SystemAir Rooft@ir 100, Installation And Maintenance Manual

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19
AIR BALANCING
A variable pulley is fitted to the motor shaft in order adjust to the blower performance to the pressure drop at the
duct work. The pulley must be adjusted when the measured external static pressure and air volume (motor current
draw) differ from the nominal values at the unit.
CASE N°1:
There is less pressure drop in the ductwork than planned, i.e. motor current draw is higher than nominal and the
external pressure is lower than nominal. The slower speed must be reduced to lower the treated airflow and re-
establish the air balance point. It is imperative to adjust the pulley, otherwise the motor’s internal protection will
trigger because of overheating taking the entire unit out of operation.
CASE N°2:
In the opposite case, i.e. the motor current draw is lower and the external pressure measured is higher, this means
that the ductwork pressure drop is too high.
Enlarge the diameter the motor pulley. This will increase the speed of the blower and the air volume. The replacement
with a larger motor may be necessary.
It should be noted that for the RT40-50 range, the maximum usable motor size is 3kW. A choice of factory-fitted
motor/blower assemblies are available for higher. Accordingly, preliminary pressure drop calculations of the installed
ductwork are vital for selecting the right equipment.
RT 40 - RT 50
BLOWER MOTOR < 3kW
RT 40 - RT110
BLOWER MOTOR > 3kW