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Unit Start-Up; Maintenance; Decommissioning; Water To Water Unit Controller - Bosch TW Series Installation, Operation And Maintenance Manual

Water to water
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16 | Unit Start-up

Set the thermostat to the highest setting.
Set the thermostat system switch to "COOL", . The
reversing valve solenoid should energize. The
compressor should not run.
Reduce the thermostat setting approximately 5
degrees below the room temperature.
Verify the heat pump is operating in the cooling
Turn the thermostat system switch to the "OFF"
position. The unit should stop running and the
reversing valve should de energize.
Leave the unit off for approximately (5) minutes to
allow for system equalization.
Turn the thermostat to the lowest setting.
Set the thermostat switch to "HEAT".
Increase the thermostat setting approximately 5
degrees above the room temperature.
10. Verify the heat pump is operating in the heating
11. Set the thermostat to maintain the desired space
12. Check for vibrations, leaks, etc.


An annual "checkup" is recommended by a licensed
refrigeration mechanic. Recording the performance
measurements of volts, amps, and water temperature
differences (both heating and cooling) is recommended.
This data should be compared to the information on the
unit's data plate and the data taken at the original
startup of the equipment.
Only authorized technicians are allowed to
decommission and dispose of equipment following
applicable requirements and local codes
WARNING: Decommissioning of this
equipment can be hazardous due to system
pressure and electrical components. Only
trained and qualified personnel should
install, repair, or service or decommission
the equipment.


Bosch water heat pump controller offers a low cost,
simple solution to the control of a water to water heat
pump unit. The control is configurable to provide cooling
only, heating only or auto change over control strategies
based on the application of the unit in a given system.


Selectable mode of operation. Cooling, Heating or
Auto Changeover.
Adjustable temperature differential for heating and
cooling set point.
6720220047 (2016/02)
Adjustable auto changeover set point with
adjustable dead band setting.
Intelligent auto reset of a fault condition avoids
nuisance hard lockouts.
LED display of control temperature and set points.
F° or C° Display.
50/60 Hertz operation.
Pump operation configurable for continuous or
cycling operation with the compressor.
Compressor lead-lag operation on units with dual
Malfunction output and service LED can be set to
steady or pulsing to indicate fault condition.
Color LED's indication of mode of operation.
Set point retention in non volatile memory in the
event of a power failure.
Five minute delay on break or power interruption for
compressor short cycling protection.
Brown out low voltage protection.


The unit controller is provided with two sensors:

Water sensor:

This sensor will control unit operation in the cooling or
heating mode based on the water temperature on the
load side. It may be field mounted for example on the
return water line or in a water tank when provided with
a field supplied inversion well. The location will depend
on the specific requirements of the job.

Changeover Sensor

This sensor will put the unit in either the heating or
cooling mode depending on the set point. It maybe
mounted in a location that would be indicative if the unit
should be in either the heating or cooling mode, for
example outdoors.
The sensor may be located up to 1000 feet from the unit
(additional field supplied wiring required)


The controller will memorize the last mode used before
power is removed and will run in that mode after is
turned on. In all modes the control will display
temperature degree differential setting for five seconds
once it is powered and this setting for five seconds once
it is powered and this settings may be adjusted during
this time. Thereafter the display will switch to the
monitored water temperature. When switching from one
mode to another the set point (the decimal point is used
to distinguish it from water temperature) for the new
mode is displayed for 5 seconds and the monitored
water temperature. During this time the set point may be

Off Mode

In the OFF MODE all outputs are disabled and mode
indication LED's will be off.
Subject to change without prior notice
TW Series Water to Water
TW Series Water to Water



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