Can I mix AWG for a COB fixture if I am running wire 10 feet?

CobKits said:

CMR 18/2 cable is good for 300V and 5A or more. not sure how you can say its not acceptable for our application

Click to expand...

CMR = communications riser rated cable. It is not for plenum use, and is only "good for 300v and 5A" at 25c or less (depending on the manufacturer). It is not good to use in this application because PVC makes toxic fumes if there were a fire, and just because the insulation is rated to 300v does not mean you should get anywhere near 300v (the resistance of pvc drops at higher temperatures even though it has good dielectric strength at lower temperatures). It would be much better to purchase something that is rated to 600v, is sunlight, oil, and water resistant. Generally, cabling rated to 300v is for low voltage use only (100-120v rms or less) unless it has extra protection (strength member, and an outer protective jacket).

Lighting circuits (I'm talking about the wire inbetween the led driver and the led) are considered class 2 by the NEC, there are a lot of requirements in the NEC that rate different conductors and you simply should not use thermostat wire for class 2 circuits.

The NEC actually specifies what cabling types should be used.

This would be a much better choice for fixture wiring:
http://www.mouser.com/ds/2/418/NG_CD_FLHT_0311_Z_flht_0311_Rev_Z-273435.pdf

It is available in solid conductor as well if you absolutely need it.

excellent post! very informative

most all of the people using the CMR cable are using it in free air for parallel conductors below 50V and below 2-3A. so i definitely think its safe for this application though possibly not ideal. im pretty sure its a code violation to use jacketed cable assemblies in conduit.

I think the appeal of CMR is that not only is it 300V rated but it is one of the more robust commonly available cable assemblies at the big box store. for those running parallel the 18/2 solid is an elegant solution that is a good fit for the holders as well

ill crack my NEC and look at the class 2 wiring references. if i recall all those old fluro fixtures were using 16 ga THHN between the ballasts and sockets, but i beleive THHN ins also PVC jacket.

the ETFE jacketed cable is probably at least as toxic in a fire. all of the fluorine-based plastics like ETFE and PTFE release extremely toxic HF gas when combusted

CobKits said:

excellent post! very informative

most all of the people using the CMR cable are using it in free air for parallel conductors below 50V and below 2-3A. so i definitely think its safe for this application though possibly not ideal. im pretty sure its a code violation to use jacketed cable assemblies in conduit.

I think the appeal of CMR is that not only is it 300V rated but it is one of the more robust commonly available cable assemblies at the big box store. for those running parallel the 18/2 solid is an elegant solution that is a good fit for the holders as well

ill crack my NEC and look at the class 2 wiring references. if i recall all those old fluro fixtures were using 16 ga THHN between the ballasts and sockets, but i beleive THHN ins also PVC jacket.

the ETFE jacketed cable is probably at least as toxic in a fire. all of the fluorine-based plastics like ETFE and PTFE release extremely toxic HF gas when combusted

Click to expand...

Jacked cable assemblies go through conduit all the time. It is just much easier to pull single conductor wire through especially if there are bends. I don't know where you are located, but municipal electrical code can be stricter than NEC in some locales so it very well may be a code violation where you are.

I haven't really looked hard, but I was at the Home Depot last week and all the tstat wire I saw was from southwire and they make tstat wire rated for 150v.

PVC will melt and cause a fire way before etfe will, that's what I was trying to get at.

THHN is thermoplastic with a nylon sheath. You also have to derate temp to 60c (the diode array on my [email protected] is 60c) for use in wet or hazardous areas (garden).

You can recommend that wire all you want, I'm just saying it is a fire hazard in some cases. People do stupid shit man.

Oh and etfe is super safe

http://www.vector-foiltec.com/texlon-etfe-system/fire/

Forgot to add this in my post

dstroy said:

I haven't really looked hard, but I was at the Home Depot last week and all the tstat wire I saw was from southwire and they make tstat wire rated for 150v.

