We received a question from Jinho regarding his Aprilaire humidifier: 

"Looking at the wiring, it appears the R - C and W/G - Cf wires go to the respective furnaces R - C(ommon) and Humm - C(ommon) connections.  Is there any way to wire it so that it comes on any time there are necessary relative humidity changes?"

Aprilaire response
The wiring configuration you have limits the humidifier to operating only during a heat call.  There are a couple of options your dealer can look at to increase your humidifier run time and corresponding level of relative humidity. 

One is to wire the control through the EAC terminals (if your furnace has them).  EAC terminals are 120V, requiring your dealer to wire through a transformer.  This would allow you to humidify any time the HVAC blower is operating.  So, if you wanted to humidify outside of a call for heat, you could flip your thermostat fan setting from "Auto" to "On" and the humidifier would operate, provided there is a call for humidity.
 

Another option is to install the Aprilaire Blower Activation Relay, part number 4851.  With this device installed, the HVAC blower is automatically activated on a call for humidity, with no thermostat interaction on your part.

Thank you for the question, Jinho, and thanks for choosing Aprilaire!