sheave sizing

[tombro]

I have some fans at work whose drives were down sized back in the 1980`s I assume for energy savings.I have original engineered specs for the systems which gives me the:
motor hp,fan rpm,cfm,static pressure( though I don`t know where it was measured),and the original driven sheave diameter.How do I calculate the motor sheave diameter and horse power or break hose power required? Thanks,tombro

 

[hydtools]

Motor rpm x motor sheave diameter = fan rpm x fan sheave diameter.

Motor sheave diameter = fan sheave diameter x fan rpm/motor rpm

Ted

 

[diskullman]

Many fan drives for AC systems use variable pitch pullies to get the ratio range close to spec. The pitch is usually opened up or closed to achieve the proper CFM. When the proper pitch is found the pulley is locked down, and usually not changed for it's lifetime. It is much cheaper and efficient to use fixed pitch pullies, as the vari-pitch pullies are much more expensive and heavier.



Russell Giuliano

 

[FeX32]

To add to the above.

Power=Energy/time=Torque*angular velocity

TTFN,

Fe