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#27362 - 07/11/03 06:43 PM Why won't these fluorescent fixtures come back on?  
maintenanceguy  Offline
Joined: Dec 2001
Posts: 300
Southern NJ, USA
Today I replaced a ballast& coil in an outside HPS light. This is a 277V fixture on the same circuit as probably a dozen F40T12 fixtures and half a dozen U-tube 40W fixtures.

When I was done with this single HPS light, I turned the CB back on and the HPS fixture came on, another HPS fixture on the same circuit came on, all the 4' F40T12 fixtures came on, three incandescent exit signs on the circuit came on, and every single one of the U-tube fixtures would NOT come back on.

They glow a dim bluish glow but never got started. I turned the cb off and on a couple of times and got the same result every time.

Both types of fluorescent fixtures have magnetic ballasts, the voltage in this building is low everywhere, around 265V. I checked this circuit when running and got 265V.

What's going on?

Work Gear for Electricians and the Trades

#27363 - 07/11/03 07:16 PM Re: Why won't these fluorescent fixtures come back on?  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,217
SI,New Zealand
Just as a ball-park guess,
I'd say that the voltage is too low at the U-tube fittings to strike the tubes.

Let's face it, these days if you're not young, you're old - Red Green grin

#27364 - 07/11/03 08:15 PM Re: Why won't these fluorescent fixtures come back on?  
Bjarney  Offline
Joined: Apr 2002
Posts: 2,527
West-Southern Inner-Northeast ...
Not sure this will help, but by a treaty of sorts between and appliance manufacturers, {ANSI Standard C84.1} “nominal 277-volt” gear should be able to operate over the range of 245-293 volts. No guarantees on efficiency, but generally equipment should not burst into flames over that voltage range.

[This message has been edited by Bjarney (edited 07-11-2003).]

#27365 - 07/11/03 09:47 PM Re: Why won't these fluorescent fixtures come back on?  
bigrockk  Offline
Joined: Jan 2003
Posts: 174
Middle of Canada
Just a guess, but is there a chance you left a ground wire disconnected
when you changed the ballast?
Some fluorescents will not start unless they have a good ground, or if the U tubes our really old they may not want to restart when powered back up.
Good luck!

[This message has been edited by bigrockk (edited 07-11-2003).]

#27366 - 07/11/03 11:25 PM Re: Why won't these fluorescent fixtures come back on?  
frenchelectrican  Offline
Joined: Feb 2003
Posts: 939
Wi/ Paris France { France for ...
one thing about u tubes with mangatic ballast they are very nortious with hard starting i have ran into alot of them both 120 and 277 volts verison and they are pain in the butt and what i did swap out get electronic ballast seems work pretty good and by the way check the u tube it should have metal foil right along the bulb length it should be there to help to start up but i know i have few mangatic ballast that ran on 277 and got started on low as 260 volts but really pushing luck with it and u tubes are very senstive with tempture for starting it useally required above 60 degrees to start if less than that it will not light up or stay bleu on end and check the open line ( bulb end) to check the voltage but there are so many diffrent verison of ballast so i cant really pinpoint it yet unless i know which type of ballast it ran

merci marc

Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

#27367 - 07/12/03 12:10 AM Re: Why won't these fluorescent fixtures come back on?  
Trumpy  Offline

Joined: Jul 2002
Posts: 8,217
SI,New Zealand
Welcome!. [Linked Image]
Guys, with the earthing on these fittings,
on the old semi-resonant start fluorescents we used to have at the local meat-works, there was a small aluminium strip, that used to sit right next to the tube(these were standard linear double-ended tubes), I assume that this strip had something to do with the ionisation of the mercury vapour in the tube,during starting, is this correct?.
BTW, these strips were directly earthed, with thier own earth wire, to the terminal block of the fitting.

