Painting old light fixtures

[drcampbell]

So what is paint? Pigment suspended in resin. Pigments are mostly metallic oxides, which are non- or semi-conductors. Resins are mostly non-conductors.

But it hardly matters. If you have a good low-impedance ground, either the paint will conduct and a fault to case will clear the OCPD, or the paint won't conduct and a fault won't energize the metal. Either way, it remains safe.

 

[jim dungar]

There is no general requirement for any electrical equipment enclosure paint to be conductive or the NEC would not require 'scrapping' down to bare metal when attaching grounding lugs.

 

[Jerramundi]

With an internal ground wire attached to a grounding screw i see no relevance to painting them.

How do you think the fault current gets to that ground wire and ultimately, the breaker?

 

[Jerramundi]

There is no general requirement for any electrical equipment enclosure paint to be conductive or the NEC would not require 'scrapping' down to bare metal when attaching grounding lugs.

I would think the requirement to scrape down to bare metal when attaching grounding lugs is a testament to my exact concerns (i.e. that the paint acts as insulator and will not properly allow the conduction of a fault current).

 

[ActionDave]

What's in that grey paint that is used on nearly all electrical gear? How conductive is it? Why is it grey? What is the thickness?

 

[LarryFine]

I still say the paint is not relevant. If a hot wire makes enough contact to energize, it will simultaneously be enough contact to trip.

In my opinion, there's no concern that this will or won't occur at the first moment the hot wire touches the nearest enclosure wall.

 

[Hv&Lv]

Why is it grey?

It’s a neutral color.
Mobile homes have panels that are white.
Old panels used to be a real dark grey. Some panels are beige.
They are painted On a production line. Changing up colors all the time would make the price higher.
Making them different colors could be a store stock nightmare.
“Do you have this panel in a light blue to match the room?”
Some manufacturers will paint them for a price.

 

[ActionDave]

I still say the paint is not relevant. If a hot wire makes enough contact to energize, it will simultaneously be enough contact to trip.

In my opinion, there's no concern that this will or won't occur at the first moment the hot wire touches the nearest enclosure wall.

I agree. Forget about paint, I've shorted wires out to bare metal lots of times with no breaker trip.

 

[Little Bill]

There is no general requirement for any electrical equipment enclosure paint to be conductive or the NEC would not require 'scrapping' down to bare metal when attaching grounding lugs.

I would think the requirement to scrape down to bare metal when attaching grounding lugs is a testament to my exact concerns (i.e. that the paint acts as insulator and will not properly allow the conduction of a fault current).

If it was a testament to your concern, the NEC would require scraping all the paint or not allow paint. You have already been given the soultion to your concern, use a toothed washer or scrape paint under where the ground screw is.

 

[Jerramundi]

If it was a testament to your concern, the NEC would require scraping all the paint or not allow paint. You have already been given the soultion to your concern, use a toothed washer or scrape paint under where the ground screw is.

That solution is in regards to attaching the EGC, whether it be a wire type or the conduit itself, to the fixture body. Which yes, the idea of using a toothed washer or scraping below the lock ring, will ensure a proper bonded connection of the EGC to the fixture body.

My concerns rests with the potential situation of a hot wire contacting the fixture body elsewhere and there being enough conductivity for current to transverse from this point of contact to the EGC and ultimately trip the breaker.

Say, for example, a loose hot wire touches the fixture enclosure. There would have to be a conductive path either along the paint layer itself, through the paint to the underlying metal, or both... back to the EGC and subsequently to the source... in order for the breaker to trip.

Let's also assume the paint DOES NOT act as a 100% solid insulator. What if there is enough resistance on the paint layer to allow current to flow to the EGC, but not enough current to trip the breaker? You would end up with an energized piece of metal (i.e. the fixture body). I admit this is a worst case scenario, but I'm just trying to be thorough.

 

[Jerramundi]

It's entirely possible I am overthinking this, but I think it's an interesting scientific debate nonetheless. I still feel my concern has merit.
If anything, I'll probably just do what Larry suggested and just paint the outside, but not the interior section that houses the wire itself.

