Another bond bushing question

[texie]

If your statement was correct then why would they produce Bonding lock rings/bonding Myers hubs/ Bonding Bushings?

Lot's of of applications require them. 250.92 for one.

 

[electrofelon]

This is incorrect. The fittings are listed under UL 514b. If you read section 42 it tells you the testing procedure which describes what my first statement said. There is no way to guarantee that the device can cut the paint or coating due to there is not one specification on how many coats and such each manufacture installs. If your statement was correct then why would they produce Bonding lock rings/bonding Myers hubs/ Bonding Bushings? You can buff the paint off on both sides and not use one of the bonding styles and be in compliance (NEC 250.12). Now the raceway only has to be bonded on one side if it is continuous or can be bonded with externally with pipe bonding clamps (as long as it is bonded with the proper size conductor NEC 250.122 (branch)) and in this case you would not have to do the bonding in the panel. So to your point most MC terminations end up in a unpainted handy box or device box that will then have a bonding screw in them which thus bonds one side of the raceway.

Also, just because you have seen or done things for 30 years doesn't make it right.

I have been doing this for 20 years, many people on here have been doing it longer than me, and I have never heard of or seen someone removing the paint for say an EMT fitting into a painted cabinet, or installing a bonding bushing if they did not remove the paint. Properly installed, the teeth of the lock nut will Pierce through the paint.

 

[infinity]

Mike Holt has a video where he states that by properly installing the locknut (tapping with pliers and screw driver) the paint does not need to be removed first. There have been proposals to requirement removal of the paint but they have been rejected by the CMP. Here's one:

5-56 Log #2658 NEC-P05 Final Action: Reject
(250.12)
________________________________________________________________
Submitter: Paul Dobrowsky, Holley, NY
Recommendation: Revise as follows:
250.12 Clean Surfaces. Nonconductive coatings (such as paint, lacquer, and
enamel) on equipment to be grounded shall be removed from threads and other
contact surfaces to ensure good electrical continuity or be connected by means
of fittings designed so as to make such removal unnecessary.
Substantiation: It is my understanding that there are no fittings that are
evaluated to make removal of nonconductive coatings unnecessary. If that is
true then this language is very misleading.
A similar proposal has been submitted for 250.96.
Panel Meeting Action: Reject
Panel Statement: The submitter provided no substantiation of an existing
problem. There is no requirement in this section for evaluation of fittings.
There are fittings with knurled bases or locknuts with turned ears that are
“designed so as to make such removal unnecessary” when installed properly.
Number Eligible to Vote: 16
Ballot Results: Affirmative: 15 Negative: 1
Explanation of Negative:
BRENDER, D.: This proposal should have been accepted. The connection of
wiring methods that are to provide a ground-fault path should be assured by
removing non-conductive coatings at connection points to assure a reliable
current-carrying connection.

 

[epelectric33]

I have been doing this for 20 years, many people on here have been doing it longer than me, and I have never heard of or seen someone removing the paint for say an EMT fitting into a painted cabinet, or installing a bonding bushing if they did not remove the paint. Properly installed, the teeth of the lock nut will Pierce through the paint.

I understand as I have been doing this for the better part of 30 years myself. I am not always right and I am still learning. I didn't learn this until later in my career as well. I have attached some pictures and literature to back up what I am saying. There was enough resistance in this situation to act as a load due to not using bonding fittings on a painted surface to not trip the breaker. We kept hearing the popping sound and luckily someone did not touch this raceway system before we figured out what was going on. I have attached the UL literature and if you take the time to call the manufacturer they will tell you that the bonding rating of their lock rings and other connectors that do not have an external method of attaching a bonding conductor on a painted surface will not be considered by them as installing to their listing as a bonding connection. I would be very interested if someone on here can prove me wrong with black and white documentations and not their opinions or experiences.

 

[infinity]

I would be very interested if someone on here can prove me wrong with black and white documentations and not their opinions or experiences.

The rejection by the code making panel in post #23 of exactly what you are saying is required is not enough proof? There was one dissenting opinion but other than that the vote was `15-1 against.

 

[epelectric33]

The rejection by the code making panel in post #23 of exactly what you are saying is required is not enough proof? There was one dissenting opinion but other than that the vote was `15-1 against.

