SERVICING
AEP* & MBE WITH SINGLE STAGE CONDENSERS When used with a single stage condenser, 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 condenser. The orange jumper wire from terminal “Y1” to terminal “O” on the VSTB inside the MBE must remain connected.
1.0Cooling Operation
1.1On a demand for cooling, the room thermostat energizes “G” and “Y” and 24Vac is supplied to “G” and “Y/Y2” of the MBE unit. The VSTB inside the MBE 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 5 and 6. The VSTB will supply 24Vac to “Y” at the condenser and the compressor and condenser are turned on.
1.2When the cooling demand is satisfied, the room thermo- stat removes the 24Vac from “G” and “Y”. The MBEand AEP* remove 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.
2.0Heating Operation
2.1On a demand for heat, the room thermostat energizes “W1” and 24Vac is supplied to terminal “E/W1” of the VSTB inside the MBEand AEP* units. 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.
2.2HR1 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 3rd and 4th heater elements if available. For the 3rd and 4th heater elements to operate on a second stage heat demand, the PJ4 jumper on the VSTB inside the MBE and AEP* 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 re- main energized until the first stage demand “W1” is satisfied and then the “W1” and “W2” demands will be removed.
2.3When 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.
S-41A AEP* & MBE WITH SINGLE STAGE HEAT PUMPS
When used with a single stage heat pump, 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. The orange jumper wire from terminal “Y1” to terminal “O” on the VSTB inside the MBE must 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 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.
3.1On a demand for cooling, the room thermostat energizes “G” and “Y” and 24Vac is supplied to terminals “G” and “Y/ Y2” of the MBE unit. The VSTB will turn on the blower motor and the motor will ramp up to the speed pro- grammed in the motor based on the settings of dip switch 5 and 6. The VSTB will supply 24Vac to “Y” at the heat pump.
3.2The heat pump is turned on in the cooling mode.
3.3When the cooling demand is satisfied, the room thermo- stat removes the 24Vac from “G” and “Y/Y2” of the MBE and the VSTB removes the 24Vac from “Y” at the heat pump. The heat pump is turned off and the blower motor will ramp down to a complete stop based on the time and
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