LED Light Wiring - "90 degree C supply conductor minimum"

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  #1  
Old 01-06-18, 07:56 AM
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Question LED Light Wiring - "90 degree C supply conductor minimum"

So I got this LED light from home depot (2900 lumens, 4' wrap around). And there is something on it that says "90 degree C supply conductor minimum". What exactly does that mean?

I am planning on installing bunch of these (although the other ones will not be this big, most area 1200 lumens) and while some of the circuits are using the new 12-2 NMB wiring and are all 20A circuits, there are indeed some which are the original BX cabling, and are only rated 15A.

House is from 1950s. There are 3 types of cables that I see around:

- The original 15A rated BX cables (two conductors inside cloth covered)
- Somewhat newer 12-2 AWG on 20A circuits (looks a lot like new romex but the outer shield is much thicker). Cables are white.
- Newest 12-2 AWG on 20A circuits. Cables are yellow.

The problem is I dont know what Celcius rating #1 above is, the old BX cables. Furthermore, I dont even know if the 12-2 NM cables are good enough.

I did do some reading on this searching the forums and I'm confused about the suggestions provided by people which mentions installing a junction box somewhere and running a 90C wiring to the light fixture. I dont understand how is this supposed to help when rest of the circuit all the way to the breaker is still not as good wiring?

Also on a side note, the entire premise of LED is that they consume very little power, correct? So how is it that I can safely put bunch of 100W light bulbs but this little thing with tiny dots of lights requires almost 200F protection?

EDIT: Just confirmed the wire types #2 and #3 are both NM-B which are as per my research rated 90C. So the question is only for #1.
 
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  #2  
Old 01-06-18, 08:06 AM
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The 90 degree requirement is referring to the insulating rating of the conductor. Newer cables such as NM-b or AC/MC cables will have 90 degree wire, but your older BX wire will not. They are likely only going to be 60 degree C wire.

The original 15A rated BX cables (two conductors inside cloth covered)
.
This does not sound like BX cable. BX is similar to AC cable without the bonding strip next to the outside metal jacket. What you have is early NM cable which is also likely only 60 degree wire.

Depending how you are installing the light you might be able to add some THHN wire to run into the fixture itself and keep the 60 degree wire inside the junction box outside the fixture.
 
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Old 01-06-18, 08:29 AM
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What I have is a metal insulation like FMC and in it are 2 conductors. They have an outer “braided” cloth which then has an inner plastic cover and inside that is the copper conductor itself.

So you are saying this is not BX?

Am i safe to keep the existing connection in a junction box and run 1’ of new NMB to the bew fixture bx and connect it there? So essentially only the exposed conductors in the fixture box have to be NMB, correct?

What if the current box is recessed in ceiling, is there a way to do this without cutting up the ceiling?
 
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Old 01-06-18, 04:20 PM
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So you are saying this is not BX?
,
No, that does sound like BX. You didn't mention the metal jacket in your first description

Again, depending on how the light fixture is installed (yours sounds like a strip fixture) any wiring that is inside the fixture will need to be 90 degree wire. If you post a link of the fixture I might be able to help how to install the fixture.
 
  #5  
Old 01-07-18, 03:39 AM
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Originally Posted by Tolyn Ironhand View Post
,
No, that does sound like BX. You didn't mention the metal jacket in your first description

Again, depending on how the light fixture is installed (yours sounds like a strip fixture) any wiring that is inside the fixture will need to be 90 degree wire. If you post a link of the fixture I might be able to help how to install the fixture.
Thanks, this is the fixture:

https://www.amazon.com/Lithonia-Ligh...ct_top?ie=UTF8

AND

https://www.homedepot.com/p/Commerci...7-HD/206040710

I have installed two of the commercial electric ones yesterday by simply converting the existing light fixture box to a junction box and adding a new box with 12-2 NMB wire.

The problem is, in the garage, that's not going to be easy (where I want to install the first one which is 2400 lumens). I need to cut up the ceiling I think, maybe if you can give me advice regarding that particular install that'd be great. What do you usually do?

There is already a single light bulb fixture, recessed in the ceiling. So the light box is flat at level with the ceiling (drywall). What is the easiest and least invasive way of doing this?

I will be installing 2 of these, one on each bay. I checked the existing wiring, it's a 3 way switch and its the same old BX wiring.
 
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Old 01-07-18, 04:11 AM
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I assume the strip fixture is going in the garage, can you post a picture of what is in there now so I can see what you are working with?
 
  #7  
Old 01-07-18, 02:24 PM
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Originally Posted by Tolyn Ironhand View Post
I assume the strip fixture is going in the garage, can you post a picture of what is in there now so I can see what you are working with?
Apologies for not getting back sooner, see attached picture. Its a pretty simple setup. I opened this up as well, there are just 3-4 wires (its a 3 way switch). The wiring is old wiring and not 90C. The box is recessed level with the drywall.
 
