Parallel use of Centrifugal fans in HVAC

[Rabindra]

Please advice the best way to use two Parallel centrifugal fans of 4000 CFM, 150 Pa each.

[Brian_UK]

It depends on what you want the fans to achieve.

Please the fan bible "Woods Flakt Fan Engineering Handbook"

http://www.google.co.uk/url?sa=t&rct=j&q=woods%20flat%20fan%20engineering%20handbook&source=web&cd=1&cad=rja&uact=8&ved=0CB8QFjAA&url=http%3A%2F%2Fwww.venttech.co.nz%2Fwp-content%2Fuploads%2F2012%2FWPG_FE%2528s%2529.pdf&ei=Kt12Va2JCcXyUN3HgrAO&usg=AFQjCNFiTWv62w4rwvuL3CGRIAlvyxNoDA&sig2=r83lw41d2eptRAoVDffiGA&bvm=bv.95039771,d.d24

[frank]

Fans in parallel = double the volume same pressure
Fans in series = same volume double the pressure

[ref717]

It depends on your requirement (flow and sp).
Operating fans in parallel approx. doubles the flow and increses the static pressure slightly.

[Magoo]

dependent on what sort of centrifugal fans you are applying. Brian UK reference to Woods Flak is a good start