Fire rated accoustic putty on electrical outlets

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bunuelbresson

Member
Location
Detroit, MI
Hi Guys,

Architect found out that he has an acoustic rating lower than what was planned partly due to electrical outlets. The walls are closed and he is asking if he can put a small membrane of putty inside the outlet.

Is this acceptable by code and by best practise? My concern is that the capacity of the outlet will be reduced, and all the acoustic insulation I had seen was putty on the outside of the box.

What is your take on that? and is there potential problems other than the capacity of the outlet?

Thanks
 
... he is asking if he can put a small membrane of putty inside the outlet.
...
What is your take on that? ...

An outlet box is not just a place to put things. An outlet box is an extension of the wiring method's sheath, conduit or cable. Anything inside the box must be specifically prescribed in the code and I don't recall seeing putty as being permitted in any of the wiring methods.
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
As long as you have enough "cubes", does it matter?

Other 'stuff' can't be calculated in 314.16(A) so I say not allowed.

314.16 Number of Conductors in Outlet, Device, and
Junction Boxes, and Conduit Bodies. Boxes and conduit
bodies shall be of sufficient size to provide free space for
all enclosed conductors. In no case shall the volume of the
box, as calculated in 314.16(A), be less than the fill calculation
as calculated in 314.16(B). The minimum volume for
conduit bodies shall be as calculated in 314.16(C).
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
An outlet box is not just a place to put things. An outlet box is an extension of the wiring method's sheath, conduit or cable. Anything inside the box must be specifically prescribed in the code and I don't recall seeing putty as being permitted in any of the wiring methods.

There are manufacturers who provide putty pads for electrical boxes placed in fire rated walls. The pads are placed on the outside of the boxes. I'm sure this would provide the sound deadening required if putting the pads inside the box is known to be effective.
 

Jon456

Senior Member
Location
Colorado
Another idea would be to squirt some of this behind each electrical box:

Great Stuff Window & Door Insulating Foam Sealant




Be sure to use the "Window & Door" version in the blue can because it's a soft foam and won't push the box out of the wall as it cures, the way the hard foams will. (A soft foam should also offer better acoustical damping.) You should be able to stick the nozzle through the gap around the box, or through one of the wire ports inside the box. You will have to prevent the foam from expanding back into the box, or pull it out of the box after it cures.

Of course, doing this will make it hell for any electrician who has to come in behind you to modify/repair the wiring inside the walls.
 

mauk

Member
Location
NY
Occupation
Electrical Engineer
I've used these coverplate gaskets on previous projects in sound-sensitive areas:

de069e5cd160059ee755f60bfa4b422a.jpg


Not sure if product links are ok here? http://www.stcsoundseal.com/box-seal.php

Typically these are used in conjunction with a putty pad enclosing the box and other measures, but it may still provide some improvement on its own.
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
Sound pads should be installed per their listing. If the wall is a rated wall, they have fire pads that have a sound rating, but again the need to be installed per their listing.
 

iwire

Moderator
Staff member
Location
Massachusetts
An outlet box is not just a place to put things. An outlet box is an extension of the wiring method's sheath, conduit or cable. Anything inside the box must be specifically prescribed in the code and I don't recall seeing putty as being permitted in any of the wiring methods.

I would like to see a code section to back that up.
 
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