Draftless Diffussers

[big johnson]

I've got an office suite with Titus MCDAA, square cieling diffussers. The occupants are complaining of drafts even after I changed the 4-way pattern to push air away from them. I'm looking for a diffuser that will spread the flow horizontaly accross the cieling.

[williamxia]

check the velocity at the diffuser neck, it shall not more than 4m/s ,

[madhat]

If the diffuser is designed for the ceiling and has the airflow in its designed range, it is NOT blowing on the occupants. I've seen smoke tests in a lab for diffuses, and the air goes across the ceiling and down the wall with room air being pulled into the center of the diffuser.

[big johnson]

So if I understand what has been said, I should not be able to feel any air movement if I'm near a diffuser, if it's right for the application. The reason I want to clarify this is that there is no commercial building I've ever done work in where I haven't had complaints of "feeling the air."

[FollettEngineer]

I had someone complain yesterday that they were feeling a draft. For some stupid reason, the mechanical company ( who wasn't too bright to begin with) decided to use an open, natural draft retun system in that specific area. Well I stood by her desk and kind of felt the cold draft, but I'm also moving constantly while she's sitting in her clostrophobic cube all day. I just ended up shutting the FPM on 2 diffusers in half by her and added filter media ontop of the return grilles, seems to work ok, haven't had a complaint yet. So you might want to try that even in your diffuser, just remember to change the filter media cause it gets dirty over a couple months time pretty quickly.

[big johnson]

I had someone complain yesterday that they were feeling a draft. For some stupid reason, the mechanical company ( who wasn't too bright to begin with) decided to use an open, natural draft retun system in that specific area. Well I stood by her desk and kind of felt the cold draft, but I'm also moving constantly while she's sitting in her clostrophobic cube all day. I just ended up shutting the FPM on 2 diffusers in half by her and added filter media ontop of the return grilles, seems to work ok, haven't had a complaint yet. So you might want to try that even in your diffuser, just remember to change the filter media cause it gets dirty over a couple months time pretty quickly.

Closing down dampers is usually my last resort. I don't like to "un-balance" a system. I also don't like the building occupants to see the filters becasue they think they are getting poisened when they see the dirt accumulation.

[FollettEngineer]

Well in my instance it was the draft from a return, and I was hesitant to close the dampers slightly due to unbalancing the system, but that's all I was left with unless I made the returns a force draft, which I'm still considering. But this was in an open office area, it won't work for all enviroments. I would just change the filters out on the weekends..lol