Help

[Walker Haglock]

Will someone please comment on my post regarding a direct vent PVC furnace flue routed inside of cold air return. Would like to know what you think. Thanks.

[H.G. Watson, Sr.]

Please don't double post.

Not allowed, its a vent.



M1801.8 Duct penetrations. Chimneys, vents and vent connectors shall not extend into or through supply and return air ducts or plenums.




M1601.1 Duct design. Duct systems serving heating, cooling and ventilation equipment shall be fabricated in accordance with the provisions of this section and ACCA Manual D or other approved methods.


M1601.1.1 Above-ground duct systems. Above-ground duct systems shall conform to the following:


Equipment connected to duct systems shall be designed to limit discharge air temperature to a maximum of 250ºF (121ºC).
Factory-made air ducts shall be constructed of Class 0 or Class 1 materials as designated in Table M1601.1.1(1).
Fibrous duct construction shall conform to the SMACNA Fibrous Glass Duct Construction Standards or NAIMA Fibrous Glass Duct Construction Standards.
Minimum thickness of metal duct material shall be as listed in Table M1601.1.1(2). Galvanized steel shall conform to ASTM A 653.
Use of gypsum products to construct return air ducts or plenums is permitted, provided that the air temperature does not exceed 125°F (52°C) and exposed surfaces are not subject to condensation.
Duct systems shall be constructed of materials having a flame spread index not greater than 200.
Stud wall cavities and the spaces between solid floor joists to be used as air plenums shall comply with the following conditions:
(7.1) These cavities or spaces shall not be used as a plenum for supply air.
(7.2) These cavities or spaces shall not be part of a required fire-resistance-rated assembly.
(7.3) Stud wall cavities shall not convey air from more than one floor level.
(7.4) Stud wall cavities and joist-space plenums shall be isolated from adjacent concealed spaces by tight-fitting fire blocking in accordance with Section R602.8.

Similar restrictions in mechanical codes and in fuel gas codes, and in standards referenced in manufacturer's instructions.

HTH.

[Bob Elliott]

Simple version is it is not right because if there is any leakage it can go through the whole house with the same rule applied to dummies that run gas lines through returns.

[Linda Swearingen]

That would be a lot like running a sewer line through a well casing.

[Scott Bennett]

As a commercial salesman for a reputable refrigeration / HVAC contractor, I'm called by many of our prospective customers to look at and propose a fix for their horror stories created by so-called professionals in this industry. I'd like to visit some of the contractor's homes, look in the fridge and check to see if they keep a can of Drano next to the milk, or store rat bait in the meat drawer.
:D

[Thomas McKay]

Yep, seen that too! :eek:

[Rod Butler]

It is permitted if it is sleeved.

[Bob Harper]

Keep in mind, any pipe penetrating a duct is severely disrupting air flow so it would also tend to screw up the performance in addtion to the aforementioned safety aspects.