FANS IN PARALLEL INSTALLATION

[oooaaa]

IF TWO FANS ARE IN PARALLEL INSTALLATION, IS IT NECESSARY TO PRIVIDE BACKDRAFT DAMPERS ON THE DISCHARGE SIDE OF EACH FAN IF THEY ARE START UP AND SHUT DOWN AT THE SAME TIME? IF NOT,DO THE FAN CAN BE DEMAGED WHEN THEY ARE START UP OR SHUT DOWN IN SERIES?
THANK YOU

 

[GMcD]

Yes, squared.

 

[remp]

They wont be damaged but the absence of a back draugh damper will result in leakage and reduce the fan overall flow rate when only one is running

 

[ChrisConley]

I disagree that they won't be damamged remp.

If you don't have a backdraft damper then you will have airflow spinning the fan backward. When the fan goes to start it will have to start against the backward momentum.

This does very bad things to the motor and belts.