Stinkin Christmas Lights

[stusviews]

Never heard of that system. All ours work on 120vac off pole top transformers feeding other loads.  HID lighting would not function well in series.

 

I never mentioned HID lighting at all. My reference is to line voltage incandescent Xmas lights wired in series that remain lit even if a bulb or two fails. And if you mean street lights, then yes, many cities use lights wired in series. The ones I worked with actually clipped in place, that is, they were pushed in. The dielectric between the clips dissolved when the bulb burned out, the clips made contact and the remaining bulbs stayed lit.

[larryllix]

I never mentioned HID lighting at all. My reference is to line voltage incandescent Xmas lights wired in series that remain lit even if a bulb or two fails. And if you mean street lights, then yes, many cities use lights wired in series. The ones I worked with actually clipped in place, that is, they were pushed in. The dielectric between the clips dissolved when the bulb burned out, the clips made contact and the remaining bulbs stayed lit.

Interesting.

Yeah that is what I was referring to. Ours are all run on 120V for sodium types, incandescents and fluorescents.

 What voltage was the system and what voltage were the bulbs rated at? Incandescents?

[stusviews]

Interesting.

Yeah that is what I was referring to. Ours are all run on 120V for sodium types, incandescents and fluorescents.

 What voltage was the system and what voltage were the bulbs rated at? Incandescents?

 

In reverse order, incandescent and/or halogen bulbs, rated at 120VAC and a 1200VAC supply. There were also sodium bulbs in some areas, but I didn't work there.

[larryllix]

In reverse order, incandescent and/or halogen bulbs, rated at 120VAC and a 1200VAC supply. There were also sodium bulbs in some areas, but I didn't work there.

Wow! That's hard to believe they would have to  use 1200 vac rated sockets and wiring for street lighting.

[apostolakisl]

Nope was regarding static electric.

I believe the device puts a brief  "spark" of high voltage low current power into the lights to break the insulator on the shunt.  The idea is that you have one dead bulb where the shunt failed to function.  The "popper" builds up a charge then you unload it as a high voltage "pop".  Once the shunt conducts, the strand lights up and you can see which bulb was dead and you replace it.  And yes, when connected to normal 120vac, the other bulbs get 1/50th of 1/35th or however many lights are in series more volts until you replace the bulb.  But that is a separate consideration from how the popper works.

[apostolakisl]

Wow! That's hard to believe they would have to  use 1200 vac rated sockets and wiring for street lighting.

Seems odd.  Why would you do that?  I can imagine doing 7,000 volts in series or whatever your pole voltage is in that area to avoid transformers.  But 1200 volts means you still have a transformer since I'm pretty sure 1200 volts is not a voltage used on any sort of transmission line. 

 

Maybe doing 1200 volts means that the voltage is low enough not to requie heavy duty insulation but still opens up the ability to do 1 or 2 thousand foot runs (10 lights) on one transformer without huge line losses?

[larryllix]

Seems odd.  Why would you do that?  I can imagine doing 7,000 volts in series or whatever your pole voltage is in that area to avoid transformers.  But 1200 volts means you still have a transformer since I'm pretty sure 1200 volts is not a voltage used on any sort of transmission line. 

 

Maybe doing 1200 volts means that the voltage is low enough not to requie heavy duty insulation but still opens up the ability to do 1 or 2 thousand foot runs (10 lights) on one transformer without huge line losses?

There are insulation classes at 300, 600, 15,000, 30,000 and a few in between. But every light socket and wire would have to be rated for full voltage and then some to fit inside those class limits.. If any bulb or wiring open circuits it gets the full voltage across it, let alone the circuit to ground has to be rated for that voltage, Lamp sockets are not usually rated over 300 vac usage. In the old days with that voltage the rubber insulation, covered with oil impregnated cloth would have to be around 3/4" in diameter. Today in the utility I retired from, the "streetlighter" used was just direct burial 12/2 coarse stranded XPE  ("pex" reformatted) cable. It just looks like household wiring with a black jacket on it. Higher voltages require many more safety protections.

[stusviews]

Wow! That's hard to believe they would have to  use 1200 vac rated sockets and wiring for street lighting.

 

The voltage drop across each socket is 120VAC, so everything is rated for 600VAC, a standard for virtually all line voltage electric products. BTW, it's been decades since I did that work and after a bit of hazy thought, I believe the voltage was considerably higher. And, yes a transformer was used. Distribution lines are usually in the of thousands.

