Ul 1738 Category Iii Venting System

What is ul 1738.

Ul 1738 category iii venting system.

Ul 1738 ul 1738 is a standard for venting systems for gas burning appliances categories ii iii and iv. Ul standard for safety venting systems for gas burning appliances categories ii iii and iv. In short it is a us standard for gas venting systems required in category iii applications. These requirements cover venting systems intended for venting category ii iii or iv gas burning appliances as defined by the standard for gas fired central furnaces except direct vent central.

Vent test temperature and rating clarification. Category iii refers to positive vent pressure which is created by exhaust blowers in unit heaters. It covers both metallic and non metallic materials and includes over 50 material and system performance tests. The following changes in requirements to the standard for venting systems for gas burning appliances categories ii iii and iv ul 1738 are being proposed.