Using non-shunted "tombstones" on a T8 ballast - Electrician Talk - Professional Electrical Contractors Forum
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Old 06-29-2009, 10:12 PM   #1
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Default Using non-shunted "tombstones" on a T8 ballast

Will this cause premature failure of the lamps and/or ballast? On a few occasions in the past I've used T12 lampholders on a T8 ballast and I did not bridge one side of the lampholder to the other per the ballast diagram. Obviously it still worked, but I'm wondering if this will cause problems down the road.
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Old 06-30-2009, 12:24 AM   #2
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Will this cause premature failure of the lamps and/or ballast? On a few occasions in the past I've used T12 lampholders on a T8 ballast and I did not bridge one side of the lampholder to the other per the ballast diagram. Obviously it still worked, but I'm wondering if this will cause problems down the road.
Should shorten the lamp life because the start up kick is uneven to one side.
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Old 06-30-2009, 03:08 AM   #3
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Will shorten life.. Seen it. Been there done that. As for why? not sure.
They do make the socket internally jumped.
I'm thinking if you are going to retro you should change the sockets as well.. May even save time an money doing so.
And it's a better job.
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Old 06-30-2009, 08:34 AM   #4
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When only one lead is connected, the cathode current only travels on one leg of the filament of the cathode instead of parallel on both leads of the cathode. This causes excessive current on one cathode leg and burns it off inside the lamp. This is quite evident with an ohm meter on a failed lamp.
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Old 06-30-2009, 07:30 PM   #5
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Thanks for the replies. Looks like I have to go back and do some rework. Oh well. Live and learn.
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Old 06-30-2009, 07:36 PM   #6
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Whats the difference between the two sockets?
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Old 06-30-2009, 07:44 PM   #7
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Whats the difference between the two sockets?
A shunted socket has both sides of the socket connected together for use with T8 lamps.
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Old 06-30-2009, 07:49 PM   #8
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Oh ok. I just did 21 fixtures from magnetic to electronic and used the original sockets..i guess, i'll have to wait and see how this works out...i'm kinda nervous now.
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Old 06-30-2009, 07:50 PM   #9
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Oh ok. I just did 21 fixtures from magnetic to electronic and used the original sockets..i guess, i'll have to wait and see how this works out...i'm kinda nervous now.
If you left the old wires in and cut them off the ballast and spliced onto them with the new wires from the ballast, you should have no trouble at all.
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Old 06-30-2009, 07:54 PM   #10
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If you left the old wires in and cut them off the ballast and spliced onto them with the new wires from the ballast, you should have no trouble at all.
Yeah this is what i did...scared me for a minute.
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Old 06-30-2009, 08:05 PM   #11
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Yeah this is what i did...scared me for a minute.
That's normally how retrofits are done - leave all the old stuff in place and just splice onto it.

In my case, I had to replace some sockets because they had cracked so I just connected the ballast wire directly to the new socket while doing the retrofit.
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Old 06-30-2009, 08:34 PM   #12
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So, in this case you didn't use a jumper wire...on the new t8 sockets, no jumper is required b/c it internally shunted.
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Old 06-30-2009, 09:23 PM   #13
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There are still plenty of t-8 rapid start/ series wired ballasts out there that cannot use a shunted lamp socket. Dimmable t-8's will probably be series wired for a long time.
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Old 07-04-2009, 07:05 AM   #14
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It will be nice if they have a marking for shunted tombstone sockets so that way we can able indentify it quick without tearing into the luminaire.

I can't remember who make them and have marking " S " on it but when I was staying in France they have marked " S " or " Shunté " one of the two.

Merci,Marc
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Old 07-04-2009, 02:44 PM   #15
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So, in this case you didn't use a jumper wire...on the new t8 sockets, no jumper is required b/c it internally shunted.
All the shunted ones I have seen only have one hole to put the wires.
Well Two.. but they are both on the same side.
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Old 11-30-2011, 05:49 PM   #16
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I am just not understanding how there is a difference between "shunting" the wires on a T8 instant start ballast & using a shunted socket. I'm trying to retro fit T8 instant start ballast to T8 rapid start ballast. This is the information that I found on the GE website:
Instant Start vs. Rapid Start Sockets
When using programmed start or dimming ballasts in fixtures,
sockets must be 2-pin rapid start type. Fixtures with T8 instant
start ballasts must use jumpered rapid start sockets or shunted
lamp holders (internal to the lamp holder) that bridge the lamp
bi-pins together into one contact on each side of the lamp. If
retrofitting
from a instant start ballast fixture with shunted
sockets to a dimming or programmed start ballast, rapid start
type sockets must be used to properly start lamps and maintain
rated lamp life.
I don't want to shorten lamp or ballast life, but don't understand why it is ok on T12, but not on T8. Thanks for any help.
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Old 11-30-2011, 09:48 PM   #17
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not that i care but this thread is VERY OLD
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Old 11-30-2011, 10:35 PM   #18
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frenchelectrician,
I recently retroed a lot of lights in a hospital. Some tombstones had to be shunted and some didnt, mostly due to wether the fixture was to be dimmed or not. The shunted tombstones have the letters "shunted" printed right on them. I will try and find one and post a pic.
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Old 11-30-2011, 10:59 PM   #19
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not that i care but this thread is VERY OLD
But, Its informative
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Old 11-30-2011, 11:26 PM   #20
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Quote:
Originally Posted by czr1760 View Post
I am just not understanding how there is a difference between "shunting" the wires on a T8 instant start ballast & using a shunted socket. I'm trying to retro fit T8 instant start ballast to T8 rapid start ballast. This is the information that I found on the GE website:
Instant Start vs. Rapid Start Sockets
When using programmed start or dimming ballasts in fixtures,
sockets must be 2-pin rapid start type. Fixtures with T8 instant
start ballasts must use jumpered rapid start sockets or shunted
lamp holders (internal to the lamp holder) that bridge the lamp
bi-pins together into one contact on each side of the lamp. If
retrofitting
from a instant start ballast fixture with shunted
sockets to a dimming or programmed start ballast, rapid start
type sockets must be used to properly start lamps and maintain
rated lamp life.
I don't want to shorten lamp or ballast life, but don't understand why it is ok on T12, but not on T8. Thanks for any help.

If you are using T-8 rapid start ballast then the wiring diagram is the same as a T-12 rapid start ballast.


An instant start ballast type T-8 is different and requires the scokets to be shunted.

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