Lamp life too short!

[iwire]

Re: Lamp life too short!

Originally posted by hurk27:
Bob isn't a neutral on a "Y" transformer always current carrying?

I do not see why it would be, if all three phases have the same load you should be able to disconnect that neutral with no effect.

 

[bennie]

Re: Lamp life too short!

I hear about this problem quite often. There has to be some logical solution that is being overlooked.

Here is a far out hypothesis;

One lamp on a 120 volt circuit line L1. One lamp on a 120 volt circuit L2.

Lamps are brighter when in series with 240 volts.

When L1 lamp is on, it will get brighter when L2 lamp is switched on. This change may not be detectable to the eye, but the math will prove it happens.

Is this change shock enough to take out the hot filament? I don't know, but it is a possible explanation.

 

[scott thompson]

Re: Lamp life too short!

Have a few thoughts in regards to this thread.

1: The 15 Watt Incandescent Lamps in recessed fixtures:
* Maybe getting too hot?
Excessive heat contributing to premature Lamp failure.

* Maybe the Lamps have only like 600 Hours Lamp Life @ 120VAC?
Run for 5 Hours each day over 120 Days (4 Months) = 600 Hours of operation.

* 15 Watt Lamp filaments may be very sensitive to inrush/start surges?
The cold Resistance of the filament will be lower than the operating (hot) Resistance.

* Possible to have >120 VAC at Lamp Starting or during operation?
May be a Transient case of higher than 120 VAC, or maybe the Switch controlling these Lamps is bouncing too much.

I like the CFL option (Compact Fluorescent Lamps). 15 Watt CFL will be as bright as a 60 Watt A17 Incandescent Lamp, designed for and running at 120VAC. The CFLs will last longer than conventional Incandescent Lamps.
Drawbacks are the unit type Ballast (longer overall length... only a visual drawback!), and the Color temperatures available are at most only around 2700K (maybe 3000K). If "Warm White" is OK to you, then the Color Temperature is no issue.

AFAIK, the "Old Lamp Life Extender Device" mentioned earlier was a Full Wave Bridge Rectifier, incorporated within a medium base screwshell type adapter.
If not a Full Wave Bridge, then maybe a single Diode Half Wave Rectifier - possibly with a ballasting Resistor.

Per the Common Conductor of a 4 wire 3? Wye Transformer setup;
Have a few thoughts towards these setups, as follows:

* Per use of a 4 Wire Multiwire circuit with all Lines having pure Resistance loads of equal value:
The Common Grounded Conductor will carry nearly zero Current.

* Per use of a 4 Wire Multiwire circuit with all Lines having pure Resistance loads of different values:
The Common Grounded Conductor will carry the "Vector Sum" of the Line(s) Current. More than zero, but less than the highest Line's Current.

* Per use of a 4 Wire Multiwire circuit with all Lines having NON pure Resistance loads of any value (AKA "Non-Linear Loads):
The Common Grounded Conductor will carry nearly the same level of Current which is found on the Line with the highest level of Current.

Just my 2?

Scott35

p.s. this common conductor loading stuff is covered a little more in detail, within my reply to the Number Of Current Carrying Conductors Thread.

 

[james wuebker]

Re: Lamp life too short!

Have you check to see want your annual voltage is to each socket? I have seen that L1 is your feeder to the socket and the neutral came in contact with L2 with very little pontenial causing a series circuit. The touch wasn't enoght to short out the breaker but it would be enoght to bring your voltage up a little. Just a thought. Hope you find the problem. I remember I had a problem just like this but getting to old to remember what I did. Sorry!
Jim

 

[william runkle]

Re: Lamp life too short!

Back to original post I seen them before and they were a rectifier changing A.C. to D.C. and stop the oscillation the filament would take in 60 cycles. Great idea but as others stated the disc could short out and when they became defective usually lost the socket it wouldn't come out.

 

[satcom]

Re: Lamp life too short!

Bob,
When they take the neutral and tie it to the box with a sheet metal screw, that is a bootleg neutral, and yes it can cook the lamp. We had one last week where the bootleg not only cooked the lamp but almost took out the homeowner, when he touched the armor on the cable in the basement. Remember in older homes the bonding is not always continuous or secure, and these are on multiwire circuits, by installing the neutral on the box he created a real hazzard. This same violation took the life of another electricians son, who was not aware of this type of hazzard, sorry bob, but just a little gun shy on bootleg work, with good reason. If the neutral is loose or open at the panel or any where along the run, and the bootleg is holding the ground, when it becomes loose you will have problems.

[ March 08, 2004, 10:49 PM: Message edited by: satcom ]

 

[oldmanriver]

Re: Lamp life too short!

If you are considering a diode remember the diode cuts the wattage and therefore the luminescence in half, because current flows only in one direction therefore only half of the power wave is available.

You would be better off to consider a dimmer, if it comes down to it.

Another thing is to check all your wire nuts. If you find loose connections replace them with knuckles. Most Electricians do not know that wire nuts are not allow on any "Controls" circuit, because it is an ASME code not NEC.

Intermittent arching will blow your lights just as much as all those other things.

 

[drg]

Re: Lamp life too short!

Would you be calling simple switching of a light bulb in a house "controls circuit" ?

What are these knuckles ....some type of mechanical crimp connection ??

John

 

[oldmanriver]

Re: Lamp life too short!

No, simply recalling experience. I do a lot of controls work, find all kinds of problems. I get called out on controls gone bezerk and problems like this mentioned in this topic.

75% of the time it is because the electrician used wire nuts. Wire nuts, always over time, work loose and start arching. It is a non-avoidable condition of wire nuts. They all do it. That is why "Knuckles" are required for these installations.

