ECN Forum Forums Photo Discussion Forums Violation Photo Forum "Outlet Strips" Am I wrong here?

Joe-

Every office I work in has many of these "outlet strips". One or two under
every desk. When I tell the office managers that these strips are no
substitute for properly wired, permanently installed outlets, they nearly
throw me out of the place. The users cite the "UL" on the device and the
fact that it has a circuit breaker in it as an OK for using them. Am I wrong
here?

A few years ago I found over 75 of these, many of them daisy chained, in the
911 dispatch center for a fire department in a major city!

Bob



[This message has been edited by Joe Tedesco (edited 01-24-2003).]

I would be incline to agree with ya, however , with the 15 amp overcurrent device in the strip, the manufacturer has covered himself. This also would be the weak link and wouldnt take a genious to fiqure out why 6 office cubicles are going "dark" at the same time. One of those " do it right the first time" deals applied with a little common sense and work ethic. No ??

Page 112 of the 2001 UL White Book discusses these "Relocatable Power Taps". They are not intended to be installed as a permanent solution to fixed wiring, nor are they to be "daisychained".

O.K.,

I'm confused here. Please help me.

Does this mean that Relocatable Power Taps are illegal?

I mean, hypothetically, if I have a duplex in the cubical wall at my desk and I have a laptop power supply, a desk light, an electric pencil sharpener, and a clock/radio loose on the desk top, must I install a second duplex? The things on my desk are not fixed.

Load is not an issue. . .looks like 200 VA total for my cubical.

Now, if I had fixed appliances at the desk, say a light fixture screwed to and mounted in the cabinet, a pencil sharpener mounted in the countertop like a high end food processor, a clock radio built into the cubical wall, etc., then I might argue I had to have fixed wiring for them, . . .

The UL White Book does not use the work "temporary or permanent" when describing the use for Relocatable Power Taps, thefore, the duration of its use is not specified.

Hypothetically, if I set up a desk on the side of a cubical partition that did not have an outlet, and then I drapped a relocatable power tap over the partition to my desk from another cubical's outlet, then I understand this to be a substitute for fixed wiring.

Inquiringly,

Al

That is the same question I posed with my post about the use of extension cords on one of the other forums - "When is temporary not temporary." I think it's in the General Discussion forum.

I normally use use these stupid things out necessity. Here at work, I have only one duplex receptacle in a doghouse under my desk.

I have two such power strips:

First one powers my computer terminal's CPU, monitor, speakers, printer. That's all one strip.

The second one shares a triple tap (more on this in a second).

This second socket strip powers my wall clock, my two radios , and the transformer for the speakerphone's power supply. I don't use both radios at the same time - the reason I have two is my original one has a cassette player and the other was a Christmas gift (it's a CD/radio combo so I could play my CDs at work).

Now onto the subject of the triple tap. The other item plugged into the tap is an extension cord powering my pencil sharpener and my time-stamp clock.

So in total, I have 9 appliances plugged into a Nema 5-15 duplex socket.

Most of these devuces are very low wattage and don't get used regularly. Still, I wouldn't mind a second pair of outlets....but by the time I found out about it, the floor was laid down, it was too late.

Sure, there are other around the room, but they're all covered by boxes of merchandise, One of these powers my box fan at the far end of the room (through a heavy-duty 14-gague extension cord with a right angle plug because the fan's power cord was not long enough to reach it! ).

I haven't blown a fuse...yet.

This is nothing. I've seen other people's desks where they've got triple-taps plugged into the outlet strips because they need more sockets, more sockets!!!!

And this is in a 1960s-vintage (modern) office tower (#1 Chase Manhattan Plaza in New York City's Financial District) that's supposed to be up-to-date -- entire floors getting gutted and renovated for new tenants who move in.

We seem to be very short on wall sockets!

This is of course subject to interpretation. But here in NJ, commercial buildings get regular inspections by the local fire marshal or state fire marshal. The rule all over (and I've worked all over the state) is that extension cords are not allowed but power strips with a breaker are.

I've been through lots of fire inspections in many towns where this was the rule and through state health department inspections where this was also the rule.

