Function Block "Maximum Limitation Of The Return Temperature, D.h.w; Operating Line; Purpose; Function - Siemens RVL471 Basic Documentation

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15 Function block "Maximum limitation
of the return temperature, d.h.w."
In plants with district heat connection, function block "Maximum limitation of the return
temperature, d.h.w." provides maximum limitation of the primary return temperature
during d.h.w. heating. Since for that purpose, the primary return temperature must be
acquired during d.h.w. heating, this function can only be implemented with plant types
where d.h.w. is heated on the secondary side of the heating circuit's heat exchanger
(plant types 3–1, 3–3, 6–1 and 6–2).
If the settings of this function block have been locked (contact H3, or on operating line
198; refer to the respective sections), the display shows
and .

15.1 Operating line

Line Function, parameter
117 Maximum limitation of return temperature, d.h.w.

15.2 Purpose

The primary return temperature of the d.h.w. circuit has its own maximum limitation in
order to
• be able to differentiate between the maximum limit value during d.h.w. heating and the
limit value during space heating only
• make certain that too hot water will not be fed back to the district heating network
• minimize piping losses of the district heating utility
• satisfy the regulations of the district heating utility

15.3 Function

The maximum limit value during d.h.w. heating is set in °C on operating line 117, the
integral action time for this function on operating line 114.
As soon as d.h.w. heating is started, the higher of the two values from operating lines
101...113 and 117 is used, independent of the kind of priority.
If no d.h.w. is heated, the interaction with maximum return temperature limitation looks
as follows:
ON
OFF
T
PRmax
117
101...113
ON D.h.w. heating ON
OFF D.h.w. heating OFF
T Maximum limit value of primary return temperature
PRmax
t Time
101...113 Maximum limitation of the return temperature in the heating circuit (operating lines 101...113)
117 Maximum limitation of the return temperature in the d.h.w. circuit (operating line 117)
The return temperature is acquired with sensor B7.
Basic Documentation RVL471

15 Function block "Maximum limitation of the return temperature, d.h.w."

Unit
°C
t
101...113
t
when pressing buttons
Factory Range
setting
--- --- / 0...140
CE1P2524E
23.10.2002