Page 1 of 1

My Christmas Can Light Dimmer

Posted: Sat Nov 30, 2013 5:24 am
by Lenp

This article is full of bad advice!
A power system neutral should NEVER be connected to be used as an earth or safety ground. Even if the neutral side of the line is identified correctly, there is usually a difference of potential between the true ground and the neutral, which will be present on the metal can. UTILITY LINE POWER IS NOT A 12 VOLT CAR SYSTEM and should not be wired as such. Doing so presents significant safety risks.

The dimmer is being installed in a manner not approved by the manufacturer so any value to the UL label is meaningless. As if that wasn't bad enough the article keeps referring to the connector as a Romex connector, which it is not. It appears to be a BX connector and it's set screw is being used for the ''ground''. The connector design offers no strain relief for the wires and since the splices are made using poorly taped joints one good tug and bare wires will be all over the inside of the can. It is certainly obvious that the ""enclosure"" is not code grade steel and that also poses certain hazards.

DO NOT BUILD THIS, and I encourage the author to stop using this in his home, and to revisit the first one he built using his "Approved water tight enclosure" if the similar construction practices were followed. The big box stores are full of the proper enclosures and materials to make the same device in a safe manner. A common electrical junction box with a receptacle and dimmer properly fitted behind a plate, with a strain relief connector for a 3 wire power cord set and proper wiring and grounding would yield the same benefits and remove the risks and dangers of this design.

I am really shocked that a quality magazine, like Nuts and Volts, would sanction the publication of such an article that presented these clear and blatant safety dangers. Is there such a lack of submitted articles that N&V uses whatever they can get? There should be some review of all articles prior to publication for their safety and proper design or the credibility and value of this publication will be diminished. Like myself, there are other experienced and long standing forum members that may be willing to review submissions prior to publication if the publishing staff does not have that ability.

Certainly if someone followed this article, built this project and were injured, the lawyers would have a feeding frenzy.

Len Powell

Re: My Christmas Can Light Dimmer

Posted: Sat Nov 30, 2013 7:50 pm
by Robert Reed
I have not read this article and from what you posted it sure sounds like its full of "traps". But as to lawyers intervention, I don't think that would apply in these situations. I may be wrong on this, but from what I have always gathered Unless it was an item that involved a money transaction and/or a suggested project for a hobbyist it is probably immune to lawsuits. Sort of like one neighbor giving advice to another over the backyard fence.

Re: My Christmas Can Light Dimmer

Posted: Sun Dec 01, 2013 6:00 am
by Lenp
Hi Robert
It was a construction project complete with drawings and pictures. An experienced person would probably not be interested in the primitive article, but a raw DIY might. Hence lies the dangers!

As for liability, with today's upside down court decisions, I would not want to place a bet on the outcome!


Re: My Christmas Can Light Dimmer

Posted: Sun Dec 01, 2013 5:37 pm
by Robert Reed

Re: My Christmas Can Light Dimmer

Posted: Fri Dec 13, 2013 5:39 am
by JohnCollier
I just read this article and was all charged up to post a rant here but I see Len beat me to it. I find it absolutely unbelievable that this made it all the way through the publication process. I realize they don't have the staff or expertise to ensure that articles meet all applicable codes, but a project like this one with such blatant disregard for safety and accepted wiring practice should never have been allowed out of the gate.

Besides everything else Len mentioned, I want to point out that if the user's receptacle is incorrectly wired (hot on wide prong, neutral on narrow--this happens more than you think), then 120V will be directly applied to the metal can, providing a nasty shock to your children on Christmas morning. I hesitate to provide suggestions for improving this train wreck, but the power plug should have been 3-prong, with the ground wire bonded to the can.

I agree that articles involving direct manipulation of high voltage should be going through an additional review process. Legal issues aside, when presenting subject matter that has the potential to cause injury or death, it is simply not ethical for the publisher to pass information along with virtually no editorial review whatsoever. This was most certainly the case with the Christmas Can Light Dimmer.

John Collier, P.E.

Re: My Christmas Can Light Dimmer

Posted: Fri Dec 13, 2013 6:03 am
by Lenp
The writer mentions an 'outdoor' unit he previously constructed. I really must wonder if it was done in a similar 'shocking' manner?

Human nature amazes me.
I once saw an article in EC&M magazine about an inspector that found a DIY floating pool receptacle.
It was enclosed in a flat faced liquid soap bottle, a duplex outlet was carefully recessed into the face, and the wire exited through the neck. The builder proudly floated it in his pool to power his poolside radio.....

Re: My Christmas Can Light Dimmer

Posted: Fri Dec 13, 2013 7:07 pm
by JoshBensadon
I have not read the article in question, but I do wish to correct Len on one point.

Len wrote:
"UTILITY LINE POWER IS NOT A 12 VOLT CAR SYSTEM and should not be wired as such."

