Heat Pump Controller
Heat Pump Controller
8733819577 (2019/02)
Subject to change without prior notice
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System Protection
Leaving Water Temperature (LWT) Sensor
The LWT sensor is installed on the Leaving Water
pipe of the coaxial water coil. The location of the
LWT Sensor is shown on Fig. 6.
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 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.
Fig. 6 LWT Sensor Location
Entering Water Temperature (EWT) Sensor
An EWT sensor is installed on the entering water
pipe of the coaxial water coil. The location of the
EWT sensor is shown on Fig. 7.
Cooling Mode
High EWT, above 110.5°F for one minute, will
result in a warning message indicating an high EWT
fault without impeded operation. This fault will
reset when EWT drops below 105°F.
Heating Mode
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 #14.
Fig. 7 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
location of the FZC sensor is shown on Fig. 8.
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 #14.) 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.)
