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Combustion air intake

Ejk Member Posts: 8
i am installing a "slant fin" caravan system which consists of 3- TR60 boilers(6 section) BTU output on system is 776,000 input is 1092000. The boiler room is on the interior of the building and i want to bring combustion air in through the roof. Any suggestions???


  • big bill_3
    big bill_3 Member Posts: 5
    fresh air

    field controls makes a fan in a can, that many btu's might take a fan in a in a big can or a drum-advantage is a smaller penetration due to mechanical combustion air ventilation-www.fieldcontrols.com
  • Constantin
    Constantin Member Posts: 3,796
    Whatever you do,

    ... make sure your inspector is in agreement with you. Ron Jr. had one less-than-informed inspector fail him for using a drop-header on a steam system because drop-headers were not mentioned in the installation manual.

    Sounds like a big system for an apartment complex or commercial application? Don't forget to share some pics! :-P
  • Brad White_9
    Brad White_9 Member Posts: 2,440
    Several Options

    Latch on to a copy of NFPA 54 (ANSI Z223.1) the National Fuel Gas Code, which may be the governing code in your area.

    As a very short version, you need one square inch of clear open area per 4,000 BTUH input if the openings are vertical or immediately to the outside. If ducted horizontally any distance this doubles to one square inch per 2,000 BTUH input.

    The input is based on the total for all appliances in the enclosure (whether they normally fire or not.) The free area is increased to account for obstructions such as louvers and screens.

    One of the openings has to be within 12 inches of the ceiling, the other within 12 inches of the floor.

    The areas derived, as I interpret them, are both high and low. In other words if your input says you need 144 square inches, you put that amount high AND low, not split it between the two. Others may disagree.

    If a damper to close these off is installed (or even allowed! Some jurisdictions do not allow dampers), the damper has to have an end switch such that if the damper is not open, the boiler cannot fire.

    Use of fan in a can systems (Tjernlund or Exhausto) are nice if the local AHJ accepts them. They work on a pressure principle, maintaining a slight positive pressure in the boiler room. As appliances fire, the fan ramps up. So long as there is +P in the room it is deemed to have enough combustion air.

    General overview only! Consult your local code, always.

    p.s. Here in MA, we allow lesser combustion air per our 248 CMR Chapter 7.00 for larger boilers. FYI

  • Keith M
    Keith M Member Posts: 78

    Please contact Slant/Fin Technical Services Department at

    800 873 4346

    One of technical services representatives will address this question.

    Thank you,
    Keith Muhlmeister

  • Ragu_5
    Ragu_5 Member Posts: 315
    To Keith from Slant/Fin...

    Thanks for stepping up to the plate; it does everybody's heart good to hear from a manufacturer! And quickly! Thanks.

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • question..

    Wondering if this is new or replacment installion? If it a replacment, what did they use for make up air? Yes, I do agree that everyones input into this post does help everyone eles' problems!
  • Constantin
    Constantin Member Posts: 3,796
    You might laugh...

    ... or cry but I was in a basement a year ago with over a million BTUs of firing capacity (NG) and no combustion air intake. The COExperts unit didn't alarm, so air was coming from somewhere, but it was scary!

    The installer of the new 650kBTU/hr boiler in that basement commented that the city of Cambridge did not require combustion air intakes... In response, I pointed out that the Commonwealth of MA does and that the PRC has not seceded yet.
  • Here's the guide

    page 9 has the requirements for combustion air.


This discussion has been closed.