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Disabling of fan speed II at
low outside temperatures
Fixed preset damper
position
Periodic pump run
(pump kick)
Forced run-up and
rundown time for fans
Supervision
Siemens Building Technologies
Landis & Staefa Division
To protect the plant, fan speed II is disabled when outside temperatures are very low.
The outside temperature at which this function is activated depends on the set value
−
(adjustable from
50 °C to +150 °C). To prevent the controlled system from oscillating
at greatly varying outside temperatures, the RWI65.02 operates with a fixed hysteresis
of 2 Kelvin.
This function is used in connection with outside air handling to save energy (predomi-
nantly in rooms with low occupancy levels).
The damper sequence (Y30) with operating action " / " is not implemented as a control
sequence. During plant operation, the damper is preset to a fixed position. The fixed
value of the manipulated variable for the air dampers is adjustable from 0 to 100 %
(Y30 minimum limitation).
• For the hot water pump (DIL switch no. 8 must be in position "Hot water heating coil")
To avoid damage during plant off times, there are three settings:
– The pump is activated permanently;
the pump is activated for 30 s at 24-hour intervals after the last operation, or
– The pump runs continuously when the outside temperature is below 5 °C; the
minimum pump running time (adjustable from 0 s to 30 min) is maintained
– The pump is periodically activated, i.e., the pump is activated for 30 s after the last
operation according to the selected time (adjustable from 5 min to 24 h)
• For the chilled water pump
To avoid damage during plant off times, it is possible to select periodic pump run. If
this function is enabled (selectable), the pump is activated for 30 s every afternoon at
15.00.
• Forced run-up
The fan is always started via the first speed. If the second speed is selected right from
the start, the first speed is first activated.
Switching to the second speed takes place only when the set time has elapsed
(adjustable from 0 to 5 min).
• Rundown time
When switching down from the second to the first speed, the RWI65.02 deactivates
the second speed, and the first speed is activated only when the preset time has
elapsed (adjustable from 0 s to 5 min).
• In plants using hot water heating coils:
– Continuous checkback signals on the operational status of the plant and on the
status of the hot water circulator, based on the signals received from supervisory
elements such as flow switch and overload protection
– Continuous supervision of risk of frost
– Switching on and off depending on the selected alarm priority ("A" or "b")
• In plants using electric heater batteries:
– Continuous checkback signals on the operational status of the plant and,
especially, on that of the electric heater battery, based on the signals received from
supervisory elements such as flow switch, overload and overtemperature protection
– Switching on and off depending on the selected alarm priority ("A" or "b")
• In plants with heat recovery systems
– Continuous efficiency evaluation
• In plants using chilled water cooling coils/chillers:
– Continuous checkback signals on the operational status of the plant and on the
status of the chilled water circulator or chiller, based on the signals received from
supervisory elements such as flow switch and overload protection
– Switching on and off depending on the selected alarm priority ("A" or "b")
.
.
.
CM2N3204E / 05.2001
7/20
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