Light string has contradictory instructions

8/27/2010 12:38 PM EDT

My guess is that the tag on the product is there for plausible denyability. A) The product is probably designed for three strings, B) The quality control on the manufactured product may not be consistent enough to guarantee safety with three strings, C) People undoubtedly have plugged many more than just three strings together and some have had fires.

You might ask, why then do they still have the receptacle at the end? Well, they know that a lot of people will only buy the string if it allows daisy chaining. They put the warning on the cord so they can say "we told you not to" and the receptacle on the cord as a "wink, wink, nudge, nudge know what I mean" so the product will sell.

8/27/2010 2:30 PM EDT

My guess is the label intended to say that the lights should not be connected to a different TYPE of lighting string. Up to 3 strings of the same type is OK. I agree that the current wording is confusing. Just don't string the party lights with your Christmas tree lights and Jack-o-lantern lights. Hopefully, you'll be OK. Where and when's the party?

8/27/2010 2:49 PM EDT

The ultimate limitation to the number of strings that can be plugged end to end is the fuse inside the plug. For the type of string shown, the fuse is usually a 7 Amp. fuse.

8/27/2010 3:29 PM EDT

If you string three in series, monitor the temperature of the plug and wire closest to the wall plug (where the power is coming in) on the first string. If this becomes very warm , cut down to 2 stings or 1. I have to agree with the first commentator that the manufacturer is not doing any quality control, and is assigning all risk to you for using the facility he supplied. With all cheap stuff, monitor closely for flaws/odd behavior. Don't trust it.

8/27/2010 4:43 PM EDT

The confusion stems from murky translation, particularly the use of the word "another". As gvictor noted above, the designer probably intended something along the lines of "Do not connect/intermix with other types of light strings..."

8/27/2010 6:19 PM EDT

What we see is a warning generated by the legal department, and application information written by humans. My question is how many amps do you want to draw through that string of #26 wire? And what about the inferior connections? Of course the fuses should fail first, and those 3/4 amp fuses do fail regularly.

8/27/2010 8:22 PM EDT

Well, apply some engineering know-how to the problem. The label states that the bulbs are 5 watts, and that they are parallel connected. So your total wattage is N x 5 where N is the number of bulbs (let's say 12) so that would be 60 watts. At the strange mains voltage of 110 that you Americans use, that's a shade over half an Amp (the label actually states 0.83A). WKetel above gave the wire's size as #26 (another strange americanism, but Google tells me that this is about 0.13 square millimetres - pretty small). Now I would not want to put much more than an amp through that size wire, so I'd stick at two strings daisy-chained maximum. And as a final test, as Carl Pawley advises, feel the plug and the wire closest to where the power comes in, and if it gets at all warm, reduce the number of strings or use double adapters and extension leads. The label says "Made in China" (isn't everything these days?) and you can be damn sure that they didn't put any more copper in those wires than they absolutely had to.

And no, I'm not biased against Americans, I just often wonder how they managed to put a man on the moon without using SI units.....

8/27/2010 11:29 PM EDT

Once again, something was probably lost in the translation. It would be interesting to see the UL report on the product, if there was one.

None the less, I'm thinking...don't use it to extend the cord on the clothes iron!

8/30/2010 12:23 PM EDT

Gentlemen, if anyone would have taken a quick tour to the actual link, there is more data that is missing in this posting.

For starters, the problem has two variables, this product is sold as a string of 10 or 20 lamp strings. In other words, 7Watt-lamp sting dissipated 70Watt total & 5Watt-lamp string dissipates 100 Watts total. (Or about 0.6Amps and 0.83 Amps respectively).

The photo is clearly for the 100Watt string version, so far so good, thinks make sense.

Also if you read the additional information posted below, it can be seen that the manufacture provides a 5 Ampere fuse. So for a typical derating of 80% of the maximum load current. If the fuse was the only weak link, there is enough safety margin to install 3 strings (from this vendor) in any combination using the same type and power limited to 100 Watts per string.

However, given that there is another variable not clearly stated in the posting or by the vendor or manufacturer, “the gauge of the electrical cable” in this case.

Cable gauge is a critical safety parameter that defines the capacity to deliver power safely power down stream, to other loads or lighting strings. Using the guesstimate by WKetel, and using the conservative 700 circular mils/Ampere rule-of-thumb the cable (AWG#26 is rated to 0.36A) would be barely safe to be connected individually since a single lowest-power string (70W) needs a rating of at least 0.6 Amps.

If the manufacturer (very unlikely), had used AWG#16 or #19, then there would be reason to feel with confidence that the 3 string configuration was safe. However, that would be a very stiff and heavy cable.

