System Operation
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11
Heat Pump Controller
8733819577 (2019/02)
Heat Pump Controller
Subject to change without prior notice
The Loop Pump output of the HPC will energize the
pump directly. 230 VAC to 208 VAC on the HPC
pump outputs will be present (voltage dependent
on supply).
Reversing Valve Operation
The Reversing Valve (RV) is energized when the
controller receives a command on the (O)
terminal. The unit will run in cooling mode when
the (RV) is energized and heating when the (RV) is
not energized. The HPC checks for an (RV) demand
every 30 seconds.
Comfort Mode
In comfort mode the controller satisfies demand as
call is presented, regardless of energy
consumption, to satisfy space comfort levels. In
comfort mode, after the first stage of cooling/
heating the system turns on the second stage of
cooling/heating, with a 10-second delay, following
a call for second stage of cooling/heating.
Economy Mode
In economy mode the controller satisfies demand
as call is presented, taking energy consumption
into consideration to operate the compressor. In
economy mode after the first stage of cooling/
heating, the second stage is initiated by calculating
progress of the current state, regardless of a call
for the second stage of cooling/heating. If there is
gradual progress with first stage, the controller
will not initiate second stage of the compressor.
Economy mode is only available if the Discharge Air
Temperature (DAT) sensor is functional.
Emergency Heating Mode
Emergency heating mode is an electrical heating
feature that is used in place of mechanical heating
when the mechanical heating (Y1 or Y2) is not
available. The unit will initiate the first stage of
electric heat immediately and will start the next
stage of electric heat (stage 2) after a 180-second
delay.
Heat Recovery Package (HRP)
The HRP can be used to heat potable water during
unit operation (heat that would otherwise be
wasted from the compressor discharge gas). The
HRP consists of three major components:
•
Double wall, vented refrigerant to water heat
exchanger
•
HRP pump
•
Control circuit
Conditions for the HRP to operate are as follows:
1. Discharge Refrigerant Temperature (DRT) is at
least 10°F greater than the domestic hot water
temperature (DWT). The DWT set point is
configurable between 110–140°F, via the
Bosch Easy Start app.
2. Loop Pump (LP) and compressor are both
energized.
3. Domestic water temperature drops 2°F below
set point (default is 120°F). The controller will
run the pump until the demanded set point is
satisfied. The pump will run four times/hour via
(configurable from two to six times/hour via
the Bosch EasyStart App) in 90-second
intervals to determine whether or not demand
for hot water is needed.
The temperature of the discharge gas from the
compressor will be monitored once compressors
are energized. Once discharge gas is hot enough to
provide useful heat to the domestic water tank, the
circulating pump will be enabled, drawing water
from the tank, through the HRP heat exchanger
and the depositing the heated water back into the
tank. If the water temperature reaches the set
point (default is 120°F), the circulating pump is
disabled to prevent over heating of the domestic
water. The HRP is provided with an on/off switch
in case the end user desires that the HRP be
inactivated (typically during the winter months
when space heating is most important).
WARNING
: Before performing service or
maintenance operations on the system, turn
off the main power to the unit. Electrical
shock could cause personal injury or death.
If the DAT sensor fails, a warning message will
broadcast to the Bosch EasyStart app and
economy mode will be disabled.