I would like to remind everyone that even a 12V Car battery is quite dangerous.
Several things can happen:
-a shorted cable that is not fuse protected can start a car fire.
-Sparks near the battery can ignite the hydrogen gas, causing the battery to explode.
-A dead short across the battery leads can also cause the battery to explode.

Always be careful when working around the battery, a wrench can slip and short the battery.

And Kudos to Len for speaking up against unsafe 120V Home wiring practices.
Sorry Len, I'm sure you didn't mean to say a 12V car battery is less dangerous than 120VAC.
(Yes, you are not likely to get shocked from 12V, but that alone doesn't make it safe).

Even the Nicad and Nimh battery packs are dangerous. What about those exploding cell phone batteries?

I think only the standard alkaline and carbon batteries are not dangerous, and even then, I'd be a little hesitant to say so because I heard it said somewhere, "Never underestimate a fools ability to defeat something fool proof".

Josh Bensadon

Re: My Christmas Can Light Dimmer

Posted: Fri Dec 13, 2013 10:06 pm
by Lenp
My reference to a car 'System' is referring to the 'hot' wire and a ground concept of wiring, not the battery.

Certainly the short circuit current in these batteries is enormous and fires can and do start. The aspect of the explosive gases from a charging wet cell battery also must be considered. Yes sealed lead acid, NiCad, NiMh, Lithium family and many other batteries also pose a similar short circuit danger. Even a 9 volt battery can get surprisingly hot if it shorts against keys or change in a pocket.

Many years ago a photographer cobbled together a battery belt pack, using many parallel 12 volt SLA batteries and shoddy wiring to power his strobe. In the middle of a wedding, absent any fusing devices, the pack shorted. I would have paid to see that smoking spectacle!

I see N&V emailed a warning and I am glad they responded in a positive manner. Thanks!


Re: My Christmas Can Light Dimmer

Posted: Sat Dec 14, 2013 1:53 am
by G8RPI
I'd not actually looked too closely at this article as it was too "simple". A close look shows it's truly shocking (no pun intended). And there are better ways to improve lamp life. A PTC (Positive Temperature Coefficient) thermistor is an established technique. This will reduce the inrush current and slightly reduce the voltage. With a view to liability, it's is an issue for the author and publisher. The publisher paid the author and charged the reader so both have a direct link, responsibility and duty of care. There have been a number of articles recently with weak safety or functionality (not just in N&V). Rather than complain I decided to try and do a better article instead. It's been accepted. Much more satisfying than ranting!

Robert Atkinson.

Re: My Christmas Can Light Dimmer

Posted: Sat Dec 14, 2013 7:38 am
by Lenp
A really simple lamp life extender for AC lamps is a common diode in series with the lamp. Because of the half wave rectification the voltage is about half. I have used diodes in outside post and wall lights for years. They reduce energy and give that warm candle glow. All for pennies! I place the diode right in the fixture but be mindful of the voltage / current rating and insulate it properly!
We had a control panel using 120v indicator lamps. After installing diodes the lamp life went into years.
This will not work on direct current, LEDs or lamps that have some electronic controls.

Re: My Christmas Can Light Dimmer

Posted: Mon Dec 16, 2013 10:22 am
by VernGraner
I got a response from the magazine so I thought I would share it here:

Attention Nuts & Volts readers

The Christmas Can Light Dimmer article in the December issue of Nuts & Volts has some safety issues if built as described. Instead of using a polarized plug on lamp cord, use three wire cord with a three pronged plug and a proper metal electrical enclosure obtainable from any home improvement store. Attach the ground wire from the cords to the ground screw of the metal enclosure. Also, a plastic enclosure could be substituted. While we liked the idea of this project, our readers have brought to our attention too many possible safety concerns to let it stand as is. If you are not knowledgeable in proper home AC wiring practices, we do not recommend building this project. You can join in on the discussion in our forum, if you are so inclined.

Happy Holidays and above all, be safe!

Re: My Christmas Can Light Dimmer

Posted: Mon Dec 16, 2013 11:45 am
by Lenp
Apparently they do read some forum posts! I got the same mail a few days ago.
The editors should really look into a peer review group so this doesn't happen again.

Re: My Christmas Can Light Dimmer

Posted: Sun Dec 22, 2013 9:26 am
by ehsjr
Yes, scary indeed.

A point worth mentioning, although not as frightening as those already covered:
the yoke is the heat sink for the triac's dimmer. In a proper installation, some of that heat is dissipated into the j-box in which the switch is installed. In the absence of mounting screws to create a solid mechanical contact to the coffee can "j-box" (to say nothing of the modified yoke itself), the dimmer switch will get hotter than it would in a proper installation.


Re: My Christmas Can Light Dimmer

Posted: Sun Dec 22, 2013 9:44 am
by Lenp
I agree with the heat sink issue. With the use of plastic boxes and faceplates this becomes a real concern. Some 'old stock' dimmers can overheat since when they were designed plastic boxes were not in use.
In this case, unless he has a huge tree and a ton of lights, the load is probably well below the dimmer's rating.