In other words, use your common sense and feel the temperature of the cable at the start of the string to see if the wiring is under rated. It should feel not higher than couple of degrees over room temperature.

So like many thing in engineering, apply common sense, and do not exceed the cable rating by applying a space heater at the lighting string end!

8/30/2010 12:25 PM EDT

Just realize that there is a 2000 character postings. And the paragraphs are not been formatted as typed in word file.

The link below and additional notes relate to the posting above.

http://www.powerstream.com/Wire_Size.htm

5 Watt lamp (x20) string
http://images.restorationhardware.com/content/catalog/product/pdfs/prod1673011_info.pdf

7Watt lamp (x10) string
http://images.restorationhardware.com/content/catalog/product/pdfs/prod1673011_AI.pdf

PARTY GLOBE LIGHT STRING
$35 - $39$31.49 - $34.99
Miniature versions of lights seen in Italy's piazzas and the Tuscan countryside.
• Illuminate outdoor gatherings
• All-weather wiring
• UL-listed for indoor or outdoor use
• Large globes (70W) come 10 lights to a string
• Small globes (100W) come 20 lights to a string
• Three light strings can be connected end to end
• Large globes: 11'L; bulb size, 2-1/4"D
• Small globes: 21'L; bulb size, 1-1/2"D
• PROPOSITION 65 WARNING: This product contains lead, a chemical known to the State of California to cause cancer and birth defects or other reproductive harm
• This item cannot be shipped to Canada

9/2/2010 6:11 PM EDT

But even those LED strings have to deal with that pesky power issue, that is, if you want to be safe and not burn the house!
In a serious note, those strings still have limits on how long can they be, and how many you are able to connect in series.

9/3/2010 5:25 PM EDT

It is clear that I did not examine the picture closely enough the first time I commented. I was thinking about the strings of 50 lamps, and the whole string may be 5, 10, or 15 watts. These are much bigger bulbs, and so the connecting wire may be as big as #18, although my guess would be #20. USA wire sizes relate inversely to the current handling capacity, a very logical arrangement, Asho #1. So it would be fine for 1 string and OK for 2, and 3 is undoubtedly the limit. The very first part to fail will be the contacts at the fuses internal to the power plug. Typically these are made with the cheapest possible injection molding process, using the cheapest possible polyethylene plastic available, and the contacts are some sort of brass alloy that develops an insulating oxide layer after a few weeks.

9/3/2010 5:28 PM EDT

One more thing, which is that in the state of California it is advised to not eat these strings of lights, based on the allegation that they contain lead. Possibly on the base of the lamp, so don't eat the lamps either. ONLY from our guardians in California do we get such vital advice.

9/4/2010 9:14 PM EDT

I don't believe this discussion. You are questioning the clarity of instructions in English from China? This is not possible. (Maybe if/when I finish learning Mandarin, I will be able to see if the instructions are any better in the original language. Unless they are in another dialect. But written Chinese characters are understandable across dialects, no?)

9/6/2010 6:36 AM EDT

@jonhp:
Please don't take it personal, but I'm too very amused when I look in an american physics textbook and see all this (in my eyes) cumbersome correction factors. When Germany changed to the SI system in the early 70es I too had some problems first to see the drive behind the "metrication" (as you put it), but later learned to love the ability to derive the correct formulas my simply looking at the units. Knowing that 1kg*m/s² is 1N unlocks half of Newtonian mechanics and dynamics and passing my tests on thermodynanics so easily was also owed to this.

I somewhat admire (or more so commiserate) US pupils for memorating all the scale factors that can't really make life easier, I think.

But it really makes me shake my head when programmers of PCB layout programs base their internal computing on mils and have to deal with many positions after decimal point and rounding errors when the other way round would solve this in an elegant way.

and @ReneCardenas:
Isn't it funny to appeal for the use of common sense to people that force the placing of "Caution - slippery when wet" signs when cleaning the floor in order to avoid suing?

NAd if there is a plug for daisychaining other loads, someone WILL plug 5 other strings or the electrical heater in there. After the house burnt down, he will then sue the dealer, the power company and whom else...

9/8/2010 12:36 PM EDT

To wswbln:

I agree, we have allowed our society to seek legal recourse at every instance of self inflicted injury and demonstration of absent common-sense.

I don’t have the solution, but would like to see the courts bring a deterrent for frivolous lawsuits, maybe by requiring payment of all court costs including defense attorneys fees in all failed cases, so may be the bar can be raised just a little to stop stupidity in courts.