Click to expand...

ive been using cerrowire which is CMR/CLR2 listed on the cable. i dont think the spec they sell for ts-atas demands that, youre prob right its sprinkler alarm cable mostly

it seems they are changing distributors. thanks for all the tips

CobKits said:

ive been using cerrowire which is CMR/CLR2 listed on the cable. i dont think the spec they sell for ts-atas demands that, youre prob right its sprinkler alarm cable mostly

it seems they are changing distributors. thanks for all the tips

Click to expand...

http://www.cerrowire.com/files/file/49223_CERRO_ThermostatLR.pdf

Yeah that stuff is 150v as well, they only have primary wire (automotive), sprinkler wire, and tstat in 18ga at my local Home Depot. I had to order wire from mouser.

dstroy said:

http://www.cerrowire.com/files/file/49223_CERRO_ThermostatLR.pdf

Yeah that stuff is 150v as well, they only have primary wire (automotive), sprinkler wire, and tstat in 18ga at my local Home Depot. I had to order wire from mouser.

Click to expand...

im not so sure of that, i think the 150V rating is for CM and CL2,CL2r and CL3R are 150V

cables marked CMR should be 300V@ 75C per NEC800 and have flame spread characteristics meeting UL1666 for multi-story installs

I'm gong to break some stuff down for people who might be reading along.

Class 3 conductors are 300v, class 2 are up to 150v. So cl3r is rated 300v. All the other ones are 150v.

The main difference between these conductor ratings is the insulation material, cmr is pvc. Cmp, or anything plenum rated (a higher rating) is insulated with something that either doesn't, or creates less toxic fumes than pvc when combusted.

A plenum is a space between floors through which breathable air passes, like an air duct.

Article 800 covers communications equipment which the NEC defines as comin from a communications utility circuit (like a fire alarm panel, or a building alarm, or internet, or telco, or hvac) to customer terminal equipment but it doesn't define what a utility provider actually is inside of the article, it's in one of the references and that defines a utility circuit as something coming from and can be owned by a utility company (like how the power company owns your meter, larger buildings have more complicated power arrangements.)

A little off topic: Conductor classes and ratings aren't the same as circuit classes for everyone who hasn't ever experienced the joy of the NEC. It will give you one answer on one page and something completely different on another.

I am very much enjoying this discussion.

dstroy said:

Class 3 conductors are 300v, class 2 are up to 150v. So cl3r is rated 300v. All the other ones are 150v.

Click to expand...

can you explain where this is in NEC? I can find definitions of class 1 and 2 and 3 circuits in article 800 but there is no mention of class 1 2 and 3 conductors in that section at least.

in any case our ballasts are not a class 1,2 or 3 communications circuit. i need to delve deep into article 410 and probably update my 2005 NEC handbook as ill bet there are more LED references in modern code

it appears per UL most of our drivers are Class 1 drivers (over 100W, over 30-60V in most cases)
https://www.1000bulbs.com/pdf/understanding-led-drivers.pdf
http://www.lightingassociates.org/i/u/2127806/f/tech_sheets/LED_Drivers_A_Practical_Understanding_for_Lighting_Applications.pdf

im trying to find code refs on the types of safety equipment required when a class 1 driver is used in a luminaire. so far all ive seen are disconnects

as far as wire type in luminaires, article 410 only says :"Luminaires shall be wired with conductors having insulation suitable for the environmental conditions, current, voltage, and temperature, to which the conductors will be subjected" (notes say see tables in 402 - where there are a ton of listings for "fixture" wire)

CobKits said:

as far as wire type in luminaires, article 410 only says :"Luminaires shall be wired with conductors having insulation suitable for the environmental conditions, current, voltage, and temperature, to which the conductors will be subjected" (notes say see tables in 402 - where there are a ton of listings for "fixture" wire)

Click to expand...

Yeah 402.3. I don't think they're strictly considered luminaires though, because it says right in that article that they can't be branch circuits and there are a ton of UL listed lights that you can daisy chain together. It also talks about the type of cabling you can use to wire it up AC, MC and another one I'm forgetting.

For now, it looks like we're concentrating on fixture wire which the NEC "doesn't consider to be a wiring method" lol.

Then we have to go back to article 100 and look at conditions of use. We're in a wet environment, so we have to derate ampacity accordingly unless the product data sheet says otherwise. And I'm full circle back around to I wouldn't use tstat wire.

