# Using non-shunted "tombstones" on a T8 ballast



## user4818 (Jan 15, 2009)

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.


----------



## k2x (May 20, 2008)

Peter D said:


> 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.


----------



## Toronto Sparky (Apr 12, 2009)

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.


----------



## MDShunk (Jan 7, 2007)

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.


----------



## user4818 (Jan 15, 2009)

Thanks for the replies. Looks like I have to go back and do some rework. Oh well. Live and learn.


----------



## NolaTigaBait (Oct 19, 2008)

Whats the difference between the two sockets?


----------



## user4818 (Jan 15, 2009)

NolaTigaBait said:


> Whats the difference between the two sockets?


A shunted socket has both sides of the socket connected together for use with T8 lamps.


----------



## NolaTigaBait (Oct 19, 2008)

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.


----------



## user4818 (Jan 15, 2009)

NolaTigaBait said:


> 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.


----------



## NolaTigaBait (Oct 19, 2008)

Peter D said:


> 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.


----------



## user4818 (Jan 15, 2009)

NolaTigaBait said:


> 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.


----------



## NolaTigaBait (Oct 19, 2008)

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.


----------



## k2x (May 20, 2008)

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.


----------



## frenchelectrican (Mar 15, 2007)

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


----------



## Toronto Sparky (Apr 12, 2009)

NolaTigaBait said:


> 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.


----------



## czr1760 (Nov 30, 2011)

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.


----------



## ampman (Apr 2, 2009)

not that i care but this thread is VERY OLD


----------



## green light (Oct 12, 2011)

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.


----------



## TOOL_5150 (Aug 27, 2007)

ampman said:


> not that i care but this thread is VERY OLD


But, Its informative :thumbsup:


----------



## HARRY304E (Sep 15, 2010)

czr1760 said:


> 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
> ...



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.

Welcome to the forum enjoy the show...:thumbup:


----------



## frenchelectrican (Mar 15, 2007)

green light said:


> 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.


 
SVP{please} do post the photo if you can find it and by the way.,, If you have any T-8 ballast that use the dimming function becarefull most of them I ran into genrally wired for rapid start so check the ballast label to make sure I know couple of them are wired for instat start.

Merci,
Marc


----------



## Scott Paullin (Dec 17, 2011)

*Unshunted sockets*



user4818 said:


> 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.


In my experience if both wires from the unshunted sockets are wired to the ballast leads ou will not have a problem. 11 years light retrofitting experience


----------

