Eng
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8.3 Selection of control mode
System application
Select this control mode
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
– very long distribution pipes
– strongly throttled pipe 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
– heat exchangers (fan coils)
– cooling ceilings
– cooling surfaces.
Proportional pressure
In systems with relatively small pressure losses in the distribution pipes.
• Two-pipe heating systems with thermostatic valves and
– dimensioned 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.
Constant differential pressure
In systems with a fixed system characteristic.
Examples:
• one-pipe heating systems
• boiler shunts
• systems with three-way valves
• domestic hot-water circulation.
Constant temperature and constant
differential temperature
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.
The pump can also be set to operate according to the max. or min. curve, like an uncontrolled
pump:
• The max. curve mode can be used in periods in which a maximum flow is required.
This operating mode is for instance suitable for systems with hot-water priority.
• The min. curve mode can be used in periods in which a minimum flow is required.
Constant curve
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