IBC AHU Series - Page 39

Required if boiler does not have an integral pump. See table 1.
Dry contact from air handler to boiler / enables call for heat.
Timer must close TT to create a boiler-on command in the HP mode. This time delay is initialized
after establishing a W1 signal.
Reversing valve (O or B) is selectable via the blower control interface.
Not used.
Figure 30 Single-stage heat pump with boiler backup - primary/secondary piping
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2.6.2 Connecting line voltage - examples for different scenarios