Service Instructions

SYSTEM OPERATION
80
AFE18-60A CONTROL BOARD
DESCRIPTION
The AFE18 control is designed for use in heat pump applications
where the indoor coil is located above/downstream of a gas or
fossil fuel furnace. It will operate with single and two stage heat
pumps and single and two stage furnaces. The AFE18 control will
turn the heat pump unit off when the furnace is turned on. An anti-
short cycle feature is also incorporated which initiates a 3
minute timed off delay when the compressor goes off. On initial
power up or loss and restoration of power, this 3 minute timed
off delay will be initiated. The compressor won’t be allowed to
restart until the 3 minute off delay has expired. Also included is
a 5 second de-bounce feature on the “Y, E, W1 and O” thermostat
inputs. These thermostat inputs must be present for 5 seconds
before the AFE18 control will respond to it.
An optional outdoor thermostat, OT18-60A, can be used with the
AFE18 to switch from heat pump operation to furnace operation
below a specific ambient temperature setting, i.e. break even
temperature during heating. When used in this manner, the “Y”
heat demand is switched to the “W1” input to the furnace by the
outdoor thermostat and the furnace is used to satisfy the first
stage “Y” heat demand. On some controls, if the outdoor thermo-
stat fails closed in this position during the heating season, it will
turn on the furnace during the cooling season on a “Y” cooling
demand. In this situation, the furnace produces heat and
increases the indoor temperature thereby never satisfying the
cooling demand. The furnace will continue to operate and can
only be stopped by switching the thermostat to the off position
or removing power to the unit and then replacing the outdoor
thermostat. When the AFE18 receives a “Y” and “O” input from
the indoor thermostat, it recognizes this as a cooling demand
in the cooling mode. If the outdoor thermostat is stuck in the
closed position switching the “Y” demand to the “W1” furnace
input during the cooling mode as described above, the AFE18
won’t allow the furnace to operate. The outdoor thermostat will
have to be replaced to restore the unit to normal operation.
WARNING
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing. Multiple power sources
may be present. Failure to do so may
cause property damage, personal injury
or death.