Protection Functions - Bosch 19 SEER Series Operation Manual

2 4 | Bosch Inverter Ducted Packaged Heat Pump

13.6 Protection Functions


Outdoor coil temperature protection (T3)
i. If T3 > 143.6°F, compressor is de-energized.
ii. If T3 < 129.2°F, compressor is energized.

Ambient temperature protection (T4)
i. If 23°F ≤ T4 < 125°F, unit can operate in cooling.
ii. If ‒4°F ≤ T4 < 86°F, unit can operate in heating.
iii. If T4 < ‒4°F, heat pump will provide 24V control to indoor unit
energizing electric heat (if installed).
See Product Specifi cation for extended performance data.

Discharge Temperature (DT) protection (T5)
i. If DT > 239°F during cooling mode, the compressor will stop.
ii. If DT < 194°F during cooling mode, the compressor will restart.
iii. If DT > 221°F during heating mode, the compressor will stop.
iv. If DT < 167°F during heating mode, the compressor will restart.

High Pressure (HP) protection (mechanical open/close
pressure switch)
i. High Pressure Switch opens at P > 580 PSIG, the compressor
and outdoor fan stop.
ii. High Pressure Switch closes at P < 435 PSIG, the compressor
and outdoor fan restart.

Low Pressure (LP) protection
i. If Low Pressure < 43.5 PSI for 5 minutes during cooling mode,
the compressor and outdoor fan will stop.The system will
attempt to run again after 6 minutes.
ii. If condensing temp. Tc < outdoor ambient temp. T4 during
heating mode, the compressor and outdoor fan will stop.

Module (inverter) protection (TF)
i. If TF > 176°F, the compressor and outdoor fan will stop.
ii. If TF < 145°F, the compressor and outdoor fan will restart.
Data subject to change
Installation & Operation Manual
03.2019 | BTC 761701105 A