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Bosch Greensource SM024 Installation, Operation And Maintenance Manual page 37

Greensource cdi series sm model water-to-air heat pumps
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Greensource CDi Series SM Model
Leaving Water Temperature (LWT) Sensor
The LWT sensor is installed on the Leaving Water
pipe of the coaxial water coil. In the case of a high
LWT, above 125°F for one minute, the HPC will
issue a warning and save it to memory. The
compressor and loop pump will remain running
once the LWT decreases below 100° F, the warning
will be cleared and the compressor and loop pump
will remain running. The HPC will record this
condition in memory without impeded operation.
Cooling Mode
During cooling operation, if the LWT is equal to or
less than the Entering Water Temperature (EWT),
the HPC will issue a warning that the unit is not
cooling.
Heating Mode
During heating operation, if the LWT is equal to or
greater than the EWT, the HPC will issue a warning
that the unit is not heating. Location of the LWT
Sensor is shown on Fig. 60.
Fig. 60 LWT Sensor Location
Entering Water Temperature (EWT) Sensor
An EWT sensor is installed on the entering water
pipe of the coaxial water coil.
Cooling Mode
High EWT, above 110.5°F for one minute, will
result in a warning message indicating an high EWT
fault.
Heating Mode
This fault will reset when EWT drops below 105°F.
Greensource CDi Series SM Model
Low EWT activates the LLWPC. Low EWT can only
occur when the EWT is low during heating
operation. Refer to Low Loop Water Protection
Control (LLWPC) on page #35. Location of the
EWT sensor is shown on Fig. 61.
There is no EWT freeze-limit trip. However, If
the application has both electric heat and
LLWPC enabled, the controller will have a low
limit for EWT. (Refer to the LLWPC section on
page #35.) Otherwise, there is no EWT low-limit
trip. (If EWT is frozen/cold, another fault will
likely occur such as FZC trip/No water flow, High
Pressure, etc.)
Fig. 61 EWT Sensor Location
Coaxial Water Coil Freeze (FZC) Sensor
The Freeze Coaxial (FZC) Water Coil sensor is
installed on the refrigerant pipe of the coaxial
water coil between coaxial coil and TXV. 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 freeze point and the
anti-short cycle (ASC) delay has expired.
Subject to change without prior notice
System Protection | 37
8733819578 (2019/02)

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