System Protection
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Heat Pump Controller
8733819577 (2019/02)
Heat Pump Controller
Subject to change without prior notice
SYSTEM PROTECTION
Consumer Enhanced Security
The unit has been engineered according to Bosch
consumer information protection standards, and it
has built-in security features that prevent
unauthorized users from changing unit
configuration and other settings.
Compressor Demand (Y1 Call)
The HPC will monitor the thermostat interface P8.
Upon receiving a (Y1) demand from the
thermostat, it will verify that all safety switches are
in normal condition prior to initiating the
compressor start sequence.
Pressure Protection
High Pressure Switch (HPS)
The HPS prevents the unit from running in a
condition of high-refrigerant pressure. If the HPS is
open upon a cooling or heating call, the HPC will
not energize the compressor output. If the
compressor is already running in normal operation
and the HPS opens, the HPC will shut down the
compressor output and will keep it off until the
switch closes and the Anti-Short Cycle (ASC) delay
has expired.
The Status Indicator will flash one time and the
controller will keep track of the number of times
the HPS opens. If within one hour the HPS strike
counter exceeds the configured soft-lockout
counter (set via the Bosch EasyStart app, see
page #5) the HPC will shutdown the compressor
and enter a hard lockout.
When the HPC enters lockout the LED flashes the
alarm code in such a way the observer can count
the number of flashes. The alarm code is
represented by a grouping of successive flash with
a two second pause in between the flash
sequence. The sequence or flash grouping will be
repeated until the fault is cleared. The LED will
only flash one error code until it is cleared. See
“Clearing a Hard Lockout” on page #8.
Low Pressure Switch (LPS)
The LPS prevents the unit from running in a
condition of low refrigerant pressure. If the LPS is
open, the compressor will not energize even if
there is a demand for heating or cooling and the
status indicator will flash two times during an LPS
fault. If the compressor is running during normal
operation and the LPS is opened, the HPC will
keep the compressor running for two minutes. If
the LPS remains open after two minutes, the
compressor will shutdown and the unit will enter a
soft lockout. The compressor will not energize
until the LPS closes and the ASC delay expires.
The controller will keep track of the number of
times the switch opens. If within one hour the LPS
strike counter exceeds the configured soft lockout
counter (set via the Bosch EasyStart app) the HPC
will shut down the compressor and enter a hard
lockout.
When the HPC enters lockout the LED flashes the
alarm code in such a way the observer can count
the number of flashes. The alarm code is
represented by a grouping of successive flash with
a two second pause in between the flash
sequence. The sequence or flash grouping will be
repeated until the fault is cleared. The LED will
only flash one error code until it is cleared. See
“Clearing a Hard Lockout” on page #8.
Operating Envelops of the Pressure Switches
Operating envelopes of both switches are shown
in the table below.
Table 5 Pressure Switches
High Pressure Switch
Open Circuit
600±15 PSI
Closed Circuit
420±15 PSI
Low Pressure Switch
Open Circuit
40±5 PSI
Closed Circuit
60±5 PSI
