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Kitchen Exhaust Through Exterior Wall

Discussion in 'Mechanical Codes' started by duckbill, Dec 2, 2019.

  1. duckbill

    duckbill Bronze Member

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    2015 IMC. Type I hood that uses NFPA 96 for installation instructions. NFPA 96 shows wall terminations must only be through noncombustible walls.

    2013 NFPA 96, Section 7.8.3, Wall Terminations. Wall terminations shall be arranged
    with or provided with the following properties:

    (1) The termination shall be through a noncombustible wall
    with a minimum of 3 m (10 ft) of clearance from the
    outlet to adjacent buildings, property lines, grade level,
    combustible construction, electrical equipment or lines,
    and with the closest point of any air intake or operable
    door or window at or below the plane of the exhaust
    termination.
    A tenant argues that this is only for a wall TERMINATION and if the exhaust is extended out away from the wall it is no longer a wall termination and the wall can be combustible construction.

    Any input would be helpful.
     
  2. ADAguy

    ADAguy Sawhorse

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    Termination vs penetration? Does he have a basis for his contention?
    This would be a metal vent, no?
     
  3. rgrace

    rgrace Sawhorse

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    I'm not really sure how you get to NFPA 96 through the 2015 IMC. The only reference in the IMC to NFPA 96 is from 507.1 Exception 3, which is applicable only to listed and labeled integral down-draft appliances and exhaust systems. There is no reference to NFPA 96 is Section 506.3.13, nor does this section prohibit termination through a non-combustible exterior wall. I would point out Sections 506.3.6 and 506.5.4 which require 18" clearance to combustibles. The grease duct AND the exhaust equipment are required to have this clearance, so at a minimum the exhaust equipment will have to be mounted at least 18" off the exterior wall and the grease duct clearances will have to be addressed to at least 18" beyond the exterior wall.
     
  4. duckbill

    duckbill Bronze Member

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  5. duckbill

    duckbill Bronze Member

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    rgrace,

    2015 IMC, Section 507.1, Exception 1, states that hoods listed and labeled under UL 710 and installed under IMC Section 304.1, are exempt from certain IMC requirements.
    IMC Section 304.1 requires installation per the manufacturer's installation instructions. The manufacturer of Hoodmart hoods requires compliance with NFPA 96.
     
  6. rgrace

    rgrace Sawhorse

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    That's helpful, but Section 507 provides requirements for hoods. Your post is not about a hood, it is about a grease exhaust system and the exhaust fan termination. That's Section 506.
     
  7. rgrace

    rgrace Sawhorse

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    To further reinforce that, 507.1 Exception 1 simply says that if you have a factory built hood listed to UL 710 and installed per the manufacturer, you don't have to comply with specifically these sections; 507.1.5, 507.2.3, 507.2.5 ... and so on. It does not say that all other requirements regarding all other aspects of a hood system, including the design of the grease exhaust system and exhaust fan terminations and perhaps a pollution control unit must comply with the hood manufacturer's installation instructions if it perhaps refers to NFPA 96. 96 is not applicable to these other aspects.
     
  8. ADAguy

    ADAguy Sawhorse

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    Non-Compliance with the mfg'f instructions may violate the warranty.
     
  9. steveray

    steveray Sawhorse

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    And the listing...
     
  10. duckbill

    duckbill Bronze Member

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    rgrace,

    Very good questions raised. The Hoodmart manufacturer's installation instructions for their hood specifically call for the ducts to be installed to NFPA 96. 2015 IMC is silent where NFPA 96 calls for wall terminations to be through noncombustible walls. To keep with the listing, the hood and ducts need to follow NFPA 96.
     
  11. rgrace

    rgrace Sawhorse

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    I've been working on this response when your latest came in. You state:

    I have not read that. All the rest of this post is fluff if you can provide the document that states exactly that. What I've read doesn't say that (hoodmart_hood_manual_19-0809).



    I have never seen a hood manufacturer dictate the design and construction of the exhaust system that connects to their hood, that's left up to the engineers and master tradesmen. I looked up the Hoodmart instructions and this was included on page 3:

    This hood is UL710 and CAN/ULC S646-10 (Reaffirmed 2016) Listed when installed in accordance with these installation instructions and National Fire Protection Association Standard “NFPA 96, Removal of Smoke and Grease-Laden Vapors from Commercial Cooking Equipment”.

    This statement refers to the installation of the hood ("This hood .... when installed"). This statement does not refer to the design and construction of the exhaust system that connects to the hood. Only Chapter 5 of NFPA 96 has provisions for the installation of a hood. Chapter 5 covers the requirements of field installed hoods just as Chapter 507 of the IMC does. Both of these documents refer back to the conditions of the listing and the manufacturer's instructions for factory built UL 710 listed hoods.

    5.4* Listed Hood Assemblies.
    5.4.1
    Listed hood assemblies shall be installed in accordance with the terms of their listing and the manufacturer’s instructions.
    5.4.2 Listed hood assemblies shall be tested in accordance with UL 710 or equivalent

    Page 11 references two items related to ductwork; material and liquid-tight weld, and this is only a reference, not a statement that the entire exhaust system that connects to the hood must comply with NFPA 96 - "As specified in NFPA 96, Ch. 7.5 (latest edition), exhaust duct systems must be constructed in the following manner:" material and liquid-tight weld.

    There is no violation of the manufacturer's installation instructions or the listing if the entire of NFPA 96 is not applied to the installation of this hood. It is not required in either the manufacturer's installation instructions or the listing.
     