Sounds about like every place i have ever been in. Last week the engineers and drafters called maint to their upstairs offices because power went out. They have a fridge, microwave, coffe pot, several radios, lights and pc's all running off the same breaker. No you lost power really i wonder why. Told them that they need do with out some stuff or put in request to maint to add some dedicated circuits for there appliances. which i think is a joke there are 2 fridges and 4 microwaves at the bottom of the steps to there offices.

I've seen this issue beat around the internet repetitively, somehow it is felt that it falls in our trades lap.

I say this is wrong.

One cannot even begin to make an educated guess (at least in the residential market) as to where these may be used or for what duration.

I also do not see many large discalimers on strip packaging that would deter marketing.

If in fact there are millions of these strips illeagally used per NEMA, UL, or whatever watchdog is to sanction thier usage let THEM deal with the issue.

The only area in the code that addresses temporary wiring is Article 305-3, which identifies that temporary electrical power and lighting shall be permitted during construction etc. for 90 days. It also addresses christmas decorative lighting (those of you who leave your x-mas lights up all year long are violating Article 305-3 in the NEC)and similar purposes. Lets face the facts here; no one wants to spend around $500.00 dollars per circuit to have installed the proper feeds to office partition systems. As we all know typical office partition systems come with the capability to have a full round robin circuit setup. We as electrical contractors have to competitively bid these projects in the real world and to get this work and we design the systems tight. All to often I will find that a partition power feed has all three hot leg connections on one branch circuit. Just about every computer has a power strip on it. Do you remember when the old computers (for the most part)had a connection for monitor power and you didnt need a strip? All too often money talks and is the bottom line. Computer manufacturers know that there are at least four devices (Monitor, Printer, Speaker power, spare for one misc device)that will need power and it sure would be nice if they included plugs for the equipment on their computers but it would cost more money to do this and buyers would rather save money then see the potential dangers in using plug strips. So now we are back to square 1. Plug strips are not so bad but what really bothers me is when office employees plug in floor heaters on these strips!!! Now we are talking dangerous. What do you think?

Sparky:

I wouldn't say it's the electrician's fault where the outlets are placed. Don't most ECs have to follow a blueprint drawn up by the architects?

I saw some the blueprints for some of my company's floors when they were being refurbished and they included drawings for light fixtures and wall sockets/switches.

That being said, I wouldn't mind a 10-gang box next to my desk instead of this rat's nest of wires.

On a side note, I've seen a few of these power strips that have lost the grounding pin on the male plug...and I had one where the switch eventually fell to pieces (literally) - the rocker broke off the workings. In fact the strip in question was a metal one with a neon-illuminated switch, exactly like the one Joe T. posted!!!

Seems like UL labels these days are about as easy to get as a USA postage stamp.

[This message has been edited by SvenNYC (edited 12-11-2002).]

Hey, those recepticals are mounted soley by the center screws! I thought that wasn't allowed anymore.

Seems like a double standard to me. Electricians are not allowed to mount recpticals in this manner but UL approves a consumer product that does?

Wow! Good eye, Gus!

I took one of those apart and there not "real" recepticals per say. It is a plastic block shaped like them with the 3 wires attach at the beggining and then there are 3 "buss" bars that provide the 3 conductors

However the one pictured (and the one that had the switch fall apart on me) has real receptacles that theoretically can be replaced if they crack or wear out. You can tell because of the middle screw that Gus mentioned.

The receptacles are hard to find in the aftermarket though...I saw a lot of them at a job-lot store. (Obviously they probably haven't sold them in years )

The wiring to these with the individual receptacles is backstabbed instead of attached to screw terminals. That should say a lot....

The difference between the sockets in these strips and the ones we put in walls is that there isn't a back-strap with plaster ears that bolt the device to the box (because of space concerns).

Rong Feng (http://www.rongfeng.com.tw)in Taiwan makes the receptacles:



[This message has been edited by SvenNYC (edited 11-15-2004).]

I don't understand this obsession with outlet strips and extension cords. The user must be assumed to be completly ignorant. If it's possible to plug something in, it shall be safe to do so. You can't expect the user to know that there is a limit to how much current can be taken from a outlet strip, let alone calculate the connected load.

(Home made extension cords often pose a significant risk of fire and/or electrocution, but if you are stupid enough to mess around with something you don't understand you deserve a Darwin Award.)

