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bunda
30-05-2014, 09:51 AM
Hi

I have a fan on a large AHU that is shuttering at approx 60% speed, has anyone ever experienced 'stall' on centrifugal fans? Both pulleys new, belts new and definantly aligned.

Anyone input would be appreciated!

RANGER1
30-05-2014, 10:25 AM
Hi

I have a fan on a large AHU that is shuttering at approx 60% speed, has anyone ever experienced 'stall' on centrifugal fans? Both pulleys new, belts new and definantly aligned.

Anyone input would be appreciated!

So bunda,
Do you mean it vibrating like it's out of balance?

Can only suggest you check fan blades intact, clean & not damaged.

Check drive shaft is running true, as well as fan wheel.

All supports & structure of it secure.

Could also require balancing.

If you speed it up past 60% does it come good?

bunda
30-05-2014, 12:00 PM
So running on a variable speed drive, up to 30hz fan runs perfect, between 32-35hz I have this issue then as it runs higher it corrects itself again.

Brian_UK
30-05-2014, 10:38 PM
Is it the fan, the motor or the inverter that is causing the problem?

install monkey
30-05-2014, 10:49 PM
maybe slow down the ramp up time- check the inverter is prog correctly for the motor size,rpm,flc etc- run it in hand at 50htz to test it

RANGER1
31-05-2014, 12:35 AM
http://www.pump-zone.com/topics/motors/motor-and-drive-system-resonance-problems-and-solutions

Suggest skip the frequencies causing the issues.

Magoo
31-05-2014, 12:54 AM
A large backward curve centrifugal will stall overload if discharge air is blocked or restricted.

CraigF
04-06-2014, 09:31 PM
Had an issue like this on a trane unit, new inverter sorted it