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Old 01-07-18, 02:42 PM
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That is what I expected. I suspect you are surface mounting the strip lights.

1)Most strip fixtures have a KO in the back for installing over a box. If your does not, your will need to drill your own. Hole should be big enough to access wiring in the box with the fixture installed (sort of). Be sure to install some type of bushing or chase nipple to protect the wires from the edge of the sheet metal.

2) Add some pig tails to the existing wire long enough to connect between the box and the fixture wiring. Be sure to add a ground wire is a grounding means is available.

3) Attach the strip light so it covers the box, routing the pigtails through the KO. Attach the light using screws or anchors.

4) Wire light as normal.
 
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Old 01-07-18, 04:45 PM
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Originally Posted by Tolyn Ironhand View Post
That is what I expected. I suspect you are surface mounting the strip lights.

1)Most strip fixtures have a KO in the back for installing over a box. If your does not, your will need to drill your own. Hole should be big enough to access wiring in the box with the fixture installed (sort of). Be sure to install some type of bushing or chase nipple to protect the wires from the edge of the sheet metal.

2) Add some pig tails to the existing wire long enough to connect between the box and the fixture wiring. Be sure to add a ground wire is a grounding means is available.

3) Attach the strip light so it covers the box, routing the pigtails through the KO. Attach the light using screws or anchors.

4) Wire light as normal.
Are you saying push the 90C wiring inside the LED through the big hole where its own black/white/green wires are coming out? So in essence, use the LED lights own box as a light fixture box?

Because this particular one is fully flat on its back (it does have a hole big enough to pass all the wires back and forth and it does have 4 screw holes predrilled, but it does not have some sort of a "groove" thats big and deep enough to hide the wires.
 
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Old 01-07-18, 07:15 PM
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Yes, that is what I am saying unless the fixture are long enough to get to the box. Basically you want to keep the older wire from being inside the light fixture near anything that might get hot.

You shouldn't need to hide any wires, there is a lens that covers everything.

Unless I am missing something.
 
  #11  
Old 01-08-18, 08:43 AM
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Most strip fixtures have a KO in the back for installing over a box. If your does not, your will need to drill your own. Hole should be big enough to access wiring in the box with the fixture installed (sort of).
I didn't realize this was a requirement. Is it against code to install a strip fixture over top of a ceiling box with only a small knockout and connector for the wire?
 
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Old 01-08-18, 12:03 PM
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Just to clarify, the KO I need is the size of a penny right? Just enough space to get 3 wires in there (black white ground). And what you are saying is, all the wiring including the fixture’s own cables will be inside the fixture hanging freely.

There is a white plastic cover which i m guessing everything will rest on? Is that safe?
 
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Old 01-08-18, 12:23 PM
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And what you are saying is, all the wiring including the fixture’s own cables will be inside the fixture hanging freely.
Your pigtails will originate inside the ceiling box, and the connections between pigtails and fixture wires will be inside the light fixture, concealed by the cover.

There is a white plastic cover which i m guessing everything will rest on? Is that safe?
Yes.
 
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Old 01-08-18, 02:42 PM
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Thanks thats simple enough. Any minimum length required for pigtails to be or just barely long enough to be able to install the fixture?
 
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Old 01-08-18, 05:46 PM
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I didn't realize this was a requirement. Is it against code to install a strip fixture over top of a ceiling box with only a small knockout and connector for the wire?
jdfjd
Yes. NEC 410.24(B) (2014) says that an electric discharge and LED luminaire surface mounted over a concealed junction box, and is not solely supported buy the box, shall be provided with suitable openings in the back of the luminaire to provide access to the wiring in the box.

Just to clarify, the KO I need is the size of a penny right?
oasi
No, See above. Most fixtures I see have a hole about 1 1/2"

Any minimum length required for pigtails to be or just barely long enough to be able to install the fixture?
asd
Nope. Whatever you need to use is fine.
 
  #16  
Old 01-09-18, 05:01 AM
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Thank you, this was super useful. You have saved me from doing a lot of drywall cutting and junction boxes. All I need to do is to make the hole larger.

Actually that brings me to my other question. One of the fixtures I want to install has no KO but it does have a quite large cavity that the wiring would fit. I’m guessing this is not allowed because the connection between the 90C wire/fixture’s own wires will make close contact with the original wiring.

The fixture in question is Commercial electric 13 in LED.

Granted this is unfinished basement and I can install a junction box but I’d rather not unless I have to.
 
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Old 01-09-18, 05:14 AM
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Actually to add to my previous question, in that case could I use one of those junction box covers with ko in the middle and cover the box fully only pigtails showing and then the pigtails and the fixture wires stay inside that cavity on the light fixture? THat way the coverplate provides a solid separation point.
 
