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PVC in return air plenum

5. Combustible materials fully enclosed within one of the following:

5.1. Continuous noncombustible raceways or enclosures.

5.2. Approved gypsum board assemblies.

5.3. Materials listed and labeled for installation within a plenum and listed for the application.
 
Here is the exception that allows CPVC

602.2.1.7 Plastic plumbing piping and tubing.
Plastic piping and tubing used in plumbing systems shall be listed and labeled as having a flame spread index not greater than 25 and a smoke-developed index not greater than 50 when tested in accordance with ASTM E84 or UL 723.

Exception: Plastic water distribution piping and tubing listed and labeled in accordance with UL 2846 as having a peak optical density not greater than 0.50, an average optical density not greater than 0.15, and a flame spread distance not greater than 5 feet (1524 mm), and installed in accordance with its listing.
 
Sorry, commercial structure, PVC for waste stack, pex tubing for water distribution. Looks like I need to check the listing on the PEX tubing for UL standard. Thanks for the guidance.
 
They can enclose it with the grease duct wrap which qualifies as a shaft per IBC......or remove it....or drop a central return....or there might be some other product out there these days....
 
$ ~ $ = %

As I recall, pvc piping is not approved for use as distribution piping
[ i.e. - inside a structure ] rather, ...only as service piping [ i.e. - piping
"to" the structure ].

% = % ~ $
 

602.2.1.7 Plastic plumbing piping and tubing.​

Plastic piping and tubing used in plumbing systems shall be listed and labeled as having a flame spread index not greater than 25 and a smoke-developed index not greater than 50 when tested in accordance with ASTM E84 or UL 723.
Exception: Plastic water distribution piping and tubing listed and labeled in accordance with UL 2846 as having a peak optical density not greater than 0.50, an average optical density not greater than 0.15, and a flame spread distance not greater than 5 feet (1524 mm), and installed in accordance with its listing.

❖ This section specifically addresses plastic plumbing pipe and tube similar to other material-specific sections under Section 602.2.1. The plastic pipe or tube must be listed and labeled as having the required flame and smoke indices. The exception to this section and Exception 5 of Section 602.2.1 are the only alternatives.

602.2.1.8 Pipe and duct insulation within plenums.​

Pipe and duct insulation contained within plenums, including insulation adhesives, shall have a flame spread index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E84 or UL 723, using the specimen preparation and mounting procedures of ASTM E2231. Pipe and duct insulation shall not flame, glow, smolder or smoke when tested in accordance with ASTM C411 at the temperature to which they are exposed in service. The test temperature shall not fall below 250°F (121°C). Pipe and duct insulation shall be listed and labeled. Pipe and duct insulation shall not be used to reduce the maximum flame spread and smoke-developed indices except where the pipe or duct and its related insulation, coatings, and adhesives are tested as a composite assembly in accordance with Section 602.2.1.7.

❖ This section addresses the burning characteristics of pipe and duct insulation materials that would be installed on the exterior of pipes and ducts. It is common for plastic piping to be installed in plenum spaces, such as above-ceiling return air plenums. Section 602.2.1 requires that materials installed within plenums be noncombustible or have a flame spread index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E84 or UL 723. Some plastic piping materials cannot meet the requirements of Section 602.2.1; therefore, if they are installed within a plenum, they must be protected by some material that does meet the fire performance requirements and that is listed for that application. Section 602.2.1 allows combustible piping to be “fully enclosed within materials listed and labeled for installation within a plenum and listed for the application.” The revised code text states that if pipe insulation is used as the enclosing material, the entire assembly of the pipe, the insulation and any coverings and adhesives must be tested as a composite assembly. Although there are insulation materials available that meet the fire performance requirements themselves, it is unknown how the entire assembly will perform unless the entire assembly is tested. Without being tested as a composite assembly, it is possible that the protected piping could break down and degrade when exposed to heat, despite being protected by a pipe insulation material.
Compliance with this section does not necessarily mean compliance with Item 5.3 of Exception 5, Section 602.2.1. See Commentary Figures 602.2.1.8(1), (2) and (3).
 
