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

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?