• Aprilaire Humidifier Troubleshooting Guide
• Aprilaire Model 700 Humidifier Manual
• Aprilaire Humidifier Model 700 Installation

The Aprilaire humidifier’s which we recommend for a horizontal HVAC system are the bypass model humidifiers; 400, 400M, 500, 500M, 600, 600M or the model 800 steam humidifier. The Aprilaire power humidifier, model 700 or 700M will not work properly on a horizontal heating system.

I've read the related posts, but they don't answer my questions. Please, help!

We had contractors installed:* Aprilaire-700 Humidifier with Auto/Manual Humidistat-Control Knob (non-digital)* York Heating-Furnace Model TG9S080C22MP11 s Serial W1B4453800 - newly installed.

Humidifier has Wires: Yellow, Blue - to 24VAC;
Green - unused to no where;
Red & White - to Humidifier;
Red & White - to Outdoor Temperature Sensor.

The YORK furnace is working fine, new upgrade. The slick contractor left the humidifier wires unconnected back to the new furnace, following replacement.

The Furnace works fine! But:Q1. How do I know which humidistat wires to connect to Furnace Control Board Terminals?Q2, Q3. Exactly which Terminals on the Furnace Control Board - which ones and how?

The children are all getting sick with dry throat, bleeding nose, dry eyes, even getting dizzy & disoriented. Please, HELP! Thanks.

2 Answers

There's two ways to wire this up. The first method is to take advantage of the HUM terminal on the furnace control board. This terminal will supply 120 volts when the furnace is running in heat mode, so you'll have to use an additional transformer.

You'll hook the primary side of the transformer to the HUM, and Neutral terminals in the furnace. Then you'll connect the 24VAC terminals of the humidistat, to the secondary of the transformer.

The other method, is to use the furnaces transformer to provide power to the humidistat. However, you'll have to make sure the transformer is large enough to supply the load.

With this setup, you'll connect the 24VAC terminals of the humidistat to the C and W terminals on the furnace control board. That way when the thermostat calls for heat, the humidistat will be powered by the furnaces transformer.

The yellow and blue wires should be connected to W and C of the control board. You will need to connect them where the thermostat wire is connected. Doing this will give your humidifier/humidistat power when the furnace is in a heating cycle.

Not the answer you're looking for? Browse other questions tagged heatingfurnacehumidifier or ask your own question.

Aprilaire Humidifier Troubleshooting Guide

So I am trying to complete the last part of my Ecobee 3 installation, the humidifier.

What I have: -Ecobee 3 Thermostat -Trane XR80 single stage furnace -Aprilaire 700 (not the M) humidifier - This humidifier has a 120v wall plug as well as two brown wires coming out.

What I have done: -Ran all new wiring to Thermostat. two 5 wire runs to the thermostat so I have enough wiring to handle any future upgrades or needs -wired Trane XR80 to the Ecobee (everything works great)

What I need to know is how do I wire the Aprilaire into this setup? I have tried a couple methods of wiring the brown wires to the ACC+ and ACC- and that didn't do anything. I also tried wiring one to the ACC+ and one to the C terminal on the furnace. I am just lost.

Aprilaire Model 700 Humidifier Manual

I was running this fine with the model 60 automatic humidistat but now that I've taken it all off I just can't figure it out.

Aprilaire Humidifier Model 700 Installation

Thanks for any help in advance. Dan