UFC 3 -520-01
June 10, 2002
level of qualification. Figure D -1 shows a typical listed surge protector properly installed
Figure D-1. UL 1449 Listed Surge Protector
D-2.1.3 Surge protectors are available on the market that have not been listed to UL
1449. In these cases, the user does not know if the manufacturer's claims can be
accepted because there has not been an independent evaluation process. Use of
unlisted surge protectors is also a violation of NEC Article 280.4(A) (2002 Edition),
which requires that "surge arresters installed on circuits of less than 1000 volts shall be
listed for the purpose." Figure D -2 shows an e xample of an unlisted surge protector.
As can be seen, this surge protector consists of two conductors in an insulator with
silica sand around the conductors; this is only a simple spark gap.
Figure D -2. Unlisted Surge Protector
D-2.1.4 To summarize, ensure surge protectors have a UL 1449 listing; this is a
fundamental design requirement. The UL 1449 listing process does not alone confirm
that all other specified capabilities in the manufacturer's literature have been met.