Siemens RVL471 - Setpoint Rise; 3-Position Control; Auxiliary Variables in Interconnected Plants; Excess Mixing Valve or Heat Exchanger Temperature

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Siemens Building Technologies Basic Documentation RVL471 CE1P2524E
HVAC Products 11 Function block "3-position actuator heating circuit" 23.10.2002
11.2.2 Setpoint rise
t
t
2522D07
T
Vw
T
Vw
∆TVw
Maximum rise: = ––––––––
∆t
tTime
∆t Unit of time
TVw Flow temperature setpoint
∆TVw Rate of setpoint increase per unit of time
The rate of increase of the flow temperature setpoint can be limited to a maximum. In
that case, the maximum rate of increase of the flow temperature setpoint is the selected
temperature per unit of time (°C per hour). This function:
• prevents cracking noises in the piping
• protects objects and construction materials that are sensitive to quick temperature
increases (e.g. antiquities)
• prevents excessive loads on heat generating equipment
This function can be deactivated (setting ---).
During d.h.w. heating, limitation of the rate of increase acts as follows:
Plant type Effect
1–x
3–0
3–2
3–4
3–5
4–x
6–x
Limitation of the rate of increase is always active
3–1
3–3
Limitation of the rate of increase only acts with shifting or parallel d.h.w.
priority
11.3 3-position control
3-position control operates as weather- or demand-compensated PI flow temperature
control. The flow temperature is controlled through a modulating actuating device (slip-
per or seat valve). Owing to the I-part, there is no control offset.
The controller’s positioning commands to the actuator of the actuating device are fed to
the output relays and indicated by LEDs.
11.4 Auxiliary variables in interconnected plants
11.4.1 Excess mixing valve or heat exchanger temperature
In interconnected plants, an excess mixing valve or heat exchanger temperature can be
entered on the RVL471. This is a boost of the respective heating zone's flow tempera-
ture setpoint. The higher setpoint is delivered to the heat source as the heat demand
signal.
The excess mixing valve or heat exchanger temperature is set on the controller that
drives the mixing valve (controller N2 in the example below) (operating line 84).
Function
Effect on d.h.w. heating