Fusible link damper in apartment range hood exhaust.

[Badeeba]

I have a contractor who is installing dampers over the range hood in R-2 dwelling unit under the 2006 I codes. Is this permitted, and if not why not. I cannot find any info within the code except specifically dryer ducts not allowing this application.

 

[Dr. J]

There is no prohibition against this. Actually, IMC/IRC requires backdraft dampers, so there is no "code worry" over collecting grease in dampers.

While an AHJ could not prevent this, there may be design alternatives - is a damper really required? If the issue is a penetration of a horizontal floor/ceiling assembly perhaps the exceptions to IBC 716.6.1 are appropriate (duct <4', serving one dwelling unit, less than 3 stories, no damper).

 

[mark handler]

2010 CALIFORNIA MECHANICAL CODE

Exhaust ducts shall tenninate outside the building and shall be equipped with back-draft dampers.

 

[klarenbeek]

Agree with Dr. J. Even though it might not be the best idea, they are not prohibited in a residential range. Also check out IMC section607.6.2.1. No damper need if it is in a wall and it does not pass through another dwelling or tenant space. I see this used alot in wood frame construciton with engineered trusses.

 

[Badeeba]

Thanks, Dr. J. I couldn't find anything either. I have been told they are not allowed and was following up. I'll check with the mfr and then move on.

 

[Glennman CBO]

I would check with the manufacturer, as it seems to me that the build up of grease might cause it to not function properly.

Other than that, I see no issues with it.

 

[Badeeba]

Thanks Glenn

 

[Dr. J]

I would check with the manufacturer, as it seems to me that the build up of grease might cause it to not function properly.

And then what? The system is still made from light gage non-liquid tight duct, the hood fan and motor are in the airstream, the fan positively pressurizes this thinwall leaky duct, and there is a code required backdraft damper in the airstream. The Code obviously does not see residental range hood systems as being grease laden.

 

[Glennman CBO]

Just because the code does not recognize grease in a residential range exhaust does not mean there will not be any grease in it. Section 505.1 of the 2009 IMC states that the duct must have smooth inner walls. Per the commentary (I know, it's not the code), the reason for this is grease. I've never seen a fire damper that would provide a smooth wall, with all the parts they have in them. In the case of the backdraft damper, that is installed at the termination end for easy maintenance.

I would check with the manufacturer to see if it is specfically prohibited from being used where there may be an accumulation of grease.

You're welcome Dee. I didn't want to blow your cover!

 

[JBI]

Dr J, I love your input, but your avatar makes me LOL. Awesome choice.

If you're installing a listed damper, it will need to be maintained in accordance with its' listing and the appropriate provisions of the Fire Code and Property Maintenance Code. That maintenance needs to be documented. That documentation needs to be provided to the Code Official upon request. ('Oh goody' said the grumpy old code official, 'more paperwork!')

 

[peach]

It won't be maintained... and it won't be inspected...

 

[RJJ]

If it is not a required inspection JBI then why the paper work. I agree we should inform all home owners of the need to maintain all systems. That a just a good practice, but are we to go back and inspect?

 

[gbhammer]

Sometimes all we can do is inform, and hope that personal responsibility kicks in.

 

[Badeeba]

I spoke with the manufacturer and they stated that as long as it is listed UL 555C that it would be acceptible. So unless prohibited by code I suppose it is ok. Also in the mechanical code commentary it mentions the use of dampers when penetrating a shaft from a domestic hood. Not solid gold but definitely faded grey.

 

[mtlogcabin]

How close is this damper to the source of heat? Is it accessible to replace the fusible link if and when it fails?

What is the FD protecting? If it is a shaft penetration a subduct may be a better choice.

 

[Badeeba]

Mtlogcabin. these are above an electric range with a microwave hood combo. They are 6' above the heat source at the ceiling line. They are accessible if and when the fusible link trips. However I don't think it will get hot enough to cook a chicken up there. These are at 165deg. Unfortunately what I did find in all of this is the damper they installed in all of the units are Ul555 so they are working with a fire protection engineer to determine if they can get 1/2 hour out of the floor ceiling assy. without dampers.