Brochure
5454
Proportional-pressure control
Proportional-pressure control strives to keep the pump head proportional
to the flow. This is done by changing the speed in relation to the current
flow. Regulation can be performed up to a maximum speed, from that point
the curve will follow this speed. The proportional curve is an approximative
system characteristic as described in section 3.1 where the needed flow and
head can be delivered at varying needs.
Proportional pressure regulation is used in closed systems such as heating
systems. The dierential pressure, e.g. above radiator valves, is kept almost
constant despite changes in the heat consumption. The result is a low en-
ergy consumption by the pump and a small risk of noise from valves.
Figure 3.12 shows dierent proportional-pressure regulation curves.
Constant-pressure control
A constant dierential pressure, independent of flow, can be kept by
means of constant-pressure control. In the QH diagram the pump curve for
constant-pressure control is a horisontal line, see figure 3.13. Constant-pres-
sure control is an advantage in many water supply systems where changes
in the consumption at a tapping point must not aect the pressure at other
tapping points in the system.
3. Pumps operating in systems