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Building Technologies
Boiler sequence controller RMK770
CE1P3132en
HVAC Products
10 Heating circuit control
23.04.2009
10.8.3 Pulse limitation
The heating circuit can accept pulses for limiting the output of heat or the volumetric
flow. Prerequisite for pulse limitation is a heating circuit plant with mixing valve.
The pulses are delivered via the meter inputs of function block “Meters”. For more
detailed information about function block “Meters”, refer to chapter 11 “Data acquisi-
tion“. After having configured one or several meter inputs, pulse limitation can be set
up.
Main menu > Commissioning > Settings > …
or
Main menu > Settings > Heating circuit > Limitations > Pulse limitation
Operating line
Range
Factory setting
Meter input
---/ 1…4
---
Type of limitation
Absolute / Scaled
Absolute
Limit value
5…4000 pulses/min
75 pulses/min
Integral action time Tn
0…255 min
60 min
The meter input is an input of function block “Meters” used for pulse limitation. Only
inputs configured to a terminal can be selected.
There are 2 types of limitation to choose from:
•
Absolute: Limitation becomes active when the limit value is exceeded
•
Scaled: The limit value is fixed at 75 pulses/min. It can be changed, but the change
has no impact.
If fewer than 5 pulses/min are received, fault status message ”No pulse signal meter
1” (or meter 2 , etc.) will be delivered after 20 seconds.
From the limit value, pulse limitation starts throttling the actuating device (mixing valve).
The setting acts only with absolute limitation. With scaled limitation, the limit value can
be changed, but the function operates with 75 pulses/min (fixed value).
The setting value determines the rate of flow temperature reduction:
•
Short integral action times lead to fast reductions
•
Long integral action times lead to slow reductions
10.8.4 Frost functions and general protective functions
It can be selected whether or not frost protection for the plant shall act on the heating
circuit pump.
The flow temperature is monitored for minimum limitation. If the flow temperature falls
below 5 °C, a heat demand signal is sent to the heat source and the mixing valve
opens. The function is ended as soon as the flow temperature has returned to a level of
7 °C. The function is active for a minimum of 5 minutes.
This setting ensures maximum limitation of the flow temperature setpoint.
This setting provides minimum limitation of the flow temperature setpoint. Minimum
limitation is only active when there is demand for heat.
Setting --- (none) deactivates the function.
The rate of flow temperature increase can be limited to a maximum (heating up brake).
In that case, the maximum rate of flow temperature setpoint increase is the set tem-
perature per unit of time K per hour). This function prevents knocking noises in the
pipework and excessive loads on the heat source.
Meter inputs
Settings
Meter input
Type of limitation
Limit value
Integral action time Tn
Frost protection for
the plant
Frost protection for
the flow
Flow temperature
maximum limitation
Flow temperature
minimum limitation
Heating up brake