I don't see any problem with daisy chaining outlet strips. Try to find a computer connected directly to a wall socket: I doubt there are more than a dozen in the whole world Outlet strips are almost always used. Adding more wall receptacles won't change that: They'll just sit there unused, with a outlet strip on the floor below...

We had this secretary at the railroad that would have made some kid a good gramma. However...
She was in charge of lunch for a special "do" we had going at the 'road, and couldn't understand why, with 2 of those 100 cup coffee pots, four crock pots, and who knows what else going, kept popping the curciut breaker.
When told that there was no way any single curciut was going to handle that load, her reply was,
"but I plugged them into a surge arrestor"
(with surge arrestor being her term for outlet strip)

TW

Until the late '70's, such outlet strips were common in UL's own lab- yet none were listed by UL.
UL was in a quandry: these things were obviously useful, but there was some concern as to how the standards would be set. Several basic NEC issues arose:
-what kind of mounting was proper?
-Did the use of SO cord and a plug conflic with the NEC prohibition on the use of temporary methods in place of permanent wiring?
-What about the NEC stipulation of 90 watts per plug for load calculations? The limitation of the number of receptacles per circuit in non-residential applications?

This was not entirely new ground; UL already listed many outlet assemblies that had been listed as components of appliances.
Eventually, UL decided to consider them as "temporary power taps." As such, UL determined that there could be no easy way to permanently mount the device- or it was obviously intended for permanent use.

Since then, technology has advanced to the point that power quality is very important for many things, such as computers. We have also seen entire families of appliances that are intended to be used together (TV/VHS/Stereo, Computer/printer/monitor, etc.). These outlet strips have become a very easy way to incorporate surge suppression.

Can anything be mis-used, over-used, or mishandled by fools? Yes. No code change will ever protect against such things. Nor will we ever eliminate the temptation to cut corners, plan poorly, or failures to predict future needs.

A lot of things would be nice. It would be nice if applianced were made to plug into each other; it ould be nice if enouch receptacles were installed in appropriate locations; it would be nice if desks had their own power distribution centers built in. It would also be nice if management would admit that one microwave isn't enough for 100 people, that setting the thermostat at 60 only means the secretaries will smuggle in space heaters, etc.

The American way is to let the individual, through market actions, make his own informed choices. We, in the trade, have to not only try to anticipate the customers' real needs, but also to educate the customer as to the importance of his decisions.

Let's be careful that we don't let "ideal" or "perfect" become the enemy of "barely adequate."

How 'bout wiring in more of these



(From Hubbell)

You will never get rid of these strips. All you can do is limit the number of outlets they can plug these into. eg installing only 4 outlets on a circuit instead of 8 outlets. Of course it is a very rare owner who will assume that cost. All we can do is give the customer a safe instalation per code. What they do with it afterwards is thier problem.

[This message has been edited by nesparky (edited 12-16-2002).]

good post John.

i wonder if these strips have had such a low incident of hazard as to warrant little attention?

Interesting that this topic comes up.

This is that I do for a living.

How many outlets per cube, how many curciuts???

As you all knoe most partitioned cubes come in panels. 1ft to 4 ft. each panel can have as much as two receps. but most cubes are small and any "returns" aren't powered witch leaves a very small amount of wall space....
But I digress. If we are installing brand new Herman Miller, the cost of an outlet power strip built in is 165.00 that gives you two duplexes per side.
So most installed only get one per cube.
three curciuts max per whip (a/b/c) three phase. each whip cost 185.00
So as you can see geting electricty to the whip is not the issue.

Also the service panels are problematic.
We had one building that required four panels to be install just for the cubes.
In existing buildings without such..is very expensive....

But lets talk old used cubes without whips.
Very popular these days because of the .COM collapse used product is very easy to get, but hard to install correctly.

Having an electrican hard wire greenfield yo a duplex box is very expensive times several dozen cubes.

We whould blame the manufactures of the cubes for charging outlandish prces and being so quick to discontinue lines of product so quickly.

just my thoughts.


[This message has been edited by RandyO (edited 12-17-2002).]

Protecting electronic equipment is very necessary, and this is one way of doing it. The problem arrises when they are plugged end to end or in a snakes nest under the desk where the cords get abused.
Surge protection receptacles are available, but they are expensive. A duplex TVSS receptacle lists for more than $63.00.

