50
SS-SVX10B-EN
Start-Up
1.
Supply Fan Proving Failure - If a Supply Fan Proving failure is detected the Supply Fan will be
de-energized after 40s of run time and the Fan Speed output will go to the corresponding
minimum speed voltage.
2. Zone Temperature Sensor Failure - If the Active Zone Temperature input goes out of range, the
unit will discontinue all Heating, Cooling, and Dehumidification operation.
3. Supply Air Temperature Sensor Failure - If the Supply Air Temperature input goes out of range,
the unit will revert back to Full Airflow, Traditional CV control. The unit will call out a Supply Air
Temperature Sensor Failure Alarm, the RTRM System LED will flash the 2-blink error code, and
Cool LEDs will flash.
2 Speed VFD Applications
General Description of Functionality
Cooling Operation (DX Cooling)
Units with a 2-Speed VFD control scheme will utilize a thermostat's heating and cooling outputs
to differentiate between high and low speed. When the unit receives a G or Y1 call from the
thermostat the supply fan will run at the user selected low speed. Once the zone load demands
the second stage of cooling, and the unit receives the Y2 call from the thermostat the supply fan
will be signaled to run at the user selected high speed. All other compressor staging will be handled
the same as all standard thermostat controlled units.
Heating Operation
Units with 2-Speed VFD controls will utilize traditional CV Heating control schemes with full airflow
provided based on the customer selected VFD controlled maximum speed. When the unit receives
the W1 call from the thermostat a relay will signal the supply fan to run at high speed. All the electric
heaters that can be outfitted in the field are wired up to interlock W1 and W2 so the supply fan will
always run at the user selected high speed during heat modes.