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Old 01-09-18, 07:48 AM
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Actually to add to my previous question, in that case could I use one of those junction box covers with ko in the middle and cover the box fully only pigtails showing and then the pigtails and the fixture wires stay inside that cavity on the light fixture? THat way the coverplate provides a solid separation point.
From what Tolyn said, it sounds like this would not be legit, unless you have full access to the wiring inside the box once you remove the cover. IOW, large knockout/cutout in the fixture housing to access ceiling box, then you could put a ceiling plate over the box with connector in the middle. Except why would you want to do this?

Tolyn, are the knockouts on most strip fixtures large enough for this purpose (4"?). I've personally never noticed, but most fixtures I have installed/replaced didn't have boxes in the ceiling so I didn't have a need to do this. If one needed to be cut, what would be the best method? Aviation snips? Is the sharp edge remaining after cutting the hole an issue?
 
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Old 01-09-18, 08:06 AM
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I’m confused.

tonyln said the KO needs to be 1 1/2” in diameter. Thats the size of standard KO in any box (receptacle, switch, X gang), no? 4” is not a KO, its more like a huge opening.
 
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Old 01-09-18, 08:16 AM
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I’m confused.

tonyln said the KO needs to be 1 1/2” in diameter. Thats the size of standard KO in any box (receptacle, switch, X gang), no? 4” is not a KO, its more like a huge opening.
I'm confused as well, because 1-1/2" doesn't seem like enough to access all the wires inside a ceiling box. Apparently it is. Otherwise they wouldn't put a 1-1/2" KO in the fixture. Enough to get a finger in and pull the wires out I suppose. I was envisioning a larger hole, about the same size as a standard ceiling box. I guess the issue with a larger hole would be that the fixture would have to be that much wider for strength/rigidity, which would not be desirable.

Standard KO in junction boxes, etc is more like 1/2". We're talking about two different things here though. The 1-1/2" KO is for accessing a junction box, whereas the 1/2" KOs are for cabling secured by a connector.

Regardless, the proper way is to remove the 1-1/2" KO, center it over the ceiling box, pigtails inside the ceiling box, connections to fixture wires inside fixture and concealed by the cover.
 
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Old 01-09-18, 06:13 PM
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Tolyn, are the knockouts on most strip fixtures large enough for this purpose (4"?
sjhdfls
The KOs in strip fixtures I have seen are about 1 1/2", maybe closer to 2". They are not 4" for sure. While I have never thought this was enough to access the box wiring it does meet code. Yes, the metal edges are sharp, but you can use a plastic bushing to protect the wires if needed. It would depend on how they are routed.

You are really not trying to separate the older wires from the fixture wires, you keeping the older wires away from anything that might get hot inside the fixture such as the driver or LED array. If the fixture wires are long enough you could run them into the existing box and connect them to the older wire. They have the higher insulation value.

If I was doing it I would just punch a hole using my hydraulic KO punch. However most DIYers don't have one available so a hole saw will work in a pinch.

You might be over thinking this a bit. Sad thing is the requirement of the box access didn't start until about 2005 or 2008 NEC code cycle. In the past we did what you are suggesting using a 1/2" KO and a small chase nipple.
 
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Old 01-10-18, 08:35 AM
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Actually, these lst posts made me rethink and ask why the 90C requirement is there. Is this simply because the light fixture itself gets hot? I was under the assumption it was the fixture cables that heat up due to voltage draw but if it is the LED strip that heats up that much how can the light fixture even get 90C?

Furthermore, in my case the cables of the light fixture are quite long. Why can’t I simply put a box cover with a KO in the middle (they sell those) between the light fixture and the fixture box and simply feed te fixture cables through that hole and connect to the old wiring? There is simply no way the old wiring is making contact with the LED strips here as you can see the fixture’s own wired are tightly sealed.

Not to mention, if the fixture itself can get 90C, thats an entirely different problem because that means I cant mount this anywhere in my house as it cannot be making contact with any paint,drywall,or wood surface. 90C is extremely hot almost boiling hot water hot. I think the 90C must be for LED strips themselves.

Attached are two different light fixtures. One is the big 2900 lumen 4’ wrap that I want to install to garage, flush with the drywallceiling.

Second is a 13” circle ones that I want to install to my basement. I already installed the second kind in my basement but the wiring was brand new. That being said, when I run this particular light, it definitely does not get anywhere near 90C. I would say not even 40C.

So I m very confused about why this requirement even exists and if I can just mount this with KO plate in the middle and be done with it.
 