Let's face it, these days if you're not young, you're old - Red Green grin

#27368 - 07/12/03 07:58 AM Re: Why won't these fluorescent fixtures come back on?  
electure  Offline

Joined: Dec 2000
Posts: 4,260
Fullerton, CA USA
Merely a guess, but there may be a loose connection in a J box somewhere.
Measure the voltage at one of the U tube fixture's supply terminals with everything turned on, and work your way back.
They should all fire up readily with a 265 volt supply...S

#27369 - 07/12/03 11:20 AM Re: Why won't these fluorescent fixtures come back on?  
bigrockk  Offline
Joined: Jan 2003
Posts: 174
Middle of Canada
Thanks Trumpy,
I have been monitoring this site for a while, but haven't participated much.
I am always amazed by the camaraderie and professionalism of the participants,
A great site, I always seem to be learning something here.

#27370 - 07/12/03 09:56 PM Re: Why won't these fluorescent fixtures come back on?  
Active 1  Offline
Joined: Feb 2003
Posts: 687
Grayslake IL, USA
I too had trouble with those U tube floresents. I was told that a floresent needs to have the best equipment ground. Run a ground wire in your wip. Clean the paint off around the ground screw. The closer the bulb sits next to the grounded case the better. The clips that hold the bulb in need to be grounded. The metal strip on the bulb needs to be grounded thru the clips that hold them in. Most lights I got did not provide a good ground to the u-bulb.


#27371 - 07/12/03 10:32 PM Re: Why won't these fluorescent fixtures come back on?  
Scott35  Offline

Broom Pusher and
Joined: Oct 2000
Posts: 2,707
Anaheim, CA. USA
So the lamps are trying to start? (that's what the glowing at the ends is all about).

This sounds like an end of life situation. Lamps have reached the end of their useful life, requiring a replacement.

The glowing ends would indicate:

[*]Both pins on one end of a lamp are in contact with the lamp holder,

[*]The wiring from the Ballast to that lamp holder is continuous,

[*]The Cathode (fillament) at that end of the lamp has continuity,

[*]The Secondary winding of the Ballast is (most likely) continous,

[*]The heater winding(s) on the Primary side are (most likely) continuous.

This would be accurate if BOTH Cathodes are glowing (both ends of the lamp). If only one end of the lamp is glowing, there are more things to consider.

If both Cathodes are glowing, try replacing a lamp with a known good / operational equivalent lamp. This lamp should strike and operate normal. If not, verify the obvious conditions, which include:

[*]Both lamp holders are connecting to lamp pins solidly,

[*]Both lamp holders have solid lead connections,

[*]Ballast is operational (not over heated or visible signs of damage or failure).

Voltage between both lamp holders should be no less than 200 VAC, and voltage across terminals of a lamp holder should be no less than 3 VAC. Any values lower than what's shown here would indicate Ballast failure, requiring Ballast replacement.

If only one end of a lamp is glowing, this indicates several things:

[*]The Cathode on the lamp end which is not glowing has no continuity - therefore it has failed,

[*]The lamp holder to the side which is not glowing is not connecting to both pins of the lamp,

[*]The circuitry to the lamp holder on the non glowing side does not have continuity,

[*]Heater winding on Primary side has failed, or the Secondary winding has failed.

Overall, simply check the obvious stuff first - such as broken lamps and lamp holders, loose lamps, very darkened lamp ends, and not to forget about correct lamp-to-Ballast matching! Trying to use an HO or VHO lamp on a 430ma Ballast will result in starting failure. If 430ma lamps are driven from HO or VHO Ballasts, the lamps' life will be drammatically reduced.

After verifying the obvious, then check voltage readings - first at the Line Input, then for Open-Circuit values across lamp holders and lamp holder terminals.

Sorry to not include enough information, but this should do fine for you.

Let us all know the results, plus feel free to ask further questions if you need to.


p.s. to assist in lamp/Ballast circuitry voltage measurement points, check out this schematic:

F40 T12 2 lamp Ballast Schematic

btw, are the "U" tubes T12 type or something different? If they are T8 compact U lamps, or T5 "Biax" or "PL" types, these would be much different than the above.

Describing the Rapid Start Hot Cathode lamp operation. Click on the above hyperlink, or go to the Technical Reference section and select it from the list of items.

For other items, check out the Menu For Technical Reference Section , by clicking on the link or going to that area manually.


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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