Randy O and kale
The NEC does not use cost as a safety consideration. A correctly wired and safe installation has inherant limits on the amount of load placed on any one circuit. The continual misuse of these strips, because owners/ managers and others who are primarly concerned with saving a dime, has caused problems for the users, and maintence people for a long time.
It will not change until those in the business educate the owners/managers about the safety risks. Those who help these "save a dimers" get by are part of the problem. If it costs a lot to retro fit a cubicle layout properly, that cost should be part of the bid.

excuse me if i simply barge into this thread guys, you see the former thread seems to have been deleted in the middle of my post, quite irritating.......

Joe this article takes the cake.

the very same people who would allow x-cords and power strips are now putting then down...

our tax dollars at work eh??

2 million in 8 years? does anyone else here see this as a major failure of the NRTL's ???


excuse me, i have not read any newdiclaimers on packaging here, or perhaps i have missed the 1/16" print????


i see, and AFCI's are what in realation to these stat's? can you say "wag-the-dog" ??

the scapegoat rears it's ugly head.....

Yes Joe,
same team.

maybe we just differ in tactics a bit.

do you find irony in that we discuss the safety issues of x-cords here, while most of America strings them on thier homes for Xmas?

i do....

Joe,

Is it a violation to use this type of equiptment as surge protection of typically valuable merchandise?

Many folks ask for quads and even two quads in TV and computer locations, they are not protected in the event of a surge.

Then we get into protecting the panel, I recomend surge protecting devices to everyone as a rule of thumb.
High voltage, as well as all low voltage, especially low voltage.

And, this way the manufacturer with his lifetime waranty upto whatever $$$ amount is the liable party.

NonLinearLoad.

We will be interested in hearing about any specific DOCUMENTED cases of a failure of a LISTED outlet strip device, or cord assembly that resulted in some kind of damage or loss of life.

It will be interesting to see the documentation that will be provided, given the numbers of these devices in use around the United States.

PS: We don't want to hear any anecdotal stories that relate to modified, or home made devices.


[This message has been edited by Joe Tedesco (edited 01-05-2003).]

If 'ya ask me, it would be cheaper to install regular outlets. (Excluding cable/conduit/wire, buy in bulk.) Figure 15 amp(Office equipment can survive on 15 amps.) outlets cost as little as 40cents, 3-4 gang boxes cost about $1.50 ea. Three outlets ($1.20) + One box (1.50) = about (2.70) Consider these basic breaker strips cost about $4.00 each, you just saved about $1.30. About 50 cubicles to an office (if it's this type of office! Still.) 50 x $1.30 = $65.00!! Go buy a new chair or something! But then again, if it protects from surges, replace $0.40 with $5.00 and the $4.00 strip cost with $7.00! (Not cheap around here!) Do that later. Still, price it out!

electrikid, Your math is a bit off IMHO. At 180va per device you are going to need to take into account all of the added distribution equipment, service size, number of panel board and breakers. Branch circuit distribution and on and on. Show me a contractor who prices just the install (T&M) on one receptacle at less than $40.00 or so and I will show you a contractor who is losing money or on the margin.

Anyway interesting topic and brings to mind an electrical inspector who would release a "temporary final" but would not release the final until all of the equipment, pc's,printers etc were in place and all of the branch circuit panel board load calcs matched the actual load served... This inspector made electrical engineers cringe!
( Steve, You know who I am talking about.... If your out there reading these post's I miss ya! Hope your enjoying retirement.)

[This message has been edited by kentvw (edited 09-08-2004).]

Any self respecting EC that installs 40 cent outlets in an office building should think about selling power strips!!!

Yes, strips are all over, I find them every day, they are usually hiding for TCO or Finals, but if & when I come back (CO or re-inspect) they magically appear. THe EC puts quads in for desks, the cubes have factory harnesses and most have 3 hots, 2 neuts and two grounds, but those strips always show up.

One guy said, "I have a heater, calc, PC, monitor, radio, clock, coffee warmer, charger for lap top, wireless hub, and a few other things" "I need the 3 strips" Heck, he had a 20 amp circuit, and 2 duplexes in the cube, What do I say????

