bonding bushing / concentric KO

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George
As I mentioned last time, I do understand that Enclosures (312), Boxes (314) and Junction boxes (a different part of 314) are not all treated the same. One can find that information as well in the UL White Book.

My conclusions have been taken from the discussions I have had with manufacturers. If you will notice, the UL White Book did make changes between the '07 and '08 versions. This confused me, hence my conversations with the manufacturers.


You are up early.:grin:
 
Insight from UL regarding Grounding, Bonding and KOs in their March 09 Newsletter

Insight from UL regarding Grounding, Bonding and KOs in their March 09 Newsletter

I consulted with my contact at UL and he has forwarded me the UL newsletter for March of this year which addresses some of the G&B issues.

The March newsletter is quite helpful, informative and is (I believe) a necessary read

The newsletter is just (slightly) too large for uploading to this thread, but can be found at UL with the link provided below. The link will also provide access to other UL Newsletters.
You are after the March Newsletter

http://www.ul.com/global/eng/pages/corporate/aboutul/publications/newsletters/electricalconnections/

? backing up provides access to a broader range of UL info?

http://www.ul.com/global/eng/pages/offerings/perspectives/regulator/electrical/newsletters/



You can sign up for the "Ultimate E-mail from UL" and you can receive these UL technical publications as well as being notified of other technical topics at the link below.

http://www.ul.com/global/eng/pages/offerings/perspectives/regulator/ultimateemail/




I also asked him:
Are the factory knockouts in auxiliary gutters and wireways listed for grounding and or bonding (such as in QCIT)? Would this encompass concentric-eccentric?

His reply:
No, these concentric-eccentric KO's have not been evaluated to maintain grounding and bonding so 250.96(A), 250.97, 250.12 and 250.4(A) must be complied with. As you noted, these gutters and wireways are identified in UL Category ZOYX and are listed to UL 870.

The following are from UL 870:

2 Glossary
2.1 For the purpose of this standard the following definitions apply.

2.2 ASSOCIATED FITTING - A part that is used in the assembly of a complete wireway system, such as an elbow, tee, cross, end closer, or hanger.

2.3 AUXILIARY GUTTER - A section of wireway used to supplement the wiring space at a distribution center, switchboard, or similar location in a wiring system.

2.4 WIREWAY, METAL - A sheet-metal trough with a hinged or removable cover for housing and protecting electric wires and cables and in which conductors are laid in place after the wireway system has been installed as a complete system.

2.5 WIREWAY, NONMETALLIC - A flame-retardant, nonmetallic trough with removable covers for housing and protecting electric wires and cables in which conductors are laid in place after the wireway has been installed as a complete system.

19 Electrical Continuity Test - Metal Wireways, Auxiliary Gutters, and Associated Fittings
19.1 The resistance of the connection between adjacent sections of wireway or auxiliary gutter, and the connection between a wireway or auxiliary gutter and a fitting shall not be more than 0.005 W.

19.2 The wireway or gutter and fittings are to be installed in the intended manner. A direct current of 30 A is then to be passed between adjacent sections of wireway or gutter, and between the wireway or gutter and the fitting. The resulting voltage drop is to be measured between a point (file mark) on the wireway 1/16 in (1.6 mm) from the connection and a similar point on the far end of an adjacent wireway or on the fitting, if of the ending-fitting type. In the case of a fitting of the feed-through type, the resulting drop in potential is to be measured between points on the two adjacent pieces of wireway or gutter 1/16 in (1.6 mm) from the connections. The resistance in ohms is to be determined by dividing the drop in potential in volts by the current in amperes passing through the raceway.



I also asked him:
No electrical fittings have ever been submitted to UL for evaluation of removal of paint etc. by their inherent design?
Meaning removal must be done by hand on both sides of the KO prior to any fitting installation into the KO?
Is this correct?

His response: (...while not precisely what I have been told in the past ..., it is here in writing, today...)
Conduit fittings are covered by UL Category DWTT and are identified for grounding and bonding where installed in accordance with the NEC. These fittings are evaluated to UL 514(B). It is up to the AHJ to determine compliance with 250.12 and 250.96(A). If the locknut is of such a design and part of a UL Listed fitting that by properly tightening it, it scratches the paint and is in direct contact with the metal of the enclosure, it would be able to comply with the testing requirements of UL 514(B). (...WOW, happy to know, this is an AHJ call ... :) )

