Comments Appreciated - UL676

[bphgravity]

Please read the following report and respond with comments and opinions. I greatly appreciate your thoughts and experiences.

BACKGROUND

UL has received requests from industry, both swimming pool and fountain luminaire manufacturers, to remove the requirement for an equipment grounding conductor (EGC) in a low-voltage luminaire. Manufacturers felt the EGC had no value and sometimes caused problems with newer LED luminaire circuits. They also pointed out that the requirements in UL 676 conflicted with the requirements for certification of the same luminaries in Europe.

BACKGROUND AND RATIONALE OF PRESENT REQUIREMENTS

Beginning with the 1972 first edition, UL 676 included the Electric Shock Test to evaluate the risk of electric shock posed by the electric current that escapes a swimming pool or spa luminaire that has a leaking gasket or a cracked or broken lens. Specifically, this test determines if the average density of electric current that conducts out of the cracks, gaps, or openings in the face of the water-filled luminaire and into a pool occupant poses a risk of ventricular fibrillation or immobilization of the muscles of the pool occupant?s arms, legs, or diaphragm (used for breathing).

Electric current will conduct out of a pool or spa luminaire only if there is a conductive path back out of the pool water to metal (current-carrying or non-current-carrying) that is part of, or connected to, the same circuit and that exhibits a voltage potential difference with respect to the water-contacting current-carrying parts of the flooded luminaire. The current path from the pool water back to the metal that is part of, or connected to, the same circuit can be through metal, pool water, earth, or any combination of these. Items (a) ? (c) below identify examples of current paths for electric current that has exited the face of a flooded luminaire and, therefore, poses a risk of electric shock to a pool occupant. These examples do not cover all possibilities. The design of the Escape Current Density Test, however, addresses these and all other possible current paths.

a) Current-carrying parts within the flooded luminaire are supplied by a grounded branch circuit (120 volts) and the current conducts out of the luminaire to return to the circuit by conducting into grounded metal of the same flooded luminaire, grounded metal of other underwater luminaires, or to the grounding electrode of the premises electric system through a ladder, reinforcing steel, or other metal object of the pool that contacts both the pool water and earth.

b) Current-carrying parts within the flooded luminaire are supplied by a normally ungrounded line voltage branch circuit (240 volts) that has experienced an insulation failure, allowing a current-carrying part of the circuit to fault to metal that, in turn, is connected to the pool water. This insulation failure can be within the same flooded luminaire, within another underwater luminaire or other (non-immersed) equipment connected to the circuit, or within the circuit wiring.

c) Current-carrying parts within the flooded luminaire are supplied by a normally ungrounded low voltage, isolated source and a conductive through-water path has formed between current-carrying metal of the circuit and either earth or metal that, in turn, has a conductive path to the water in the pool. This situation can develop, for example, as described in items (i) and (ii) below.

i) The gasket of another luminaire connected to the same ungrounded circuit leaks, allowing water to form a conductive water path from the current-carrying parts within the second luminaire to the pool water in front of the that luminaire or to metal of the luminaire that, in turn, has a conductive path to the pool water.

ii) A flexible cord connected to the same ungrounded circuit becomes damaged or deteriorates as a result of continual immersion in the chemical-treated pool water. The flexible cord may be of a wet-niche or removed-for-service no-niche luminaire and located within the water-filled forming shell, water-filled space behind the luminaire, or inside the pool-water-filled conduit supplying the luminaire. Where cracking or water permeation of the cord jacket and conductor insulation occurs, water will pass into the cord and form a through-water conductive path between the current-carrying conductor and the water around the cord. This conductive water path will extend, for example, through water within the conduit to pool water behind the wet-niche or removed-for-service no-niche luminaire, which is contiguous with the water in front of the luminaire through water passage openings in the luminaire design. A path from the water around the flexible cord to the earth around the conduit (and then to the pool water) will exist if the conduit is nonmetallic and has cracked to allow water from within it to pass out of the conduit into the earth or if the conduit is metal.

FIELD HISTORY OF LOW-VOLTAGE WET-NICHE AND NO-NICHE LUMINAIRES

After researching the issue, UL believes the scenarios detailed in items c(i) and c(ii) above have not manifested in the field. An equipment-grounding conductor was believed to be necessary in the low voltage luminaire and forming shell in order to collect stray currents. If these scenarios need not be addressed, then UL believes the requirement for an equipment-grounding conductor in a low-voltage luminaire and its forming shell could be deleted. UL requests industry input on this possible revision to UL 676.

