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12. Selection of control mode
System application
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 balancing valves
– differential-pressure regulators
– large pressure losses in those parts of the system through which the total quantity of
water flows, for example 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.
In systems with relatively small pressure losses in the distribution pipes.
•
Two-pipe heating systems with thermostatic valves and the following:
– sized for natural circulation
– small pressure losses in those parts of the system through which the total quantity of
water flows, for example boiler, heat exchanger and distribution pipe up to the first
branching, or modified to a high differential temperature between flow pipe and 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.
In systems with a fixed system characteristic.
Examples:
•
one-pipe heating systems
•
boiler shunts
•
systems with three-way valves
•
domestic hot-water circulation.
If an external controller is installed, the pump is able to change from one constant curve to
another, depending on the value of the external signal.
You can also set the pump to operate according to the maximum or minimum curve, like an
uncontrolled pump:
•
Use the maximum-curve mode in periods in which a maximum flow is required. This
operating mode is for instance suitable for systems with hot-water priority.
•
Use the minimum-curve mode in periods in which a minimum flow is required.
In systems requiring a constant flow, independently of pressure drop.
Examples:
•
chillers for air-conditioning
•
heating surfaces
•
cooling surfaces.
In systems requiring a constant tank level, independently of the flow rate.
Examples:
•
process-water tanks
•
boiler-condensate tanks.
Select this control mode
Proportional pressure
H
H
set
H
set
2
Q
Constant differential pressure
H
Q
Constant temperature and constant
differential temperature
H
Q
Constant curve
H
Q
Constant flow rate
H
Q
Q
set
Constant level
H
Q
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