2-Speed Boiler Pump - Siemens LMS14 User Manual

Additional parameters
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6.5.40 2-speed boiler pump

This function affords control of a 2-speed boiler pump. Use of the second pump speed
is made only if the first pump speed is activated. To enable the function, a
multifunctional relay output must be set to the 2nd boiler pump speed Q27. The
function supports 2 operating principles. Changeover of the operating principle is
effected via Pump speed min (2322) and Pump speed max (2323):
Operating principle 1 applies when:
Pump speed max = Pump speed min
Operating principle 2 applies when:
Pump speed max > Pump speed min
Operating principle 1:
In DHW mode, the second speed of the boiler pump is always On. This also applies to
pump overrun. In Heating mode, the second speed is used if at least one of the heating
circuits calls for it.
Operating principle 2:
In principle, the 2-speed boiler pump can be regarded as a modulating pump with 3
speeds (Off/1st speed/2nd speed). For this reason, control is effected in accordance
with PWM of the modulating boiler pump. When the first speed of the boiler pump is
deactivated, the second speed is deactivated also. For changeover between the first
and the second speed, a switching point with a hysteresis is calculated, depending on
Pump speed min (2322) and Pump speed max (2323).
Switching point = ((Pump speed max – Pump speed min)/2) + Pump speed min
Hysteresis = (Pump speed max – Pump speed min)/20
The 2-speed boiler pump kicks its second speed – like the modulating boiler pump.
Second speed On:
Boiler pump speed >= switching point + hysteresis
Second speed Off:
Boiler pump speed <= switching point
Line no. Operating line
2322 Pump speed min
2323 Pump speed max
Line no. Operating line
8308 Boiler pump speed
Note!

The speed of the boiler pump is displayed only if Function output P1 (6085) is set
to Boiler pump Q1. This parameterization is not required for the 2-speed boiler
pump function

If the second speed needs a potentialfree or inverted relay output, an
intermediate relay is required
User Manual LMS14...
6 The settings in detail
hysteresis
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CC1U7471en
07.05.2014