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Reversing Valve Operation; Comfort Mode; Economy Mode; Emergency Heating Mode - Bosch Greensource SM024 Installation, Operation And Maintenance Manual

Greensource cdi series sm model water-to-air heat pumps
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32 | System Operation

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.
If the DAT sensor fails, a warning message will
broadcast to the Bosch EasyStart app and
economy mode will be disabled.

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

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
HRP pump
8733819578 (2019/02)
Control circuit
The heat exchanger is rated for use with potable
water and is acceptable for use as a domestic
water heating device in most building codes. The
pump circulates water between the domestic hot
water tank and HRP heat exchanger in the heat
pump. The control circuit ensures that the HRP
only operates when there is available heat from the
compressor. The HRP pump will run under the
following conditions:
1. When the 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. When the Loop Pump (LP) and compressor are
both energized.
3. When the 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.
When the heat pump compressor operates, the
HRP will monitor the temperature of the discharge
gas from the compressor. 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).
In case of DWT/DRT sensor failure, the HRP
operation will be disabled.
NOTICE: Keep the HRP configuration setting
set to disabled if there is no domestic water
supply available.
Subject to change without prior notice
Greensource CDi Series SM
Greensource CDi Series SM Model

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