John

"If 'ya ask me, it would be cheaper to install regular outlets. "

But these Surge Strips are not regular outlets. They protect against surges and spikes in the power. Consider the cost of replacing a server, or all the PC's in a building if there is a nearby lightning strike, and it is not cheaper to install regular outlets.

So, what is the situation with a lab bench that has outlets built into it, all connected to a building outlet though single 14 gauge SJ cable? Some posters in this thread argued for desks and the like with recpts built in; is this different from that? Is this any different from outlet strips?

Thanks for telling me guys. Sorry, I forgot to add up all of that stuff, breakers, cable, ect... I guess your right, these things could save all of your equipment. (Computers, printers, monitors, fax machines, ect.)

Since my last post, I have been called to several sites to replace the outlet strip/extension cord assemblies with recognised permaent wiring assemblies ("plugmold").
I find it interesting that UL isn't concerned about the possibility that you might use plugmold to put 'too many receptacles' on a branch circuit.
In many of these sites, plugmold is used, because there is a desire to not disturb the asbestos in the walls.
I also note that the various plugmold products do not provide the surge protection often associated with outlet strips. As some plugmold is set up as a multiwire branch circuit, I consider surge protection very important.

It sure is a lot easier to find a violation, than to solve problems.

As a footnote, I see no justification for the ways we apply code to the numbers of receptacles on a circuit. Nor do I see an easy way for code to address this 'design' issue.
While too few circuits is often the cause of problems, and complicates troubleshooting, there are many times when we know what a receptacle will be used for- and the load is known to be trivial.
There is no substitute for good design. Yet, I doubt that we will see every desk have its' own two circuits!

The first post reminds me of a sewing shop in NJ. It had about 30 6Amp sewing machines plugged into about 10 daisy chained outlet strips! One of the strips appeared to be homemade, with a cardboard box with 8 outlets/4 duplexes and a real regular service panel circuit breaker. (Don't ask me how they connected it.) And one of the strips was industrial sized!! I mean big! About 30 outlet big! Plugged into a 6-outlet version, into a gemtap, plugged into an 8outlet strip, into a sixoutlet strip, and finally through the cord to the regular floor mounted outlet! And one more thing, I've seen these strips wired w/ 18 gauge cord. I know 18AWG copper can't carry 15 amps. How do they manage to make this work? (I know this because one time I fried one's switch and ecide to take a screwdriver and pair of wire cutters to it.)

Let's face it. It is not politically expedent to crack down on the strips in any meaningful way. Government works because, in some way, the people allow it to. If there have been over 2,000,000 recalled, how many do you suppose there are in use? Make them illegal and try to take them away and you have a huge number of people united against one policy.
I have 3 of them under my computer desk at home. I don't have 18 devices but I do have several "wall wart" transformer power supplies that occupy the space of several outlets for a load of 20 watts. Until someone makes a practical device/panel to meet the needs of the modern computerized office, the strips are a reality.

I would be interested to know if that one is actually listed. It doesn't have a number on the box and it doesn't say it is listed. What does the strip have on it for marking?

- - - - - - - - - - - - - - - - - - - - - - - - - - -
Charlie Eldridge, Indianapolis, Utility Power Guy

I am a bit perplexed that as long as this thread has been posted, no one has actually answered the questions posed in the first post.

First of all, this "strip" appears to have been approved under UL 1449 according to the picture supplied. The scope of this standard covers "transient voltage surge suppressors (TVSS) intended for permanently connected, cord-connected and direct plug-in applications, designed for repeated limiting of transient voltage surges as specified in the Standard on 50 or 60 Hz power circuits not exceeding 600 V."

So... yes you can use these devices permanently.

However, if the device was approved under UL 1363 "Relocatable Power Taps" then the scope of the standard says that the equipment is designed for temporary use.

Now to get to the "daisy chaining" issue. As the scope (see above) of 1449 indicates, this type of device is only approved for "direct plug-in applications" (i.e., into an approved permanently wired receptacle). In July 2004, UL 1363 was updated to specifically prohibit daisy chaining. This standard now says, "A cord-connected Relocatable Power Tap is not intended to be connected to another cord-connected Relocatable Power Tap."

