On 2 recent jobs of replacing high-output tubes while the fixture was still on, I was getting small shocks when I was installing the tubes in the sockets. I was only holding the glass and was not grounded. My question is: Is this a capacitive path through me while the tube is trying to fire? I've never had this happen before - both of these jobs involved replacing the tubes in an outdoor sign.

Are the ballasts grounded properly?

Actually I have had that happen while replacing regular 4' T-8 lamps.
I wonder if this all has something to do with how fluorescent tubes must be within like 1/2" of GROUNDED metal to fire correct, and even why some of those U-bents have foil strips on them??

A.D

Have you ever noticed ust how dust loves to collect on fluorescent tubes, as well as TV screens?

The operation of the lights generates some static electricity. I expect that you wer, in fact, grounded... and allowed the static to drain.

I usually use leather gloves and wear safety glasses just in case the tube breaks.

Yes, the ballasts are grounded. For one of them, I was on a fiberglass ladder under a canopy and I was making sure that I wasn't grounded after I got the first couple of shocks, yet it still happened. It's bizzarre getting a shock when all you are doing is holding onto the glass tube.

Sixer, I once saw the outside of a rubber gas line act as a conductor. The 10.000V impulse ran along the coil wire, jumped a 1" gap, ran alon the surface of the hose....then grounded to the engine.

Static electricity has phenominal voltages. Many thing that we think of as "non conductive" will, in fact, carry current at such high voltages.

When a Discharge Lamp is brought into operation (initial Arc becomes a Plasma), a charge is placed on the Lamp's "Envelope" (the outermost part of a Lamp).
This charge is the result of the internal ionization of materials, which rapidly threw things from a steady state (prior to passing the precursive initiating Arc), into a different state.

Normally, this charge will drain off the Lamp, and allow the full Plasma to be achieved without impeding the start process - or if the start process is completed, the charge levels become low enough to not be noticed from someone touching a Lamp bare-handed.

This is very common with "Low Output" and Low Power Fluorescent Lamps, being very close to metallic items.

Most HID Lamps fall into this category too, mainly because they have their Arc Tubes enclosed by separate envelopes, so the charge simply drains off through the socket connection, into a larger metallic body (also I have no wish to touch any HID Lamps in operation!!!).

On the other hand (OTOH), Fluorescent Lamps having High Output classifications (like F40 T12 HO - an 800 ma High Output Lamp, or F96 T12 VHO - a 1500 ma Very High Output Lamp), will leave a much higher charge on the Lamps, and these charges may not always completely drain off to metallic items in close proximity of the Lamps - resulting in "EEEOWWW" from the person grabbing a Lamp bare-handed.

The phenomina taking place here is not an actual (or required) "Path To Ground" for the charge on the Lamp to "find", but the "ability" for charges on the Lamp to flow to "something" having a different charge (could be higher or lower in charge state).

This is the old statement: "Difference Of Potential"

In the case of the Lamp zapping, one would not need to be connected to the Earth, or any other Ground Bonded Metallic structure/equipment - one simply needs to have a different state of charge, and there will be "A Difference In Potential" - thus allowing charges to transfer (in hopes to become "Neutral" or "Ground State").

Sadly, the unwilling victim has never been asked to nullify the Potential Difference!
Physics just assumes you are in full agreement, and never asks / says a thing!

Scott35

Ray,
Good call there, mate.
I learned that lesson when I first started my time as a sparky, removing an old T12 (series start) tube from a fitting.
As was common, the end cap that holds the pins had jammed in the lampholder and as I twisted it, I must have squeezed the tube, because it exploded into pieces.
I have had a scar on my left hand ever since that took years to heal properly.
I've worn gloves ever since that day, when working with fluoro tubes and as Ray stated, safety glasses.
Getting a shard of phosphorus coated glass in your eye would not be fun at all.
I'm glad that they don't use mercury in fluoro tubes anymore, but the risk is there with older tubes.
Be careful.

Not to mention those old pcb filled ballasts too. Those old fluro fixtures are just one big health hazard.

Since when don't they use Mercury in Fluorescent tubes?? They reduced it but its still there

Waste Management here will not pick up my customers trash if fluro bulbs are in there.

We have to collect the bad ones, but haven't found where to get rid of them yet.

Dnk,

Just how many lamps are you guys dealing with.

Google for fluorescent tube recycling and you will find lots of companies who deal with small numbers of lamps, but they all cost...almost more than the new lamps.

But they seem to have bulk containers that are more economical. I've never needed to use bulk services.

-Jon

[This message has been edited by winnie (edited 11-03-2006).]

about a hundred or so.

Thanks jon, didn't think of that.

Its illegal to throw them in the trash in Maine. They are known as Universal waste. It costs me 11 cent a foot to get rid of them, 75 cents for metal halide, HP sodium etc

walrus,
New tri-phosphor (sp??) tubes do not require mercury to enable the arc to light the phosphor layer.
Newer T8 and T5 tubes do not use mercury.

As far as Philips is concerned their T8s are low mercury not mercury free http://www.prismaecat.lighting.philips.com/LightSite/Whirlwind.aspx?eca=LNPPLA&cpf=USNPUS&stg=ACT&lan=US+&ecu=LMP|PLC|NP&cnt_key=F_T8PSL%20+|PLC&t=1&tree=0&scr_md=1111&nav=Null&loc =us_en&leftnav=1_1

Dnkldorf

http://www.bethlehemapparatus.com/

Somewhat local recycler. They offer cartons so you can ship bulbs to them.

Larry C

Thanks Larry,

Scott

I can see where you are comming from with the PD. I would have thought that by holding the tube before conecting a supply both you and the tube are part of an unbroken circuit therefore no PD would exist. ahhh just thought that would be true untill you let go

Kenbo,

I agree.

If the person installing the Lamp is "Bonded On" (in such terms) to the Lamp, then installs the Lamp across the power supply, both bodies should have equal Energy Status - so, a very, very low Potential Difference should exist between the Lamp, and the Bonded Person.

Once the installer removes the last physical Bond between the two bodies (last finger is coming off the lamp), the Potential Difference begins to increase rapidly (IMHO).

Furthermore, IMHO, since the installer has a much larger surface area (not to mention a very high MHO state), the resultant charges from the Lamp will flow very easilly into the installer, and are drained out from the installer in extremely higher levels - as compared to what the Lamp may drain out alone.

The sudden and rapid change, when the finger begins to move away from the Lamp, throws the "free-flowing" state into a now limited state.
Now the circuit opposes the rapid change the only way it can, in order to keep charges flowing: an Inductive or Capacitive "Kick" is born.

I am viewing it as the way current surges across contacts, when the "Breaker Points" of an Automotive Ignition System first begin to open.
If the Capacitor (or "Condenser" for those preferring to use that term) is removed, we can get some large levels of surge currents flowing between closely separated contact points (may be drawn across a gap as wide as 1/16" and still keep a hefty Arc going!)

So, in an effort to both keep things flowing as they were before, and to "nullify" the now rapidly increasing Potential Difference (because the desire is still there to move charges into the installer), the installer will still receive an "Owww-eee" when clearing the last body part from the operating Lamp.

This is only my opinion, so please feel free to de-bunk as required.

Scott35

edited to fix spelling blunders!

[This message has been edited by Scott35 (edited 11-05-2006).]