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Old 01-10-18, 09:01 AM
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I believe the main concern here is that you would effectively be concealing a junction box by installing the fixture in the way you propose. Hence the reason it was recommended to create a 1-1/2" to 2" knockout in the base of the fixture so access to the ceiling box is not blocked. Although if the only wires inside the ceiling box are for switch legs for the lights, then concealing the box doesn't seem like such an issue to me (what's the difference between this and any other lighting fixture that covers a box?). I don't know what code says though. Looks like the fixture requires a ceiling box for mounting (based on the holes shown in the left photo), which would make it pretty clear that there is a box behind it. If it were me, I would just hang them without creating a knockout. Again, I don't know what the code is and I'm not recommending you do this, but it appears that is how the fixture is intended to be installed.
 
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Old 01-10-18, 09:14 AM
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Looks like you're okay without a knockout for box access...

410.24 Connection of Electric-Discharge Luminaire.

(B) Access to Boxes. Electric-discharge luminaires surface mounted over concealed outlet, pull, or junction boxes and designed not to be supported solely by the outlet box shall be provided with suitable openings in the back of the lumi-naire to provide access to the wiring in the box.

Since that type of fixture is designed to be supported by the box, you don't need to create knockout. I was assuming you had the type that is hung with toggle bolts or screwed into ceiling joists.
 
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Old 01-10-18, 09:15 AM
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Originally Posted by mossman View Post
I believe the main concern here is that you would effectively be concealing a junction box by installing the fixture in the way you propose. Hence the reason it was recommended to create a 1-1/2" to 2" knockout in the base of the fixture so access to the ceiling box is not blocked. Although if the only wires inside the ceiling box are for switch legs for the lights, then concealing the box doesn't seem like such an issue to me (what's the difference between this and any other lighting fixture that covers a box?). I don't know what code says though. Looks like the fixture requires a ceiling box for mounting (based on the holes shown in the left photo), which would make it pretty clear that there is a box behind it. If it were me, I would just hang them without creating a knockout. Again, I don't know what the code is and I'm not recommending you do this, but it appears that is how the fixture is intended to be installed.
All these fixtures are being mounted on a light fixture box. I would never kount them otherwise because it would look ugly. I also think this is the safest way as the only thing touching the wires is the metal nothing else and that metal is grounded.

I didnt even know you could mount a fixture differently. Are you saying you could mount the fixture say 2’ away from where the box is and just run bare wires to the fixture? That doesnt sound good
 
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Old 01-10-18, 10:51 AM
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I didnt even know you could mount a fixture differently. Are you saying you could mount the fixture say 2’ away from where the box is and just run bare wires to the fixture? That doesnt sound good
What I meant is some strip fixtures are mounted without boxes at all, in which case you punch out a 1/2" KO, install a connector, strip and connect your wires. The only box is the wall switch. These type of fixtures are secured with screws (joists present) or toggle bolts (sheet rock). The cable is concealed and secured inside the ceiling like normal, but the wire is stubbed out of the sheetrock as opposed to having a box. All wire connections are made inside the fixture. IOW, the fixture serves as your junction box (similar to a recessed fixture--kind of).
 

Last edited by mossman; 01-10-18 at 11:09 AM.
  #27  
Old 01-11-18, 03:03 AM
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So yesterday I took my laser gun and checked the temperature of the LED strip fixtures as well as the 70 year old original fixtures.

Results were very interesting

- Basically the entire LED base, lights, the electrical fixture box averages around 65-80F
- The bulbs however are much hotter. The bulbs are around 180F where their bases including the light fixture box is as much as 150F!

I am beginning to think this 90C (200F) thing for LEDs are rather ridiculous. Furthermore, these wires are running like this for 70 years and nothing melted. I m not sure if its worth the effort of installing second junction box or drill ko or anything else to make this work with NMB wire. Although the OCD and gear head in me will probably do it anyways.
 
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Old 01-11-18, 05:31 PM
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IMO - Light manufactures slap the 90 degree requirement on everything so they cover their butts.
 
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Old 01-12-18, 10:03 AM
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I am beginning to think this 90C (200F) thing for LEDs are rather ridiculous.
I was reading through the thread, and was considering making that statement... but wouldn't want to suggest not following the manufacturer's instructions.

I believe the 90deg requirement came from a large number of enclosed ceiling fixtures with 2 or 3 60w incandescent bulbs in them, sometimes over-lamped to 100w, heating up the fixture and wiring for hours on end. The older wire insulation would over time dry out, crack, and fall off - which of course caused other issues. With lower wattage LED fixtures, it's certainly less of an issue these days.
 
  #30  
Old 01-15-18, 06:54 AM
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Added about 12 LED fixtures to my garage and basement. Did every one of them the right way (junction box etc). I did use about 150 ft of 12-2 wire because I wasnt happy with the state of the existing wires so I pretty much ripped every single cable away (except the ones I couldnt touch because they came in from upstairs from inside walls), box, and nail and redid 5 circuits brand new. All good so far. Thanks everyone for your valuable advice.
 
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