How far from a Transfer air grill should a smoke detector be?

[scottam99]

This is a grill on both sides of the wall. No Duct work connected to it. I would assume this would be the same as a return grill for A/C.
It should be 3 feet from this grill. Others thoughts, Comments Etc.??

 

[rc/retired]

I don't believe a transfer grill is the same as a return air system.
IMO you can put a smoke alarm where you wish in question.
Exception, the instructions specify otherwise.

Ron

 

[ron]

I consider a transfer opening to be different than a supply or return duct grille. I wouldn't be concerned with spacing.

 

[Dennis Alwon]

I don't agree with the others as it is often part of the cold air return. Theoretically it is pulling air from one room to another which could influence the smoke direction away from the return.

I believe 3' is the distance but all that info is given to you inside the smoke alarm box.

 

[gadfly56]

Transfer grills are not mentioned in NFPA-72. While they may serve a purpose for return air flow, they do not have the same velocity profiles as ducted supply and return grills. In fact, I'd argue that return air grills have negligible effect on smoke movement. You have to get much closer than 3 feet to observe any significant air movement around a return grill. A case might be made under the wording of 17.7.4.1, but the annex notes specifically discuss supply and return grills.

 

[kwired]

Transfer grills are not mentioned in NFPA-72. While they may serve a purpose for return air flow, they do not have the same velocity profiles as ducted supply and return grills. In fact, I'd argue that return air grills have negligible effect on smoke movement. You have to get much closer than 3 feet to observe any significant air movement around a return grill. A case might be made under the wording of 17.7.4.1, but the annex notes specifically discuss supply and return grills.

If you have significant velocity at a return air inlet, you probably have poorly designed or even undersized return system as well. It probably is a rather noisy return grill during operation also.

 

[rc/retired]

IMO a transfer grill is a hole in the wall. Nothing less.
Somewhere around 2003 the mechanical code had to come up to date for energy code reasons. IIRC
Hence, the mechanical contractors started installing a central return air system which saved them from having to duct return air.
So, a central RA system, yes it is more noisy than a fully ducted system, becomes the norm.
I still believe a transfer grill has no bearing on the location of a smoke alarm.

Ron

 

[gadfly56]

IMO a transfer grill is a hole in the wall. Nothing less.
Somewhere around 2003 the mechanical code had to come up to date for energy code reasons. IIRC
Hence, the mechanical contractors started installing a central return air system which saved them from having to duct return air.
So, a central RA system, yes it is more noisy than a fully ducted system, becomes the norm.
I still believe a transfer grill has no bearing on the location of a smoke alarm.

Ron

I will say, in general, that I agree. Since it is sometimes difficult to predict edge cases, I'd probably just put it 3 feet from the grill and call it a day.

 

[kwired]

Such grill that does nothing but allow air to pass between adjacent rooms is no different than having a window/door opening that has no closable window or door associated with it other than the grill does block a certain percentage of the main opening.