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DWV in Return Air Ducts

Discussion in 'Mechanical Codes' started by jar546, Aug 15, 2019.

  1. jar546

    jar546 *****istrator

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    Such as this. What is your opinion?
    IMG_9897.JPG
     
  2. ICE

    ICE Sawhorse

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    Fluid dynamics is a complicated subject. Sometimes it comes down to which way the wind is blowing.
     
  3. steveray

    steveray Sawhorse

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    What's my opinion? or what code section would I use to deny that crap?

    307.6 Piping materials exposed within plenums. Piping
    materials exposed within plenums shall comply with the provisions
    of the International Mechanical Code.

    308.3 Materials. Hangers, anchors and supports shall support
    the piping and the contents of the piping. Hangers and strapping
    material shall be of approved material that will not promote
    galvanic action.
    308.4 Structural attachment. Hangers and anchors shall be
    attached to the building construction in an approved manner.
     
    jeffc likes this.
  4. mtlogcabin

    mtlogcabin Sawhorse

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    I assume this is a SFR and since the IRC is silent on this I will use the IPC and IMC.

    2012 IPC
    307.6 Piping materials exposed within plenums.
    All piping materials exposed within plenums shall comply with the provisions of the International Mechanical Code.

    602.2.1 Materials within plenums.
    Except as required by sections 602.2.1.1 through 602.2.1.5, materials within plenums shall be noncombustible or shall be listed and labeled as having 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 E 84 or UL 723.
    Exceptions:
    1. Rigid and flexible ducts and connectors shall conform to Section 603.
    2. Duct coverings, linings, tape and connectors shall conform to Sections 603 and 604.
    3. This section shall not apply to materials exposed within plenums in one- and two-family dwellings.
     
    ADAguy and Ty J. like this.
  5. HForester

    HForester Member

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    "I assume this is a SFR and since the IRC is silent on this, I will use the IPC and IMC."

    The IRC is intended to be an all encompassing bible for SFRs. Everything that one needs to build SFRs is in that book. The IRC covers ductwork/return air chases ("plenum") and DWV piping. The IRC does have not a prohibition of PVC piping in a plenum. Cherry picking regulations from other I-Codes to apply to an SFR is standing on shaky ground.
     
  6. Ty J.

    Ty J. Sawhorse

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    Since when?

    It is the exact opposite. The IRC is intended to represent the most common and typical configurations and construction methods and is not intended to be all encompassing. Where not covered by the IRC, more expansive codes such as the IBC/IPC/IMC/etc. are to be used.

    R104.11 Alternative Materials, Design and Methods of Construction and Equipment
    The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, not less than the equivalent of that prescribed in this code. Compliance with the specific performance-based provisions of the International Codes shall be an alternative to the specific requirements of this code. Where the alternative material, design or method of construction is not approved, the building official shall respond in writing, stating the reasons why the alternative was not approved.
    IRC is the prescriptive "conventional/typical" playbook, whereas the other codes (IMC, IPC, etc.) allow for performance based "non-conventional/atypical" methods where supported by quantitative testing.
     
  7. mtlogcabin

    mtlogcabin Sawhorse

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    You missed the point of the code path that I outlined

    It was to verify that since the IRC was silent on this installation and the mechanical code has an exception for materials in a plenum in a one and two family dwelling that the installation in the photo is not a violation of the IRC and therefore allowed.
    Inspectors will sometimes call out things that just don't look right. As a building official I have to make the final determination if it is not specifically addressed in the code. Finding an answer in the IMC for a IRC building and basing my decision on another adopted code is not "shaking ground".
     
    jar546 likes this.
  8. Pcinspector1

    Pcinspector1 Platinum Member

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    Seams are taped and the tape meets UL 181, nonmetallic insulated duct board meets a Class 1 rating, though I hardly see information on the duct material.
     
  9. HForester

    HForester Member

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    You have missed my point. Here's a simple example: The IPC requires a 3 inch drain when the fixture drain from an ACW combines with another drain. The IRC does not have that requirement. Should you apply the IPC requirement to the IRC building? No, because the IRC has everything you need to know about drainage piping for ACW standpipes and branch drain sizing. On the other hand, if someone installs a urinal in an IRC building, what do you do because the IRC doesn't cover urinals. That's when you go to the IPC for guidance on urinals.

    There will always be questions as to how far you go in enforcing the requirements of another code (over the IRC) and does the IRC "sufficiently address" the general subject matter such that those who are developing the code, didn't see fit to make the IRC anymore complex and ultimately, more expensive to build homes. "Cherry picking" requirements out of other codes for construction of an IRC building could be viewed as arbitrary, depending on the situation. If it comes down to deposition time, what code section are you going to cite in the IRC that says that the arrangement is prohibited? This is why I used the "shaky ground" point. How are you going to look in front of a lawyer or in court when you try to support your grounds for making the installer do something that is not in the IRC.
     
  10. Ty J.

    Ty J. Sawhorse

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    Well, fortunately for me, WA state does not adopt the plumbing sections of the IRC, but adopts the UPC for both residential and commercial.

    As for your point, I still disagree. The IRC is a conventional cookbook; if provisions for the desired system are not covered by the IRC, the code directs that the performance-based codes (IMC, IPC, etc.) be used.
     
  11. mtlogcabin

    mtlogcabin Sawhorse

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    M1301.1 Scope.
    The provisions of this chapter shall govern the installation of mechanical systems not specifically covered in other chapters applicable to mechanical systems. Installations of mechanical appliances, equipment and systems not addressed by this code shall comply with the applicable provisions of the International Mechanical Code and the International Fuel Gas Code.
     

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