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Cat IV Vent Termination Guidelines

Mike Lamb

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I'm looking for cat IV termination guidelines specifically whether they van be vented under decks. For some reason I'm not finding installation manuals easily.

I did come up with this from http://www.hvacwebconnection.com/hvacar ... today1.htm

but I'm not sure what their source is for the under the deck statement. Bold red is mine.

Some of the typical requirements:

• Vent terminal must be at least 1 foot from any door, window, or gravity inlet into the building.

• The double pipe (Example: The vent and air intake terminals must be at the same height and their center lines must be between 12 and 36 inches apart. Both terminals must be on the same wall)

• All terminal bottoms must be 12 inches above normal snow line or no less than 12 inches above grade. (Note: it is often difficult to determine normal snow line)

• 7 feet above public walkway

• Do not install directly above windows or doors

• The bottom of the vent terminal must be at least 3 feet above any forced air inlet located within 10 feet.

• A horizontal distance of at least 4 feet between the vent terminal and gas meters, electric meters, regulators and relief equipment. Do not install vent terminal over this equipment dues to condensate.

• Do not locate vent under decks.

• Top of vent terminal must be at least 5 feet below eves, soffits, or overhangs. Maximum depth of overhang is 3 feet.

• Vent terminal must be 6 feet from an inside corner.

• Be aware that condensate may freeze and cause damage to structures nearby.

• Install vent termination away from prevailing winds in excess of 40 MPH.

• Air intake must not be near possible combustion air contaminants.

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I just looked at a Vitodens 100W boiler system (by Viessmann). The manual detailed this as part of the venting requirements:

A vent must NOT terminate...

8 ....underneath a veranda, porch or deck, unless

* the veranda, porch, or deck is fully open on a minimum of two sides beneath the floor,

* and the distance between the top of the vent termination and the underside of the veranda, porch, or deck is greater than 1 ft. / 0.3 m.

12 ....so that the flue gases are directed toward brickwork, siding, or other construction, in such a manner that may cause damage from heat or condensate from the flue gases.

(pg 45 of http://www.viessmann.ca/etc/medialib/in ... ing_ii.pdf)

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