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I just wanted to let you guys know about a situation that I came across while building a Hot Coals prop with LED string lights. As most of you probably have seen on here, you can create some awesome glowing hot coals with LEDs and Great Stuff insulation foam. However, as I was finishing up my project, I ran into a potential disaster.

I was in my garage with the lights off and was playing with the settings on the LED string. I had used several strands that I got off of E-bay for about $6 or $7 a strand. Well, everything looked great, in fact is was so realistic I could swear I even could smell it... and then I actually saw a tiny trail of smoke drifting up. After much inspection and debating about it, I tore my prop apart. I tried best I could to remove the strands from the great stuff without damaging them so hopefully I could reuse them (yeah right, it wasn't happening). Anyway, as you can see from the picture below, I'm glad I did it. I could have been setting myself up for much more than I bargained for...

IMAG0261.jpg

Seems these strands, made in China (of course!) are really cheap, literally and figuratively. Here you can see the black scorch marks from a faulty LED strand. This is definitely a product flaw, yet I'm not positive that it couldn't have been exacerbated by the Great Stuff. I had a can of the foam that didn't come out all fluffy as usual. Instead, this can came out thicker and didn't expand the same, and after drying it was much denser than normal. It sure seemed like many of the scorched LEDs were in those areas, but I can't say for sure. Regardless, proper LEDs shouldn't be generating that type of heat in the first place.

So there it is. Consider yourself warned! I'd hate to have some of you out there get "hot coals" far, far more realistic than intended. A fire trap isn't a good thing especially if it ends up harming kids along with destroying your props.

Here's a picture of the box that the strands came in, but I think pretty much all of these super cheap LED strands are the same thing. Two out four of my strands had scorch marks, so a 50% failure rate is WAY TOO HIGH in my book.

IMAG0262.jpg
 

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Interesting. Remember LEDs DO generate heat! It is not as much as normal incandescent but there is still heat generated. One should not put foam over the element itself as that could very easily make that element over heat. That is why the residential light bulbs have so much exposed aluminium, it's a big heat sink and it does get quite warm. I wonder if the LEDs over heated and the heat traveled down the wires into the cheap insulation. Either way not a good situation.
 

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The Great Crazy
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I like to use the Phillips low energy brand lights its a heavier wrap wire and the price is right. After building a Halloween or Christmas prop I like to let them run for a couple of hours to see if anything is broken or getting hot. Looks like the brand you have is very cheap sorry to hear what happened glad your were there when it did!
 

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Obssessed Haunter
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Wow am I glad that when I built my "coal" I actually put plastic over my lights and then sprayed the foam over the plastic. Once it set up I then peeled the plastic off the foam. So now, my lights and foam are seperated which leaves and air space between them. I hope this eliminates this problem.... I would be so disappointed to have my fake coals become real!
 

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I have heard of many instances where China completely reverse-engineers things they make, right down to a duplicate of the UL Approved label. It's just a little tag with writing on it, right? Sure, we can make those. No problem!
 

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I don't know why those LEDs would be producing much heat at all, unless the circuit is so cheaply wired that there was something wrong from the get-go. Yikes! Good to know, though! Are they UL approved/certified?
 

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I bought a set of led net lights from China via ebay, and they too are very cheap quality. They look like the same crappy thin gauge clear insulated wire in you photo. I definitely wouldn't recommend them, and won't be leaving them on unattended. Lesson learned, you get what you pay for.
 

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Evil Wizard
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Good to know. Had been watching a few of those Chinese auctions on eBay, but ultimately decided to go with a set of 10 green submersible LEDs (for lighting the interior of my cauldron fog chiller) that I found fairly cheap on Amazon.

A few months ago, I purchased a set of these solar-powered orange LED lights, for the glowing coals effect: http://www.gardenfun.com/solar-string-lights-orange50.html
 

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Glad you noticed the problem before it became a larger problem. Member warnings like these tend to stick in people's minds so I really appreciate seeing your pics and hearing what your experience was.

And LEDs definitely do still produce some heat. Current is still passing thru. I suspect the foam was a contributing factor and maybe the lights would have been fine without the foam. Hard to say though. I know very little about LEDs but do know from building some LED eyes for a prop that different colored LEDs require different resistors, otherwise the LED's life will be compromised--overheat and burn out prematurely. Is it possible the circuit could have led to an overheating problem like this? Regardless, the important lesson I think is not to cover up any electrical wiring product that precludes air circulation.
 

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Better safe than sorry, that's for sure! I'm always on the prowl for anything suspiciously producing heat in or near ANY of my props. That's why I think LEDs are great for projects like scares. Very minimal heat ( I won't put you to sleep with the power consumption calculations) and quick response time so you can flash them very rapidly, to the point where the flashing isn't seen as individual flashes (great for fading effects).

Again, thanks for the warning! Sorry you almost lost your prop, but at least you found the problem BEFORE it "LED" to much worse (sorry... couldn't resist the pun).
 

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The problem might be in the application more than in the lights. In my "Glowing "hot" coals thread, you see I made a point of placing the light bulbs loosly under wiffle balls and ping pong balls, then loosly covering the wires and balls with great stuff. I suggested that you leave gaps, but not let the bulbs be seen from the front of the prop.

In my prop, no Great Stuff ever touched a bulb and I used only a thin layer of GS with venting towards the back. I used incondescent bulbs that create much more heat than LED, so it stands to reason that this application would be safe for LED.

 

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The Mrs. to a MysterE
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I used different-sized whiffle balls cut in half to create a 'shell' over my lights. I didn't have any problems last year.

The whiffle ball cage used to protect and elevate the Great Stuff used in making the hot coals (building technique) is a good way to help avoid any trouble with lights catching the Great Stuff on fire.. Scary situation - and thanks so much for the Mokknoir warning. Ii will hope that the airflow around my whiffle balls do a good job of keeping things cool....
 

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I altered the plans to make my coals 24x18 boards. So I can "adjust" the size
of the fire as needed.

Ran the lights first, taping the wire down, lights standing up. Notched my
plastic bottles at the bottoms for air-flow. Then shot it with foam.
 

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The whiffle ball cage used to protect and elevate the Great Stuff used in making the hot coals (building technique) is a good way to help avoid any trouble with lights catching the Great Stuff on fire.. Scary situation - and thanks so much for the Mokknoir warning. Ii will hope that the airflow around my whiffle balls do a good job of keeping things cool....

Here's the link to the first HF how to thread for this type of prop. This will be the fourth Halloween we've used this prop. It is stored in a plastic bag at the side of the house and continues to work without problems.
http://www.halloweenforum.com/tutorials-step-step/86951-glowing-hot-coals.html
 

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Just thought i would trough this out there, great stuff makes a fire rated foam that i use in all my props with lights in it. This way i know i wont have a problem later. its a little more money but i feel its way worth it.
 

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That might work just fine. OR the lights could overheat and stop working. Incondescent and LED lights, generally, are designed to be open to the air, not trapped in foam. I've seen others use the bottoms of soda pop or water bottles to cover / insulate the wires from the foam. Just poke a couple holes in them with a hot knife.

Also, if you are displaying the prop outside where the weather is cold, you should need less ventilation for the lights.

FWIW
 

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One more note about using an "enclosure" to assure the foam is not touching the lights - if you are mixing lights like I did (Lots of orange, some red and some purple), you can layout your strings so that you have the mix of colors you want in a single [wiffle ball / water bottle bottom / etc]. The result, after applying the foam, will yield sort of a blurry mixture of the colors coming from a single spot, rather like a live ember pulsing in its different heat ranges. Hope this is clearly expressed.
 
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