Let’s continue looking at the changes to Chapter 5, which I started going over in last month’s column.

500.7 Protection Techniques. Section 500.7 provides a list of the recognized protection techniques for use in hazardous (classified) locations. A new Table 13, “Equipment Suitable for Hazardous (Classified) Locations,” has been added to Chapter 9, summarizing this information in tabular form. A reference to the new table was added to 500.7. This table replaced tables 505.9(C)(2)(4) and 506.9(C)(2)(3). Table 13 includes the protection techniques for the IEC classification system and the traditional class/division classification systems.

500.8(E)(3) Unused Openings. Unused threaded openings must be closed with blanking elements or close-up plugs listed for the location. If the equipment has threaded entries of NPT-threaded conduit or fittings, the NPT-threaded entries must be made up with at least five threads fully engaged. For listed explosion-proof equipment, joints with factory-threaded entries must be made up with at least 4½ entries fully engaged. For metric threaded entries, either the entry must be listed as being metric or listed adapters must be used.

501.10 Wiring Methods, Class I. The exception to 501.10(A)(1)(1) was converted into positive text and now appears as 501.10(A)(1)(2).

The installation requirements for Type P cable in 501.10(A)(1)(8) were revised. In Class I, Division 1 locations, Type P cable is permitted with metal braid armor and an overall jacket if terminated with fittings listed for the location and installed in accordance with Part II of Article 337.

The term “restricted industrial establishment” used in 501.10(A)(1)(4), (5), (7) and (8) is defined in Article 100 as “Establishment with restricted public access, where the conditions of maintenance and supervision ensure that only qualified persons service the installation.”

501.15 Sealing and Drainage. The boundary seal requirement in Division 2 locations has been relocated to 501.15(A)(4). This requires Division 1 wiring methods up to the seal fitting in the Division 2 location. A revision to 501.15(B)(2) permits Type RTRC to be used from the boundary conduit seal to the point where it exits the Division 2 location. Type TC-ER-HL and Type P cable (now Type IM cable) were inadvertently omitted from the cable seal requirements in 501.15(D)(1) in the 2020 Code.

501.141 Flexible Cables, Class I, Division 2. A new Section 501.141 was added to provide requirements for flexible cables in Class I, Division 2 locations. This new section is primarily focused on permitting Type P cable use. The means of terminating the cables requires using cable connectors listed for Class I, Division 2 locations.

501.145 Receptacles and Attachment Plugs, Class I Locations. Receptacles and attachment plugs are now required to be listed for the location, except as permitted by 501.105(B)(6) for meters, instruments and relays. Listing for Class I, Division 2 locations is not required if the circuit only involves nonincendive wiring. Listing is also not required in certain Class 1, Division 2 locations in restricted industrial establishments.

502.10 Wiring Methods, Class II Locations. PVC-coated metal conduit is now permitted in Class II, Division 2 locations, even where there is not an increased level of corrosion. EMT with compression-type fittings or connectors is now permitted in Class II, Division 2 Locations. Type RTRC-XW conduit is permitted in industrial establishments with restricted public access where conditions of maintenance and supervision ensure that only qualified persons service the installation.

502.15 Sealing, Class II, Divisions 1 and 2. The informational note to this section was changed to become 502.15(5) because it violated the NEC Style Manual. The text of this requirement now indicates that electrical sealing putty is a recognized means to prevent the entrance of dust into a dust-­ignition-proof enclosure. Informational notes cannot be used to provide permissions or recommendations. Seal fittings are required to be accessible, but not explosion-proof.

502.30 Grounding and Bonding. References to Article 250 were changed to refer to Article 250, Part VI for grounding and Part V for bonding. Cable trays were added to 502.30(B)(1), which addresses specific bonding means, to make it clear that cable trays must be bonded in the same manner as raceways. Requirements were added for bonding of metal struts, angles or channels if used with Types TC-ER, PLTC-ER or ITC-ER. Section 502.30(B)(2)(3) was changed from “not a power utilization load” to “part of a meter, instrument, or relay circuit.”

503.10 Wiring Methods. Type P cable is now permitted in Class III, Division 1 locations in restricted industrial establishments. Criteria is also established for the installation of Type P cable in cable trays. It is important to note that wiring in Class III, Division 2 locations must comply with the Division 1 requirements. However, in sections, compartments or areas that do not contain machinery and are used solely for storage, open wiring on insulators is permitted.

503.30 Grounding and Bonding. The previous title of this section indicated that it applied to Class III, Division 1 and 2 locations. “Class III, Division 1 and 2” was deleted from the title, because the requirements for Division 1 and Division 2 locations are the same. Under 503.30(B)(1), cable trays were added to make it clear that they require bonding, much like raceways. New requirements were added for metal struts, angles and channels to make it clear that when they are used with Types TC-ER, PLTC-ER or ITC-ER, they must be bonded.

504.30 Separation of Intrinsically Safe Conductors. Section 504.30(A) originally included five exceptions and six informational notes, which made the section difficult to interpret. When there are five exceptions to a short section and six informational notes to explain it, it is time for a rewrite. This section was rewritten in positive text, and it is a major improvement without technical changes. There were also informational notes that provided interpretations and recommendations, which are prohibited in informational notes, so the text of these was incorporated into the Code language for easy use.

Article 505 Zone 0, 1, and 2 Locations. Several changes were made in Article 505 that are consistent with changes made in Article 500. There is no longer any overlap with Article 500. The classification scheme in Article 500 does not include the zone classification scheme covered in Article 505. The scope of this article was rewritten to clearly delineate the installations covered from those that are not. It does not cover any of the class/division requirements or zones 20, 21 or 22. It also clarifies that Article 505 does not cover explosives, pyrotechnics or blasting agents.

505.8 Protection Techniques. Section 505.8 covers the protection methods that are permitted in zones 0, 1 and 2 hazardous (classified) locations. Many of the permitted techniques are covered by IEC standards. Three new protection techniques have been added to this section. Impedance heating is now a recognized protection technique. A pressurized room “p” is a protection technique recognized for zone 1 or 2 locations. Special protection “s” is a protection technique recognized for zones 0, 1 and 2.

505.16 Sealing and Drainage. Section 505.16(B)(3) on pressurized enclosures has been expanded to include pressurized rooms. An informational note has been added to reference IEC 60079-13, Equipment protection by pressurized room “p” and artificially ventilated room “v.” New requirements were added for cable seals for cables that enter restricted breathing enclosures “nR.” Cables passing from an enclosure or room that is unclassified due to Type Z purging into a Zone 2 location are not required to have a seal at the boundary. Shielded cables and twisted-pair cables do not require removal of the shielding or separation of the twisted pairs if the termination is listed for the location.

505.20(C), Exc. Nos. 5 and 6 Equipment Requirements, Zone 2. Two exceptions were added to the requirements in 505.20(C) that require equipment installed in Zone 2 locations to be specifically listed and marked as suitable for the location. Exception No. 5 addresses the use of space heaters to reduce condensation during shutdown periods. This is consistent with the permission in 501.125(B)(4) for Class I, Division 2 locations. This text was added rather than a cross-­reference to a requirement in Article 501 because of the effort in this cycle to eliminate cross-references between the traditional class/division system and the zone classification system. Exception No. 6 was added to permit a sliding contact shaft bonding device used on certain motors for the purpose of maintaining the rotor at ground potential where the potential discharge energy is determined to be nonincendive for the application. This exception is consistent with a similar permission in 501.125(B)(5).

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