GROUNDING
All metal fittings for metal cable, conduit and tubing are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with the NEC, except as noted for flexible metal conduit fittings and liquid-tight flexible metal conduit fittings.
FITTINGS
Flexible Metal Conduit Fittings - Flexible metal conduit fittings designed for connection to the conduit by clamping around the circumference of the conduit are considered suitable for grounding for use in circuits over and under 250 V and when used in accordance with the NEC and containing conductors protected by overcurrent devices rated 20 A or less. Flexible metal conduit fittings of types other than the clamping type mentioned previously in the 3/8 through 3/4 in. trade size and containing conductors protected by overcurrent devices rated 20 A or less are considered suitable for grounding when used in accordance with the NEC. All other trade sizes that have been investigated for grounding are marked "GRND" or the equivalent.
Liquid-tight Flexible Metal Conduit Fittings - Liquid-tight flexible metal conduit fittings in the 1-1/4 in. and smaller trade sizes are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with the NEC. A straight metallic fitting for use in direct contact with earth is marked "Direct Burial."
Liquid-tight Flexible Nonmetallic Conduit Fittings - Liquid-tight flexible nonmetallic conduit fittings are marked as follows:
1. A fitting for Type A conduit only is marked "Liquid-Tight Flexible Nonmetallic Conduit Type A Only," "LFNC-A only" or "FNMC-A only."
2. A metallic fitting for Type B is marked "Liquid-Tight Flexible Nonmetallic Conduit Type B Only," "LFNC-B" or "FNMC-B."
3. A nonmetallic fitting for Type B conduit only is marked "Liquid-Tight Flexible Nonmetallic Conduit Type B Only," "LFNC-B only" or "FNMC-B only."
4. A nonmetallic fitting for Type C conduit only is marked "Liquid-Tight Flexible Nonmetallic Conduit Type C Only," "LFNC-C only" or "FNMC-C only."
5. A straight metallic fitting for use in direct contact with earth is marked "Direct Burial."
Nonmetallic Fittings - Nonmetallic fittings suitable for use with rigid nonmetallic conduit are identified by the appropriate marking on the carton. Such fittings are inherently resistant to atmospheres containing industrial corrosive agents and will also withstand vapors or mists of caustic, pickling, acids, plating baths, hydrofluoric, and chromic acids. Fittings that have been investigated for exposure to other reagents may be identified by the designation "Reagent Resistant" printed on the surface of the fittings. Such special uses are described in greater detail in the individual carton markings or instructions packed with the device. Nonmetallic fittings for use with rigid PVC conduit are suitable with wires rated 90?C or less.
Threadless Fittings - Threadless fittings for use with electrical metallic tubing, rigid metal conduit, intermediate metal conduit or threaded couplings which split to fit over the ends of threaded rigid metal or intermediate metal conduit and then are bolted in place are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with the NEC.
Additional Fittings - For additional Listings of conduit fittings, see Outlet Bushings and Fittings (QCRV ), Insulating Bushings (NZMT ), Rigid Ferrous Metal Conduit (DYIX ), Intermediate Ferrous Metal Conduit [for elbows] (DYBY ) and Armored Cable Connectors [for connectors which may also be suitable for use with flexible cord, flexible metal conduit and metal-clad (Type MC) cable] (AWSX ).

UL 514(B) tests the fitting as follows:
8.9.1.3 A LOCKNUT shall be hand-tightened and then further tightened 1/4 turn with a hammer and a standard screwdriver or by an equivalent method.

8.9.1.4 For 3/8 - 1-1/4 (12 - 35) trade sizes, a FITTING shall be tested with:
a) a steel enclosure or plate of thickness 1.35 - 1.40 mm (0.053 - 0.055 in) at the currents specified in Table 21 or Clauses 8.9.2, 8.9.4 and 8.9.5, as applicable, and

b) a steel enclosure or plate of thickness 0.66 - 0.71 mm (0.026 - 0.028 in) at 470 amperes for 4 seconds.

A FITTING of the 3/8 - 1-1/4 (12 - 35) trade sizes shall be allowed to be tested with only a steel enclosure or plate of 0.66 - 0.71 mm (0.026 - 0.028 in) thickness when the FITTING is tested at the currents and for the times specified in Table 21.

8.9.1.5 For 1-1/2 - 6 (41 - 155) trade sizes, a FITTING shall be tested with a steel enclosure or plate of 1.35 - 1.40 mm (0.053 - 0.055 in) thickness in accordance with Table 21 or Clauses 8.9.2, 8.9.4 and 8.9.5, as applicable.

8.9.1.6 After having carried the test current, continuity shall exist between the parts of the test assembly when measured between a point on the raceway and a point on the enclosure 6.4 mm (1/4 in) from the FITTING. An indicating device, such as an ohmmeter or battery-and-buzzer combination, shall be used to determine whether continuity exists.

Fittings used on flexible metal conduit, metal cables, threadless fittings are all subjected to additional testing.




I do hope this is helpful,

mweaver
 
In the March UL Newsletter, Page 2 under "Other Types of Metallic Enclosures" such as: Cabinets and Cutout Boxes (governed under Article 312) are discussed.

What is required for grounding and bonding around eccentric, concentric and or tangential knockouts for enclosures governed under Article 312 is covered...
 
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