GSZH5 Service Manual
64
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 second stage heat
AEPF must be cut. With the PJ4 jumper cut, the VSTB
indoors will continue to drop. The room thermostat
seconds and heater elements #3 and #4 will be turned
thermostat will remove the 24Vac from “E/W1” and the
element(s) and the blower motor ramps down to a complete
stop.
GSZ, SSZ, ANZ, ASZ, and VSZ Heat Pumps
When used with a single stage GSZ, SSZ, ASZ, or VSZ
heat pumps, dip switch #4 must be set to the ON position
on the VSTB inside the MBE. The “Y” 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” at the heat
pump.
be removed.
3.0 Cooling Operation
On heat pump units, when the room thermostat is set to
the cooling mode, 24Vac is supplied to terminal “O” of the
VSTB inside the MBE/AEPF unit. The VSTB will supply
24Vac to “O” at the heat pump to energize the reversing
valve. As long as the thermostat is set for cooling, the
reversing valve will be in the energized position for cooling.
3.1 On a demand for cooling, the room thermostat
energizes “G” and “Y” and 24Vac is supplied to terminals
“G” and “Y/Y2” of the MBE/AEPF unit. The VSTB will turn
on the blower motor and the motor will ramp up to the
speed programmed in the motor based on the settings of
dip switch 5 and 6. The VSTB will supply 24Vac to “Y” at
the heat pump.
The heat pump is turned on in the cooling mode.
3.3
thermostat removes the 24Vac from “G” and “Y/Y2” of the
MBE/AEPF and the VSTB removes the 24Vac from “Y” at
motor will ramp down to a complete stop based on the time
and rate programmed in the motor.
4.0 Heating 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. Some installations may use one or
more outdoor thermostats to restrict the amount of electric
heat that is available above a preset ambient temperature.
Use of optional controls such as these can change
the operation of the electric heaters during the heating
mode. This sequence of operation does not cover those
applications.
4.1
the room thermostat energizes “Y” and “G” and 24Vac is
supplied to “G” and “Y/Y2” of the MBE/AEPF. The VSTB
will turn on the blower motor and the motor will ramp up to
the speed programmed in the motor based on the settings
of dip switch 1 and 2. The VSTB will supply 24Vac to “Y”
at the heat pump and the heat pump is turned on in the
heating mode.
heat pump, the temperature indoors will continue to drop.
The room thermostat will then energize terminal “W2” for
second stage heat and 24Vac will be supplied to “E/W1”
of the MBE/ AEPF. The VSTB will supply 24Vac to heat
sequencer, HR1, on the electric heater assembly.
4.3 HR1 contacts M1 and M2 will close within 10 to 20
seconds and turn on heater element #1. At the same time,
if the heater assembly contains a second heater element,
HR1 will contain a second set of contacts, M3 and M4,
which will close to turn on heater element #2.