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70-252 Report on Proposals A2007 Copyright, NFPA NFPA 70
70-252
Report on Proposals A2007 Copyright, NFPA
NFPA 70
ARTICLE 285 TRANSIENT VOLTAGE
SURGE SUPPRESSORS: TYSSs
___________________________________________________________
5-349 Log #2604 NEC-P05 Final Action: Accept in Principle
(285)
________________________________________________________________
TCC Action: The Technical Correlating Committee advises that Article
Scope statements and Titles are the responsibility of the Technical
Correlating Committee and the Technical Correlating Committee accepts
the Panel Action.
Submitter: Joseph P. DeGregoria, Underwriters Laboratories Inc.
Recommendation: Revise text to read:
ARTICLE 285 Surge Protective Devices (SPDs) Transient Voltage Surge
Suppressors: TVSSs
I. General.
285.1 Scope. This article covers general requirements, installation
requirements, and connection requirements for SPDs transient voltage surge
suppressors (TVSSs) permanently installed on premises wiring systems.
285.2 Definition. Transient Voltage Surge Suppressor (TVSS). A protective
device for limiting transient voltages by diverting or limiting surge current; it
also prevents continued flow of follow current while remaining capable of
repeating these functions.
285.3 Uses Not Permitted. A SPD TVSS device shall not be installed in the
following:
(1) Circuits exceeding 600 volts
(2) On ungrounded systems, impedance grounded systems, or corner
grounded delta systems unless listed specifically for use on these systems
(3) Where the rating of the SPD TVSS is less than the maximum continuous
phase-to-ground power frequency voltage available at the point of application
FPN: For further information on SPDs TVSSs , see NEMA LS 1-1992,
Standard for Low Voltage Surge Suppression Devices. The selection of a
properly rated SPD TVSS is based on criteria such as maximum continuous
operating voltage, the magnitude and duration of overvoltages at the suppressor
location as affected by phase-to-ground faults, system grounding techniques,
and switching surges.
285.4 Number Required. Where used at a point on a circuit, the SPD TVSS
shall be connected to each ungrounded conductor.
285.5 Listing. A SPD TVSS shall be a listed device.
285.6 Short Circuit Current Rating. The SPD TVSS shall be marked with a
short circuit current rating and shall not be installed at a point on the system
where the available fault current is in excess of that rating. This marking
requirement shall not apply to receptacles.
II. Installation.
285.11 Location. SPDs TVSSs shall be permitted to be located indoors or
outdoors and shall be made inaccessible to unqualified persons, unless listed
for installation in accessible locations.
285.12 Routing of Connections. The conductors used to connect the SPD
TVSS to the line of bus and to ground shall not be any longer than necessary
and shall avoid unnecessary bends.
III. Connecting SPDs Transient Voltage Surge Suppressors
285.21 Connection. Where a SPD TVSS is installed, it shall comply with
285.23 through 285.27. 285.21(A) through (C).
285.23 Type 1 SPDs
(A) Type 1 SPDs shall be connected to the supply side of the service
disconnect as permitted in 230.82(4). Type 1 SPDs shall be permitted to be
connected as specified in 285.24.
(B) When installed at services, the grounding conductor of a Type 1 SPD
shall be connected to one of the following:
(1) Grounded service conductor
(2) Grounding electrode conductor
(3) Grounding electrode for the service
(4) Equipment grounding terminal in the service equipment
285.24 Type 2 SPDs
(A) Location.
( 1 A ) Service Supplied Building or Structure. Type 2 SPDs The transient
voltage surge suppressor shall be connected on the load side of a service
disconnect overcurrent device required in 230.91, unless installed in
accordance with 230.82(8).
( 2 B ) Feeder Supplied Building or Structure. Type 2 SPDs The transient
voltage surge suppressor shall be connected at the building or structure in
accordance with (1) or (2)
(1) On the load side of the first overcurrent device where the main disconnect
for the building or structure consists of a circuit breaker or fused disconnect
switch.
(2) On the load side of a branch circuit overcurrent protective device in the
first panel where the building or structure main disconnect does not contain an
overcurrent protective device. on the load side of the first overcurrent device
at the building or structure.
Exception to (1) and (2): Where the TVSS is also listed as a surge arrester, the
connection shall be as permitted by Article 280.
( 3 C ) Separately Derived System. The SPD TVSS shall be connected on
the load side of the first overcurrent device in a separately derived system.
(B) 285.25 Conductor Size. Line and ground connecting conductors shall not
be smaller than 14 AWG copper or 12 AWG aluminum.
(C) 285.26 Connection Between Conductors. A SPD TVSS shall be
permitted to be connected between any two conductors ungrounded
conductor(s), grounded conductor, grounding conductor. The grounded
conductor and the grounding conductor shall be interconnected only the normal
operation of the SPD TVSS during a surge.
285.2 5 7 Grounding. Grounding conductors shall not be run in metal
enclosures unless bonded to both ends of such enclosure.
Substantiation: This is one of several related proposals affecting Articles 100,
230, 250, 280, 285, 501, and 502 based on the following:
1) UL intends to combine the categories of Surge Arresters (Article 280) and
Transient Voltage Surge Suppressors (Article 285) into one category and
Standard, UL 1449, renamed Surge Protective Devices(SPDs).
UL 1449 will include SPD designations Type 1 and Type 2 for permanently
connected devices for use on circuits not exceeding 600 V.
The technology of both low voltage Surge Arresters and TVSSs are now
basically the same, thereby justifying coverage under one Standard, UL 1449,
and one test program with consideration given to the installation location on
the line side (Type 1) or load side (Type 2) of the service disconnect
overcurrent protection.
2) The Surge Arrester designation will only be retained for devices used in
circuits of 1 kV and over and evaluated to IEEE C62.11-1999.
Panel Meeting Action: Accept in Principle
ARTICLE 285 Surge Protective Devices (SPDs) 1kV or less Transient
Voltage Surge Suppressors: TVSSs

I. General

285.1 Scope. This article covers general requirements, installation
requirements, and connection requirements for SPDs transient voltage surge
suppressors (TVSSs) permanently installed on premises wiring systems 1 kV
or less .
FPN: Transient Voltage Surge Suppressors (TVSSs) are also known as SPDs.

285.2 Definition. Transient Voltage Surge Suppressor (TVSS). A protective
device for limiting transient voltages by diverting or limiting surge current; it
also prevents continued flow of follow current while remaining capable of
repeating these functions.
285.3 Uses Not Permitted. A SPD TVSS device shall not be installed in the
following:

(1) Circuits exceeding 600 1 kV volts
(2) On ungrounded systems, impedance grounded systems, or corner
grounded delta systems unless listed specifically for use on these systems.
(3) Where the rating of the SPD TVSS is less than the maximum continuous
phase-to-ground power frequency voltage available at the point of application

FPN: For further information on SPDs TVSSs , see NEMA LS 1-1992,
Standard for Low Voltage Surge Suppression Devices. The selection of a
properly rated SPD TVSS is based on criteria such as maximum continuous
operating voltage, the magnitude and duration of overvoltages at the suppressor
location as affected by phase-to-ground faults, system grounding techniques,
and switching surges.

285.4 Number Required.
Where used at a point on a circuit, the SPD TVSS shall be connected to each
ungrounded conductor.

285.5 Listing. A SPD TVSS shall be a listed device.

285.6 Short Circuit Current Rating. The SPD TVSS shall be marked with a
short circuit current rating and shall not be installed at a point on the system
where the available fault current is in excess of that rating. This marking
requirement shall not apply to receptacles.

II. Installation

285.11 Location. SPDs TVSSs shall be permitted to be located indoors or