There are other insulation materials besides ETFE that are suitable for this application. But I wouldn't want my breakdown temp to be anywhere close to 60c, since that's what temperature my diode arrays are @1.4A.

I don't have the newest copy of the NEC either, and I know that they shoved a bunch of stuff about LED's and drivers into the newer versions.

As far as cable markings go, the UL has a whitebook that I don't have. I requested it from them but who knows when it will get here.

@CobKits @dstroy @VegasWinner please continue with the communication of this type of info in your future posts. This is an area that needs attention (safety in general) here in diy land. Personally, i think the temperature ratings are what puts most tstat and other multi strands out of consideration for this application. Having operational specs in the 100C range for cobs, qbs probably a different story, also I solder to cob using holder might reduce the wires heat exposure enough to justify lower rated wire.

Again please repost this info it appears to me the discrepenancies in your posts are a result of trying to communicate over this forum and not a disagreement about electrical safety in general.

SSGrower said:

Again please repost this info it appears to me the discrepenancies in your posts are a result of trying to communicate over this forum and not a disagreement about electrical safety in general.

Click to expand...

i blame the code, lol

CobKits said:

i blame the code, lol

Click to expand...

For real lol

Nothing like government burocracy getting in the way of open effecient communication? Abudawahh?
My mind keeps going back to first opening up a rohs/ul certified chinese led how does a product get certed when the exterior trademarked printed label doest match the actual unit, its a good thing it doesent draw the wall watts advertised, you arent getting what you paid for and this is a good thing! great consumer protection on top of paying the "china price".......

I got my hands on the 2014 edition

Luminaire. A complete lighting unit consisting of a light
source such as a lamp or lamps, together with the parts
designed to position the light source and connect it to the
power supply. It may also include parts to protect the light
source or the ballast or to distribute the light. A lampholder
itself is not a luminaire.

table 400.4 lists flexible cords and cables and their insulation temps

402.3 lists different types of fixture wire, and their insulation types with thermal properties.

p 402.5 no conductor shall be used under such conditions that its operating temperature exceeds the temperature specified in table 402.3 for the type of insulation involved.

table 402.5 (allowable ampacity for fixture wires) lists max ampacity under ideal conditions for 18awg (stranded or solid) as 6A

p 402.6 fixture wires shall not be smaller than 18 awg.

p 402.10 fixture wires shall be permitted in (1) for installation in luminaires and in similar equipment where enclosed and protected and not subject to bending or twisting in use, or (2) for connecting luminaires to the branch-circuit conductors supplying the luminaires.

410.10 (a) wet and damp locations
Luminaires installed in
wet or damp locations shall be installed such that water
cannot enter or accumulate in wiring compartments, lampholders,
or other electrical parts. All luminaires installed
in wet locations shall be marked, "Suitable for Wet Locations."
All luminaires installed in damp locations shall be marked "suitable for wet locations" or "suitable for damp locations"

This means the entire luminaire assembly must be suitable for damp or wet locations, including the wiring.

What this tells me is that we can use the rating tables for fixture wire

From here, we take into consideration normal operation conditions of the environment and begin derating conductors (the reason to derate something is to reduce the chance of fire, or electrical shock)

Our environment is damp, not usually wet but it can get wet (from condensation) if you let humidity get too high inside of an enclosed space.

410.24 Connection of Electric-Discharge and LED Luminaires.
(A) Independent of the Outlet Box. Electric-discharge
and LED luminaires supported independently of the outlet
box shall be connected to the branch circuit through metal
raceway, nonmetallic raceway, Type MC cable, Type AC
cable, Type MI cable, nonmetallic sheathed cable, or by
flexible cord as permitted in 410.62(B) or 410.62(C).

Choose a flexible cord to connect the lighting assembly, thermostat wire isn't suitable from the led driver to the luminaire assembly. You can get flexible cord that is suitable, or you can mount the led driver onto the luminaire itself and choose an appropriate flexible cord to power the led driver.

410.46 Equipment Grounding Conductor Attachment.
Luminaires with exposed metal parts shall be provided with
a means for connecting an equipment grounding conductor
for such luminaires.

410.56 (E) Stranding. Stranded conductors shall be used for wiring
on luminaire chains and on other movable or flexible
parts.