NEWSLETTER

Are Your Surge Protective Device Specifications UL 1449 3rd Edition Compliant?

By Joe I. Moreland, PE (GA PE#26321)

If your specs still refer to transient voltage surge suppressors (TVSS), the answer to this question is most likely "no". This is because the most noticeable change in UL 1449 3rd Edition (effective September 29, 2009) is the change in terminology from transient voltage surge suppressors (TVSS) to surge protective devices (SPDs). "Surge protective device" is more than just a new name, however, as the term now refers to more than just the devices formerly known as TVSS.

Surge Protective Devices and UL 1449 3rd Edition

Think of "surge protective device" as an umbrella term, as it now covers four different types of devices:

• Type 1:  Permanently connected on either line or load side of the service disconnect overcurrent protection device, with internal overcurrent protection required. This type closely resembles the devices formerly known as surge arrestors.
• Type 2:  Permanently connected only on the load side of the service disconnect overcurrent protection device, with external overcurrent protection allowed. This type closely resembles the devices former known as transient voltage surge suppressors.
• Type 3:  Point of use devices installed at least 30 feet of conductor distance from the service entrance or separately derived system disconnect. This type includes receptacles and cord-connected plug-in strips.
• Type 4:  This type includes discrete components and component assemblies.

UL 1449 3rd Edition also includes new product testing requirements:

New Nominal Discharge Current Testing:  The SPD is subjected to repeated impulses at the nominal discharge current selected by the manufacturer while being energized at the maximum continuous operating voltage between impulses. Type 1 SPDs are rated at 10 kA or 20 kA and Type 2 SPDs are rated at 3 kA, 5 kA, 10 kA, or 20 kA. Higher nominal discharge current ratings indicate more robust devices.

Revised Measured Limiting Voltage Testing:  Voltage protection rating (VPR) replaces the previous suppressed voltage rating (SVR). Since the revised test utilizes a test surge with six times the current used in the previous tests, typical VPR values are higher than the previous SVR values. The most obvious "tell" of an outdated spec (other than use of the term TVSS) is the use of these obsolete SVR values.

Surge Protective Devices and National Electrical Code (NFPA 70) 2008 Edition

UL isn't alone in the transition to new surge protective device terminology and classifications. Article 285 of the NEC was revised with the 2008 edition to coincide with the UL changes and includes requirements for connecting Type 1, 2, and 3 SPDs.

Surge Protective Devices and SpecLink

BSD's new Section 26 4300 - Surge Protective Devices is based on UL 1449 3rd Edition and includes extensive master note content to assist in editing. There's even a link to a national weather service lightning map in the master note for surge current rating to assist in determining exposure risk!

Since the desired product ratings and options usually depend on location in the electrical distribution system, BSD's section is arranged based on three separate product applications — for installation at service entrance, distribution, and branch panelboard locations. These applications can be edited or combined as necessary.

SPDs can be specified as either field-installed, externally mounted or factory-installed, internally mounted, or both may be included to allow the contractor to choose. Protection circuits can be specified as either field-replaceable modular or non-modular, or both may be included to allow the contractor to choose. Reasonable median surge current ratings have been included as default choices, with two ratings above and below them as available choices for higher or lower exposure.

If you've been using an outdated manufacturer's spec, now's the time to update. Even if you've been using a manufacturer's spec that's based on UL 1449 3rd Edition, you will find our spec to be more comprehensive and versatile. SPD manufacturer's specs are usually based on specific models and are often tailored with language to exclude products other than their own. For example, external SPD manufacturers' specs often include language excluding internal SPDs and vice versa. BSD's section is written with a broad palette of choices to allow customization according to the project requirements and engineer preferences.

The Device Formerly Known as "TVSS"

The NEC does still include parenthetical and fine print note references to surge arrestors and TVSS, no doubt to reduce confusion during the transition. However, most manufacturers now use the surge protective device terminology exclusively. Although you may have wiped the term "TVSS" from your specs, or hopefully at least decided to after reading this article, it may not be as easy to wipe it from your memory. You might as well resolve to do it though because unlike "the artist formerly known as Prince," this name change is here to stay.