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Application Guide / NEOSYS-AGU-1801-E
eDrive™ VARIABLE WATER FLOW SAVES YOUR MONEY IN THE ENERGY COST
• Through the elimination of the energy normally lost in the water
fl
ow control valve during unit full-load operation (Variable water
fl
ow = perfect pump curve adjustment to the required nominal water
fl
ow and delta P)
• Through pump rotation speed reduction during unit part-load operation.
• Thanks to pump running at minimum speed during Chiller “off” period (night, unoccupied)
Fixed speed pump
Variable speed pump
100% load
75% load
50% load
25% load
Off
Chiller load
Energy
PUMP AFFINITY LAWS
“The power required for pumps varies as the
cube of the fl ow rate.”
20% water
fl
ow reduction = 50% energy reduction.
40% water
fl
ow reduction = 80% energy reduction.
A variable primary
fl
ow design uses fewer components than primary–secondary systems as the pumps of the secondary distribution
loop and the mixing tank are eliminated.
When compared with constant primary
fl
ow systems, terminal units can equipped with two-way control valves instead of three-way valves
often used in constant volume systems. Using two-way valves instead of three-way valve on fan coils represent a budget reduction
that pays for the variable frequency driver cost. On top of that, the water
fl
ow set valve is eliminated as the pump adjustment to real
installation needs can be done electronically. These factors may reduce the initial cost of the chilled water system
Pump energy consumption
Fan coil with 3 way valves and constant
T
eDrive™ VARIABLE WATER FLOW MAY SAVE MONEY IN THE SYSTEM DESIGN COST
HYDRAULIC EQUIPMENT
Water pressure
transducer
Terminal unit
1
Terminal unit
2
Variable primary
fl
ow system with constant pressure
By-pass valve
Control
valve
Balancing
valve
Pump
Variable speed
drive
Terminal unit
...
