IBC AHU 800 - Page 41

Required if boiler does not have an integral pump. See table 1.
Dry contact from air handler to boiler / enables call for heat
W1 = boiler + low fan, W2 = boiler + high fan
Not used
Figure 32 Two-stage cooling with boiler heating (2-stage thermostat)
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2.6.2 Connecting line voltage - examples for different scenarios