IBC AHU Series - Operation; Checklist for Electrical Conditions, Ducting and Water Connections

Required if boiler does not have an integral pump.
Dry contact from air handler to boiler / enables call for heat
W1 = boiler + low fan, W2 = boiler + high fan
Not used
Figure 45 Two-stage cooling with boiler heating (2-stage thermostat)
43
2.6.2 Connecting line voltage - examples for different scenarios