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A-A Wiring – COOLING & HEATING Air Handler (A)*
Our Air Handlers are equipped with a pump relay that is activate in heating call. Connect the R (24 VAC)
and the W heating call to the thermostat. When an external room thermostat calls for heating it will
activate a “W” heating call. This in turn will signal the fan coil to optimize its speed for heating. Because
the L and A3 are jumpered, the A3 (common) and A1 (L1) connections will be energized at 120 Volts. This
connection switch will send power directly the heating pump and cause hot water to circulate through
the internal heating coil.
In cooling mode, a “Y” call will be signaled causing the Air Handler to change to cooing mode and
optimized its fan speed for cooling. A separate cooling heat exchanger is used separate from the heating
HX. A Caleffi ZSR 101 Zone Relay is needed for the second cooling pump – Connect the Y1 and C to the C
and W thermostat terminals on the ZSR 101 board. On a Cooling call Y1 on the output of the air handler is
energized, this in turn will cause the relay contact to close turning on the cooling circulation pump.
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