Glanded Pumps - THERMO-ECO-ENGINEERING úvod

Switching and Control Devices
Wilo-VR, CRn, and CR control devices
Control modes
Differential pressure – variable (p-v)
Delivery head H [m]
Power requirement P [%]
100
36
16
100
25
12
n = 60%
n = 40%
n = 60%
n = 100%
n = 100%
n = 40% Q [%]
Q [%]
∆p = constant
Control range
Control range / savings potential
Fig.: Pump curve behaviour for stepless variable differential-pressure control (p-v)
When refurbishing or upgrading existing
systems it is not always possible to evaluate
the point in the circuit which shows the
lowest differential pressure. Original installations
have been completed years ago and
now, after installing thermostatic valves,
noise problems have developed. The index
circuit of the system is not known or it is not
possible to integrate new sensor connections.
A control-range extension is nevertheless
possible using the p-v control mode (recommended
for single-pump systems).
A processor unit of the control system
adapts the differential-pressure setpoint
value to a predetermined variable differential-pressure
curve by means of setpoint /
actual-value comparison.
In addition operation, the differential pressure
is kept constant at the design level
after the first peak-load pump has been cut
in.
>Required accessory:
- DDG differential-pressure sensor
176 Subject to change without prior notice 09/2006 WILO AG