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DEFROSTING
The defrosting aim is to maintain the external coil free from ice during the winter mode : to do that the unit is periodically
commuted in “summer” mode for few minutes and the fans are stopped.
The defrosting phase is started when the evaporating pressure falls below a fixed value . A count starts and at its end, if the
temperature on the coil is lower than the threshold, the defrosting starts .
The count changes according to the external temperature and to the ice quantity on the coil ( by some indirect variables ) .
When defrosting is complete, the unit returns automatically to the Winter mode.
Defrosting is managed according to the external temperature and humidity in the air:
•
more humidity = frequent defrosting
•
external temperature next to 0°C = frequent defrosting
By the EXTERNAL HUIDITY PROBE option cod PE2N0005 the defrosting is optimised according to the external temperature
and humidity .
CIRCULATION PUMP
The pump is always activated with the units ON.
The delivery capacity is variable to soften the thermal shock to the compressors when the plant temperature is close to the
threshold limits.
Delivery capacity depends on the intake temperature:
•
SUMMER: high water temperature reduces delivery
•
WINTER: low water temperature reduces delivery
CIRCULATION PUMP – CONDENSER (RUNNING WATER)
The pump is started BEFORE the compressor start and stopped AFTER the condenser stop .
VENTILATION
Fans are controlled with a variable speed:
•
in SUMMER, the speed increases according to the increase of external air temperature
•
in WINTER the speed increases according to the decrease of the external tempe
SET POINT
SUMMER - WINTER
The thermoregulator manages two set points:
•
SUMMER set-point for cooling (parameter 32)
•
WINTER set-point for heating (parameter 33)
The control is performed on the OUTLET TEMPERATURE, comparing it with the actual set-point value (visible at status 1).
SET-POINT CALCULATION:
•
desired medium outlet water temperature = 7°C
•
Project temperature differential = 5°C (that is inlet water = 12°C)
•
¼ of the project temperature differential = 5 / 4 = 1.25°C
•
set-point to be set = 7 – 1.25 = 5.7°C
SECONDARY SET POINT – ECO
A secondary set point can be used with different levels to the “normal” set point.
It is normally set to give lower energy consumption with respect to the comfort setting:
•
The SECONDARY SUMMER set point is higher than the SUMMER setting.
•
The SECONDARY WINTER set point is lower than the WINTER setting.
It can be set according to individual requirements.
•
Secondary summer set-point parameter 29
•
Secondary winter set-point parameter 30
It can be activated from the keyboard, supervisor unit or the remote control. To change it using the remote control refer to the
ELECTRIC WIRING paragraph.
MAINTENANCE
This way, the plant can be kept within the operating limits even when the unit is OFF or on STANDBY, for example during the
weekend or the night-time.
Periodically the system activates the circulation pump, measures the water temperature and activates the compressor, if
required, to take the water temperature to the set-point level.
•
Summer maintenance set-point par 42
•
Winter maintenance set-point par 43
This function is activated by parameters 44 (activate summer maintenance level) and 45 = 1 (activate winter maintenance
level). In this mode on the service keypad is displayed : STB
Summary of Contents for WSAN-XPR 21
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