UL 1449 4th Edition


UL 1449 4th edition assigns type designations to Surge Protective Devices (SPD) (1, 2, 3, 4, 5) reflecting the installation locations within the electrical distribution system. These designations were adopted from IEEE categories C, B, & A respectively

Comprehending the various location categories presented by UL 1449 4th Edition will not only provide a better understanding as to where these type of products are installed, but will also assist in selecting the proper SPD for that particular application.

The newly issued UL 1449 4th Edition is the standard for safety and is the preferred standard for all AC surge protection devices (SPDs).

Official Definition

Requirements that cover surge protective devices (SPDs) designed for repeated limiting of transient voltage surges as specified in the standard on 50 or 60 Hz power circuits not exceeding 1000 V.

UL SPD standards

SURGE PROTECTIVE DEVICES — UL 1449, 4th Edition, Section 1 effective August 20, 2014, states the following on UL Types covering enclosed and open-type Surge Protective Devices (SPDs) designed for repeated limiting of transient voltage surges as specified in the standard on 50 or 60 Hz power circuits not exceeding 1000 V and for PV applications up to 1500Vdc and designated as follows:

Type 1 — one port, permanently connected SPDs, except for watt-hour meter socket enclosures, intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures and Molded Case SPDs intended to be installed without an external overcurrent protective device. Type 1 SPDs for use in PV systems can be connected between the PV array and the main service disconnect.

Type 2 — permanently connected SPDs intended for installation on the load side of the service equipment overcurrent device; including SPDs located at the branch panel and Molded Case SPDs.

Type 3 — Point of utilization SPDs, installed at a minimum conductor length of 10 meters (30 feet) from the electrical service panel to the point of utilization, for example cord connected, direct plug-in, receptacle type and SPDs installed at the utilization equipment being protected. See marking in 80.3. The distance (10 meters) is exclusive of conductors provided with or used to attach SPDs.

Type 4 Component Assemblies — Component assembly consisting of one or more Type 5 components together with disconnect (integral or external) or a means of complying with the limited current tests in 44.4.

Type 1, 2, 3 Component Assemblies — consists of a Type 4 component assembly with internal or external short circuit protection.

Type 5 — Discrete component surge suppressors, such as MOVs that may be mounted on a PWB, connected by its leads or provided within an enclosure with mounting means and wiring terminations.


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