System Operation And Troubleshooting; Control Logic Description; Sensors (Thermistors/Pressure Transducer) - Bosch 19 SEER Series Operation Manual

2 2 | Bosch Inverter Ducted Packaged Heat Pump

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.
ON
1 2
3 4
OFF
Figure 28
ON
SW4-1
OFF*
ON
SW4-2
OFF*
ON
SW4-3
OFF*
ON
SW4-4
OFF*
Table 14
*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.
Data subject to change
Must be set at "ON" position
Unused
Unused
Must be set at "OFF" position
Adaptive capacity output disabled
Adaptive capacity output enabled
Accelerated cooling/heating
Normally cooling/heating

13.2 Sensors (Thermistors/Pressure Transducer)


T3 = Outdoor Coil Temperature (Table 27)
—
High/Low temperature protection
—
Outdoor fan control (cooling mode)
—
Defrost control (heating mode)

T4 = Ambient Temperature (Table 27)
—
Operating condition permission
—
Defrosting condition permission
—
Outdoor fan control (heating mode)

T5 = Compressor Discharge Temperature (Table 28)
—
High/Low temperature protection
—
Electronic Expansion Valve (EEV) (ODU/heating
mode only)

Th = Compressor Return Temperature (Table 27)

T3L = Liquid Line Temperature (Table 27)

TF = IPM Radiator Temperature (Table 28)
—
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)
Installation & Operation Manual
03.2019 | BTC 761701105 A