MARKINGS AND BACKWARD COMPATIBILITY WITH EXISTING FORMING SHELLS

To prevent confusion with inspection authorities, UL believes a marking on low-voltage luminaires not requiring grounding might be needed. UL suggests a simple marking such as ?Low-Voltage Luminaire Not Requiring Grounding.? This would reflect the text in Sections 680.23(B)(2) of the National Electrical Code, NFPA-70-2008. Before UL attempts to develop any revisions to the marking requirements for low-voltage luminaires, UL needs industry input concerning issues involved with ungrounded low-voltage luminaires and the existing installed base of forming shells.

 

[Buck Parrish]

It IMO would be stupid to remove the egc from a swimming pool lv luminare.
So stupid the article seems fake. JMHP

 

[bphgravity]

I assure you this is not fake. I serve on the UL 676 Standards Technical Panel, and this is a real matter that has been brought to the table.

If you think it is "stupid", tell me why and substantiate it.

I need to provide my findings and report by September 10th.

 

[Pierre C Belarge]

My understanding of the necessity for any kind of equipment grounding for wiring means of pools, has been to ensure the safety of the swimmers at all costs. An extra added sense of protection, with redundancy.

Now there is conversation based on a manufacturing group to remove this additional safety means in a sensitive type of installation.

I think the members of the UL Standard Group, should not let the fact that such great protection needs to be removed to let the manufacturer keep from developing a product that can perform with the safety in place.
Lets keep the safety in place and put the onus on the manufacturer to design the product in a different manner for pool installations.


Maybe in the future there will not be the need for the redundancy of safety, until that can be proven, let this portion of the standard stay as is.

P.S.
Has the manufacturer performed a thorough study to show that the change of redundancy will not affect the ultimate safety of the swimmers?

 

[Buck Parrish]

Sorry, I should not have used the word stupid. Pierre put it much more eloquently.

It's just that drownings from electric shock ( Where it is just enough to make muscles draw up) have been a topic of discussion lately.

 

[bobsherwood]

I am always concerned about 120V crossing a bad transformer.... then it's not an issue of a 12 volt system. Keep the grounds.

 

[LJSMITH1]

I think the EGC requirement should be left alone. While a perfectly installed and functioning LV system may not require an EGC, it is the probability of a poorly installed or functioning system that the EGC may help increase the margin of safety. Even the report acknowledges

These examples do not cover all possibilities.

IMHO, that is the #1 reason to leave the EGC requirement in place.

As Bobsherwood pointed out, the main concern would be 120V coming from somewhere 'upstream' into the LV enclosure or other metallic parts. If that metal surface (such as a wet niche, or a metal housing) is in contact with the pool water, the situation could be fatal.

 

[highendtron]

I buy a lot of material from home Depot and Lowe's, both stores encourage the DIY's to install electrical work, especially LV stuff! No problem, if they observe the NEC and local jurisdiction expectations.
The other day I turned down a job where a HO tried installed a LV system on his pool. He set LV lights in his pool wall and brought his LV wires to the outside of his 3' walkway. He ran 120volt plugs and LV wires in 1/2" pvc from the walkway to his swimsuit changing shed where his panel was located. The plugs were installed in monuments at the outboard edge of the walk around the pool. All he wanted me to do was to terminate his wiring to his panel. Keep the redundant grounds. Keep the knowledge and skill barrier high to protect the innocent!

 

[donselectric]

it's redundant bonding as the forming shell is hit outside (its the same lug most times). is it needed i honestly don't think so but with my luck both sides of the 8 solid would break...:roll:
the wire manufactures must be reeling over that one...
seeing it is a manufactures driven code..all about product....

 

[Sierrasparky]

Are they trying to tell us that there is no risk of electric shock from a damaged LO VO or LED fixure?
I think there rationale is rediculous. "interferes with newer fixtures"
That's probably because they are faulty made in the first place. I think some hands on testing and sceintific proof is necessary before the change is made. We all can speculate but hard tested proof is the only true way to make a decision.

 

[iMuse97]

this does not address all contingencies!

this does not address all contingencies!

Bryan, thanks for putting this out there. I'll be very interested to see the discussion it generates.

