New Inline Exhaust Fan ??

[michael333]

To Whom Can Help:

I've designed a new 13 inch dia SS exhaust duct route to connect to an existing exhaust duct (please see attached system diagram). The new exhaust duct serves (2) engravers. Each engraver requires 900 cfm each. So I have 1800 cfm total in the new 13 inch dia duct. I wanted to use a new 14 inch dia, but my fieldwork confirmed that a 13 inch dia was the largest duct I could run. TAB tech has tried to balance the exhaust to each engraver. He's getting about 300 cfm to each engraver. I'm the ENR, what's my solution? My thought is to install a new inline EF (do have room for it)as I've shown on the attached system diagram. The main existing EF for the existing system, that I'm tieing this new 13 inch into, just isn't doing it.
?? for and advice from Senior Engineers out there:
1) Will the new inline EF, as I've shown on the attached diagram, work as long as it runs simutaneously with the main existing EF??
2) Simply, if the existing main EF is ever OFF, then my inline EF needs to be OFF - correct?
3) I was thinking that if the existing main EF has a current sensor on it, with an input to their existing BAS,
whenever the main existing EF is OFF, a command could be sent to my new inline EF to be OFF and vice versa?
4) Does anyone have any wise advise or input on my proposed solution to get more exhaust air for the engravers?

Thank You,
Michael333

 

[willard3]

Be careful to match fan characteristics, ie, BI with BI or FC with FC and their operating curves or you may have odd pressure variations and noise. Fans in series is not a simple problem.

 

[MintJulep]

Pushing into the T to the right of the in-line fan is potentially problematic.

Be sure that you don't turn the left branch positive.

 

[chicopee]

Graph the combined fan characteristic curves and the system curve to get an idea where the intersection point will lie. The graph should show in English units PSI vs CFM.

 

[trashcanman]

Simple solution: Separate fans and ducts for each engraver. That way, there is no interference from the other fans, whether they run on not.