Brochure
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Underwriters Laboratories (UL) Standard for Safety, Transient Voltage Surge Suppressors (UL 1449) has undergone a number of changes
and will continue to drive application changes throughout the industry. is includes a change in nomenclature from transient voltage surge
suppressors (TVSS) to surge protective devices (SPD) and recognition of the standard by the American National Standard Institute (ANSI).
e adoption of the third edition of UL 1449 also aects performance testing methodologies, SPD ratings and the appropriate application
of SPDs.
Prior versions of the standard did not take into account the performance of the protector. So many products have entered the market that
essentially provided no benet, but were ‘safe for use’. To address this, UL under took these major changes and introduced a 2nd edition
to the standard. Once the new standard was put into practice, it became clear there were still some more issues that needed to be addressed,
therefore, UL decided to make further changes in the form of a 3rd edition to UL 1449.
ANSI/UL 1449 ird Edition Revisions Field Summary
SPD Locations by UL 1449 Types:
UL now categorizes surge protective devices (SPD) into categories based on its
intended application.
• TYPE 1 - Connect anywhere in the customer’s facility –
we strongly urge this to be specied for all critical installations.
• TYPE 2 - Connect downstream on load side of main breaker.
Be aware that some competitors may have “conditions of acceptability”
that can limit how the device is installed.
• TYPE 3 - Typically cord connected, plug in devices.
• TYPE 4 - Components
Nominal Discharge Current (I Nominal Rating):
is is the peak value of surge current which goes through the SPD (15 surges).
• TYPE 1 - UL tests to 10kA or 20kA. Not to be confused with maximum kA rating of the device. We recommend 20kA I Nominal
rating be specied. While this is the highest UL rating, it is a low level surge which should be required by any device in
even moderate exposure installations.
•TYPE 2 - UL tests to 3kA, 5kA, 10kA or 20kA I Nominal ratings. Again, 20kA is recommended for all specied SPD located at
service entrances.
Voltage Protection Rating (VPR):
ese ratings replace the Suppressed Voltage Ratings (SVR) of the prior standard. UL uses a surge six times the current level of the
SVR testing, so ALL measured VPR ratings are higher than the previous SVR rating.
All facilities that employ mission-critical electronic equipment should have a properly sized surge protective device (SPD) installed at the
main electrical service entrance and throughout their facility at the distribution and branch levels. e surge protection connected to the
incoming power line provides the rst line of defense against transient surges which are typically caused by nearby utility grid switching,
lightning or other power disturbances. However, disturbances can be internally generated as well as externally generated so employing
SPDs at key panels throughout your facility will also provide suitable downstream protection from external surges and local protection
from internal high-energy transients caused by motors, inductive loads, and various equipment load switching that can also cause damage
or costly downtime.
IEEE Standard 1100-2005, e Emerald Book: IEEE Recommended Practice for Powering and Grounding Electronic Equipment
recommends a tiered SPD protection from your Service Entrance down to branch panel level.
7.2.4 Surge suppressors: “…Eective surge protection for an entire building power distribution system requires the coordinated use of
large-capacity current-diverting devices at the service entrance followed by lower capacity voltage-clamping devices applied strategically
throughout the power system.”
UL 1449 AND IEEE