GSZH5 Service Manual
66
SYSTEM OPERATION
1.1 On a demand for cooling, the room thermostat
energizes “G” and “Y1” and 24Vac is supplied to “G” and
“Ylow/Y1” of the MBE/AEPF unit. The VSTB inside the
MBE/AEPF will turn on the blower motor and the motor
will ramp up to 60% of the speed programmed in the
motor based on the settings for dip switch 5 and 6. The
VSTB will supply 24Vac to “Ylow/Y1” at the condenser and
the compressor and condenser fan starts in low speed
operation.
room thermostat will energize “Y2” and supply 24Vac to
the MBE/AEPF unit. The blower motor will change to the
cfm for high speed operation and the VSTB will supply
24Vac to “Y/Y2” at the condenser and the compressor and
condenser fan will change to high speed operation. When
“Y2” demand and the VSTB will remove the 24Vac from “Y/
Y2” at the condenser.
The blower will drop to 60% of the programmed cfm and
the compressor and condenser fan will change to low
speed.
demands will be removed.
1.3
the room thermostat removes the 24Vac from “G” and “Y1”.
The MBE/AEPF removes the 24Vac from “Ylow/Y1” at the
condenser and the compressor and condenser fan are
stop based on the time and rate programmed in the motor.
On a demand for heat, the room thermostat energizes
“W1” and 24Vac is supplied to terminal “E/W1” of the
VSTB inside 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 for
dip switch 1 and 2. The VSTB will supply 24Vac to heat
sequencer HR1 on the electric heater assembly.
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 and turn on heater element #2.
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
VSTB removes the 24Vac from HR1. The contacts on HR1
element(s) and the blower motor ramps down to a complete
stop.
MBE/AEPF With Two Stage ASZ & DSZ Heat Pump
Units
3.0 Cooling Operation
When used with the ASZ & DSZ two stage heat pumps,
dip switch #4 must be set to the OFF position on
The “Y1” output from
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 “Y” at the heat pump. 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 heat
pump.
be removed.
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 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.