Operating Principle - Siemens RMB795B Basic Documentation

Activation
Request signals
Setting values
"Limit value request on"
"Heating flow setpoint",
"Flow temperature
reduction max"
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Building Technologies
For the "Heat request" function to become activated, a heat distribution zone must
be assigned to it on the consumption side:
Main menu > Commissioning > Communication > Distribution zones
Operating line
Heat distribution zone

11.2.2 Operating principle

The RMB795B central control unit receives the following types of request signals
via bus:
• Heat demand in %,
e.g. from a room control system "RXB/RXL with heating coil"
• Valve position in %,
e.g. from a control system "RMU7... as basic type A or U" for an air handling
plant with heating coil / cooling coil
• Temperature request in °C,
from an RMH760 controller (heating circuit controller or cascaded primary
controller)
All these signals are handled simultaneously.
Main menu > Commissioning > Settings > ... or
Main menu > Settings > Heat request >
Operating line
Limit value request on
Limit value request off
Heating flow setpoint
Flow temperature reduction
max
Control action
Evaluation of request
The %-request signals received (heat demand or valve position) are passed on
only when they have exceeded the level of "Limit value request on". This function
prevents the heat generation plant from being switched on when heat request is
only small.
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 heat demand in a way that the valve
position of the heat 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
Central control unit RMB795B
Distribution zones
Range
----, 1...31
Range
0...100 %
0...100 %
0...140 °C
0..0.100 K
Slow, medium, fast.
Average, maximum.
[%]
Factory setting
1
Factory setting
10 %
5 %
40 °C
0 K
Medium.
Maximum.
CE1P3122en
18.01.2012