My Carrier furnace does not have a humidifier connection on the control panel. I have two wires from the humidistat. Do I use W-C or R-C connections for a normal operation?
Which humidistat terminals should I use for the humidifier
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Related Solutions
The terminal circled in red should be labeled HUM-H, which is the humidifier (hot) terminal. This terminal is energized to 120 V when the system is running in heating mode.
The terminal circled in blue is EAC-N, which is the electronic air cleaner neutral. This terminal should be tied to the other neutral terminals, as well as the system neutral.
If you move the humidifier transformer wire from HUM-H to EAC-H, the humidifier will run whenever the fan is on. However, this also includes when the system is in cooling mode, which is not recommend.
What you could do, is install an override switch, which will allow you to manually turn off the humidifier during the cooling season. So you'd run a wire from the EAC-H terminal, to one side of the switch. Then connect the humidifier transformer wire, to the other side of the switch. This way when the switch is closed, the humidifier will run with the fan. But when the switch is open, the humidifier will not run.
If you don't want a manual switch, you could mess around with a relay or other control circuitry.
Using a relay, it could be wire up like this.
That way the humidifier will run whenever the fan is running, except when the thermostat is calling for cool.
From the website:
The summer shutoff damper on bypass units increases efficiency and saves energy. [...] The humidifier and the connecting water valve must be turned OFF at the end of each heating season. On bypass units, the shutoff damper should be turned to SUMMER.
More in the owner's manual.
Best Answer
W-C at the thermostat terminals on your furnace's control panel is the answer to your question. This way has a few drawbacks and pitfalls, so manufacturers don't recommend it. If you know what you're doing, then you'll probably be able to get it to work that way.
If you don't have a humidifier terminal on your furnace's control panel, manufacturers recommend switching the humidifier with a current sensing relay attached to the Hot 120 volt blower fan wire that is connected to the Heat terminal. The other wires coming from the blower fan will be connected to Cool, Park, and Neutral terminals, but we don't want to use them.
The most common switching voltage for humidifiers is 24VAC, but verify what you have. If you need to switch 24VAC, then use a Model A50 Current Sensing Relay. If you need to switch 120VAC, then use a Model A51 Current Sensing Relay.
Here is a link to the Installation Instructions for Models 50 and 51 Current Sensing Relays.