Idfan damper

[osmanmom]

http://www.plctalk.net/qanda/showthread.php?t=27555

base on this similar system or boiler system what the different/advantage controlling the IDfan with VFD(Auto) while the damper in manual
or controlling the Damper (Auto) and IDfan with VFD in manual/constant.

Thanks in advance for any info/tips.

 

[boneless]

Hi Osmanmom,

To achieve optimum combustion, you need a pretty constant air pressure. Both on the combustion air side as on the exhaust gas side. So it is likely that the fan maintains a constant combustion air pressure according to the current load (perhaps with a O2 fine tuning).

The dampers are usually designed such that bypass/block open and close equal, so the pressure drop over the WHRU/economizer or bypass is equal. So FE bypass opens 25% and block closes 25%. This is controlled by temperature.

Not sure if that answers your questions?