System Protection
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17
Heat Pump Controller
8733819577 (2019/02)
Heat Pump Controller
Subject to change without prior notice
The freeze limit trip is factory set for open-loop
protection (26°F) but can be set for all values
between (26°F) and (15°F) via the Bosch EasyStart
app. If the temperature drops below or remains
constant at the configured freeze point for more
than 30 seconds after the compressor is
energized, the control will shutdown the
compressor to prevent the water coil from
freezing. The compressor will not be re-energized
until the temperature increases 10°F above the
configured freeze limit and the ASC delay has
expired.
Lockout
If the number of freeze faults detected exceeds
two to four times (based on configuration set via
the Bosch EasyStart app) within one hour, the
controller will go into hard lockout. The status LED
indicator will flash three times and the alarm relay
will pulse three times as well, if configured for
pulse. See Table 7:Status LED Information on page
#20. Also see “Clearing a Hard Lockout” on page
Fig. 8 FZC Location
Evaporator Air Coil Freeze (FZE) Sensor
The Freeze Evaporator Coil (FZE) is installed on
the entering refrigerant pipe after the thermal
expansion device and before the air coil. The
location of the FZE is shown on Fig. 9.
The freeze limit trip is set to factory default at
30°F. If the temperature drops below or remains
constant at the freeze point for more than 30
seconds after the compressor is energized, the
controller will shut down the compressor to
prevent freezing the air/evaporator coil. The
compressor will not be re-energized until the
temperature increases 10°F above the freeze limit
and the ASC delay has expired.
If the number of freeze faults detected exceeds
two to four times (configurable via the Bosch
EasyStart app) within one hour, the controller will
go into hard lockout. The status LED indicator will
flash six times, alarm relay will pulse six times as
well, if configured for pulse. See Table 7:Status
LED Information on page #20. Also see “Clearing a
Hard Lockout” on page #8.
Fig. 9 FZE Sensor Locations
Discharge Refrigerant Temperature (DRT) Sensor
The Heat Recovery Package (HRP) controller will
monitor the DRT sensor and only allow the HRP
pump to run when the DRT is suitable for hot water
production or enabled via the Bosch EasyStart
app. The HPC will issue a warning if the DRT sensor
is invalid or not within range (via the live monitor
screen on the Bosch EasyStart app).
The Freeze Evaporator sensor limit trip is not
configurable.
