Editing Surge protector (section)

=== Clamping voltage ===
Also known as the '''let-through voltage''', this specifies what spike voltage will cause the protective components inside a surge protector to short or clamp.<ref name="Grouper_C">{{cite web|url=http://grouper.ieee.org/groups/spd/html/terms_c.html|title=Terms C|website=grouper.IEEE.org|access-date=18 January 2018|archive-url=https://web.archive.org/web/20160303172757/http://grouper.ieee.org/groups/spd/html/terms_c.html|archive-date=3 March 2016|url-status=dead|df=dmy-all}}</ref> A lower clamping voltage indicates better protection, but can sometimes result in a shorter life expectancy for the overall protective system. The lowest three levels of protection defined in the [[UL rating]] are 330 V, 400 V and 500&nbsp;V. The standard let-through voltage for 120 V AC devices is 330 volts.

[[Underwriters Laboratories]] (UL),<ref>{{cite web|url=http://www.ul.com/global/eng/pages/corporate/aboutul|title=About UL |date=18 July 2014|website=UL.com|access-date=18 January 2018}}</ref> a global independent safety science company, defines how a protector may be used safely. UL 1449 became compliance mandatory in jurisdictions that adopted the NEC with the 3rd edition in September 2009 to increase safety compared to products conforming to the 2nd edition. A measured limiting voltage test, using six times higher current (and energy), defines a voltage protection rating (VPR). For a specific protector, this voltage may be higher compared to a Suppressed Voltage Ratings (SVR) in previous editions that measured let-through voltage with less current. Due to non-linear characteristics of protectors, let-through voltages defined by 2nd edition and 3rd edition testing are not comparable.<ref name="SiemensUL1449">{{Cite web |url=http://w3.usa.siemens.com/us/internet-dms/btlv/PowerDistributionComm/PowerDistribution/docs_EABU%20docs/UL1449_3rd_Edition%20Revised.pdf |title=UL 1449, 3rd ed.: SPD/TVSS Changes Effective September 29, 2009}}</ref>

A protector may be larger to obtain a same let-through voltage during 3rd edition testing. Therefore, a 3rd edition or later protector should provide superior safety with increased life expectancy.

A protector with a higher let-through voltage, e.g. 400 V vs 330 V, will pass a higher voltage to the connected device. The design of the connected device determines whether this pass-through spike will cause damage. Motors and mechanical devices are usually not affected. Some (especially older) electronic parts, like chargers, LED or CFL bulbs and computerized appliances are sensitive and can be compromised and have their life reduced.