1 Scope

1.1 These requirements cover limit controls, furnace fan controls, and other interlocks which are essentially switches responding to changes in liquid level, pressure, or temperature. Although not limited to such specific applications, these safety controls include those intended primarily to safeguard heating appliances, heating systems, processing systems, and air-conditioning and ventilating systems.

1.2 These requirements do not cover thermal protectors for motors and fluorescent-lamp ballasts.

1.3 These controls are for use in ordinary locations. Requirements for the installation and use of limit controls are included in Standards of the National Fire Protection Association, such as those for Installation of:

Air-Conditioning and Ventilating Systems, NFPA 90A-1993,

Warm-Air Heating and Air-Conditioning Systems, NFPA 90B-1993,

Oil-Burning Equipment, NFPA 31, ANSI Z95.1-1993,

National Fuel Gas Code, NFPA 54-1990,

Ovens and Furnaces, NFPA 86-1990, and

Prevention of Furnace Explosions in Fuel Oil and Natural Gas-Fired Watertube Boiler Furnaces With One Burner, NFPA 85C-1991.

1.4 These requirements cover equipment rated not more than 600 volts and intended for installation in accordance with the requirements of the National Electrical Code, ANSI/NFPA 70.

1.5 A product that contains features, characteristics, components, materials, or systems new or different from those covered by the requirements in this standard, and that involves a risk of fire or of electric shock or injury to persons shall be evaluated using appropriate additional component and end-product requirements to maintain the level of safety as originally anticipated by the intent of this standard. A product whose features, characteristics, components, materials, or systems conflict with specific requirements or provisions of this standard does not comply with this standard. Revision of requirements shall be proposed and adopted in conformance with the methods employed for development, revision, and implementation of this standard.

Summary of Topics

These revisions to UL 353 are being issued to revise the requirements covering surge protective devices in Section 3A.