LED Christmas Lights Question

[Steve Oakes]

Hello,

I purchased several sets of Noma LED Faceted C7 - 50 light sets to
decorate a large tree I have. I realize these lights aren't as bright
as the traditional C7 lights, however they are supposed to last 25 times
as long as a traditional set and use far less electricity (2.4W for 50
lights vs. 124.8W for a 25 light traditional set. I figured I'd give
them a try. The strings can be connected end to end, however there is a
warning label on one end which states not to connect more than 3 strands
together at a time. My question is: Why can't I connect more than three
2.4 watt strands together? If I hooked 10 strands together, I would
only be using 24 watts of power total, not enough to blow a fuse or over
heat the wiring. Does anybody know the answer to this question?

Thank You,
Steve

 

[Anthony Matonak]

I purchased several sets of Noma LED Faceted C7 - 50 light sets to
decorate a large tree I have. I realize these lights aren't as bright
as the traditional C7 lights, however they are supposed to last 25 times
as long as a traditional set and use far less electricity (2.4W for 50
lights vs. 124.8W for a 25 light traditional set. I figured I'd give
them a try. The strings can be connected end to end, however there is a
warning label on one end which states not to connect more than 3 strands
together at a time. My question is: Why can't I connect more than three
2.4 watt strands together? If I hooked 10 strands together, I would
only be using 24 watts of power total, not enough to blow a fuse or over
heat the wiring. Does anybody know the answer to this question?

I don't have an answer, as such, but perhaps this is an LED
retrofit of an existing product and the "3 sets" limit is a
carryover from the original incandescent lights. If the old
strings took 250W each then 4 sets totaling 1000W might be
too much for the wires.

Anthony

 

[daestrom]

Hello,

I purchased several sets of Noma LED Faceted C7 - 50 light sets to
decorate a large tree I have. I realize these lights aren't as bright as
the traditional C7 lights, however they are supposed to last 25 times as
long as a traditional set and use far less electricity (2.4W for 50 lights
vs. 124.8W for a 25 light traditional set. I figured I'd give them a try.
The strings can be connected end to end, however there is a warning label
on one end which states not to connect more than 3 strands together at a
time. My question is: Why can't I connect more than three 2.4 watt
strands together? If I hooked 10 strands together, I would only be using
24 watts of power total, not enough to blow a fuse or over heat the
wiring. Does anybody know the answer to this question?

Well, it could be a 'carryover' as Anthony suggested.

On a lot of lights though, there is an internal fuse in the plug. Maybe
with the LED string they put in a smaller fuse and it would blow if loaded
more than three strings?

Now, why would they need to step down to a 0.06 amp fuse, I don't know.
Surely, the wire can stand that much.

daestrom

 

[Steve Oakes]

The instructions say it is a 3 amp / 125V fuse. It probably is a
generic label and they left it on there because A) It was cheaper than
removing it and B) Just in case some idiot hooks up 1,000 strings in
series (like that Griswald guy in the Christmas Vacation movie). I also
just found a web site for the manufacturer and I wrote to them asking
the same question. I will probably wait for their response before I
ruin my lights at $11.99 a set.

Thanks for your responses,
Steve

 

[Daniel Armstrong]

The instructions say it is a 3 amp / 125V fuse. It probably is a generic
label and they left it on there because A) It was cheaper than removing it
and B) Just in case some idiot hooks up 1,000 strings in series (like that
Griswald guy in the Christmas Vacation movie). I also just found a web
site for the manufacturer and I wrote to them asking the same question. I
will probably wait for their response before I ruin my lights at $11.99 a
set.

Thanks for your responses,
Steve

Strangely enough my local TV station did a Christmas safety segment once
where they said not to plug more than 3 sets of any style light into a
single wall outlet and I cannot figure that one out either. I once had
about 6 strings of 100 count lights each plugged into my Xantrex Xpower 300C
250 watt continuous modified sine inverter, light, compressor(dead), and
jump start pack and it held them up fine for about the 10 minutes till I
unplugged them. A standard 15 amp branch circuit is designed for a
continuous load of 12.5 amps/1500 watts (this is why all space heaters are
either at or below that number) at that rating you could use 625 sets of
those LED based light strings safely but how would you plug them all in (6 6
outlet power strips plugged into another 6 outlet power strip and 18 sets of
lights plugged into each of the resulting 36 outlets would do it but it
would be a royal wiring mess) and how would you afford them. It would be
interesting to see how bright it would be IMHO.

 

[RoughRider]

Just looked at my LED xmas lights... they don't have any warning about the
number of strings that can be attached together. Just a Wattage limit. I
don't recall seeing any of my lights (from various manufacturers) having a
"string" warning on it and I just put them up last week. I would suggest it
may be a legal catch all that the manufacturuer can point to if some some
ingnormaus finds a new way to burn down their house that no one has figured
out yet.

Popular engineering saying: "You can only do so much to protect people from
their own ignorance". Lawyers don't subscribe to this saying, rather:
"Ignorance pays huge liability awards"

 

[Dale Farmer]

The instructions say it is a 3 amp / 125V fuse. It probably is a
generic label and they left it on there because A) It was cheaper than
removing it and B) Just in case some idiot hooks up 1,000 strings in
series (like that Griswald guy in the Christmas Vacation movie). I also
just found a web site for the manufacturer and I wrote to them asking
the same question. I will probably wait for their response before I
ruin my lights at $11.99 a set.

Thanks for your responses,
Steve

Could be coming from a number of places. Maybe their UL cert?
COuld be some sort of federal regulation, CPSC or whatever? Maybe
one of their large markets has such a local regulation. Maybe they
made the conductor's smaller to save on cable cost?

--Dale

 

[Derek Broughton]

Hello,

I purchased several sets of Noma LED Faceted C7 - 50 light sets to
decorate a large tree I have. I realize these lights aren't as bright
as the traditional C7 lights, however they are supposed to last 25 times
as long as a traditional set and use far less electricity (2.4W for 50
lights vs. 124.8W for a 25 light traditional set. I figured I'd give
them a try. The strings can be connected end to end, however there is a
warning label on one end which states not to connect more than 3 strands
together at a time.

Really? My LED lights - at 4W per strand - said not to connect more than
480W in series! I shudder to think what might actually happen if you
connected 120 of them, but I can't see a problem with four or five of yours
(I have five in series).

My question is: Why can't I connect more than three
2.4 watt strands together?

Because they took their figures from the old spec sheet for their
incandescent strings - I bet the sentence is _exactly_ the same.

If I hooked 10 strands together, I would
only be using 24 watts of power total, not enough to blow a fuse or over
heat the wiring. Does anybody know the answer to this question?

That's probably 2-300 feet of cable, so there will be a significant voltage
drop over 10 strands. Is it hazardous? I'm not sure.

 

[David Kopf]

That's probably 2-300 feet of cable, so there will be a significant
voltage
drop over 10 strands. Is it hazardous? I'm not sure.

Well, the manufacturer has to consider the worst case. If only the hot side
is internally fused, a short in the last strand from the neutral to another
hot wire (possibly the neutral in another strand which is plugged in
backwards) needs to pull enough current to blow the recepticle breaker
before the wires light up. This requirement is independent of the type of
light or wattage of each strand. Supposing a 200 amp short current is
wanted (20 amp breaker), the resistance would need to be less than 0.6 ohm
at 120 volts or ~ 150 feet of 16 gauge wire, or a maximum of 75 feet per
strand series. It's also possible that someone would add several
incandescent strands to the end if the connectors are compatible, and demand
warranty replacement after blowing an internal fuse.