Siemens RMB795B Basic Documentation page 102

Setting values
"Limit value request on"
"Chilled water flow
temperature setpoint",
"Flow temperature
increase max"
"Control action"
Request evaluation
Note
102 / 144
Siemens
Building Technologies
All these signals are handled simultaneously.
Main menu > Commissioning > Settings > ... or
Main menu > Settings > Refrigeration request >
Operating line
Limit value request on
Limit value request off
Chilled water flow
setpoint
Flow temperature
increase max
Control action
Request evaluation
The received request signals received are passed on only when they have
exceeded the level of "Limit value request on". This function prevents the
refrigeration generation plant from being switched on due to a slight request.
On
Off
Limit value Limit value
req off req on
From the request signals received, a resulting flow temperature is determined.
This flow temperature is matched to the actual refrigeration demand in a way that
the valve position of the refrigeration consumer with the greatest heat demand is
90 %.
• If the valve position is <90 %, the flow temperature will be increased
• If the valve position is >90 %, the flow temperature will be decreased
The maximum flow temperature readjustment can be parameterized.
With valve positions ≤ 90 %, the current flow temperature is:
"Chilled water flow temperature setpoint" + "Flow temperature increase max".
To adapt the control system to the plant, the control action of the flow temperature
can be adjusted to the setpoint shifts in 3 steps (fast, medium, slow).
Setting "Request evaluation" is used to determine if the max value or the average
of the requests is to be used:
• When using the "Maximum" setting, the flow temperature will be readjusted in a
way that the valve position of the consumer with the greatest heat demand is 90
%
• When using the "Average setting, the flow temperature will be readjusted in a
way that the valve positions of the 4 largest consumers will be 90 % on average
This setting does not ensure that the refrigeration demand of all consumers can be
satisfied. However, in ensures that an individual consumer cannot force the flow
temperature to a low level (e.g. because a window is open).
Central control unit RMB795B
Distribution zones
Range
0...100 %
0...100 %
0...140 °C
0...100 K
Slow, medium, fast.
Average, maximum.
[%]
Factory setting
10 %
5 %
6 °C
0 K
Medium.
Maximum.
CE1P3122en
18.01.2012