Third Stage ∆T Supervision; Pwm Pump Control; H-Q Chart (Example) - Siemens LMU54 Series Basic Documentation

Third stage
∆T supervision
Application

PWM pump control

H-Q chart
(example)
Siemens Building Technologies
HVAC Products
Like the first stage plus limitation of the minimum volumetric flow to ensure the
measured ∆T will not exceed the adjusted ∆Tmax (dTkTrMax)
→ Control of ∆Tmax via the volumetric flow.
100
90
80
70
Required flow temperature
60
50
Required flow temperature
40
30
20
20 15 10
Range of reduced volumetric flow
(= NqmodMin)
Modgrad [%]
100
NqmodMin
(= 40)
0
20 10
∆T supervision
Condensing boilers with return temperature sensor to increase the efficiency of
condensation and when there are limitations with regard to the heat exchanger's
maximum ∆T.
No bypass allowed.
• As before, the pump is activated and deactivated via the AC 230 V line. The pump's
speed is adjusted via a separate control line
• The pump is controlled by means of a pulse width-modulated DC signal (PWM =
Pulse Width Modulation)
• Automatic maximum operation should the control line become faulty
6
FoerderMax
(= 5.9)
5
4
3
2
1
FoerderMin
(= 0.6)
0
0.0 0.5
Speed = 1
H-Q chart of PWM pump
Basic Documentation LMU54... / LMU64...
3 Functions
at NqmodNenn
dTkTrMax
(= 30)
Acquired return
temperature
5 0 -5 -10
Outside temperature [°C]
Range in which the delta-T controller
adjusts the volumetric flow
0 -10
Outside temperature [°C]
Speed = QmodDrehzStufen
1.0 1.5
Q [m
TkSNorm
(= 70)
dTkTrNenn
(= 20)
Theoretical return
temperature at NqmodNenn
TiAussenNorm
(= -20)
-15 -20
NqmodNenn
(= 18)
corresponding to 100 %
-20
2.0 2.5 3.0
3
/ H]
3.5 4.0
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CC1P7494en
07.11.2002