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OPERATING CHARACTERISTICS
Temperature control
Control is performed based on the system water return tem-
perature.
The set points refer to the water return temperature.
The water outlet temperature depends on the difference
between inlet and outlet, usually 5°C (rated).
This temperature difference may change depending on the
type of water circuit.
For example, if the HEAT set point is set to +30°C, the outlet
temperature will be +35°C.
The return temperature is also used to activate the
resources inside or outside unit (e.g. electric heaters).
The controller features Full Floating technology that optimis-
es, when the scan time elapses, the water temperature set
points (COOL/HEAT/DHW) in relation to the compressor
operating time and the water temperature.
To display the actual set point, select directory Sr and the
active operating mode (Cool, Heat, DHW), as described in
the paragraph "Displaying installer parameters ".
Cooling set point
(factory setting) = 12°C, Hysteresis = 3°C.
The compressor starts at outlet water temperatures above
12°C+3°C (15°C).
The compressor stops at water temperatures below 12°C.
Heating set point
(factory setting) = 40°C, Hysteresis = 3°C.
The compressor starts at outlet water temperatures below
37°C.
The compressor stops at water temperatures above 40°C.
In the event of temporary power failure, when power returns,
the mode set previously will be retained in the memory.
COMPRESSOR START UP DELAY
Two functions prevent the compressor from starting up too
frequently.
- Minimum time since last shut-down 3 minutes.
- Minimum time since last start-up 5 minutes.
SYSTEM CIRCULATING PUMP
The electronic board has an output for managing the circu-
lating pump, always on in COOL and HEAT modes, and off
with a 1 minute delay when unit shuts down (standby).
After the first minute of pump operation when the water flow
is at full speed, the water flow alarm functions are activated
(differential pressure switch and flow switch).
SOURCE PUMP ON BWR MODELS
The electronic board has an output for managing the source
pump with phase control, allowing the flow-rate to be modu-
lated in both heating and cooling modes.
The source pump starts before the compressor starts, and
shuts down a few seconds after the compressor stops.
MODULATING VALVE ON WWR MODELS
The electronic board has a 0-10V output for managing a 2-
way modulating valve to control flow-rate in both heating
and cooling modes; this extends operating limits of the unit.
The modulating valve is opened before the compressor
starts and closed a few seconds after the compressor stops.
When the compressor is off the valve remains closed.
FROST ALARM
The frost protection function for the system and source side
heat exchanger is active even if the controller is in standby
mode.
To prevent the water freezing and damaging the plate heat
exchanger, the microprocessor shuts down the compressor
and activates the plate heat exchanger heating element if
the temperature measured by the heat exchanger outlet
temperature sensor is less than +4°C.
The frost prevention temperature set point can be modified
by an authorised service centre only and only after verifying
that the water circuit contains antifreeze.
Tripping of this alarm shuts down the compressor but not
the pump, which remains active.
To reset normal functions, the water outlet temperature must
rise to more than +7°C. Reset is automatic.
If the frost alarm is tripped more than 3 times in one hour,
reset becomes manual.
For BWR MTD units only, frost protection for the ground sour-
ce loop heat exchanger is activated if the outlet temperature
is less than -5.5°C. To reset normal operation, the heat
exchanger outlet temperature must rise back above -3°C.
DOMESTIC HOT WATER FROST PROTECTION
The domestic hot water frost protection function is only
active if an auxiliary resource is installed for the domestic
hot water storage (parameter CL61=28).
The auxiliary resource is activated if the water temperature,
measured by sensor BT4, is less than +5°C, and is deacti-
vated at +7°C.
3-WAY VALVE MANAGEMENT FOR DOMESTIC
HOT WATER (YV3)
The HSW12 controller manages domestic hot water produc-
tion using a 3-way valve installed outside of the unit.
The production of domestic hot water is guaranteed in both
summer and winter, according to the operating limits shown
in this manual.
An electric heater should be installed inside the DHW stor-
age cylinder to ensure the temperature does not fall below
15/20°C in the event of extended periods of heat pump inac-
tivity (standby).
Domestic hot water production is only enabled if the follow-
ing conditions are satisfied:
- DHW storage temperature (sensor BT4) less than the
DHW set point (AS01) minus the hysteresis (AS04); 3-way
valve changeover to the domestic water storage;
- the time set for parameter AS10 has elapsed
- an Anti-Legionella cycle is not in progress (if activated by
parameter)
Changeover from domestic hot water production to heating
system hot water production:
- if the DHW storage temperature (sensor BT4) has reached
the DHW set point (AS01); 3-way valve changeover to
system;
- if the return water temperature (sensor BT1) has reached
the DHW set point (AS01) plus a differential (AS05) that
considers the possible temperature difference between the
domestic water storage and the system return water tem-
perature.
- if the maximum time (AS09) domestic hot water production
time has elapsed.
GB 03/2010 WWR MTD - BWR MTD
I A
27
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