Bosch 15 SEER2 Series - System Operation and Troubleshooting; 13.1 Control Logic Description; 13.2 Sensors (Thermistors;Pressure Transducer)

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Installation Instructions
Bosch 15 SEER2 Inverter Ducted Packaged Heat Pump - BTC 761701319 A (12.2022)
13 System Operation and Troubleshooting
13.1 Control Logic Description
 The variable speed system adopts the same 24VAC control as any
conventional heat pump.
 The compressor’s speed is controlled based on coil pressures
monitored by the unit's pressure transducer. To ensure stable and
adequate capacity, the compressor speed will modulate relative
to evaporator pressure during cooling operation and relative
to condensing pressure during heating operation. The target
pressure can automatically adjust based on compressor operation
so optimal capacity can be achieved. Target pressure can be
manually adjusted (SW4) to achieve improved dehumidification
and capacity demands.
Figure 28
ON
OFF
1 2
3 4
SW4-1
ON* Must be set at "ON" position
OFF Unused
SW4-2
ON Unused
OFF* Must be set to "OFF" position
SW4-3
ON Adaptive capacity output disabled
OFF* Adaptive capacity output enabled
SW4-4
ON Accelerated cooling/heating
OFF* Normally cooling/heating
Table 18
*Factory Default
 Adaptive capacity function is a "self-learning function" which
allows a range of target coil temperatures to adapt for better
unit operation and reduced short cycling.
 Accelerated cooling/heating function changes the initial target
coil temperature to provide "enhanced comfort" by increasing
unit capacity.
13.2 Sensors (Thermistors/Pressure Transducer)
 T1 = Return Air Temperature
— Indoor Fan Control
 T2 = Indoor Coil Temperature
— Anti-cold air function in heating mode
 T3 = Outdoor Coil Temperature
— High/Low temperature protection
• Outdoor fan control (cooling mode)
• Defrost control (heating mode)
 T4 = Ambient Temperature
— Operating condition permission
— Defrosting condition permission
— Outdoor fan control (heating mode)
 T5 = Compressor Discharge Temperature
— High/Low temperature protection
— Electronic Expansion Valve (EEV) (ODU/heating
mode only)
 Th = Compressor Return Temperature
 T3L = Liquid Line Temperature
 TF = Control Board Module Temperature
— Inverter High Temperature Protection
 Pressure transducer
— Compressor frequency control
— Electronic Expansion Valve (EEV) control (in
both heating and cooling modes)
— High pressure protection (heating mode)
— Low pressure protection (cooling mode)