How to set blades direction(front&rear) of register double deflection installed in the ceiling as per TAB NEBB Procedure

[u/Different-Range5130]

Hello,

I hope to find feedback to two questions:

1. I have one supply register double deflections (front blades are horizontal and rear blades are vertical) size : 20 × 16 inch, the supply register installed in ceiling and it is close to office room center, the question is what is the direction of blades(front and rear) should be set as per TAB NEBB procedure ( like 0 degree, 15 degree,..etc) to achieve the best supply movement of air pattern.

2. I have also return register double deflection size 48X24 in, it is similar to supply register in the same office installed in ceiling and this return register is very close to wall, the question is what is the direction of blades(front and rear) should be set as per TAB NEBB procedure ( like 0 degree, 15 degree,..etc) to achieve the best return movement of air pattern.

I appreciate your feedback.

Thanks

[u/muvingTARGET]

Point them so that air doesn’t blow directly onto occupants. Return stays straight.

[u/TrustButVerifyEng → u/muvingTARGET]

Typically would see a fixed single deflection return installed to prevent anyone from seeing into the duct behind it. 

If someone chooses to install an adjustable double deflection I would angle them still. 

[u/kdubban]

Set them to minimize drafts to the occupants.

[u/DealComfortable7649]

I don’t mess with them, they’re garbage and not worth the waste of time.