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We have an air handler that moves 27000 cfm with inlet vanes…

Customer Question
We have an air...

We have an air handler that moves 27000 cfm with inlet vanes controlled by static. all of a sudden we lose cfm and inlet vanes go to 100% and cfm drops to 20,000 some times less. If we close inlet vanes to 10% and slowly open them we get to about 50-60% and static comes back and cfm is back to 28,000 cfm any ideas?

Contractor's Assistant: Did you double-check the thermostat's settings? And what about the filters?

Filters good, dat temp stays around 55 def

Contractor's Assistant: Do you plan on doing the work yourself?

Maybe we have checked about everything I can think of.

Contractor's Assistant: Anything else we should know to help you best?

We have fire dampers but all seem to be open, any chance the 3ph motor could slow down?

Submitted: 7 months ago.Category: HVAC
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Answered in 1 day by:
2/17/2018
HVAC Technician: Bill, HVAC Technician replied 7 months ago
Bill
Bill, HVAC Technician
Category: HVAC
Satisfied Customers: 114
Experience: Service Mgr
Verified

Hello,

I am sorry for the delay in getting a response to you.

I just logged on and saw you had not been assisted yet.

This sounds like a freq drive issue. If you have 27,000 cfm you have a freq drive assisting the motor. I would have this checked as it is what controls the volume of air in the system. It will not be related to motor or vanes but most likely the frequency drive

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Customer reply replied 7 months ago
No Freq drive as I said it has inlet vanes. Wondering if we could be past fan curve as we cleaned coils and fixed some dampers that didn't open all the way.
HVAC Technician: Bill, HVAC Technician replied 7 months ago

I would check the motor operation. It is obviously a supply air issue and without a freq drive you should have a constant deck.

Is there a static bypass damper anywhere that releases deck pressure?

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