 

Another tidbit: I worked on subways, too. Those bulbs were left-handed. Besides being an enigma for the everyday rider, they didn't fit if someone managed to remove one

[apostolakisl]

There are insulation classes at 300, 600, 15,000, 30,000 and a few in between. But every light socket and wire would have to be rated for full voltage and then some to fit inside those class limits.. If any bulb or wiring open circuits it gets the full voltage across it, let alone the circuit to ground has to be rated for that voltage, Lamp sockets are not usually rated over 300 vac usage. In the old days with that voltage the rubber insulation, covered with oil impregnated cloth would have to be around 3/4" in diameter. Today in the utility I retired from, the "streetlighter" used was just direct burial 12/2 coarse stranded XPE  ("pex" reformatted) cable. It just looks like household wiring with a black jacket on it. Higher voltages require many more safety protections.

None of this really explains the logic of doing 10 120vac fixtures in series on a 1200 volt source though.

[stusviews]

None of this really explains the logic of doing 10 120vac fixtures in series on a 1200 volt source though.

 

One wire in and one out is all that's needed for a series circuit, instead of two wires in and two wires out for a parallel circuit. Miles and miles of copper ends up adding quite a bit to the cost. Also, a larger conduit is needed. BTW, all electric distribution from the source to the building in NYC is underground. Telephone cables, too

[apostolakisl]

One wire in and one out is all that's needed for a series circuit, instead of two wires in and two wires out for a parallel circuit. Miles and miles of copper ends up adding quite a bit to the cost. Also, a larger conduit is needed. BTW, all electric distribution from the source to the building in NYC is underground. Telephone cables, too

OK, but that seems like it would be a relatively small cost compared to the total price of the fixture and labor.  Then you have to deal with higher risk of electrocution.  1200 volts pushes its way through "insulators" like skin a whole lot more readily than 120.

[stusviews]

OK, but that seems like it would be a relatively small cost compared to the total price of the fixture and labor.  Then you have to deal with higher risk of electrocution.  1200 volts pushes its way through "insulators" like skin a whole lot more readily than 120.

 

Considering the many, many decades ago when the street light was installed, copper added considerably to the cost. At that time, material was more costly than labor for all building trades. The bulbs were special, too. Large quantities were produced, ensuring the same system for years to come. After a sufficient number of years and thousands of street lights, it became too expensive to rewire and too cumbersome to have two lighting systems. Some of that has changed as both energy costs and energy consciousness have increased

 

Also, the only people who worked on street lighting were highly trained electricians. Someone has to install, maintain and repair kV systems, often while live. As I mentioned in post #33, I believe the voltage was actually greater than 1.2kV.

 

Changing the bulb was actually quite safe. After the protective glass was removed, the bulb was pulled out while wearing rubber gloves. It did take a bit of force. The contacts/clips touched to maintain continuity and the new bulb was pushed into place. On a few occasions, a fine abrasive tool was pushed between the contacts to burnish them. Interestingly, now that I look back, arcing was very minimal when the bulb was removed

 

Wow, reminiscing is fun

[apostolakisl]

I'm assuming that nobody does this currently who isn't stuck with a legacy setup.

[stusviews]

It's been quite a while since I was involved in street lighting, but I'm sure than any wiring change in NYC would be prohibitively expensive. We're talking thousands of lights. What has probably changed is the lighting technology and possibly the lamp housing.

 

They haven't even been able to maintain the city's main arteries, the subway, let alone update them. BTW, the cars on each of the three lines, Interborough Rapid Transit (IRT), Independent Line (IND) and Brooklyn-Manhattan Transit (BMT) aren't interchangeable. They began as competitors, the track sizes (distance between the rails) are different, also two lines use AC and one uses DC.

[apostolakisl]

Just had a full string of 50 lights all burn out simultaneous.  Every bulb worked yesterday, all burned out today.  None of them shunted, they just all burned out (or at least every one I tested had not shunted).

[stusviews]

That's a relatively common occurrence with incandescent bulbs, especially those recently unpacked. Thet's the real reason many people leave then on the house year round. Or did you have that experience with a different bulb type?

 

A trick from the past was to plug light strings into an adjustable power supply and gradually increase the voltage.