In the Mar/Apr 2002 issue of IAEA News, this question was also addressed in the UL Question Corner. http://www.iaei.org/magazine/02_b/02_b_ULQuestionCorner.pdf

On a related note, UL in its spring04 electrical newsletter discussed the safe or should I say unsafe use of RPTs in healthcare occupancies. http://www.ul.com/tca/spring04/taps.html

As has been pointed out in several other posts... the real problem is not the "permanent" use of these devices... it is the overloading of the device. I am sure that many of you are aware of the requirement in NEC 210.21(B)(2) essentially says that outlet devices must not be loaded beyond 80% of their capacity. OSHA has a similar requirement in 1910.304(b)(2) that while not as specific covers the same usage issue.

"Strips" like the equipment discussed here are outlet devices and therefore users must be "trained" if necessary in how to properly use the device. In workplaces in the US, this training is required (under OSHA 1910.332) to ensure that unqualified persons are informed of safe electrical work practices that "are necessary for their safety." This is obviously a requirement for the employer and not a contractor.

However, we can't police the stupid things people do in the privacy of their own homes.

Joe... I wish I always had my camera with me. I have personally found numerous examples of these devices that have failed. Listed and labeled devices that have been abused by the user. I have two photos, the best one I actually found in .... hold your breath... a fire department. No dispespect meant to any fire inspectors that may read this post... but, it has been my experience that fire inspectors have a thorough understanding of NFPA 101 but minimal understanding and training in NFPA 70.

Sorry about the edits, I was kicked off the server twice while composing this post.

[This message has been edited by safetygem (edited 11-09-2004).]

Great response, Safetygem!

UL standards are not often actually seen, are pricey, etc. This makes it hard to have an informed opinion. If I had my druthers, UL would post them on the web- for free!

Which brings up a point that often gets overlooked: darn few thing are ever submitted to UL composed of materials designed for the intended application. Rather, UL takes the assembly, and evaluates it to see if it measures up. They really don't care if the thing is made of peanut butter!
So, it is conceivable that the infamous handybox/extension cord combo would, if submitted, pass UL's tests. Absent access to the UL standard, we really don't know.
I can say, with a reasonable degree of certainty, that not a single "outlet strip" made would pass UL tests for "pendant" devices- and OSHA tries to apply NEC "pendant" rules to such made-up assemblies.

From Safetygem





(Pictures re-added to thread)

[This message has been edited by Webmaster (edited 01-22-2005).]

If you have customers that ask about protection instead of using power strips, I have found that installing GFCI's have the best protection. Since I have installed GFCI for my entertainment center ( 3-VCR, satalite dish and Teevo and TV) I have not lost a single electronic from power surges. I live in the Blue Ridge mountains and we are constantly hit with power surges. I also installed a GFCI for my computer and that has not lost a modem in 3 years. My neighbor on the other hand has replaced his modem 3 times in one year. Just my 2 cents worth.

What happened to that strip?

John... I agree, it would be nice if the UL standards were free. While they don't give up the goods without cash, they do give a sample and provide the information in the "White Book" on the website and the entire scope of all of their standards. This at least gives the inquiring mind a starting point for determining whether or not equipment is being used according to the listing.

ComputerWizKid... this strip was found in a fire department captain's office. The office had poor heating, so... he used a portable heater, had a coffee pot at one time and a variety of other appliances plugged in to the device. The most surprising thing to me (or maybe not) was that the device was still in use despite the obvious damage. Before snapping the picture I actually unplugged two other devices from the strip to show that every plug had been overloaded at one time or another.

Can we really expect the average person to understand how to safely use these devices if "professionals" that are trained to recognize hazards are unable to safely use the equipment???

As I implied in my earlier post, I don't believe that there is anything inherently unsafe about these devices. The problem is that people don't read directions. They also don't have a clear understanding of the hazards associated with short (no pun intended) cuts and electricity in general. I do a lot of electrical safety seminars and am continually amazed at the level of understanding (or misunderstanding) most people have of electrical safety issues.

Safetygem posted:
Wow - a municipality ignoring a safety code? That'd never happen!

Mike (Trumpy)- you left too soon!

[This message has been edited by DougW (edited 11-11-2004).]