I am amused by that line: "These examples do not cover all possibilities." One would think that engineers at UL would attempt to address all contingencies and variables and scenarios that could be included in the installation of this luminaire. One that I can think of immediately is: What about the properly bonded, stainless steel pool ladder, or diving board or slide mounting plates, bolts, etc.? Could not the water provide a path to the equipotential plane through such as these? And don't they still use stainless plumbing fittings, which must be bonded. These are just some musings of a person who owns a pool, has worked for a pool installing company, and is now just your average electrician, always trying to learn something new.

Thanks, Karl

 

[petersonra]

I would be willing to bet the same kind of comments were made when double insulated items first came out, and they have turned out to be very safe, perhaps safer than non-double insulated items.

I don't think the EGC provides a whole lot of extra protection, and as the report mentions, field experience has shown that it may not. If it doesn't, why have it?

 

[cadpoint]

Please read the following report and respond with comments and opinions. I greatly appreciate your thoughts and experiences.

First off, I'm not familiar enough with how the rules of how a UL certification work, or of a listing which the UL applies as I'm reading it!
Well I read the UL 676 article (I think) and the first thing that jumped out as to what the article also qualified what other articles which where linked to this article, etc. If you read the scope of 676, well thats the wiring to the device, the assembly that holds the light is another UL number.( maybe I couldn't get past my own mis-read of or understanding as previously stated!)

First thought is how does the UL work! How does it work in respects to how other articles are listed with-in another? Is it a case of meet every requirement of the UL to make the device a certifiable? An example if you build this oh yeah include this too? seems like the NEC in that one aspect, but I don't know for sure!

If the NEC gains its aspects from the IEEE & UL, won't this action blast a big whole in Grounding, bonding for the future. What does the IEEE have to say about this one aspect.?

Thinking about the EU here's is this the same article of how they approached it, is this the refernce of how this all started, the big picture unifiing electrical device aspects of LV equipment to market? Is this the one in the same to your "BACKGROUND AND RATIONALE OF PRESENT REQUIREMENTS"
maybe this has lead to the present EU submittal problem of American manufactures? This covers or outlines 0 to 50V AC & 0 to 75V DC.

I read somewhere recently that low voltage wiring was ready to go up to 60V AC in circuit power! May be I got that wrong as well.

What is the argument of compliance to the EU. I don't exactly understand EU wiring in general but think of it as to two hots and a ground. If, I missed that one part, I apologize.

A) How can this get by 250.4(A)(3) ? Put a green screw on the equipment chassis? Or how do you get by 250.20 but what they really want to change it or add to is250.21

B) That's why we bond equipment!

C)

This situation can develop, for example, as described in items (i) and (ii) below.

I think they mean "A and B" not (i)(ii) (again I might have missed it)

(i) is one of those articles covering construction of a pool light and another UL article/listing

FIELD HISTORY OF LOW-VOLTAGE WET-NICHE AND NO-NICHE LUMINAIRES

After researching the issue, UL believes the scenarios detailed in items c(i) and c(ii) above have not manifested in the field. An equipment-grounding conductor was believed to be necessary in the low voltage luminaire and forming shell in order to collect stray currents.

If these scenarios need not be addressed, then UL believes the requirement for an equipment-grounding conductor in a low-voltage luminaire and its forming shell could be deleted. UL requests industry input on this possible revision to UL 676.

MARKINGS AND BACKWARD COMPATIBILITY WITH EXISTING FORMING SHELLS

To prevent confusion with inspection authorities, UL believes a marking on low-voltage luminaires not requiring grounding might be needed. UL suggests a simple marking such as “Low-Voltage Luminaire Not Requiring Grounding.” This would reflect the text in Sections 680.23(B)(2) of the National Electrical Code, NFPA-70-2008. Before UL attempts to develop any revisions to the marking requirements for low-voltage luminaires, UL needs industry input concerning issues involved with ungrounded low-voltage luminaires and the existing installed base of forming shells..

In the second paragraph is this a case where the AHJ doesn't understand the future bonding requirements of a pool, Or are they now going to apply a retro-fit of the shell casing of the light and not apply the bond or grounded conductor new install or retro up fit, ok N/A for the Bond, because our NEC Code requirement will be changed in the future? Again back to 250.4(A)(3) As crazy as it sounds guess how you get to service a lamp in a pool, well it’s usually from the pool side!

