T5 flashes the lamps, then goes out. Tried new lamps, ballast, and tombstones.

[MAC702]

Please forgive my post count. I've been reading Mike Holt's forum for many years, but this is the first time I haven't found an answer in a search.

I have a regular commercial client (BR31 ice cream shop) with some T5 fluorescent lighting. It is a row of three ceiling fixtures on the same switch. Each is a two-lamp. They've worked fine for many years. I was not the original installer.

He said it flashes when he turns it on, and then goes out. He said he replaced the lamps. Same thing. He suspects ballast and asks me to change it. I would suspect ballast, too, but I have no experience in troubleshooting T5's. None have ever failed on me before. So I replaced the ballast with the equivalent. But I get the same problem. It flashes, and then goes out. Sometimes, it will flash while manhandling fixture, but usually not. I've tried duplicating that on purpose by tapping various locations and connections, to no avail. Usually, if you toggle to the switch, it only flashes that first time, until you leave it alone for a while.

So I bring the fixture home and replace the tombstones, and use power at my bench to test it. SAME THING. What parts are there besides lamps, ballast, and tombstones? That's rhetorical unless I've just gone insane, finally.

Two times it actually stayed on, which eliminates some theories, probably. The first time it did this was after I replaced the tombstones and tested it on the bench. IT WORKED. I took it back to the store and reinstalled it in the ceiling, in a very PITA fixture. SAME PROBLEM. Took it back to the shop again, and now the problem is here, too, so that one fluke of staying on cost me half a day of traveling and installing and removing. Very upsetting.

Voltage at test bench is 122; voltage at point of connection in the store, which I also redid, under load, is 119.

I'm at my wit's end on this one. Any ideas? Please tell me I'm really stupid and missed something really obvious.

 

[GoldDigger]

Please forgive my post count. I've been reading Mike Holt's forum for many years, but this is the first time I haven't found an answer in a search.

I have a regular commercial client (BR31 ice cream shop) with some T5 fluorescent lighting. It is a row of three ceiling fixtures on the same switch. Each is a two-lamp. They've worked fine for many years. I was not the original installer.

He said it flashes when he turns it on, and then goes out. He said he replaced the lamps. Same thing. He suspects ballast and asks me to change it. I would suspect ballast, too, but I have no experience in troubleshooting T5's. None have ever failed on me before. So I replaced the ballast with the equivalent. But I get the same problem. It flashes, and then goes out. Sometimes, it will flash while manhandling fixture, but usually not. I've tried duplicating that on purpose by tapping various locations and connections, to no avail. Usually, if you toggle to the switch, it only flashes that first time, until you leave it alone for a while.

So I bring the fixture home and replace the tombstones, and use power at my bench to test it. SAME THING. What parts are there besides lamps, ballast, and tombstones? That's rhetorical unless I've just gone insane, finally.

Two times it actually stayed on, which eliminates some theories, probably. The first time it did this was after I replaced the tombstones and tested it on the bench. IT WORKED. I took it back to the store and reinstalled it in the ceiling, in a very PITA fixture. SAME PROBLEM. Took it back to the shop again, and now the problem is here, too, so that one fluke of staying on cost me half a day of traveling and installing and removing. Very upsetting.

Voltage at test bench is 122; voltage at point of connection in the store, which I also redid, under load, is 119.

I'm at my wit's end on this one. Any ideas? Please tell me I'm really stupid and missed something really obvious.

You have replaced ballast with identical or equivalent, but have you verified that ballast and lamps are an allowed combination? Possibly it was incorrectly configured from the start but worked for awhile anyway?

Sent from my XT1585 using Tapatalk

 

[MAC702]

Now, see, you could have saved a lot of typing but just saying: "Yes, you're really stupid and missed something really obvious."

These lamps (that he supplied) are F28T5, which is not listed on either the old or the new ballast. Why didn't I look at that before? Because, on the first visit, I swapped lamps around between two fixtures to confirm that the lamps worked. They worked just fine in the other fixture, which I ASSume has the same ballast. It at least looked similar enough for me not to scrutinize its label.

So, I think you nailed it. I'm stupid. I'm going to go buy two lamps marked F54T5HO or FT55W or one of the other ones specified on these ballasts, which are the same. I'm also going to check all the other lamps in the store to verify that he doesn't have the same problem ready to occur elsewhere.

This is one of those times I just trusted the client to have the right part, and it bit me in the butt! My only experience with T5's is installing new Lithonia low-bays and didn't realize there were different lamp types that used the same tombstones. Because, why would they do that, right? Dang.

 

[GoldDigger]

Just be careful not to give him more light than he wants (or needs?)
And watch the color temperature. Even if light color is acceptable, a difference between fixtures can look really cheap.

 

[MAC702]

To his credit, he actually had the lamp with him at the store and bought the same ones. Turns out, the other fixtures have the wrong lamps as well. He took over this franchise only a few months ago so it wasn't his bad the first time. I would have made the same error, then, too. It was just the different brand of new lamps that wouldn't work with the wrong ballast, which is hidden from view without the huge PITA to take the fixture apart over your head. He said they worked for two months before doing the flashing thing, too.

You can really see the difference. The new lamps are twice as bright. So we'll be getting the same lamps and they will all match.

Even the old 8' T12 lamps have different pin configurations for standard v. HO. I learned that one the hard way, too, as I've never even seen an HO fixture and bought the wrong lamps once. I still didn't know there were standard or HO T5's to start with, being as I ASSumed these modern tubes would all be a high output. But I especially wouldn't have expected the darn things to use the same pin configurations. There's got to be a ton of these things out there with the wrong lamps in them.

Thank you very much for the brainstorm.