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B Vent Wall Termination?


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I think you answered your own question.

Also, IRC 2427.6.7 sez: A gas vent extending through an exterior wall shall not terminate adjacent to the wall or below eaves or parapets, except as provided in 2427.2.1(direct vent) & 2427.3.3 (mechanical draft).

Also, is the termination at least 5' above the water heater's draft hood?

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Is a furnace with an induction fan considered mechanically vented?

No.

Then what is?

Marc

Well, I'm chagrined to say that it is. At least it's one type, according to the IRC.

MECHANICAL DRAFT SYSTEM. A venting system designed to remove flue or vent gases by mechanical means, that consists of an induced draft portion under nonpositive static pressure or a forced draft portion under positive static pressure.

  • Forced-draft venting system. A portion of a venting system using a fan or other mechanical means to cause the removal of flue or vent gases under positive static pressure.
  • Induced draft venting system. A portion of a venting system using a fan or other mechanical means to cause the removal of flue or vent gases under non positive static vent pressure.
  • Power venting system. A portion of a venting system using a fan or other mechanical means to cause the removal of flue or vent gases under positive static vent pressure.

That said, the exception under 2427.3.3 still doesn't allow the installation in Mike's photo.

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B-vent is listed and approved for CAT I gas appliances only. This means no positive vent pressure such as forced draft appliances. It can be used with a termination draft inducer.

In referencing the IRC Ch. 24, NFPA 54, NFPA 211, and UL 441, there is no application where a CAT I appliance under natural draft can be sidewall terminated. More specifically, there are several places in these standards that expressly prohibit it.

UL 441 does not recognize sidewall termination of B-vent nor does it include a test for it. The tests on vertically terminated above the roof vents include temperature, wind, draft loss, & rain. Obviously, you cannot take a termination designed for a vertical application, mount it horizontally in the test structure then run the tests.

On a natural draft appliance, you must have a minimum of 5 feet of total vent height from the draft hood or appliance collar. This requirement is echoed in the ANSI Z21.47 listing for forced warm air furnaces. HTH,

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