I still don't understand what happened to the outlet strip posted by SafetyGem. Every outlet strip I've every seen has a circuit breaker built into it. (I beleive I can see that off to the right in the photo.) So, unless the breaker was defective, it will open if the load exceeds the load for which the assembly was designed. Therefore, there should never be more than a momentary overload on the receptacles. Also, the branch circuit into which the assembly is plugged should be protected by an OCPD rated no more than 20 amps, which is only a slight overload above the 15 amps for which the receptacles are designed.

How then did it get burned like that?


[This message has been edited by SolarPowered (edited 11-11-2004).]

OK... I'll take a shot at explaining what I think happened... (someone else might be able to offer a better explanation). Fundamentally what has occurred is an arc-fault.

Conventional breakers usually trip before the insulation can be damaged by excessive temperature, and the time of the response is designed to prevent a circuit overload. However, arcs are usually fairly short in duration and breakers cannot detect the fault.

Yes, all RPTs and TVSSs are equipped with circuit breakers (at least all that I've seen). But, because of a bimetal heating effect that happens during an arc-fault, conventional circuit breakers may never trip because the RMS current level associated with the intermittent rise in current could be considerably less than the RMS rating of the breaker.

There are two basic types of arc faults and circuit breakers usually cannot detect either. You can have a high-energy arcing (parallel) or high-resistance (series) faults.

High energy are caused by insulation failures between conductors of different potentials. Once the insulation is compromised, arc heat melts the actual conductors (6000+ degrees C) creating a new path which causes intermittent arcing. A circuit breaker may not trip, because, a magnetic breaker requires a minimum peak current, and a thermal breaker requires a minimum duration of the peak current.

A high resistance arc fault usually happens because a layer of oxide has formed at the conductor connection points. This "corrosion" creates a high resistance path that generates heat. Broken or damaged conductors can also cause this type of arc fault.

This is really the reason why AFCIs have been developed and required by the NEC on some circuits. I didn't take the strip apart to identify the actual cause of the arc fault damage... in my job, I don't have to identify the cause of a hazard, just that the hazard exists. I let one of you (contractors/electrical engineer) figure out the cause and the solution. Talk about passing the buck!

So that you don't think I'm an electrical engineering genius here... I liberally paraphrased this answer from an article on AFCIs in the Feb/Mar 2002 issue of the NEC Digest.

As I said at the beginning, someone else may have a better explanation.

Feel free to take a stab at it...

Safetygem, thanks for your extended answer.

I'll take a shot at the "Reader's Digest" version of it: It's a cheap outlet strip that doesn't make very good contact, and it overheated because of the lousy connections.

Or, in other words, even though it's supposed to be good for 15 amps, it's not.

Is that a reasonably accurate translation?



[This message has been edited by SolarPowered (edited 11-15-2004).]

That's a great "Reader's Digest" explanation.

The only thing I would add, is that while this strip was definitely a "cheap" (probably under $10 US) strip, I have found much more expensive devices with similar failures. It was probably more prone to a fault, but, the fundamental principal in my earlier response would also apply to the fixed outlet that this strip was plugged into... I have seen those with similar damage because the $50+ circuit breaker on the branch circuit did not detect the arc fault.

Misuse and abuse. It really ticks me off that people can't follow directions.

That's the point where you're losing me. It seems to me that misuse and abuse didn't have anything to do with the problem. Rather, it appears that the problem is due to a penny-pinching design of the outlet strip that results in it not being safe for its intended application; that is, supplying power to six plugs with a total load of less than 15 amps, on any combination of the six receptacles.

Am I missing something here?

Boy... you're tough to convince SolarPowered.


Every time I have found a strip in this condition, it could be directly attributed to user abuse. These strips are intended to be used with low wattage/amperage equipment. For example, I have never come across a damaged unit that was used for computer or other similar office equipment.

But, when you plug (and this is a real life example) a microwave, refrigerator, toaster oven/or toaster, coffee pot, and a portable heater, all into the same strip... bad things happen pretty quick.

Heck in the scenario I laid out, the portable heater alone (usually rated at 1500 or 1800W) either takes the strip to its intended load or way beyond (80% of 15 amps = roughly 1440W). See, NEC 210.21(B)(2)

So, even though the strip may be designed for 15 amps, when you load it with 30 amps... and you have the bimetal heating effect occuring... fire happens, circuit breaker doesn't trip... people choke on smoke.

