Another flue question

[Jim Katen]

Jim K.....Would you know where I can find detailed descriptions on furnace categories?

Marc

Here are the definitions from the 2006 IRC.

VENTED GAS APPLIANCE CATEGORIES. Appliances

that are categorized for the purpose of vent selection are classified

into the following four categories:

Category I. An appliance that operates with a nonpositive

vent static pressure and with a vent gas temperature that

avoids excessive condensate production in the vent.

Category II. An appliance that operates with a nonpositive

vent static pressure and with a vent gas temperature that is

capable of causing excessive condensate production in the

vent.

Category III. An appliance that operates with a positive

vent static pressure and with a vent gas temperature that

avoids excessive condensate production in the vent.

Category IV. An appliance that operates with a positive

vent static pressure and with a vent gas temperature that is

capable of causing excessive condensate production in the

vent.

Category I appliances include gas furnaces that has draft hoods as well as the more modern fan-assisted furnaces.

Category IV appliances include the high efficiency condensing furnaces that are so popular now.

Category II and III appliances are very rare. I can't remember the last one that I saw of either type.

- Jim Katen, Oregon