistat was going up to the connector on the control board in the furnace labelled "C".

Does that make sense, or is there a chance that I am making a mistake?
 
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Old 02-19-11, 05:05 AM
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Chances are, No there is no C wire on the humidistat. As hvactechfw said, it's an "on-off" switch.

But from what you are saying/see it could be wired "backwards". MOst of the time we wire humidistat between the transformer, and humidifier.

Where does the other wire from the humidistat go to?
 
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Old 02-19-11, 06:17 AM
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how many wires do you have at the thermostat?
Venstar Add-A-Wire 5 Wire to 4 Wire Adapter: Electronics
The accessory can also be used to fix a broken wire, to make one thermostat work like two, to add cooling to a heat-only system, or to add a common wire to a 4-wire system.
 

Last edited by hvactechfw; 02-19-11 at 11:22 AM.
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Old 02-19-11, 09:01 AM
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I have 4 wires at the thermostat and two at the humidistat. I will trace the wires more carefully today
 
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