15-minute fire resistance rating for NM

[takelly]

1/2-inch gypsum wallboard has the required Thermal Barrier required by code. ½ EMT has very little thermal barrier, it's pretty much the same temperature inside as outside

 

[wwhitney]

Indeed the type of construction matters here. If one refers back to the uses permitted section of NM you will see that what is **permitted to be** of Types III, IV and V one is allowed to run NM concealed in the wall. As we established earlier, in these types of buildings we DO NOT run NM exposed, not in EMT or otherwise.

If we are looking further down in the section we find Types I and II addressed. Here one is allowed to run NM in any raceway that is allowed to be run in those types of construction. Exposed AND concealed.

FWIW, Type I construction is more fire resistant than any of the other types, if I understand correctly. So the idea that the use of NM inside an exposed raceway is less restricted in Type I than in Type III, IV, and V doesn't make sense to me. I expect that 334.10(5) should really just allow NM inside a raceway in any construction type.

Of course, that's not what it currently says.

Cheers, Wayne

 

[acrwc10]

Hello

Inspector here. I failed someone for running Romex in a commercial building. Per 334.10(3) if they want to do that they will have to conceal that in the wall. They have EMT sleeved over it running up the walls (unfinished walls). They are asking if EMT can qualify as a 15 minute barrier. I said no as the code specifically mentions 15-minute rated assemblies such as walls, ceilings or floors. The "or raceways" remark is missing. Raceways also do not have a fire resistance rating associated to them as far as I know, only ratings for what assemblies they are allowed to penetrate.

My question is, would anyone be talked into letting them run Romex In EMT?

EMT does not need to be "fire Rated".
Here is a quote from the Steel Tube Institute,
"NOTE: It is often incorrectly assumed that if steel conduit or EMT penetrates a fire-resistance-rated assembly, these products also must be “fire-resistance-rated.” Steel conduit and EMT are non-combustible and do not require a “fire-resistance-rating.” The codes require that the annular space around the steel conduit ..."

 

[don_resqcapt19]

EMT does not need to be "fire Rated".
Here is a quote from the Steel Tube Institute,
"NOTE: It is often incorrectly assumed that if steel conduit or EMT penetrates a fire-resistance-rated assembly, these products also must be “fire-resistance-rated.” Steel conduit and EMT are non-combustible and do not require a “fire-resistance-rating.” The codes require that the annular space around the steel conduit ..."

That has nothing to do with the requirement that the NM be protected by thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.

The 15 minute finish rating meas that under fire exposure to the material providing the 15 minute thermal barrier the temperature of the NM jacket will not exceed 250°F. No metal conduit would provide a 15 minute thermal barrier as required by the code rule.

 

[acrwc10]

That has nothing to do with the requirement that the NM be protected by thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.

The 15 minute finish rating meas that under fire exposure to the material providing the 15 minute thermal barrier the temperature of the NM jacket will not exceed 250°F. No metal conduit would provide a 15 minute thermal barrier as required by the code rule.

Yes but, my reply is directed to the comment in the original post that "raceways do not have a resistance rating to them".
I still think it is silly to think THHN in EMT is somehow MORE heat resistant than NM.

 

[Christoph]

FWIW, Type I construction is more fire resistant than any of the other types, if I understand correctly. So the idea that the use of NM inside an exposed raceway is less restricted in Type I than in Type III, IV, and V doesn't make sense to me. I expect that 334.10(5) should really just allow NM inside a raceway in any construction type.

Of course, that's not what it currently says.

Cheers, Wayne

My wild guess is that Type 1 doesn't burn as bad or as quickly to begin with as more combustible buildings, thus you have more than 15 minutes to get out anyway.



I believe we are all in agreement here and recirculating the same concepts.

NM is to be enclosed in a building finish in our case, EMT doesn't help and it doesn't matter how fast EMT burns or how hot it gets. Them's the rules.