Condensing Unit & Heat Pump R410A Service Manual

83
SYSTEM OPERATION
AFE18-60A Control Board

The AFE18 control is designed for use in heat pump applicaons
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 o when the furnace is turned on.
An an-short cycle feature is also incorporated which iniates
a 3 minute med o delay when the compressor goes o. On
inial power up or loss and restoraon of power, this 3 minute
med o delay will be iniated. The compressor won’t be
allowed to restart unl the 3 minute o 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 oponal outdoor thermostat, OT18-60A, can be used with
the AFE18 to switch from heat pump operaon to furnace
operaon below a specic ambient temperature seng, i.e.
break even temperature during heang. 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 sasfy the rst stage “Y” heat demand.
On some controls, if the outdoor thermostat fails closed in this
posion during the heang season, it will turn on the furnace
during the cooling season on a “Y” cooling demand. In this
situaon, the furnace produces heat and increases the indoor
temperature thereby never sasfying the cooling demand.
The furnace will connue to operate and can only be stopped
by switching the thermostat to the o posion 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 posion
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 operaon.
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.