Brownout Protection; Low Loop Water Protection Control (Llwpc) (Boilerless Control); Water Flow Detection; Sensor Monitoring - Bosch Greensource SM024 Installation, Operation And Maintenance Manual

Greensource CDi Series SM Model

Brownout Protection

The HPC controller will constantly monitor the
power supply. If the nominal voltage supplied to
the HPC drops below 18 VAC, the unit will enter
brownout protection mode. All outputs will be
de-energized, the controller will enter the soft
lockout mode, and the status LED indicator will
flash five times as an error code. ASC is engaged
when de-energized. The controller will pulse the
brownout code at the display and alarm outputs
for 20 seconds. The unit's brownout fault history
can be found in the Fault Log when connected with
the Bosch EasyStart app.
Low Loop Water Protection Control
(LLWPC) (Boilerless Control)
The LLWPC prevents a condition of low loop water
during heating operation. The HPC constantly
monitors the Leaving Water Temperature (LWT
sensors) and Entering Water Temperature (EWT
sensors). If the entering water temperature falls
below 34°F (configurable between 20°F to 50°F via
the Bosch EasyStart app) the controller will
disable compressor operation for 15 minutes to
allow the loop to warm up to the operational
temperature range. If a call for heating is still
present, the unit will run auxiliary heat by
energizing AUX1 and AUX2. The controller will
resume mechanical heating operation when EWT
has increased at least 10°F from the temperature
at which the fault occurred and a 15-minute timer
has expired. Low Loop Water Protection Control is
disabled if the EWT or the LWT sensors are out of
their operational range.
If the EWT or LWT sensor fails, a warning
message will be broadcast to the Live Monitor
screen on the Bosch EasyStart app and LLWPC
mode will be disabled.

Water Flow Detection

The HPC constantly monitors the Freeze Coaxial
(FZC), EWT, and LWT sensors to diagnose
potential problems associated with water flow.
The HPC will enter a hard lockout when it senses a
condition of no water flow. See "Clearing a Hard
Lockout" on page #29.
Cooling Mode
The controller evaluates the following after the
unit has run in cooling mode for 90 seconds:
• If LWT is 5°F to 15°F higher than the EWT, the
unit is running in nominal operating conditions.
Greensource CDi Series SM Model
• If LWT and EWT are the same and the
compressor is enabled (CS1), the FZC and
Freeze Evaporator Coil (FZE) temperatures are
sampled every 10 seconds for 30 seconds.
Rapid temperature changes on the freeze
sensors will be used by the controller to report
a "No Water Flow" fault and de-energize all
compressor outputs.
• If the LWT is at least 20°F higher than the EWT,
the FZC in and out temperatures are sampled
every 10 seconds for 30 seconds. The rapid
temperature changes on the freeze sensors
will be used by the controller to report a low
water flow fault.
Heating Mode
The controller evaluates the following after the
unit has run in heating mode for 90 seconds:
• If LWT is 4°F to 12°F lower than the EWT, the
unit is running in nominal operating conditions.
• If LWT and EWT are the same and the
compressor is enabled (CS1), rapid
temperature changes on the freeze sensors
will be used by the controller to report a "No
Water Flow" fault and de-energize all
compressor outputs.
• If the LWT is at least 20°F lower than the EWT.
If the EWT or LWT sensor fails, a warning
message will be broadcast to the Live Monitor
screen on the Bosch EasyStart app and LLWPC
mode will be disabled.

Sensor Monitoring

Condensate Overflow Sensor
The Condensate Overflow Sensor monitors the
condensation present in the drain pan. When the
condensation reaches the overflow level (water
touching the sensor) the HPC will enter a hard
lockout and de-energize the compressor outputs.
The status LED indicator will flash four times, and
the alarm output will pulse four times as well, if
configured to do so. (See the Alarm Mode section
on page #29.) The compressor will remain off until
the ASC delay has expired and the condensate has
been removed. See "Clearing a Hard Lockout" on
page #29. Location of the Condensate Overflow
Sensor is shown in Fig. 56.
Subject to change without prior notice
System Protection | 35
8733819578 (2019/02)