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Siemens Building Technologies
Basic Documentation RVP540 / RVP550
CE1P2488en
HVAC Products
Description of the EXP settings
18.10.2002
5.8 Pump overrun time
•
Boiler:protection
against
overtemperature
•
Use of residual heat in the boiler
Overrun of the primary, bypass, boiler, heating circuit and d.h.w. charging pump en-
sures that residual heat will be carried away from the boiler circuit. This makes certain
that overtemperature in the boiler will not occur, thus preventing the safety limit ther-
mostat from responding.
Setting range
Unit
Factory setting
0...20
min 5
All pumps that - at the time of burner shutdown - were operating, continue to run for the
period of time set here. The behavior is the same as with burner shut-down when, with
the burner deactivated, the demand for heat from the boiler becomes invalid. At the
same time, the previous flow temperature setpoint remains valid, allowing the mixing
valves of the controllers connected to LPB to stay open.
ON
OFF
t
BR
Q
t
TVNw
TVRw
237
3Z28
Y
t
tPN
t
HK
ON
OFF
HK Operating
mode
BR Burner
Q Pumps
Y
Extenal mixing valve (via LPB)
TVNw Nominal flow temperature setpoint
TVRw Reduced flow temperature setpoint
Nominal
operation
Reduced
operation
tPN Pump
overrun
time
Boiler pump overrun may get interrupted.
This is the case when the boiler temperature falls by 5 K below the actual value of the
flow temperature. Boiler pump overrun will be resumed, however, when the boiler tem-
perature lies only 2 K below the flow temperature. During the interruption, the time set
above continues to elapse.
Only plants with a pressureless header (ZuFu 12) and a common flow temperature
sensor (B10) allow the boiler pump overrun time to be interrupted.
Benefit
Description
Setting
Effect
Example
Pump overrun of
boiler pump