# diffuser support



## TheCommish (Nov 13, 2011)

It is my felling that HVAC diffusers in suspended ceiling grids should be independentaly secured to the structure like electrical light fixtures.

Can anyone point to a section  in any of the ICC code famly that requires the diffuser to be secured?


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## mtlogcabin (Nov 14, 2011)

We are in a seismic zone D and ASCE 7 would apply. IBC Chapter 16 will direct you to ASCE 7. 



*ASCE 7*

*13.1.3 Component Importance Factor. *All components shall be assigned a component importance factor as indicated in this section. The component importance factor, _Ip, _shall be taken as 1.5 if any of the following conditions apply:

1. The component is required to function for life-safety pur­poses after an earthquake, including fire protection sprinkler systems.2. The component contains hazardous materials.3. The component is in or attached to an Occupancy Category IV structure and it is needed for continued operation of the facility or its failure could impair the continued operation of the facility.All other components shall be assigned a component importance factor, _Ip, _equal to 1.0.

13.1.4 Exemptions. The following nonstructural components are exempt from the requirements of this section:

1. Architectural components in Seismic Design Category B other than parapets supported by bearing walls or shear walls provided that the component importance factor, Ip, is equal to 1.0.2. Mechanical and electrical components in Seismic Design Category B.3. Mechanical and electrical components in Seismic Design Category C provided that the component importance factor, Ip, is equal to 1.0.4. Mechanical and electrical components in Seismic Design Categories D, E, and F where the component importance factor, Ip_, _is equal to 1.0 and either:a. Flexible connections between the components and asso­ciated ductwork, piping, and conduit are provided.

b. Components are mounted at 4 ft (1.22 m) or less above a floor level and weigh 400 lb (1780 N) or less.

5. Mechanical and electrical components in Seismic Design Categories D, E, and F where the component importance factor, Ip, is equal to 1.0 anda. Flexible connections between the components and asso­ciated ductwork, piping, and conduit are provided.

b. The components weigh 20 lb (89 N) or less or, for dis­tribution systems, weighing 5 lb/ft (73 N/m) or less.

When the lights or grills exceed 20lb then they need altenate supports or bracing. What is your seismic zone?


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## north star (Nov 14, 2011)

** - - - - - - **



From the `06 IBC,

Section 803.9:*Acoustical ceiling systems.* 

The quality, design, fabrication and erection of metal suspension systems

for acoustical tile and lay-in panel ceilings in buildings or structures shall

conform with generally accepted engineering practice, the provisions of

this chapter and other applicable requirements of this code.



Section 803.9.1.1:*Suspended acoustical ceilings.*

Suspended acoustical ceiling systems shall be installed in accordance

with the provisions of ASTM C 635 and ASTM C 636.

** - - - - - - **


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## ICE (Nov 14, 2011)

How about the listing for the ceiling grid?


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## mark handler (Nov 14, 2011)

ICE said:
			
		

> How about the listing for the ceiling grid?


Listing does not matter, *you shall*, based on the Seismic Design Category.


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## gbhammer (Nov 14, 2011)

:agree With mt and mark, it's all about seismic and the weight of the device.


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## Dr. J (Nov 14, 2011)

Given the OP is in MA, it is likely not a Seismic Design Category D, E, or F.  Even if it is, the diffusers would have to be in a Design Category IV (Hospital or other critical building), AND they must be determined to be needed after the big one hits.  A non-critical building would not need seismic bracing, and even a critical building could have portions that do not need to operate after the event.


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## TheCommish (Nov 14, 2011)

easy guys, Massachussets is in a B simisc zone.

The reasion I ask is it is normal for the electrical inspector to require independent support on light fixtures usaly over 20 pounds is the firefighter pulling a ceiling doe not want to be wacked by a light fixture. Likewise the firefighter should no be wacked by the diffuser less than 20 pounds swinging on flex duct.


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## ICE (Nov 14, 2011)

TheCommish said:
			
		

> easy guys, Massachussets is in a B simisc zone.The reasion I ask is it is normal for the electrical inspector to require independent support on light fixtures usaly over 20 pounds is the firefighter pulling a ceiling doe not want to be wacked by a light fixture. Likewise the firefighter should no be wacked by the diffuser less than 20 pounds swinging on flex duct.


The electrical inspector has a code for that.  Diffusers are an apurtinence to a duct.  Duct requires support per the Mech. Code.  With flexible duct, common sense calls for measures to keep the duct from ripping loose during an earthquake and tearing the grid apart.  Here in Ca. the approach has been to provide wires for the diffusers.  And although some may disagree, the grid system listing may or may not address the support of diffusers by the grid.  Most diffusers weigh little more than the tiles but the attachment of duct makes the difference.

EDIT:  I should point out that wires are not called for in all cases.  The length of the duct and it's configuration may render it to be not a problem in an earthquake.


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## High Desert (Nov 16, 2011)

TheCommish said:
			
		

> Likewise the firefighter should no be wacked by the diffuser less than 20 pounds swinging on flex duct.


That reminds me too much of the movie "Brazil." Brudgers should know that one.


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## TheCommish (Nov 17, 2011)

thanks for the insite


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