Wiring help for humidifier


Old 10-04-04, 12:24 AM
Visiting Guest
Posts: n/a
Question Wiring help for humidifier

Hi. I just installed a Waite 5000 flow-through bypass humidifier. My furnace is a Lennox about 25 years old with a dual-speed fan. I installed the humidifier on the return but had to install the bypass on a duct higher up on the heat side due to space restrictions. The furnace exhaust and AC stuff is in the way. The humidifier is designed to be triggered by the humidistat and a temperature sensor in the bypass collar of the unit. Problem is that since the humidifier and bypass are so far from parallel that the temperature triggering doesn't turn the unit off after the heat cycle is over. It'll just run forever. The maunual mentions interlocking the humidifier to the furnace fan but doesn't explain how. I guess what I'm asking is how can I hard-wire the humidifier to turn on and off with the heating cycle? Explicit instructions if possible. Thanks in advance.
Old 10-04-04, 05:43 PM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,386
Received 0 Votes on 0 Posts

I would say the best way for you to go now is with a "current sensing relay" this works like a amprobe. it just goes around the blower wire no cut or tie in at all. So you have a hot wire to it and on up to the humidifier. this way any time the blower comes on the humidifier can also come on. Be sure and turn it off when you go to AC in the summer

Old 10-04-04, 09:27 PM
Visiting Guest
Posts: n/a
Okay... I have to go the local HVAC supply store for a limit switch anyways. I'm guessing they'll know what relay to sell me?
Old 10-08-04, 09:52 PM
Join Date: Sep 2004
Posts: 281
Received 0 Votes on 0 Posts
Relay and Wiring

Relay: Aprilaire series 50 current sensing relay. Wire it in series with the existing wiring from the solenoid to the humidistat. Put the relay on the motor speed tap for heating mode. If you put the relay on the neutral lead, then you can humidify if the "fan" position is selected on the t-stat.

Wiring option: If you connect the 24 VAC solenoid wires on the bypass humidifier to the R and C terminals on the furnace, in series with the humidistat, you get 24 VAC to turn on the solenoid when there is a call for heat. No relay needed.

Caution: Using the relay electrically isolates the humidifier from the furnace board. It is possible, if there is a problem with the humidifier solenoid and it is a direct connection, that it could take out the board.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: