venting codes

[mattmctree]

I am at a site where I noticed a lot of the new unit heater. Induced draft have 5 inch c vent running about 10 feet or so and then connecting to 12 inch venting. I know this is against code but can't find the codes for the life of me in the code book. Also what is the defenition of a vent connector. Is it just the peice attatching the appliance to the b vent or can it be several feet of c vent?

[Admin]

For chimneys serving more than one appliance see Clause 8.13.2,

Clause 8.13.2 - A vent or a chimney serving more than one appliance shall provide effective venting and shall be sized;
(a) for two appliances with draft hoods the effective chimney flue area is not less than that of the largest draft hood outlet plus 50% of the smaller draft hood outlet area, or greater than seven times the smaller draft hood outlet area; or
(b) in accordance with good engineering practice, such as by the use of
(i) Table C.3, C.4, C.7, or C.8 of Annex C for a draft-hood-equipped or a fan-assisted Category I appliance, or
(ii) engineering methods acceptable to the authority having jurisdiction.

I attached Table 8.5 below.  This Table deals with which types of venting can be used.  I know there are some unit heaters that do allow single wall vent connectors in their installation manual.  If you have more than 1 appliance then Table C4 is likely what you would use to size the capacity of the common vent (chimney).

Vent connector — that part of a venting system that conducts the flue gases from the flue collar of an appliance to a chimney or vent, and that may include a draft-control device.