Grundfos MAGNA3 Manual page 19

MAGNA3
Proportional pressure
Proportional pressure is suitable in systems with
relatively large pressure losses in the distribution pipes
and in air-conditioning and cooling systems:
• Two-pipe heating systems with thermostatic valves
and the following:
– very long distribution pipes
– strongly throttled pipe balancing valves
– differential-pressure regulators
– large pressure losses in the parts of the system
through which the entire amount of water flows,
for example a boiler, heat exchanger and
distribution pipe up to the first branching.
• Primary circuit pumps in systems with large
pressure losses in the primary circuit.
• Air-conditioning systems with the following:
– heat exchangers (fan coils)
– cooling ceilings
– cooling surfaces.
Characteristics and key benefits
• The head of the pump increases proportionally to
the flow rate in the system.
• Compensates for large pressure losses in the
distribution pipes.
Technical specifications
H
H
set
H
set
2
Fig. 18 Proportional-pressure control
The head against a closed valve is half the setpoint
H .
set
Constant pressure
A constant pressure is advantageous in systems with
relatively small pressure losses in the distribution pipes:
• Two-pipe heating systems with thermostatic valves:
– dimensioned for natural circulation
– small pressure losses in the parts of the system
through which the entire amount of water flows,
for example a boiler, heat exchanger and
distribution pipe up to the first branching.
– modified to a high differential temperature
between the flow pipe and the return pipe (for
example district heating).
• Underfloor heating systems with thermostatic
valves.
• One-pipe heating systems with thermostatic valves
or pipe balancing valves.
• Primary circuit pumps in systems with small
pressure losses in the primary circuit.
Characteristics and key benefits
• The pump pressure is kept constant, independent of
the flow in the system.
Technical specifications
H
Fig. 19 Constant-pressure control
Q
4
Q
19