Page 3 - ferraz-usa-solar-brochure-short

Codes & standards for

pV applications

National Electric Code (NEC)
• 1 to 3 strings of modules: no fuse needed: In this kind of system, the fault current is barely higher than operating
current. Properly sizing the wiring between the strings of panels to withstand the maximum fault current is enough to avoid
any fire hazard.
• Installation with at least 4 strings of modules: In this configuration the fault current can reach a level capable of heating
and damaging the insulators. For this type of installation, ungrounded systems must be fused for both polarities, positive and
negative, grounded systems only require fusing of the positive conductors.
• Sizing Fuses per the National Electric Code (Article 690.8): As defined in Article 690.8, two multiplication factors must be
applied when sizing overcurrent devices for photovoltaic application, the maximum PV source circuit current and the
overcurrent device loading factor. The maximum photovoltaic source circuit current is equal to the module rated short circuit
current (I ) multiplied by 125 percent. When determining the sizing of overcurrent device ampacity, the device shall be sized
sc
to carry not less than 125 percent the maximum current. Module I ratings are required by code to be listed on the PV module
sc
nameplate. Typical I ratings are 110-125% of the maximum power point current (I ) value of the PV module.
sc pm
Nominal Fuse Rating = I (Module Short Circuit Current) x 1.25 (Max Current Multiplier) x 1.25 (Overcurrent Device Sizing Multiplier)
sc

Nominal Fuse Rating = Isc x 1.56
If the calculated nominal fuse rating value is not available it is allowed to go to the next highest available fuse current rating.

Canadian Electric Code (CEC)
Section 50 of the Canadian Electric Code outlines the requirements for solar photovoltaic systems. Within Section 50 there are
references to Section 14; specifically, to Rules 14-414 Connection to different circuits; 14-700 Restriction of use; 14-200, Fuses;
and 14-300, Circuit Breakers. Within Section 50, Rule 50-020 also refers to Section 84, Interconnection of electric power production
sources, where the grounding and bonding requirements may be found. Ultimately, NEC Article 690 should be used when
determining requirements for PV systems (while supplementing with information from CEC Section 50 for Canadian applications).

Underwriters Laboratories (UL)
UL 2579 – Fuses for Photovoltaic Systems is a product standard written specifically for fuses intended to be used for
photovoltaic circuit protection. Unlike UL standard 248, “Low Voltage Fuses”, fuses listed to UL standard 2579 are subject to
additional testing, simulating the service environment conditions of photovoltaic installations. Additional testing includes, (1)
Verification of Freedom from Unacceptable Levels of Thermally Induced Drift, (2) Verification of Functionality at Temperature
Extremes and (3) Current Cycling. For more information regarding UL standard 2579 visit Mersen at us-ferrazshawmut.mersen.
com > Resources > Articles and White Papers.

UL 4248-18 – Photovoltaic Fuseholders applies to fuseholders rated up to
1500VDC, intended for use with Photovoltaic Fuses as described in the Outline of
Investigation for Fuses for Photovoltaic Systems, Subject 2579.

UL 98B – Enclosed and Dead-Front Switches for use in Photovoltaic
Systems covers enclosed and dead-front switches rated up to 1000VDC,
intended for use in DC photovoltaic (PV) systems and installed in accordance with
Article 690 of the National Electrical Code.
International Electrotechnical Commission (IEC)
IEC 60269-6 – Fuse-links for the Protection of Photovoltaic Energy Systems:
IEC standard 60269-6, “Fuse-links for the Protection of Photovoltaic Energy
Systems,” defines supplemental requirements applied to fuse-links for protecting PV
strings and PV arrays in equipment for circuits of nominal voltages up to 1500VDC.
Fuses complying with IEC standard 60269-6 shall be marked “gPV” indicating fuse-
links with a full-range DC breaking capacity for photovoltaic energy systems.

4