T-8 Ballast/Lamp

[Taylorwoorobertson]

I just relamped my store with T-8 bulbs about 4 weeks ago. They are already showing signs of black rings on the end of the bulbs and/or going out. I have checked voltage on the service to make sure I wasn't experiencing a voltage spike but I show less than 2% increase. The fixture/ballast are only about 4 years old. What else can I check or what should be done?

 

[Fordean]

I seen ballasts that have to have Plunger on specific side only. Connected to yellow I think. Was given me problem until I read it. Usually wiring wrong. Think it was t12 while back. Conversion to T8. Also some ballasts are not as good as they should. Make sure name brand. Counterfiets out there as well.

 

[GoldDigger]

I just relamped my store with T-8 bulbs about 4 weeks ago.... The fixture/ballast are only about 4 years old.

Just to make sure not to overlook the obvious, if the previous bulbs were T-12, I am pretty sure that you need to replace the ballasts when changing to T-8.

 

[hurk27]

This can also be a problem in fixtures which require a grounded metal case to be within a half of inch of the lamps, this helps to ignite the lamps much faster and lowers the start up time, also it can be because the fixtures are just cycled on and off allot, we find this problem on fixtures tied to motion detectors for rooms not used much or frequently with people going in and out through out the day tend to have a lot of cycles on them.

the black ends you see are the anode in the end of the lamps that are burned off a little each time you start the fixture, voltage drops can also cause a longer starting time as with the lack of grounding as mentioned above.

This should give you a basic check list, also cheap lamps can also be subject to this as they are not very well engineered and take longer to start.

The only other thing I can think of is cheap home grade fixtures will sometimes come with very cheap ballast, these many time have barely enough voltage and current to even start the lamps and can result to having a much longer strike time, many of these ballast are much smaller then the good quality ballast you find in commercial grade fixtures, Home Depot many time has the same fixture with one a home grade and one listed as a commercial grade, and what a difference between the two.

This is one case where you get what you pay for:happyyes:

 

[hurk27]

Just to make sure not to overlook the obvious, if the previous bulbs were T-12, I am pretty sure that you need to replace the ballasts when changing to T-8.

So very true while many ballast are listed to supply both T-12 and T-8 lamps, doing this can cause longer start times and over voltage/current to the anode of the lamp, it is always best to use the correct lamp for the ballast that it was primarily design for, instant start electronic ballast is about the best for long life T-8's as they have a extremely very short starting cycle.

 

[TOOL_5150]

Also, if there used to be T12s installed, and no one changed the tombstones, that could be a problem too. T8 lamps need shunted tombstones, or both blue/red wires tied together.

 

[hurk27]

Also, if there used to be T12s installed, and no one changed the tombstones, that could be a problem too. T8 lamps need shunted tombstones, or both blue/red wires tied together.

that would only apply if the ballast was also changed, if the fixture had T-12s then the existing ballast would still have a 6 wire output (two lamp), there are some T-8 ballast that also have a 6 wire output including electronic, but if I'm going to change to electronic I always get the 3-wire output ballast, less wires to deal with.

6 wire ballast will have two yellows two reds and two blues
3 wire has (depending upon the manufacture) one blue and two reds, the blue connects all the yellows and the reds, one will connect to both reds, and one will connect to both blues

the other colors I ran into was two blues and one red but wire the same as above just swap the colors

4 lamp single ballast electronic will have a 5 wire output wired kind of the same with one red going to all the yellows and 4 blues (again depending upon manufacture) with one each going to the other end of each lamp.

T-8 lamps have preheat filaments in them and rapid start ballast (6 wire) still use the preheat to start the lamps, instant start and program start ballast don't use this and only use the filament as an electrode so it only requires one wire to each lamp end.

 

[kwired]

Originally Posted by Taylorwoorobertson
I just relamped my store with T-8 bulbs about 4 weeks ago.... The fixture/ballast are only about 4 years old.

Just to make sure not to overlook the obvious, if the previous bulbs were T-12, I am pretty sure that you need to replace the ballasts when changing to T-8.

Completely agree.

Is the new lamp type one listed on the ballast?

You must match the lamps and ballast, if you don't you likely will not get good performance, even if the lamp does light.

 

[roger]

Taylor, have you asked one of the electricians you manage this question? It wouild probably be a good idea to consult with them or even let them do the work.

Roger

 

[TNBaer]

Just to make sure not to overlook the obvious, if the previous bulbs were T-12, I am pretty sure that you need to replace the ballasts when changing to T-8.

Yep. T12 ballasts operate at nearly twice the current of T8 ballasts. I bet there's a huge heat issue as well.