For poops and giggles, I might test this out just for fun, but probably not until December, January when things slow down.

 

[LarryFine]

Let's also assume the paint DOES NOT act as a 100% solid insulator. What if there is enough resistance on the paint layer to allow current to flow to the EGC, but not enough current to trip the breaker? You would end up with an energized piece of metal (i.e. the fixture body). I admit this is a worst case scenario, but I'm just trying to be thorough.

To me, this is the only questionable scenario; the contact occurring without the OCPD tripping. I, too, enjoy a good, healthy, theoretical discussion, which is what this is. Either contact will be made, and trip the breaker, or it won't.

Unless there is major resistance in the EGC pathway, the housing would still remain at (almost) zero volts to earth, just like any loaded grounded conductor, and the majority of the voltage would be across the arcing contact point.

Bottom line: I don't believe OEM paint is any more conductive than after-market pain is.

 

[Jerramundi]

For visual reference... this is what I'm talking about...

 

[Jerramundi]

I, too, enjoy a good, healthy, theoretical discussion, which is what this is.

Exactly. That's all this is. Just stretching those mind muscles.

 

[Jerramundi]

I just found this from an old EC&M article. Which makes clear, at least as of 2005, that "scraping away the paint" is required to ensure continuity where connecting a lock ring or ground screw (i.e. the EGC).... but again if there isn't good continuity between this point of connection to the EGC and the point of the fault, which may be on the painted surface, it all seems for not.

Furthermore, if it's required regarding "nonconductive coatings such as paint" at the point of making the bonded connection to the EGC, it would stand to reason the same logic applies to the entirety of the ground fault path (i.e. if paint is used, it should somehow to some degree be conductive).

As per 250.12 of the 2005 NEC, “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.”

www.ecmweb.com/national-electrical-code/whats-wrong-here/article/20896112/whats-wrong-here

 

[ActionDave]

....Furthermore, if it's required regarding "nonconductive coatings such as paint" at the point of making the bonded connection to the EGC, it would stand to reason the same logic applies to the entirety of the ground fault path (i.e. if paint is used, it should somehow to some degree be conductive).

No it doesn't stand to reason. By your logic you can't even use green insulated wire for an equipment grounding conductor.

 

[Jerramundi]

No it doesn't stand to reason. By your logic you can't even use green insulated wire for an equipment grounding conductor.

With all due respect, NO.. my logic does NOT say that. I'm hard pressed to see how you come to that conclusion using my logic.

 

[gadfly56]

For visual reference... this is what I'm talking about...

View attachment 2553778

Are you claiming that the internal surfaces are currently unpainted and that there is only bare metal?

If the internal surfaces are already painted, take a meter on the ohms setting and lightly touch the probes to the surface a foot or so apart. No conductivity? Stop worrying. then.

 

[Jerramundi]

Are you claiming that the internal surfaces are currently unpainted and that there is only bare metal?

If the internal surfaces are already painted, take a meter on the ohms setting and lightly touch the probes to the surface a foot or so apart. No conductivity? Stop worrying. then.

I'm arguing that there SHOULD be conductivity/continuity. If not between any two points on the metal fixture, then at least between any two points that are metal and internally house wiring or another would-be-live electrical component.

 

[Jerramundi]

No it doesn't stand to reason. By your logic you can't even use green insulated wire for an equipment grounding conductor.

If anything... my logic would indicate that you have to remove any insulating material, such as wire insulation (OR PAINT), at the point of bonding the green insulated wire / EGC to the metal enclosure, which is accurate... and the above 2005 NEC code reference supports that. But that's not the precise point I'm concerned about. I'm not concerned about the point where the EGC bonds to the metal. That was never in question.

My question/concern was about the point where the fault occurs on a painted surface and the subsequent path between that point and where the EGC bonds to the metal.

It WOULD indeed stand to reason that if you are required by code to remove the paint, which the NEC explicitly refers to as a "nonconductive coating," where making a bonded connection.... that any point at which a ground fault could potentially occur, would also have to have said "nonconductive coating" removed to ensure continuity between the point of the fault and the point where the EGC is connected.