Control Relay

Description

Replacement Aprilaire 4740 Fan Relay. This relay powers up the circulator fan in the newer style 700, 700A and 700M power humidifiers manufactured starting in 2008. Older models used part 4238 which had a small circuit board in them containing a low voltage transformer. Newer versions of the model 700 series used an external transformer to power up the control circuit as well as this fan relay.