I know we've kicked this around a few times already, but I figure some new information is bound to show up sooner or later.

Is there anything on the market that will 'upgrade' the temperature rating of conductors? I'm referring to situations where a Fixture, sorry, Luminaire is being replaced and the wiring in the ceiling box is an older 60C or 75C type.

In 'Your Old Wiring' by David Shapiro he mentions (box on pg 292) that in his other book he describes "a specialty product for upgrading their ratings" (temperature ratings of conductors)
Does anyone know what that would be?

Bill

Go to "mcmastercarr.com".
Look for electrical insulating sleeving.
catalog page 686.
That is what the book I have refers to.
I use it when I have to.

[This message has been edited by Redsy (edited 07-25-2003).]

Redsy,

Thanks!
Would this be an AHJ approved method for installing a newer fixture to older 60C or 75C wiring?

Is this a heat-shrink type of thing? Or if not, what would keep it in place?
[This message has been edited by Bill Addiss (edited 07-25-2003).]

They send that type of sleeving in some lights I've installed. Its only been about 6 or 8 inches long so it barely covers the feeders. The stuff is about 1/4 to 3/8 inside dia. so it doesn't stay in place on #12. It does protect the wire in the lights I've been into afterwards.

Most installers throw it away

In some cases, acrylic- or silicone-impregnated woven glass-fiber sleeving can be used to cover conductors in ceiling boxes where heat has hardened or cracked thermoplastic or thermoset wire insulation. Cover entire exposed/affected/damaged length of conductor, extending well past the point of undamaged material.

http://www.suflex.com/pdfs/AcryflexMR%20DataSheet.pdf http://www.varflex.com/NewFiles/varfprodline.html

Colored conductor identification may no longer be visible. If fastening is needed, consider Scotch#27 tape. Expect repairs to be time-consuming, fragile, dirty and tedious work.




[This message has been edited by Bjarney (edited 07-26-2003).]

Bill,
I've used it a few times, in an emergency, and every time, I wonder if it is a legitimate fix. I'm fairly comfortable with it though, it's inexpensive and it's good to have some on the truck, but it is indeed a second choice.
It is not heat-shrinkable. Slip it on back to the jacket, and the wire-nuts will prevent it from coming off. It comes in a range of diameters. If you buy some, note that it is sized based on bare conductor gauge.
If you want it to fit over NM cable with insulation, you'll need to order 2 or 3 wire sizes larger.

[This message has been edited by Redsy (edited 07-26-2003).]

So just to clarify (again), the temperature rating for the conductors is based on an external source of heat, such as a lightbulb, and not heating of the conductor due to the current flow, correct?

Is it possible to splice higher-rated conductors to the lower-rated ones, after shortening the lower-rated ones, and thus have less of a length to protect?

Also, are there any charts/statistics on the temperature based on the wattage of the lightbulb?

Redsy,

Yes, it would be nice to have an answer, but it seem like nobody wants to commit themselves.

Also, I would like to know if the requirement for 90C conductors is just a result of worst case testing conditions and is really not an issue in uninsulated cavities and spaces between floors. I have a feeling that is the case, (because of something I found years ago) but it would be nice to know for sure because many existing fixtures are identical to the ones sold now except for the warning label.

It just seems to me that this is a blanket cya situation for the lighting manufacturers and the 90C wiring would not be necessary in all cases. But because the warning does exist, the liability is passed on to the installer. Most customers don't want to hear that you won't change a simple fixture without replacing the wires. It just puts us in a bad position, it would be real nice to have more detailed information on the hazard itself and what legal options are available.

Bill

It seems to me to be a CYA for the installer also at least in the case of when they are supplied by manufacturer for a particular light. Of course that doesn't really answer your question of when they are used to retrofit.

walrus,

When they come with a fixture is there anything written anywhere that tells you what they are for and how to use them?

Bill

Its been awhile but I rarely read directions after all its just a light on a canopy. But yes I believe its says to slide the mesh sleeves over the feeders before connecting. I don't believe it said how long to have the feeders though and generally the sleeves don't cover the whole length of the feeder so what good are they?? In these same lights I've seen many wires with cracked insulation due to heat from fixture(400 watt metal halide). Some installers used them some didn't, some insulation failed(cracked) with them some without hasn't. Not sure why.

