Compressor Crankcase Heater Description; Reversing Valve Operation; Protection Functions - Bosch BOVB 18 Series Installation Instructions Manual

2 6 | Bosch IDS BOVB 18
Defrost Termination Settings (SW5) offers different defrost termination

options for enhanced defrost for different geographical and outdoor
conditions.
SW5
ON
1 2
OFF
Figure 44
Defrosting Choice SW5-1
Operating time is
ON
reduced by 10%
OFF Normal
Remarks Enter defrost
Table 12
 Manual Defrost:
1. System must have a call for heat and have been operating for a minimum
of 8 minutes.
2. Press "Force" button on inverter board for 6 seconds to begin forced
defrost.
3. Wait approximately 40 seconds for defrost to initiate.
4. Once defrost initiates, the display will indicate "dF".
5. Defrost test will terminate automatically, after which the display will
indicate running speed.
6. If a second defrost test is required, repeat steps 2-5 after 5 minutes.

15.5 Compressor Crankcase Heater Description

Refrigerant migration during the OFF cycle can result in noisy start-ups, therefore
a CrankCase Heater (CCH) is used to minimize refrigerant migration thereby
minimizing start-up noise and/or bearing "wash out". All CCHs must be installed
on the lower half of the compressor shell. Its purpose is to warm the compressor
during the OFF cycle, driving refrigerant from compressor. After extended shutdown
periods in cold weather, it is recommended to allow CCH to be energized for at least
12 hours prior to compressor operation by applying line voltage to heat pump with
thermostat OFF.
CCH operation energizes:

1. First time line voltage is applied and compressor discharge temperature
T5 < 53.6°F.
2. Compressor stops running for 3 hours (outdoor ambient temperature T4
< 41°F OR compressor discharge temperature T5 < 53.6°F).
 CCH operation de-energizes:
1. Compressor discharge temperature T5 ≥ 60.8°F.
2. Compressor start running.

15.6 Reversing Valve Operation

Data subject to change
SW5-2 Remarks
Defrosting extended
for 60 seconds
Normal Default
Quit defrost
Reversing valve energizes during heat mode and de-energizes in cool mode.

During a heat call on fi rst time operation the unit will run about 1 minute in
cooling to build up pressure for reversing valve to change.

15.7 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 40°F ≤ T4 < 125°F, unit can operate in cooling.
ii. If 5°F ≤ T4 < 86°F, unit can operate in heating.
iii. If T4 < 5°F, heat pump will provide 24V control to indoor unit
energizing electric heat (if installed).
See BOVB 18 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 < 154°F, the compressor and outdoor fan will restart.
Installation Instructions
10.2020 | Bosch Thermotechnology Corp.