GSX14 Service Manual

SERVICING
136
“Y1”. The MBE/AEPF removes the 24Vac from “Ylow/
Y1’ at the condenser and the compressor and condenser
fan are turned off. The blower motor will ramp down to
a complete stop based on the time and rate programmed
in the motor.
2.0 Heating Operation
2.1 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.
2.2 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.
Note: If more than two heater elements are on the heater
assembly, it will contain a second heat sequencer, HR2,
which will control the 3
rd
and 4
th
heater elements if available.
For the 3
rd
and 4
th
heater elements to operate on a second
stage heat demand, the PJ4 jumper on the VSTB inside
the MBE/AEPF must be cut. With the PJ4 jumper cut, the
VSTB will run the blower motor on low speed on a “W1” only
demand. If the first stage heat demand, “W1” cannot be
satisfied by the heat pump, the temperature indoors will
continue to drop. The room thermostat will then energize
“W2” and 24Vac will be supplied to HR2 on the heater
assembly and the blower motor will change to high speed.
When the “W2” demand is satisfied, the room thermostat will
remove the 24Vac from “W2” and the VSTB will remove the
24Vac from HR2. The contacts on HR2 will open between 30
to 70 seconds and heater elements #3 and #4 will be turned
off and the blower motor will change to low speed. On most
digital/electronic thermostats, “W2” will remain ener-
gized until the first stage demand “W1” is satisfied and
then the “W1” and “W2” demands will be removed.
2.3 When the “W1” heat demand is satisfied, the room
thermostat will remove the 24Vac from “E/W1” and the
VSTB removes the 24Vac from HR1. The contacts on
HR1 will open between 30 to 70 seconds and turn off the
heater 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 VSTB inside the MBE/AEPF. 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 con-
nected to “Y/Y2” at the heat pump. The orange jumper
wire from terminal “Y1” to terminal “O” on the VSTB
inside the MBE/AEPF must 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.
3.1 On a demand for cooling, the room thermostat energizes
“G” and “Y1” and 24Vac is supplied to “G” and “Ylow/Y1”
of the MBE unit. The VSTB inside the MBE 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 “Y”
at the heat pump and the compressor and outdoor fan
starts in low speed operation.
3.2 If first stage cooling cannot satisfy the demand, the room
thermostat will energize “Y2” and supply 24Vac to “Y/
Y2”of the MBE unit. The blower motor will change to the
cfm for high speed operation and the VSTB will supply
24Vac to “Y2” at the heat pump. The compressor and
outdoor fan will change to high speed operation. When
the “Y2” demand is satisfied, the thermostat will remove
the “Y2” demand and the VSTB will remove the 24Vac
from “Y2” at the heat pump. The blower will drop to 60%
of the programmed cfm and the compressor and outdoor
fan will change to low speed operation. On most digital/
electronic thermostats, “Y2” will remain energized
until the first stage cooling demand “Y1” is satisfied
and then the “G”, “Y1” and “Y2” demands will be
removed.
3.3 When the first stage cooling demand, “Y1”, is satisfied,
the room thermostat removes the 24Vac from “G” and
“Y1”. The VSTB removes the 24Vac from “Y’ at the heat
pump and the compressor and outdoor fan are turned off.
The blower 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 On a demand for first stage heat with heat pump units,
the room thermostat energizes “G” and “Y1” and 24Vac
is supplied to “G” and “Ylo/Y1” of the MBE/AEPF. The