To me, the 90ºC minimum Conductor rating for supply wires is definitly _cya_ for the Luminare maker and the Luminare installer, along with the local AHJ!
I say this because with a normal Medium Screw-Shell base, one could use a Lamp size of upto 150 Watts. If the Luminare has 4 lampholders, that would allow 600 Watts of lighting power to be used in a relatively small space.
That will raise the ambient temerature at the point of connection to a really high level!
Continuous load time, plus frequent usage (like 4 hours a day, 365 days a year), results in Barbequed Thermoplastic!

Similar may be said for Ballast driven Lamps - especially for surface mounted Luminares.
Heat concentration is greater than the thermal conduction can dissipate, so much heat sinks through the supply Conductors.

To see if this is a valid point, perform a simple experiment.
Take a simple table light fixture (which has an open top shade), and install a 100 Watt A-19 Lamp in it.
Turn on the Lamp, and let it run for a minute or so.
With the Lamp still on, place a Thermometer above the Lamp. Any type of Thermometer will work
(some may prefer to use the ones intended for "back-door" use, but that's another subject and probably another forum! ).
After about 30 seconds, the Thermometer will be upto 80ºC - maybe more!

Advanced Experiment

Cut a 4"Ø hole on a piece of metal, then place it on top of the same table fixture - so all the heat has to flow through the 4" hole.
Now, with the same 100 Watt Lamp running, place the Thermometer across the 4" opening and observe the reaction!

***Be Sure To Shake The Mercury In The Thermometer Back Down Before Beginning Each Experiment!!!***

Simple formulas will describe the resultant heat produced (more like transfered) from an Incandescent Lamp's Filament.

Energy Transmission figure for one Watt would be one Joule per Second. This translates each Watt as heat crossing a surface, divided by time.
Specific heat capacity (heat capacity divided by mass) = Joule per Kelvin Kilogram.
4.184 Joules = 1 Calorie.
1 BTU = 1054 Joules.
105 Watt Lamp running for 10 seconds results in almost 1 BTU.

An example of heat transmitted to an open space:
150fc of light will transmit 8½ Watts per Ft². This would cover transmitted heat into a normal size room, and if the occupants produced 1 Watt per Ft² and the heat losses of the room equal upto 9 Watts per Ft², the room would increase in overall heat concentration by a factor of ½ Watt per Ft² per second.

To answer Thinkgood's question, yes this is referring to the Ambient Temperature of which the Conductors will be operating under. This may result from any source - including the actual Current flowing in the Conductors.
High operating temperatures require proper selection of Conductor Insulation and maximum load Current per instance.

Operating Enviroment constraints must be considered on all installations (which is constantly quoted in NEC Articles - and being the basis of Chapters 1 thru 9!).
The level of heat in which the Conductors will be subjected to in normal operation, is the Ambient Temperature.

Scott35

OK,

In an existing situation with older 60C or 75C wiring, (take your pick) I go out to buy a new builders' grade ceiling fixture that's identical to the one I have (but mine has years of paint splatter on it). I notice the warning label on it says must connect to 90C wiring. It seems I can't legally put this fixture up without doing something to the wiring system (and no one will officially commit to any remedy other than replacement). Does this mean I should be worried about the fixture that is already there? (identical to new one).

If this existing fixture is a hazard, is it because someone may have added insulation over the years or situation involving free air space or dissapation of heat may have somehow changed? Or has it been discovered in recent years that this fixture (and most others) is, or was not suitable for connection to the older wiring types in the first place?

Bill

Very good points, Bill!

Seems to me that the legacy fixtures have the same heat problems as the new ones, just that the new ones have the disclaimer label attached now (probably due to Manufacturers being sued for house fires!).

The potential hazard is, and always has been present, when a fixture incorporates a Medium Based Screw Shell.

150 Watt lamps can be easily installed to them, and even some 250 Watt "sun lamps".

120-130 VAC Medium Based Incandescent Lamps rated 0-150 Watts (some upto 250 Watts) come in commonly used Lamp packages, such as "A", "R", "ER", "PAR" and "T".
Some reflect heat away better than others.

Nevertheless, with so many various power ratings and packages available to the consumer, replacing a failed lamp with "Anything That Fits" becomes normal operating procedure.

There have been disclaimer notes on older fixtures - circa mid 1970's - which state lamp wattage maximum and package type. That may have been their "Transition" period into the 90°C minimum wire rating disclaimers.

