KO seal clarification.

[Rockwalker]

Recently I have been in a discussion regarding closing unused openings in junction boxes and the acceptable means or materials used for closing the openings. Some of the electricians on our project are under the impression that any unused openings in their junction boxes are considered effectively sealed/closed by the installation of the external fire pads and do not require an actual KO seal prior to the installation of the fire pad. Please see the attached photos for reference.

After reading through NEC article 110.12 (a) Unused Openings I found that this article states “Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to the wall of the equipment. Where metallic plugs or plates are used with nonmetallic enclosures, they shall be recessed at least 6mm (1/4”) from the outer surface of the enclosure”. This does not specifically state that metal KO seals are required.

The underlined section “substantially equivalent to the wall of the equipment” is what seems to be the part that requires better definition. Article 100 Definitions does not cover this.

The question is, does the fire pad count as an acceptable means of closure? Technically it is approximately twice as thick as the wall of the 4S boxes that are being used.

 

[jumper]

First thought is no.

Would not the rating of the box and putty pad together make up the fire rating of the assembly?

If the box is not sealed with metal and then the pad applied, it would seem the overall rating would be compromised.

 

[gadfly56]

First thought is no.

Would not the rating of the box and putty pad together make up the fire rating of the assembly?

If the box is not sealed with metal and then the pad applied, it would seem the overall rating would be compromised.

I would agree. An intact box is part of the listing, along with the various miscellaneous holes they come with from the manufacturer. Everywhere there isn't a hole you have the putty pad plus a metal wall. Putty isn't metal.

 

[petersonra]

substantially equivalent to the wall of the equipment

On the one hand the pad is not metal so maybe it is not substantially equivalent. However, a lot of people use plastic hole plugs for such things.

I guess it depends on what they mean by "substantially equivalent". if they mean that it plugs up the hole as well, then maybe it meets that criteria.

 

[sameguy]

On the one hand the pad is not metal so maybe it is not substantially equivalent. However, a lot of people use plastic hole plugs for such things.

I guess it depends on what they mean by "substantially equivalent". if they mean that it plugs up the hole as well, then maybe it meets that criteria.

Ahh the old what the meaning of is is, (Clinton).

 

[Rockwalker]

Ahh the old what the meaning of is is, (Clinton).

Thank you all for the input. I would have to agree that a metal box with metal KO seals fully constitutes a complete assembly. As far as plastic KO seals, personally I would reserve those for LV, Comm and FA closures. We'll check with AHJD for their view as well.

Thanks again.

 

[jumper]

Thank you all for the input. I would have to agree that a metal box with metal KO seals fully constitutes a complete assembly. As far as plastic KO seals, personally I would reserve those for LV, Comm and FA closures. We'll check with AHJD for their view as well.

Thanks again.

Just look in the IBC, 714.xx something, for fire rated walls, the boxes have to be installed according to their listing and instructions. Pretty sure that the putty is not a listed item for a proper knock out seal.

The putty and the box together form the rating when required, so both have to used and installed correctly.

 

[JFletcher]

If you're talking about using a putty pad in lieu of a proper KO plug, then no, that's not legal imo. Now if you're talking about using a pad to cover the small openings in plastic boxes if one of those little plastic 'wings' falls out, that fine; imo, a piece of putty is substantially equivalent to those thin, flimsy wings, probably much more sturdy...

The first part of 110.12 is this:

"Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, or those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to the wall of the equipment. Where metallic plugs or plates are used with nonmetallic enclosures, they shall be recessed at least 6mm (1/4”) from the outer surface of the enclosure”.

Like gadfly mentioned, the various small holes that come with metal boxes are there from the factory and dont require sealing. If a putty/sound pad is used on the box, those small factory openings dont need to be sealed with metal first.

Missing round KOs are a violation in and of themselves and putty pads cannot be used as the sole means to seal those openings; that missing KO in pic #2 is a violation

 

[petersonra]

What does the manufacturer of the pads say about it? Seems to me that the assembly that's created is what matters not individual pieces

 

[Jraef]

What does the manufacturer of the pads say about it? Seems to me that the assembly that's created is what matters not individual pieces

I agree. Fire stop material works by “charring” to form a barrier against the fire moving from one area to another for a specific time. Generally there is a maximum space allowable against a physical barrier, because it is NOT intended to be used as such. So for example if you have a conduit penetration through a firewall that was cut for 4” conduit, and someone runs 1” through it, you can’t stuff the big hole with putty and expect it to work. IIRC the annular space can’t be more than 1/2”, maybe less. So to me it would follow that the pads can’t cover an opening any larger than that. It’s likely in the instructions for the pads because it would be part of their listing.

 

[petersonra]

I agree. Fire stop material works by “charring” to form a barrier against the fire moving from one area to another for a specific time. Generally there is a maximum space allowable against a physical barrier, because it is NOT intended to be used as such. So for example if you have a conduit penetration through a firewall that was cut for 4” conduit, and someone runs 1” through it, you can’t stuff the big hole with putty and expect it to work. IIRC the annular space can’t be more than 1/2”, maybe less. So to me it would follow that the pads can’t cover an opening any larger than that. It’s likely in the instructions for the pads because it would be part of their listing.

i looked at the instructions for several of the products available and it did not mention a maximum opening it can cover. In at least one case though, it specifically restricted its use with plastic boxes to a specific brand of plastic boxes.

 

[jumper]

What does the manufacturer of the pads say about it? Seems to me that the assembly that's created is what matters not individual pieces

The box itself has a 2 hr rating when installed according to its instruction/ listing.

Those instructions/listing and code requires that the hole be plugged with a listed/proper method. That putty is not one of them.

The putty merely maintains the 2 hr rating when the box is installed in certain conditions of the fire wall. The putty cannot maintain the rating if the box does not meet the conditions needed to have the rating in the first place.

An improperly installed box does not have a 2 hr rating. The unsealed hole kills it.

Trying to double dip what the putty is doing ain’t kosher. The box has to correctly installed first.

https://multimedia.3m.com/mws/media...oldable-putty-pads-mpp-product-data-sheet.pdf

 

[petersonra]

The box itself has a 2 hr rating when installed according to its instruction/ listing.

Those instructions/listing and code requires that the hole be plugged with a listed/proper method. That putty is not one of them.

The putty merely maintains the 2 hr rating when the box is installed in certain conditions of the fire wall. The putty cannot maintain the rating if the box does not meet the conditions needed to have the rating in the first place.

An improperly installed box does not have a 2 hr rating. The unsealed hole kills it.

Trying to double dip what the putty is doing ain’t kosher. The box has to correctly installed first.

https://multimedia.3m.com/mws/media...oldable-putty-pads-mpp-product-data-sheet.pdf

the instructions you linked to provide no guidance at all about what size holes it can cover.