Gas Appliance Categories

Servicewiz_3

Could I be provided a list , of all gas categories , along with there characteristics?

Thanks in advance for the help!!

EdTheHeaterMan

If you are talking about venting Categories here they are:

• Category I: Non-condensing with negative draft.
• Category II: Condensing with negative draft
• Category III: Non-condensing with positive vent pressure.
• Category IV: Condensing with positive vent pressure.

Cat. I would include 80% efficient cast-iron and steel boilers equipped with draft hoods and automatic vent dampers. Gas furnaces with draft hoods for warm air systems are also in this catigory. If they are not equipped with vent dampers, then they would generally be less than 80% efficient.

Cat. II is uncommon. It would be a condensing appliance designed so the vent remains under negative pressure, usually using a specially engineered vent/chimney system. You don't encounter many residential appliances listed this way today.

Cat. III examples include power-vented, non-condensing gas water heaters, some unit heaters, and some non-condensing boilers or furnaces with an induced-draft fan that pressurizes the vent. Because the vent is under positive pressure, the joints have to be gas-tight, and the venting system must be listed for that application. A clothes dryer may also fit in this category, however that appliance is not usually considered in this way.

Cat. IV appliances are very common and are generally rated at 90% AFUE or higher. Many residential furnaces are condensing appliances with positive-pressure venting. Modulating-condensing boilers are also positive-pressure venting systems. Just about anything that is vented with Schedule 40 PVC would probably fall into this category.

There is one more type of gas appliance that is not accounted for in this category rating system:

Unvented appliances: These are not classified as Category I, II, III, or IV because they do not have a venting system. Examples include vent-free gas space heaters and vent-free gas-log fireplaces. The products of combustion, including water vapor, are discharged directly into the occupied space.

To be listed for use inside residential buildings, unvented room heaters are subject to input limitations and must be equipped with an oxygen-depletion-sensitive safety shutoff system (ODS). Under the ANSI Z21.11.2 standard, unvented room heaters are generally covered up to 40,000 BTU/hr, although codes impose much lower limits in certain locations—for example, 10,000 BTU/hr in bedrooms and 6,000 BTU/hr in bathrooms under the IRC/IFGC provisions.

More on ODS upon request.