YHJF60 Add-On Heat Pump
Re: Low Heat When Cold Outside
Unlike all other sizes of the YHJF Heat Pump, the 5 Ton model has a 2-Stage compressor and a YorkGuard VI module.
In an Add-On Heat Pump application, the YorkGuard VI module uses its Outdoor Ambient Sensor and a field-installed Bonnet Sensor (mounted between the furnace & indoor coil) to control "Fossil Fuel" operation.
Qty |
Possible Causes: |
1 |
Gas Furnace not Operating |
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YorkGuard Mis-Configured or Mis-Wired |
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Thermostat Mis-Configured |
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2-Stage Furnace not Running 2nd Stage |
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Bad Ambient Sensor |
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Gas Furnace Under-Sized |
CHECKOUT:
1. YorkGuard VI - "Fossil Fuel" Sequence of Operation
For Fossil Fuel Operation, the following setting must be made on the YorkGuard:
- FFUEL = Set to "On"
- BP = Set for 45, 40 or 35 deg.
- LTCO = Set for 20, 15 or 10 deg.
- Bonnet Sensor installed & wired to "BS" and "BSG"
2. Outdoor ABOVE Balance Point (BP)
- On a call for "Y1" the YorkGuard energizes the compressor for 1st Stage heating.
- On a call for "Y2" the YorkGuard energizes the compressor unloading solenoid to put the compressor in full operation.
- The YorkGuard also energizes "Y2 Out" to tell the variable speed indoor fan to go to "High Heat" speed.
- On a call for "W" (or "Aux") the YorkGuard will keep Aux Heat outputs "W1 Out" and "W2 Out" de-energized.
- If the heat pump goes into a Lockout condition, the YorkGuard will automatically energize "W1 Out" to satisfy heating demand.
3. Outdoor BELOW Balance Point (BP)
- On a call for "Y1" the YorkGuard energizes the compressor for 1st Stage heating.
- On a call for "Y2" the YorkGuard energizes the compressor unloading solenoid to put the compressor in full operation.
- The YorkGuard also energizes "Y2 Out" to tell the variable speed indoor fan to go to "High Heat" speed.
- On a call for "W" (or "Aux") the YorkGuard will energize "W1 Out" to start the furnace while keeping the compressor operating.
- The compressor continues to operate until the Bonnet Sensor temperature reaches 90 deg.
- If the furnace fails to operate the heat pump will continue to operate to try to maintain heating.
4. Outdoor BELOW LTCO
- The YorkGuard basically enters Emergency Heat mode.
- On a call for "Y1" the YorkGuard keeps the compressor off and energizes "W1 Out" to start the gas furnace.