GSX14 Service Manual

SERVICING
133
the “W3” demand is satisfied, the room thermostat 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. On most digital/electronic thermostats,
“W3” will remain energized until the first stage heat
demand “Y” is satisfied and then the “G”, “Y”, “W2”
and “W3” demands will be removed.
4.4 As the temperature indoors increase, it will reach a point
where the second stage heat demand, “W2”, is satis-
fied. When this happens, the room thermostat will
remove the 24Vac from the coil of HR1. The contacts
on HR1 will open between 30 to 70 seconds and turn off
both heater element(s). The heat pump remains on
along with the blower motor because the “Y” demand for
first stage heat will still be present.
4.5 When the first stage heat demand “Y” is satisfied, the
room thermostat will remove the 24Vac from “G” and “Y”.
The heat pump is turned off and the blower motor turns
off after a 65 second off delay.
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.
5.2 The defrost control in the heat pump unit checks to seeif
a defrost is needed every 30, 60 or 90 minutes of heat pump
operation depending on the selectable setting by monitor-
ing 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 HVDR
relay on the defrost board open and turns off 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 contactson HR1 close and turns
on the electric heater(s). The unit will continue to run in this
mode until the defrost cycle is completed.
a.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
turn the compressor off for 30 seconds while the revers-
ing 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.
5.6 When the defrost cycle is terminated, the contacts of the
HVDR relay will close to start the outdoor fan and the
contacts of the LVDR relay will open and turn off the
reversing valve and electric heater(s). The 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.
MBE/AEPF WITH GSX, SSX, ASX, DSX, VSX
MBE ELECTRONIC BLOWER TIME DELAY RELAY
AEPF AIR HANDLER
SEQUENCE OF OPERATION
This document covers the basic sequence of operation for a
typical application with a mercury bulb thermostat. When a
digital/electronic thermostat is used, the on/off staging of the
auxiliary heat will vary. Refer to the installation instruc-
tions and wiring diagrams provided with the MBE/AEPF
for specific wiring connections, dip switch settings and
system configuration.
MBE/AEPF WITH SINGLE STAGE GSX, ASX, SSX, and
VSX CONDENSERS
When used with a single stage GSX, SSX, ASX, and VSX
condensers, dip switch #4 must be set to the on position on
the VSTB inside the MBE/AEPF. 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
condenser. The orange jumper wire from terminal “Y1”
to terminal“O” on the VSTB inside the MBE/AEPF must
remain connected.
1.0 Cooling Operation
1.1 On a demand for cooling, the room thermostat energizes
“G” and “Y” and 24Vac is supplied to “G” and “Y/Y2” of the
MBE/AEPF unit. The VSTB inside the MBE/AEPF will turnon
the blower motor and the motor will ramp up to 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 condenser
and the compressor and condenser are turned on.
1.2 When the cooling demand is satisfied, the room thermo-
stat removes the 24Vac from “G” and “Y”. The MBE/
AEPF removes the 24Vac from “Y’ 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