ACHE Air Side Control

[SNSR]

Happy New Year 2019!

Client's specification requires only 50% of the fans in each bay to be VFD driven. Reason why 50% and not 100% is unclear. Before bouncing this question to Client, thought I'll check here first.


Question:

1. If airside control is to be via VFD, it is really necessary to have all 100% of the fans in each bay be subjected to VFD if only 50% (or less maybe) could provide the desired results?


I think the answer appears to be quite straightforward, but anyone here with experience using the 50% arrangement above?

Any help will be appreciated.

 

[greenche]

The thought process is likely that for low air flows, the on/off-controlled fan is off and the VFD-controlled fan provides adjustment. For higher air flows, the on/off-controlled fan is on and the VFD-controlled fan provides adjustment. As to whether this would provide the desired results would depend on the level of control needed by the process.

 

[georgeverghese]

VFD requirements at this air cooler would be directly related to the turndown expectations imposed on the system - check with the process engineer on turndown.