Knuckles are those copper bolts with the sliding compress in the Nut.

Maybe you never used one but they will always ensure arch free connections. True they cost more and take longer to install, but they work.

 

[drg]

Re: Lamp life too short!

Oh, i did not know what those knuckles were, never have heard that term before.


All electricans find loose wire nuts as a problem, quite often I am sure .......but its not the wire nut itself that is the problem ......its the way (some) people put them on that is the problem.

John

 

[hurk27]

Re: Lamp life too short!

Old Man River
I think the requirment went by the way side when wire nut manufactures started installing the spring threads in them as I agree before this they would come loose, this is where the tapeing of wire nuts came from. but I have been doing control work now for almost 30 years and the only time I hear this is when I run into a well seasond electrician. I had one plant EE that uses to require those type of connections (Knuckles) Until a 3&M rep. stoped by and showed him that wire nuts have changed. If properly installed I have yet to see a wire nut fail. Of course I hated those Scotch Locks wire nuts ever since. as they are even hard to try to get off after installing them ( you know how it goes right after you get the wire nut on then you see that last wire dangling) LOL

 

[drg]

Re: Lamp life too short!

When I first started electric work there was not a lot of thought put into twisting some wire together, im sure all you guys have had to fix stuff like this.

now every connection is important and done with thought behind it....and it shows.

Its the thing that makes the difference here.

The wire nuts that come with fixture and do not have the steel insert we just simply throw in the garbage where they belong.

John

 

[iwire]

Re: Lamp life too short!

Originally posted by drg:

The wire nuts that come with fixture and do not have the steel insert we just simply throw in the garbage where they belong.

John

 

[oldmanriver]

Re: Lamp life too short!

Back to the original problem. Rich, did you check the wire nuts and was this any help?

 

[iwire]

Re: Lamp life too short!

Originally posted by oldmanriver:
Back to the original problem. Rich, did you check the wire nuts and was this any help?

Still want to know why that would shorten lamp life, unless it is a feeder neutral or multiwire circuit neutral.

Less voltage = longer lamp life.

 

[richwaskowitz]

Re: Lamp life too short!

I'm not going to lie to you and tell you I checked the wire nuts because I did not. However, there are 6 can lights that I myself installed and I am pretty confident that all the connections are well made and tight and still I am constantly chasing all six of these, replacing lamps on a regular, too frequent, basis. When I started this post, I was not necessarilly looking for an electrical reason for the short lamp life, I was willing to concede to the probability that it was due to the lamps themselves and the duty cycle. What I was looking for was a simple method to lengthen their pathetic little lives. But I do appreciate the help.

 

[drg]

Re: Lamp life too short!

Rick how does "duty cycle" apply to the lights ??

I look at duty cycle as for a transformer such as a welder with a duty cycle of 20 % which to me means you can run the welder 2 minutes out of 10 minutes without causing the transformer to overheat.

Hope i explained that right, this only my opinion how duty cycle works........ just don't understand that term used with common house lighting .....can you help me out here so I can learn a little something today.

John.

 

[oldmanriver]

Re: Lamp life too short!

Gang,

I'm going to try to answer all this input one by one.

1. Wayne/Hurk, No the requirement has not gone away. To anyone in controls there is no such thing as a "good" wire nut. If anything the requirement has gotten stronger. If you check on it under ASME (American Society of Mechanical Engineers) you will find it applies to all control, conveyor, and elevator circuits, bar none. If you have been using wire nuts and anything fails, a death, dismemberment or any such thing then you and you alone will pay all cost associated therewith. "Do Not" I repeat "Do Not" put yourself in that place of liability. Research the code, follow it and get off the liability hook.

2. Iwire - The reason arching causes the shortening of the lamp life is two fold, first the current rush into the filament is the primary thing that causes bulb burn-out, because the cooling/heating effect in the filament causes the filament to physically change, stressing it and giving it "metal fatigue" this is why bulbs fail.
Second, arching causes voltage fluctuations, if you understand the physics of current vs. capacitance (the principle used in florescent lamps to boost the voltage to over 2KV - the voltage difference at the bulb across opposite ends) then you will understand why the voltage in an arching circuit will easily jump to over 240 volts and blow the lamp. That's why I told Rich to check them.

3. Rich - Correct me if I'm wrong but I recall that you said these were overhead outside lamps, your wire nuts are in the worst place to cause you problems. Attic spaces have all the heating/cooling problems causing expansion/contraction in the wire nut, therefore making it fail at the earliest possible time. Furthermore unless you put them in a weatherproof box you can add condensation/moisture to your list of "why it failed".

I suggest going back taking off the wire nuts, twisting the wires, well, soldering them, then re-install the wire nut. It may not fix the problem, if you have another situation, but at least you will know it is not a wire nut arching problem.

 

[peter d]

Re: Lamp life too short!

oldmanriver,

then you will understand why the voltage in an arching circuit will easily jump to over 240 volts and blow the lamp.

Not trying to give you a hard time but I'm very curious to understand this. Could you present some calculations to show how this is possible on a 120 volt, non-multiwire circuit?

[ March 10, 2004, 01:38 PM: Message edited by: peter d ]

 

[steve66]

Re: Lamp life too short!

Old man river is correct about a 120v circuit producing higher voltages during an arc. When a bad connection breaks the circuit, any stray inductance in the circuit tries to keep the same current flowing. The magnetic field around the wires collapses and produces a voltage high enough to cause an arc.

However, the high voltage is created across the bad connection. Not across the light bulb.

Steve