My OP!
Pools are just one of those odd applications where a device needs to bonded, with an EGC, this is an umbrella coverage of bonding and grounded for the sake of the pool! Even the EEU in there sudo purpose statement says to uphold public safety.

If they get this LV marking requirement through will it cause a ground of other future application of devices and services to also be suspect or even dropped?

 

[petersonra]

If they get this LV marking requirement through will it cause a ground of other future application of devices and services to also be suspect or even dropped?

There are many things that are not bonded already. It has not proven to be a safety hazard.

If they can come up with a safe way to do it, more power to them.

Think of this scenario. LED lights fed by 6 volts. LED lights are hermetically sealed, and the can it is in is plastic.

How is this a hazard in a pool or anywhere else for that matter?

 

[cadpoint]

There are many things that are not bonded already. It has not proven to be a safety hazard.

If they can come up with a safe way to do it, more power to them.

Think of this scenario. LED lights fed by 6 volts. LED lights are hermetically sealed, and the can it is in is plastic.

How is this a hazard in a pool or anywhere else for that matter?

The OP asked :

Please read the following report and respond with comments and opinions. I greatly appreciate your thoughts and experiences.

I have no answer to your statement, frankly I have no defense either, here's why!

My fault was trying to understand or state some opinion of which I don't deal in day in or day out!

 

[bphgravity]

Here is my response:

1. The background does not describe the exact problem the EGC is causing LED luminaire circuits. Is the problem a design issue that needs to be corrected by the manufacturers or is there a real need to remove an important, redundant safety wiring practice?

2. The section below indicates, “These examples do not cover all possibilities.” I think it is due diligence on the part of the industry and UL to ensure ALL possibilities have been covered and seriously considered.

3. The section below does indicate remote circumstances which would result in a hazard if the EGC is not present. The removal of a safety requirement should not be made until any possibility, no matter how remote, is mediated or completely avoided by some other means. While not generally referenced for swimming pool installations, Section 250.4 of the NEC outlines the exact reasons equipment is grounded and bonded. Removal of the EGC in this circumstance would be in direct violation of this section.

4. The section below does not take into consideration future installations and improperly wired circuits. The EGC provides a redundant safety path for fault currents in the event of an improperly wired or luminaries not suitable for use in a swimming pool which could occur some point in the future. It’s just too risky to remove the EGC as a safety device.

In short, I would need to see additional data and more in-depth research that clearly shows the EGC serves NO purpose and that manufacturers are taking more steps to ensure ground-faults and other hazards are reduced in their designs.

 

[Pierre C Belarge]

Bryan
Is that your response to us or to the board?

 

[don_resqcapt19]

All electrical equipment can fail. Some of these failure modes will put voltage in the poll water. The EGC provides some protection to pool users when this failure occurs.

The best thing that UL676 could do is to completely prohibit the manufacture of any pool light that has any electrical parts within 5' of the water. It is my opinion that that only reasonably safe pool light is a remote light with fiber optics to the pool itself.

 

[bphgravity]

Bryan
Is that your response to us or to the board?

It's kind of a draft response to some of the issues brought up here and that I will submit to the panel.

All electrical equipment can fail. Some of these failure modes will put voltage in the poll water. The EGC provides some protection to pool users when this failure occurs.

Here is a statement from the principal engineer on the UL staff:

A low-voltage luminaire on the secondary of a transformer with a grounded shield between primary and secondary is a different issue. The whole point of the design is that there is no voltage to ground at the luminaire. Any voltage at the luminaire is only in reference to the return to the transformer. In such a design an EGC would have nothing to do even in a partial or totally flooded luminaire situation. It would however provide a path to the luminaire for voltages above ground reference that are from other sources. Some would argue that the luminaire would be safer if the metal in it were not bonded.

 

[don_resqcapt19]

Brian,
If everything works as it is designed the UL statement is correct, but not everything always works perfect. If the grounded shield is not connected to an EGC for some reason and there is a primary to secondary fault, the secondary can end up with line voltage on it. (maybe the result of lightning damage or other high voltage surge)

As far as the last part of the statement.."It would however provide a path to the luminaire for voltages above ground reference that are from other sources. Some would argue that the luminaire would be safer if the metal in it were not bonded."; I agree with that and that is the very reason why we should not have any electrical equipment in or near pools. All lights should be remote fiber optic type and all pumps should be double insulated and the pool bonding should not be required to be "energized" as is required by the current code rules.