  12. rgrace

    rgrace Sawhorse

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    2015 IMC is not silent when it comes to clearances to combustibles (506.3.6, 506.5.4507.2.6) and terminations through exterior walls (506.3.13). What it doesn't require is that a grease duct only be permitted to terminate through an exterior wall that is noncombustible. Since we are not directed to Section 7.8.3 of NFPA 96 in any way, there is no conflict (304.2) that we need be concerned with.
     
  13. rgrace

    rgrace Sawhorse

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    duckbill, FYI, I love this discussion :)
     
  14. duckbill

    duckbill Bronze Member

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    rgrace,

    Hoodmart, Revised August 2019 Manual, Page 11. Requires ducts to be installed per NFPA 96 as shown.
     
  15. rgrace

    rgrace Sawhorse

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    Yup, that's the one I'm looking at (Hoodmart, Revised August 2019 Manual, Page 11). Page 11 says exactly what I said in post 11. Page 11 does not say that ducts be installed per every requirement of NFPA 96, only material and liquid-tight weld.

    Oh ! Here's something new ... what happens if someone chooses to use a factory build grease duct listed to UL 2221? The manufacturer requires a 16 gage, steel, liquid-tight welded duct per NFPA 96. 96 is more stringent. Will you require that the factory built grease duct be liquid-tight welded per NFPA 96 because the manufacturer requires it to be?
     
  16. rgrace

    rgrace Sawhorse

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    Forget that last question, lets not get off topic :)
     
  17. ADAguy

    ADAguy Sawhorse

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    Key word you are ignoring "system"; a "complete" system is inclusive of entry and exit points and connecting transitions in order to be operational and fire safe.
     
  18. mtlogcabin

    mtlogcabin Sawhorse

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    The code does not care about a manufactures warranty it is only concerned about violating the listing.
    2018 IMC
    304.1 General.
    Equipment and appliances shall be installed as required by the terms of their approval, in accordance with the conditions of the listing, the manufacturer’s installation instructions and this code. Manufacturer’s installation instructions shall be available on the job site at the time of inspection.
    304.2 Conflicts.
    Where conflicts between this code and the conditions of listing or the manufacturer’s installation instructions occur, the provisions of this code shall apply.
    Exception: Where a code provision is less restrictive than the conditions of the listing of the equipment or appliance or the manufacturer’s installation instructions, the conditions of the listing and the manufacturer’s installation instructions shall apply.

    It is quite common for a hood manufacturer to reference NFPA 96 a nationally recognized standard for their hood to connect to since they have no idea what code if any has been adopted where their hood maybe installed. Referencing a standard does not automatically make it a part of the listing
     
  19. rgrace

    rgrace Sawhorse

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    Nope, not ignoring that. The manufacturer is quoting only two items from NFPA 96, not the whole thing. Here is the entire quote from the manufacturer as it relates to exhaust ductwork:

    Ductwork

    Exhaust - As specified in NFPA 96, Ch. 7.5 (latest edition), exhaust duct systems must be constructed in the following manner:


    Materials: Ducts shall be constructed of and supported by carbon steel not less than 1.37 mm (0.054 in.) (No. 16 MSG) in thickness, or stainless steel not less than 1.09 mm (0.043 in.) (No. 18 MSG) in thickness, UL listed Factory Made.

    Installation: All seams, joints, penetrations, and duct to hood collar connections shall have a liquid-tight external weld. If you have an automatic fire damper, please refer to that manual for installation instructions now.

    If the manufacturer wanted to include wall terminations, it would have included:

    Wall termination: The termination shall be through a noncombustible wall with a minimum of 3 m (10 ft) of clearance from the outlet to adjacent buildings, property lines, grade level, combustible construction, electrical equipment or lines, and with the closest point of any air intake or operable door or window at or below the plane of the exhaust termination.

    But it didn't.

    If the manufacturer wanted to stipulate that the entire design and construction of the grease exhaust "system" that connects to their hood must comply with Chapter 7 NFPA 96, they would have said precisely that and not just picked out two specific sections of NFPA 96 (7.5.1.1 and 7.5.2.1).

    Here's a challenge :) Contact this manufacturer (any hood manufacturer for that matter) and ask them if the ductwork section on page 11 is meant to indicate that the entire design and construction of the grease duct exhaust system must comply with NFPA 96. Seriously, if that were the intent of hood manufacturers, or even UL 710, why wouldn't IMC Section 506.1 simply send you to NFPA 96? When would the IMC provisions for commercial kitchen hood ventilation system ducts and exhaust equipment ever be applicable? If only a specific hood manufacturer sent you to NFPA 96 and another didn't, could you then terminate your "system" through a combustible exterior wall? What sense does that make? None of these hood manufacturers are dictating the design and construction of the grease duct system, and their instructions and listings are not dictating that NFPA 96 be the only source for the design and construction of a grease duct system. Again, if that were the case, IMC Section 506 would have been deleted a long time ago.
     
  20. Builder Bob

    Builder Bob Sawhorse

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    The IMC is clear - the Duct work has to be 18" away from combustibles just like the hood - So technically, a kitchen hood and kitchen equipment can be placed against combustible construction
    as long as clearance reduction of the IMC or Manufacturer's installation guides are met. No different than a gas flue passing thru a combustible roof......

    Also as a gentle reminder, the contractor is responsible for installation - I hope your insurance is paid in full because an insurance company would love to pin poor workmanship on a fire caused by lack of clearances to combustibles. Been in a few lawsuits (they were settled out of court - but the contractor failed to install equipment in accordance with codes and/or manufacture's installation guides; therefore the contractor's insurance companies settled out of court.)
     
    ADAguy likes this.

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