 

We all had adjustable power supplies that we used on electronic gear, especially that which was not used for a while to protect the filaments of sometimes costly tubes

[apostolakisl]

not sure what "recent" means, but this strand of lights has been on every day since Thanksgiving day.  The strand is several years old and I have replaced about 10% of the bulbs as they burned out one at a time over that time.  Then, yesterday, all at once, all of them burned out in an instant.  Since the shunts weren't tripped, that means they must have all burned out at exactly the same instant, as though there were some huge power surge, but there wasn't. 

[stusviews]

"Recently" in the case I referred to wass usually a few hours, a day or two at most. That's clearly not your situation. Were the bulbs you replaced, over time, the identical wattage as the others?

[apostolakisl]

"Recently" in the case I referred to wass usually a few hours, a day or two at most. That's clearly not your situation. Were the bulbs you replaced, over time, the identical wattage as the others?

yes.  And I didn't replace any bulbs this year.

[stusviews]

I do have yet another explanation (not entirely different), but only if the event occurred at the moment the lights were turned on, not if it happened while they were on.

[apostolakisl]

I do have yet another explanation (not entirely different), but only if the event occurred at the moment the lights were turned on, not if it happened while they were on.

I wasn't there when they were turned on, or shall I say attempted to be turned on.  

 

Like I said, though, I have had this happen when I plug the strands in right of the storage box when I knew they worked as I put them away.  No flicker or anything.   Just nothing.  Again, either all or nearly all of the bulbs are burned out when tested.  So I don't know how this happens.  I have had it where literally 100% were burned out, but I have also had it where a handful of bulbs in the strand were still working (when tested).

[stusviews]

Incandescent bulb filaments get brittle as they get used due to being heated. Bulbs in lamps don't get moved much, those in ceiling fixtures even less so. Not so with bulbs that are decorative which get moved a lot. The more brittle the filament, the more likely it is to break, most especially when power is first applied. That's why a bulb is most likely to burn out when it's turned on.

 

Bulbs that have been packed, most especially if they were warm when packed, and unpacked a lot are especially likely to have a filament break, even if they've not seen a lot of use. If the bulb was clear, then you can actually see the break. If it's a string of lights in series, then a string of them will burn our concurrently. That's less likely if they are wired in parallel, but even those are subject to the brittleness problem. LED bulbs don't have that problem.

[apostolakisl]

Incandescent bulb filaments get brittle as they get used due to being heated. Bulbs in lamps don't get moved much, those in ceiling fixtures even less so. Not so with bulbs that are decorative which get moved a lot. The more brittle the filament, the more likely it is to break, most especially when power is first applied. That's why a bulb is most likely to burn out when it's turned on.

 

Bulbs that have been packed, most especially if they were warm when packed, and unpacked a lot are especially likely to have a filament break, even if they've not seen a lot of use. If the bulb was clear, then you can actually see the break. If it's a string of lights in series, then a string of them will burn our concurrently. That's less likely if they are wired in parallel, but even those are subject to the brittleness problem. LED bulbs don't have that problem.

Yeah, but they are in series, and the shunts not tripped.  So as soon as one bulb fails, the other would no longer have any flow of electrons to burn them out.  That means they must have all burned out almost precisely at the same instant.  I haven't heard any reasonable explanation of how that can happen.  A power spke, sure, but there is no evidence that my house had a power spike.  The strand that burned out the other day was just sitting there.  Hadn't been moved in weeks.

[stusviews]

It doesn't matter how long they've been sitting around, even years. It's how much they were moved while still warm (storage) and how much they are jostled while installing them (usually a lot). By then, the filaments are already brittle. A spike is not needed,, just turning them on is a spike to the bulbs.

[apostolakisl]

It doesn't matter how long they've been sitting around, even years. It's how much they were moved while still warm (storage) and how much they are jostled while installing them (usually a lot). By then, the filaments are already brittle. A spike is not needed,, just turning them on is a spike to the bulbs.

I dont' think you understand.  They were working, they weren't moved, they stopped working.  Movement that happened 3 weeks earlier is not going to break a fillament today.

 

And again, all 50 bulbs burned out all at the same time.  Movement that burns out 50 bulbs at precisely the same instant seems highly unlikely.

 

Only an electrical condition would have affected all 50 bulbs at precisely the same instant in time.