It is still an opinion doesn't matter who stated it. I have had personal experience and conversations with the manufacturers to prove otherwise (which some of this was posted in my previous email). If someone can get a manufacturer to say that their product is UL listed (state the UL listing) to be installed on a painted surface for grounding and bonding without the use of external conductor attached to it by means of “designed so as to make such removal unnecessary” then I would agree. The problem you will run into is that there is not a manufacturer that will do this due to what I stated earlier about the unknown amount of paint coatings or other coatings that can or will be applied to be able to guarantee a solid connection (it would be a legal nightmare to do so). Part of why I know this is because we did seek out the manufacturer on this instance and they came back with the UL 514b testing procedure which states on an unpainted surface. Which all comes back to NEC 110.3(B).

250.12 Clean Surfaces. Nonconductive coatings (such as paint, lacquer, and
enamel) on equipment to be grounded shall be removed from threads and other
contact surfaces to ensure good electrical continuity or be connected by means
of fittings designed so as to make such removal unnecessary.

These types of fittings are the bonding bushings and such that allow an external bond to the fitting which would MAKE SUCH REMOVAL UNNECESSARY. The code article says nothing about the fitting being able to scrape the paint away enough to satisfy the proper electrical connection.

 

[Terminator5047]

This is incorrect. The fittings are listed under UL 514b. If you read section 42 it tells you the testing procedure which describes what my first statement said. There is no way to guarantee that the device can cut the paint or coating due to there is not one specification on how many coats and such each manufacture installs. If your statement was correct then why would they produce Bonding lock rings/bonding Myers hubs/ Bonding Bushings? You can buff the paint off on both sides and not use one of the bonding styles and be in compliance (NEC 250.12). Now the raceway only has to be bonded on one side if it is continuous or can be bonded with externally with pipe bonding clamps (as long as it is bonded with the proper size conductor NEC 250.122 (branch)) and in this case you would not have to do the bonding in the panel. So to your point most MC terminations end up in a unpainted handy box or device box that will then have a bonding screw in them which thus bonds one side of the raceway.

Also, just because you have seen or done things for 30 years doesn't make it right.

Most boxes With kos are ul listed to require no additional bonding required hence the reason MCAP is allowed again

 

[epelectric33]

Most boxes With kos are ul listed to require no additional bonding required hence the reason MCAP is allowed again

What UL listing are you referring to? The raceways are still required to be bonded. MCAP has a bare conductor that runs the course of the cable along side of the metal sheath and then ties to the ground bus bar thus bonding the raceway.

 

[Carultch]

What UL listing are you referring to? The raceways are still required to be bonded. MCAP has a bare conductor that runs the course of the cable along side of the metal sheath and then ties to the ground bus bar thus bonding the raceway.

Metal raceways are required to be bonded, that isn't the issue in question. They are made out of conductive material, and aren't intended to carry current, ergo require bonding in some form or another. The concept in question is whether or not you automatically get electrical bonding of the raceway, with what you do to terminate it mechanically (e.g. standard locknut teeth that cut in to the enclosure wall). Some situations specifically require more substantial means of bonding. Such as the impaired continuity of ring KO's remaining at >250V to ground, service raceways, and ferrous raceways containing GEC's.

 

[epelectric33]

Metal raceways are required to be bonded, that isn't the issue in question. They are made out of conductive material, and aren't intended to carry current, ergo require bonding in some form or another. The concept in question is whether or not you automatically get electrical bonding of the raceway, with what you do to terminate it mechanically (e.g. standard locknut teeth that cut in to the enclosure wall). Some situations specifically require more substantial means of bonding. Such as the impaired continuity of ring KO's remaining at >250V to ground, service raceways, and ferrous raceways containing GEC's.

OK. I'm going to give someone else to chime in here on this topic as it is all wrong. I know I sound like a broken record but this is very much misleading.Hint 250.122[/QUOTE]

 

[infinity]

OK. I'm going to give someone else to chime in here on this topic as it is all wrong. I know I sound like a broken record but this is very much misleading.Hint 250.122

We don't always agree on everything on this forum and that is fine but you say "it is all wrong", there must be tens of millions of RMC locknuts, EMT and AC/MC connectors installed in painted metal panel cabinets and pull boxes and none of them have bonding bushings. It seems impossible that no electrician or inspector in the past five decades ever picked up on the fact that the bonding bushings are required. It's more likely that no one came to that conclusion because they're simply not required.

What does your hint 250.122 mean?

 

[Fred B]

I just don't know the issue, I've installed a lot of lock nuts, without exception when properly tightened an approved Locknut will remove the paint off the cabinets under the nut. (Most have either "teeth" on underside, or the curve in sharpish edge to the nut.) Hand tightening doesn't make the connection properly but if use a wrench or as suggested hammer and screwdriver I've seen that not only paint removed but can actually get a little metal shave up, even on concentric KO. And if that is not going to make it a low resistance connection you'll never get one and millions of connections need to be changed and code cannot allow metal conduit to act as a grounding conductor. It seems to me if the approved Locknut fails to make a proper low impedance connection for conduit it is a 110.12 failure, where all other standards have been met.