Convinced??? Anyone else want to help me argue this point?

But what if the breaker was rated at 15 amps and the wire was 16AWG rated at 13 amps? And most of the so-called, "surge protectors" are just circuit breakers, no surge protection!

I think usually to handle the "surge protection" three MOV's (metal oxide varactor) are soldered across the cord leads. They look like a disc capacitor. And do little more.

That's exactly what it is, Physis.

In addition, some up-market models have a little circuit for noise supporession, consisting of a few capacitors and a toroid.

The cheapest of the cheap are just a box with six outlets molded into the plastic case. They may have a circuit breaker but there is no surge protection or noise suppression.

I actully like the coil and capacitor job. It makes a second order (12 db per octave) filter. The smaller the coil the higher the frequencies it operates on though. The little coil ones can miss a lot of slower noise that has more energy.

Hey Joe... any reason you took out my picture of the fried RPT from this thread?

Just curious. It's a good example and it's worthwhile for people to see what can happen to a strip that is not used according to its listing and labeling.

If it's a space issue, maybe we should put the picture into a thread of its own. Let me know if there is another problem.

Glenn

Glenn:

The link to the image was on my FTP site and with recent changes was lost, so "Yes" please resend it to the webmaster here and start a new message to reaffirm the issues.

Speaking of that image, I'd suspect that that damage could, or maybe even did, occur using it within the maufacturers instructions.

Update:

Pictures have been reposted above.

I'm from Ireland and spent a little time in the USA over the last few months and would have to agree that there is some rather scary misuse of powerstrips going on over there.

e.g. I saw a 15A powerstrip plugged into a 2-pin zipcord extension cord using a "grounding adaptor"... this was supplying power to a small window mounted A/C unit & computer equipment! ... out of curiosity I touched the zipcord and it was actually hot!

Anyway, the situation in the UK and Ireland is simlar in many ways, people have the same need to plug in large number of small appliences (computer equipment, mobile phone chargers, desk lamps, audio/video equipment etc) and we also use powerstrips to do this... however, there are a few differences... Powerstrips are always wired with cable that can carry at least 16Amps with a comfortable margin of safety. All of our plugs contain an individual fuse rated 3 to 13Amps. If you overload the strip, the fuse in the plug blows.

Also, because all plugs are fused, it's very difficult to overload a wall outlet as you would have to bypass the plug fuse.

Also, there is no such thing as a non-grounded plug, so all extension cords and other devices are fully grounded.

I've also seen office systems here that have fused outlets to prevent employees from plugging heaters, coffee makers and other heavy appliences into circuits that are intended for use with IT equipment. The outlets under their desks could be fused at 5amps.

(I know this kind of fusing arrangement would be more difficult in the USA as you guys don't have any sort of commonly available standard cartridge fuse. In the UK and Ireland because every applience has a fused plug, these small fuses are available easy and cheaply in any hardware store / corner shop.)

The tiny resetable breakers used on US powerstrips seem really cheap and nasty, I'd much rather see a simple fuse used.

Also, in an office system, why not use IEC connectors under the desks for computer equipment? IEC powerstrips are quite common place in Europe for server and studio equipment to avoid the risk of people connecting non-IT equipment to these circuits.



Non-standard UK plugs and socket outlets are also available for these kind of situations e.g. for use on UPS or filtered circuits.

[This message has been edited by djk (edited 02-26-2005).]

I mentioned this elsewhere:
At Wally World (AKA Wal*Mart) in the lobby there are vending machines, kids' rides, lights, and a coffee machine occasionally, all plugged into an outlet strip with the breaker removed! eek! The stipr plugs into a homebrew 18AWG speaker cord extension cord. No worries, fire dept. is right across the street! Also, at a motorcycle dealer in NJ, a nice, shiney new plasma TV was installed, along with a DVD player and a S-VCR. So, where do you plug these in when there's not an outletv within 15 ft? Two two wire zip-cord ext. cords, a grounding adapter, and a powerstrip. The zip cords, outlet plate, and power stip were all hot!
Ian A.

[This message has been edited by Theelectrikid (edited 07-08-2005).]