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Building Technologies Division User Manual LMS14… CC1U7471en
6 The settings in detail 28.01.2015
6.21 Instantaneous water heater
To prevent scalding, DHW consumption and the keep-hot function are both inhibited if
there is a fault on sensor B38 (or sensor B39, depending on the system).
Any request from space heating is immediately satisfied, even if the DHW flow switch is
active.
To ensure protection against scalding, DHW consumption via the tap must be accepted
only in the case of instantaneous water heaters with primary heat exchanger (partial
diagram BwDl2). Burner startup is prevented in this case. During the time DHW is
consumed, a pending request from space heating cannot be satisfied, since this would
affect the water temperature at the tap as well.
6.21.1 Control
Line no. Operating line
5420 Flow setpoint boost
Here, set the boost of the flow temperature setpoint for instantaneous water heater
operation. The boost acts only if control is not dependent on sensor B38 and only
applies to consumption and Keep hot operation.
Line no. Operating line
5429 Switching diff
Here, set the switching differential for the instantaneous water heater. It applies to
consumption and Keep hot operation.
6.21.2 DHW consumption (flow)
Line no. Operating line
5444 Threshold flow detection
DHW consumption is detected when:
DHW flow > threshold flow detection
.
Line no. Operating line
5445 Switching diff flow detection
DHW consumption is no longer detected when:
DHW flow < threshold flow detection minus switching differential flow detection
.
The measured DHW flow can be read via parameter DHW flow (8860).
Line no. Operating line
8860 DHW flow
Behavior in the event of
sensor failure
Flow setpoint boost
Switching diff
Threshold flow
detection
Switching diff flow
detection
Info/diagnostics
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