Venting - commercial application

[Attavior]

Does any one have the document from the Tssa that states venting in a commercial application can be b or c vent if allowed by the manufacturer and not stainless per the code? 

[Admin]

What are you trying to install?

I know some unit heaters are considered Category I when vertical venting is used and allow B-vent.  Table 8.5 of the B149.1-20 supports this.  Only in the US have I seen them allow C-vent vertically.

If the appliance is vented horizontally they want you to treat it as a Category III appliance and use stainless steel venting.

If the unit was manufactured before 2011 you might have an argument to use B-vent horizontally.

[Attavior]

It's a cat3 appliance being with the venting installed horizontally. Manufacturer says it can use  c or b vent but I know there is the requirement to run z venting for horizontal venting.

Wasn't there something from the tssa that allowed the installer to use b or c vent in a commercial setting if the manufacturer allowed it?