diffuser in gypsum board ceiling 2

[lilliput1]

How is a surface mount diffuser with round flex duct mounted on gypsum board ceiling? I though It mould be screwed through the ceiling flange to the drywall but I was told by the manufacturer this is not so. The celing trim oiece do not have screw holes. The diffuser is the perforated type and the plenum panel behind would interfere with the framing for the gypsum boaed ceiling. Does the mechanical contractor coordinate have to coordinate with the ceiling contractor or does the MC just cut holes in the ceiling and ceiling framing as required? I suppose the MC would have to install the flex duct beforehand before the ceiling is installed. I would also require that the diffuser face panel (which swings down) be locked close with tamper proof screws sice this is for patient room in psychiatric ward. Standard does not require true security diffusers, onlt that they be the perforated type. Makes sense to me because the security type diffusers available have square lattice openings that one can thread a cord through an can pose hanging hazard.

 

[Vellum]

I've seen lay-in kits or frames for square diffusers in drywall ceilings, they also double as access panels too. Typically though the border that comes with the diffuser (if ordered for surface mounting) will attach to the drywall. Also for balancing if you don't do a neck mounted damper, you could also go with a remote adjustable volume damper (I've used Young Regulator). As for coordination I would think the ceiling contractor would be working with a reflected ceiling plan with all ceiling devices in it, so I would start there.

 

[lilliput1]

Thanks vellum! Do you know where these lay in kits are available?

 

[DrRTU]

We have used a lot of plaster frames such as

http://www.metalaire.com/products/acc/acc-overview.htm

as an adaptor for gypsum wall board ceilings. Titus, Price and Metalaire all offer the same parts, just different part numbers and prices. The nominal 2’x2’ layin frames work great. The carpenter / metal stud subcontractor sometimes do not like them; they frame on 24” centers to hang the ceiling. The layin adaptor is wider than the ceiling stud spacing. They must cut multiple studs and frame an opening over three studs. In smaller room like washrooms, we use a grille like

http://www.metalaire.com/Products/DCD/DCD-Overview.htm

. I like the 9”x 9” neck size. The boot is cheap to make with an 8” spin collar. I run the 8” up to 250 CFM. We cut in an 8 round with flex and leave the flex above the metal stud. The carpenter frames a 9x9 opening, ceiling gets rocked and opening cut. When we return to trim space, we reach above ceiling and pull flex thru hole. The outer cone of the grille is attached to the framed opening and grille face w/damper is attached to outer cone. Air balance is accomplished by the face damper due to you cannot get to trunk.

 

[AbbyNormal]

Its common to use an inslulated plenum can as well, however the diffuser usually has a sqaure neck. They have STR adapters for them.

Can gets framed into the ceiling, usually to a joist/truss holding up the ceiling and then a scrap piece in between the joists

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[quark]

I have a bit difficulty in understanding the scheme. However, we generally use removable core type diffusers for false ceiling applications. Branch drops (vertical) are guided by extra framing around the drop and screwed. The diffusers, we use, have tapered portion above the grill (damper size is generally smaller than that of grill). The assembly is then screwed to the duct by using 'C' channels at inside duct periphery. The 'C' channels seal the air incase the drops are not exactly matching with the false ceiling bottom and also provides no room for people to go above false ceiling. The removable core type diffusers are snap fit and can be removed easily.

 

[AbbyNormal]

Fitting T-bar diffusers into sheet rock is always a pain.

This is common residentially, pre-made

http://www.miamitech.com/boxes.html

Or they can make and insulate a box. Square neck surface mount diffusers screw through the sheet rock into the boxes.

Then frame something across the joist to support a second side of the box.





Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[itrinitron]

I had a similar question. I have a sheetrock ceiling (actually 400 of these) in bathrooms where I have a 6x6 exhaust grille. The owner complains that when the cleaning crew cleans the register they change the setting on the built-in damper on the register. They want a way to remote mount a manual volume damper. So the contractor recommended changing the register to be a lay-in damper that could be pushed up to access a mvd installed on the exhaust ductwork. However I can't find what type of frame can be used to lay the diffuser into. This is a VERY high-end hotel so nothing cheesy will do.