GSZH5 Service Manual
65
SYSTEM OPERATION
If more than two heater elements are on
the heater assembly, it will contain a second heat
heater elements if available. For the 3rd and 4th heater
elements to operate on a third stage heat demand,
indoors will continue to drop. The room thermostat will
4.4 As the temperature indoors increase, it will reach
a point where the second stage heat demand, “W2”, is
remove the 24Vac from “E/W1” of the MBE/AEPF. The
contacts on HR1 will open between 30 to 70 seconds and
along with the blower motor because the “Y” demand for
4.5
room thermostat will remove the 24Vac from “G” and “Y/
Y2” of the MBE/AEPF. The VSTB removes the 24Vac from
blower motor will ramp down to a complete stop based on
the time and rate programmed in the motor control.
5.0 Defrost Operation
On heat pump units, when the room thermostat is set to
the heating mode, the reversing valve is not energized.
As long as the thermostat is set for heating, the reversing
valve will be in the de-energized position for heating except
during a defrost cycle.
5.1 The heat pump will be on and operating in the heating
mode as described the Heating Operation in section 4.
The defrost control in the heat pump unit checks to see
if a defrost is needed every 30, 60 or 90 minutes of heat
pump operation depending on the selectable setting by
monitoring the state of the defrost thermostat attached to
the outdoor coil.
5.3 If the temperature of the outdoor coil is low enough to
cause the defrost thermostat to be closed when the defrost
board checks it, the board will initiate a defrost cycle.
5.4 When a defrost cycle is initiated, the contacts of the
outdoor fan.
The contacts of the LVDR relay on the defrost board closes
and supplies 24Vac to “O” and “W2”. The reversing valve is
energized and the contacts on HR1 close and turns on the
electric heater(s). The unit will continue to run in this mode
until the defrost cycle is completed.
5.4a For models with defrost control PCBDM133 or
PCBDM160, a 30 second compressor delay at defrost
initiation/termination is optional. As shipped from the
factory, the control is set for the delay (“DLY”), which will
valve shifts to/from the cooling mode position. To bypass
the delay, which typically reduces sound levels during
defrost mode, change the pin settings from “DLY” to
“NORM”.
5.5 When the temperature of the outdoor coil rises
high enough to causes the defrost thermostat to open,
the defrost cycle will be terminated. If at the end of the
programmed 10 minute override time the defrost thermostat
is still closed, the defrost board will automatically terminate
the defrost cycle.
When the defrost cycle is terminated, the contacts of
the HVDR relay on the defrost board will close to start the
outdoor fan and the contacts of the LVDR relay will open
unit will now be back in a normal heating mode with a heat
pump demand for heating as described in the Heating
Operation in section 4. See section 5.4a.
1.0 Cooling Operation
When used with the ASX & DSX two stage condensers,
dip switch #4 must be set to the OFF position on the
the indoor thermostat must be connected to the purple
wire labeled “Ylow/Y1” inside the wire bundle marked
“Thermostat” and the purple wire labeled “Ylow/Y1” inside
the wire bundle marked “Outdoor Unit” must be connected
to “Ylow/Y1” at the condenser. The “Y2” output from the
indoor thermostat must be connected to the yellow wire
labeled “Y/Y2” inside the wire bundle marked “Thermostat”
and the yellow wire labeled “Y/Y2” inside the wire bundle
marked “Outdoor Unit” must be connected to “Y/Y2” at the
condenser.
must remain connected.