This changed under the 2021 code cycle, before you could protect pipes in a plenum with a listed insulation, now you have to find one that is listed as an assembly with the pipe installed. I am unaware of any products like that in existence yet, if someone finds some please send them my way.
 
steveray said:
Like you are from Massachusetts....
Click to expand...
Every commercial construction job that has plumbing in a plenum space uses cast iron. I've even seen it in a new SFR to keep the noise down. Sounds to me like something that was not caught on plan review. Copper is just too expensive right now for DWV.
 
MA used to require it on all commercial PERIOD....they have rolled back slightly recently....We often do not get the pipe called out specifically so I wouldn't be too quick to throw the plan reviewer under the bus, but we do look for the plenums...
 
Now if your HVAC system meets 606.2.2 is IMC 602.2.1.8 even a concern from a life safety point since the smoke will not be distributed throughout the building?

Just a thought for discussion since the code for materials in a plenum is over 60 years old that I am aware of, and smoke detection has improved dramatically over the last twenty years.

606.2.2 Common supply and return air systems.
Where multiple air-handling systems share common supply or return air ducts or plenums with a combined design capacity greater than 2,000 cfm (0.9 m3/s), the return air system shall be provided with smoke detectors in accordance with Section 606.2.1.

Exception: Individual smoke detectors shall not be required for each fan-powered terminal unit, provided that such units do not have an individual design capacity greater than 2,000 cfm (0.9 m3/s) and will be shut down by activation of one of the following:

1. Smoke detectors required by Sections 606.2.1 and 606.2.3.

2. An approved area smoke detector system located in the return air plenum serving such units.

3. An area smoke detector system as prescribed in the exception to Section 606.2.1.

In all cases, the smoke detectors shall comply with Sections 606.4 and 606.4.1.
 
mtlogcabin said:
Now if your HVAC system meets 606.2.2 is IMC 602.2.1.8 even a concern from a life safety point since the smoke will not be distributed throughout the building?

Just a thought for discussion since the code for materials in a plenum is over 60 years old that I am aware of, and smoke detection has improved dramatically over the last twenty years.

606.2.2 Common supply and return air systems.
Where multiple air-handling systems share common supply or return air ducts or plenums with a combined design capacity greater than 2,000 cfm (0.9 m3/s), the return air system shall be provided with smoke detectors in accordance with Section 606.2.1.

Exception: Individual smoke detectors shall not be required for each fan-powered terminal unit, provided that such units do not have an individual design capacity greater than 2,000 cfm (0.9 m3/s) and will be shut down by activation of one of the following:

1. Smoke detectors required by Sections 606.2.1 and 606.2.3.

2. An approved area smoke detector system located in the return air plenum serving such units.

3. An area smoke detector system as prescribed in the exception to Section 606.2.1.

In all cases, the smoke detectors shall comply with Sections 606.4 and 606.4.1.
Click to expand...
I hate to give that up entirely, because we are also dancing the line of how much whatever we can put above a dropped ceiling before sprinklers should be installed....But that is irrelavent to plenum or not....
 
Yes there are products out there listed as an assembly with plastic pipe, including PVC. One of the fire wrap manufacturer's has a product called Plenum Wrap made specifically for this purpose. It basically looks like light duty fire wrap. Johns Manville Microlok HP which is a rigid fiberglass pipe insulation is also listed as an assembly with plastic pipe. It has to be the HP product, their straight Microlok insulation is itself plenum rated but not for use to cover plastic pipe. it can only be used on pipe that already meets plenum requirements.
 
As far as PEX, some PEX is plenum rated and some isn't, you'd have to get the specs on the product used. Typically from what I've seen the blue and red PEX that you see in houses isn't plenum rated. I usually see either white or black PEX on commercial, and those are usually plenum rated but check the specs. There may be some size limitations, spacing requirements, or only in systems where the pipe always full of water.
 
For future individuals who find this thread, this only applies to commercial work covered by the IBC and the IMC.

One and two family houses and townhouses are regulated out of of the IRC, and the only two items I know of that are regulated in plenums IRC are romex sheathing and foam plastic.
 
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