Danfoss BW10 020-090, Operation Instructions Manual

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5.3 - Heat exchanger water pump control
The unit can control one water pump per heat exchanger. The
pump is turned on when this option is configured (see
PUMPCONFIG) and when the unit is in one of the on modes
described above or in delay mode. Since the minimum value for
the delay at start-up is 1 minute (configurable between 1 and 15
minutes), the pump will run for at least one minute before the
first compressor starts.
The pump is kept running for 2 minutes after the unit goes to stop
mode. The pump keeps working when the unit switches from
heating to cooling mode or vice-versa. It is turned off if the unit
is shut down due to an alarm unless the fault is a frost protection
error. The pump can be started in particular operating conditions
when frost protection of the heat exchanger is active (see chapter
“Control point”). See chapter “Master/slave assembly” for the
particular heat exchanger pump control for the slave unit
(master/slave assembly).
If the pump with variable flow option has been selected
(factory-installed option), it is possible to control the water
flow in three ways (service parameters):
• adjusted fixed flow rate,
• constant temperature difference,
• constant pressure difference.
In this way it is possible to adjust the water loops and to
optimise pump operation.
The control provides a means to automatically start the pump
each day at 14.00 hours for 2 seconds when the unit is off (pump
anti-stick function). Starting the pump periodically for few
seconds increases the life-time of the pump bearings and the
tightness of the pump seal.
5.4 - Control interlock contact
This contact checks the status of a loop (water flow switch and
customer safety loop, see chapter 3.6). It prevents the unit from
starting if it is open when the delay at start-up has expired. This
open contact leads to an alarm shut-down, if the unit is running.
5.5 - Control point
The control point represents the water temperature that the unit
must produce. The heat exchanger entering water temperature
is controlled by default, but the heat exchanger leaving water
temperature can also be controlled (requires a Service
configuration modification).
Control point = active se reset
5.5.1 - Active setpoint
Three setpoints can be selected as active in cooling mode and
two in heating mode. Usually, the second setpoint is used for
unoccupied periods.
Depending on the current operating type, the active setpoint can
be selected:
• by choosing the item in the GENUNIT menu,
• via the user’s volt-free contacts,
• via network commands
• via the setpoint timer program (schedule 2).
5.2.2 - Heating/cooling/auto selection
The table below summarises the unit heating/cooling opera-tion,
based on the following parameters:
• Control type: indicates whether the unit operates in local,
remote or CCN mode. See section 5.1.
• Unit on/off status: indicates whether the unit is shut down
(not authorised to start) or in operation (or authorised to
start).
• Heating/cooling/auto selection in local mode: operating
mode selected via the user interface. See GENUNIT
menu.
• Remote heating/cooling contacts: these contacts are only
active if the unit is under remote control.
• HC_SEL: this network command permits heating/cooling/
auto control, if the unit is in CCN operating mode.
• Outside temperature: determines the operation, if the unit
is in automatic heating/cooling/standby changeover mode.
PARAMETER STATUS
ON/OFF STATUS
CONTROL TYPE HEATING/COOLING
SELECTION IN LOCAL
MODE REMOTE HEATING/
COOLING CONTACTS HC_SEL OUTDOOR TEMPERATURE OPERATING MODE
Off - - - - - Cooling
On Local Cooling - - - Cooling
On Local Heating - - - Heating
On Local Auto - - > Cooling threshold Cooling
On Local Auto - - < Heating threshold Heating*
On Local Auto - - Between cooling and heating thresholds Standby
On Remote - Cooling mode - - Cooling
On Remote - Heating mode - - Heating
On Remote - Auto mode - > Cooling threshold Cooling
On Remote - Auto mode - < Heating threshold Heating*
On Remote - Auto mode - Between cooling and heating thresholds Standby
On CCN - - Cooling - Cooling
On CCN - - Heating - Heating
On CCN - - Auto > Cooling threshold Cooling
On CCN - - Auto < Heating threshold Heating*
On CCN - - Auto Between cooling and heating thresholds Standby
* Does not apply to cooling only units that do not control a boiler.