Brochure

Functions
MAGNA3
8
21
Cooling systems
Fig. 21 Functional drawing of a cooling system in a commercial building
Primary and secondary pumps
Due to variations in the cooling demand and water flow
rate, we recommend to use speed-controlled MAGNA3
pumps in a cooling system, either single-head pumps
connected in parallel or twin-head pumps. Single-head
pumps connected in parallel have several advantages.
In alternating operation, each pump is sized for 100 %
flow. In this operating mode, the second pump
functions as back-up for higher reliability. As the
pumps alternate, an equal number of operating hours
is ensured. Cascade operation of pumps connected in
parallel meets demands in high-flow systems with low
differential temperature (Δt), and 50 % back-up is
ensured at the same time.
The twin-head pump saves installation time and costs.
By speed-controlling all pumps, it is possible to obtain
maximum energy saving as the pumps will run at their
best efficiency point (BEP).
In a variable-flow system, we recommend to control
secondary pumps in proportional pressure or
AUTO
ADAPT
mode with a differential pressure sensor
in the flow pipe with the lowest pressure. This ensures
maximum energy saving.
The built-in heat energy meter allows monitoring of the
heat energy consumption in the system.
Air handler cooling coils
The performance of cooling surfaces is controlled by
the cooling-water temperature and flow. For this
purpose, we recommend to install variable-flow mixing
loops at the cooling surfaces. A speed-controlled
mixing-loop pump is ideal for adaptation to the varying
load in a cooling surface. In this case, the MAGNA3
will have full authority, making external pump throttling
valves superfluous. The FLOW
LIMIT
ensures that the
rated flow is never exceeded.
Heat recovery system
The heat recovery system is of paramount importance
for the overall energy efficiency of an air-conditioning
or cooling system. Pumps used for this purpose should
be controlled by a setpoint from the building
management system. Due to high load and
temperature variations in the system, it is important to
use variable-speed pumps in a heat recovery system.
Cooling tower
Due to chiller load variations and changes in the
temperature and moisture of the ambient air, the
cooling-tower flow rate is continuously changing. In
order to achieve maximum energy saving,
cooling-tower pumps have to be able to adapt to these
varying conditions. The pumps are controlled by a
temperature setpoint which is measured at the chiller’s
condenser. In this system, the MAGNA3 will have full
authority, making pump throttling valves superfluous.
The FLOW
LIMIT
ensures that the rated flow is never
exceeded.
TM05 2156 1312
Pos. Description
Primary and secondary pumps
Air handler cooling coils
Heat recovery system
Cooling tower
Mixing loops
1
2
3
4
5