 

[epelectric33]

We don't always agree on everything on this forum and that is fine but you say "it is all wrong", there must be tens of millions of RMC locknuts, EMT and AC/MC connectors installed in painted metal panel cabinets and pull boxes and none of them have bonding bushings. It seems impossible that no electrician or inspector in the past five decades ever picked up on the fact that the bonding bushings are required. It's more likely that no one came to that conclusion because they're simply not required.

What does your hint 250.122 mean?

I will first start off by saying that the entire population used to think the world was flat until someone proved them wrong so statements of opinions really do not matter. I have shown the proof and asked to be proven wrong but all I get here are opinions. Your statement "It seems impossible that no electrician or inspector in the past five decades ever picked up on the fact that the bonding bushings are required. It's more likely that no one came to that conclusion because they're simply not required." is incorrect. There are plenty of places and people who agree with what I am saying they are just not on this forum (gas plants/refineries/power plants/etc.).

Now for the real discussion at hand. I will say that most of the tradesmen that I run across know how to do something, but not WHY they are doing it. That is the most important part of an installation in my opinion. I gave a hint at NEC 250.122 to lead us down the right road. I will explain why and then present an example to help process it.

250.122 Size of Equipment Grounding Conductors.
(A) General. Copper, aluminum, or copper-clad aluminum
equipment grounding conductors of the wire type shall not be
smaller than shown in Table 250.122, but in no case shall they
be required to be larger than the circuit conductors supplying
the equipment. Where a cable tray, a raceway, or a cable armor
or sheath is used as the equipment grounding conductor, as
provided in 250.118 and 250.134(A), it shall comply with
250.4(A)(5) or (B)(4).

So anything that has to be bonded (raceway, panel, motor, etc.) has to have a certain size conductor to be able to carry the fault current enough to be able to trip the OCPD. Right? I hope this is not debated.

The purpose of the UL listing (testing) is to prove that the device is able to have a good enough connection to be able to do this. In the testing not only is the lock ring in contact with the metal surface, but also the entire shoulder of the fitting (this is important). If you have a painted surface the shoulder of the fitting is not in contact with a metal surface which also neglects the UL listing now.

Now for the purpose of the raceway to be bonded properly (not just have continuity). If you have a insulation failure inside the raceway and it is not bonded properly enough for it to carry the fault current to trip the OCPD then you will have a "live" conduit that can KILL someone.

Example:

At a school yard there is an outdoor conduit along the wall. Over time we know that there will be a certain amount of condensation build up and when winter came along they had a sudden hard freeze. This freeze ended up causing the insulation on the conductor to split and come in contact with the raceway. Unfortunately the bonding connection was not good enough to cause the OCPD to trip and now the raceway is "live". Well the next warm day the children went out to play in the yard and it was a race to the wall. Well the first child to the wall ended up touching the "live" raceway and died.

These are the reasons WHY we do things properly and not just what we have seen (do the work and research yourself to understand why). I will not be the electrician that has to explain to the parents why their child died playing in the school yard.

Now can anyone prove me wrong????

 

[wwhitney]

This is incorrect. The fittings are listed under UL 514b. If you read section 42 it tells you the testing procedure which describes what my first statement said. There is no way to guarantee that the device can cut the paint or coating due to there is not one specification on how many coats and such each manufacture installs.

For the current version of UL 514B (available to read online with a free account at ul.com), the section is 8.10. For discussion, the relevant excerpts are below.

Cheers, Wayne


8.10 Current Test

8.10.1 General

8.10.1.1 . . .

8.10.1.2 Each FITTING shall be assembled to a minimum 152 mm (6 in) length of raceway of the intended size and an unpainted, plated or unplated, steel enclosure (as shown in Figure 6) or steel plate simulating an enclosure (as shown in Figure 7). The thickness of the enclosure or plate shall be as specified in Clauses 8.10.1.4 and 8.10.1.5.

8.10.1.3 A LOCKNUT shall be hand-tightened and then further tightened 1/4 turn with a hammer and standard screwdriver or by an equivalent method. A copper wire lead, not less than 610 mm (2ft) long shall be connected:

(a) to the enclosure by a pressure wire connector, and
(b) to the raceway, 0.8 mm (1/32 in) from the FITTING, by a ground clamp that is sized accordingly.

. . .