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Building Technologies Division User Manual LMS14… CC1U7471en
6 The settings in detail 28.01.2015
When the Keep hot function is activated, the burner is controlled via the selected
control sensor.
The following sensors are available as control sensors:
Boiler flow (sensor B2)
Boiler return (sensor B7)
Sensor B38
The control sensor for the Keep hot function is selected via parameter Control sensor
keep hot (5475).
The temperature setpoint for the Keep hot function is adjusted via parameter Setpoint
keep hot (5460). If this parameter is set to OSV (---), the current DHW setpoint is also
used for the Keep hot function.
When the Keep hot function is activated, the burner’s output is not modulated. Also, the
burner operates at minimum output. It is switched on when the temperature acquired by
the keep hot sensor lies at least one switching differential (Switching diff on DHW
(2460)) below the setpoint of the Keep hot function. The burner is switched off again
when the temperature at the keep hot sensor exceeds the setpoint of the Keep hot
function by the minimum switch-off differential (Switching diff off min DHW (2461)).
When the burner has shut down, it may be practical to also deactivate the pump
(charging pump or boiler pump). The 2 parameters Pump overrun time keep hot (5072)
and Pump overrun time keep hot (5473) can be used to set the period of time the pump
shall overrun when – in the case of the Keep hot function – the burner has shut down.
The first parameter is used for setting the minutes (0…255 minutes), the second for
setting the seconds (0…240 seconds). The resulting pump overrun time is then the sum
of both parameters. If set to 255 minutes, the pump is not switched off during the time
the Keep hot function is active, even if the burner is not in operation.
On applications with diverting valve, the valve maintains the DHW position during the
time the Keep hot function is active. If there is no diverting valve, requests from space
heating can be considered – in addition to the Keep hot function. In that case, burner
modulation is enabled. The burner’s output is controlled according to the control sensor
parameterized for the Keep hot function.
Line no. Operating line
2460 Switching diff on DHW
2461 Switching diff off min DHW
5460 Setpoint keep hot
5464 Keep hot release
5468 Min cons time for keep hot
5470 Keep hot time wo heating
5471 Keep hot time with heating
5472 Pump overrun time keep hot
5473 Pump overrun time keep hot
5475 Control sensor keep hot
5482 Flow switch time cons
Line no. Operating line
8003 State DHW
8852 DHW consumption temp
8853 Instant WH setpoint
Keep hot function
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