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Building Technologies Division User Manual LMS14... CC1U7471en
6 The settings in detail 07.05.2014
6.5.38 Behavior in the case of burner cycling
When the burner shuts down, the amount of heat available is not sufficient after a
certain time to satisfy the demand (actual value of flow temperature < flow temperature
setpoint). Speed control would respond to this situation by increasing the pump’s
speed. But this would lead to shorter burner off times. Also, due to pump modulation to
a higher speed, the noise level would increase. For this reason, modulation of the
heating circuit pump was matched to the situation of burner cycling.
When the burner shuts down, the pump’s modulation is maintained at the
parameterized minimum level.
When the burner is switched on, the speed of the heating circuit pump remains
unchanged for a selectable period of time.
It is only on completion of this delay time that modulation of the heating circuit pump is
again calculated and delivered based on the current common flow temperature (boiler
flow temperature). This means that the pump’s speed is increased only if the filtered
common flow temperature is lower than the flow temperature setpoint. An increase of
the pump speed leads to longer burner on times.
Then, filtering of the common flow temperature prevents the speed from dropping
rapidly if the boiler temperature already lies above the setpoint, but the burner’s switch-
off point is not yet reached.
When the burner shuts down, the pump’s speed is reduced again to the parameterized
minimum level.
Line no. Operating line
HC1 HC2 HC3
[4291.1] [4291.2] [4291.3] Delay speed ctrl HCx
Here, the delay for speed control after Burner On can be set.
6.5.39 2-speed heating circuit pump
This function facilitates the control of a 2-speed heating circuit pump, allowing the
pump’s capacity to be lowered in Reduced mode (e.g. during night setback).
To provide this function, a multifunctional relay output must be set to 2nd pump speed
HC1/HC2/ HC3 (Q21, Q22, Q23).
The second speed is switched on when the heating circuit’s operating level is Comfort
(including optimization) or when the Floor curing function is active.
Relay HC pump
(1st speed) Q2/Q6/Q20
Relay 2nd speed
Q21/Q22/Q23
State
OFF OFF OFF
OFF OFF Low-fire
ON ON High-fire
Note!
If the second speed needs a potential-free or inverted relay output, an intermediate
relay is required.
Delay speed ctrl HCx
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