Any one else got some input?

Scott35

Scott,

I'm thinking the recent warnings are more than an over-lamping issue, but with the amount of information we are privy to ... who knows?

I haven't noticed in awhile, but I swear that some of these warning labels said something similar to the following : (paraphrasing)

'WARNING: RISK OF FIRE' most wiring installed before 19XX is rated for ..C 'consult a qualified Electrician'.

Now, this doesn't really give much information or any instructions one way or the other, but it does state the possibility of a real danger (without giving any details) and effectively sheds responsibility to the purchaser/installer. It also infers that an installing Electrician should or must have some wealth of information on the subject.

Is there a way to get a report on how fixtures are/were tested and what the results were?

Bill

[This message has been edited by Bill Addiss (edited 08-02-2003).]

What About Heat Shrink Tubinng? Can You Put that over the wires?

Bill:

I would guess that somebody at the UL has the answer.

Relative to heat-shrink tubing, maybe a test would be to slide the tubing onto the conductors, and if it shrinks, that means the lamp is too hot?

A_Sparky,

Some things shouldn't be for us to decide. We don't have the ability and resources to test and evaluate things we think might work. For the benefit of the customer, and our own liability we have to be sure.

I'd like to hear that there is an acceptable fix, or that the problem, in most cases is not severe, but so far I've come up blank.

TG,

Yes, I'd expect that UL does have the answer.
... I wonder if they take requests?

Bill

Short lengths of fiberglass sleeving have been supplied with some light fixtures in England for years.

They don't always allow enough if the cable enters from the far end of the fixture though, and you can bet that on DIY installations nobody will go out and buy a longer length.

I am confused here, (not unusual) no matter how much heat shielding/insulation around the conductor, given enough time the conductor will reach the temperature of the surrounding environment, perhaps short a few degrees from the heat that travels back the conductor towards a cooler environment.

The only thing I would think that would work is the silicone sleeves as they could actually replace the existing insulation.

How would you handle the transition from the old to the silicone?

The suggestion about sleeving the over-aged, hardened/cracked vinyl/rubber wire insulation is for a retrofit case only. This is meant as a reasonable fix where a little old lady with bad eyesight has put a 200-watt lamp in her kitchen so she can still work. It is not difficult to obtain lengths of ~3/8-inch sleeving from motor-repair shops, with the intent of fully covering all accessible individual conductors in the typical 4-inch round box. If the existing wire insulation has hardened and cracked but is/is not separable from the 12-14 gauge conductor, it should be entirely contained by the sleeving too. Thsi approach assumes that the condutors are undamamged. This approach assumes that the conductors are undamaged—that only wire insulation has deteriorated to an unacceptable degree.

Such a practice is in no way “approved” by an enforcement hierarchy, but once you’ve opened an old ceiling box, it may be a reasonable alterative to tearing up wallboard to access attic wiring. It is a compromise solution, and one’s best judgment has to be used, for there are too many unknowns until the box is opened. Experience, reasonable caution and common sense have to apply. If wire insulation is too far gone, wholesale changeout of wiring external to the ceiling box is certainly in order.

Offhand, my guess is that plain-vanilla polyolefin heatshrink tubing would have poorer aging properties than acrylic-/silicone-glass sleeving.


[This message has been edited by Bjarney (edited 08-03-2003).]

On an other note:

What is that donut of fiberglass wool in the canopy used for? Some old fixtures never had this sort of thing. Although they may have and people just ripped them out and tossed the pad away.

When I moved in here, I had to take down the existing defective light fixture in the bedroom. I was graced with the presence of a wad of CHARRED fiberglass wool stuffed up INTO the ceiling box and around the wires.

I'm not kidding -- this stuff looked like a singed steel wool pad!!!!

After I pulled this stuff out, I stuck my hand into the box to bend the wires down so I could undo the wire-nuts, I heard that telltale crackling sound.....you know the one.

I look at the fixture canopy and the two bulbs still stuck in the lampholder . Sure enough -- two 100 watt bulbs were plugged into that thing. *SEEETHE*

The rubber pigtail socket that I put in there as an interim (until I replace all the cabling -- damaged because of overfusing and just general rot) because I was too afraid to move the wires any more is still dangling there....but with a 60 watt lamp now.