Bosch BRBA-36HWD1N1-M18 - System Operation and Troubleshooting; Control Logic Description; Sensors (Thermistors;Pressure Transducer)

22
|
Installation Instructions
Bosch 18 SEER2 Series Inverter Ducted Packaged Heat Pump - BTC 761703103 A (11.2022)
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 29
ON
OFF
1 2
3 4
Switch Description
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 17
*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)