Aprilaire 700 Series Two Wiring - 2008 to Present
The Aprilaire model 700A, 700M and 700 manufactured in 2008 and later are Series Two and designed primarily for an automatic humidistat. To turn-on these units require a humidistat that sends 24v to the humidifier.
The 700 series two has a controller relay (pn 4740) that turns on the fan when the humidistat sends 24v to the humidifier. The 24v is also routed to the solenoid valve. The diagram above shows the operation of this controller relay.
The operation of the series two controller relay is significantly different than that in the previous model 700. For simplicity the above diagram does not show the wiring to the humidistat necessary to sense when the furnace is running. Or the outdoor temperature sensor.