ECN Forum Forums General Topics of the Trade General Discussion Area T8 lamps swirling.....why?

I replaced some 8' T12 fixtures the other day in a restaurant with 8" T8's. All was good when I left, until the owner called the next day. The lamps are now swirling or spiraling. They have been installed now for more than a week and are still doing it. I even tried to replace some of the lamps and they still do it. Anyone have an answer for this?? Thanks, Merlin.

Merlin,
Is it cold in there?
Usually the swirling is caused by low temperature, because the mercury inside the tube doesn't fully vapourise.

No it is in no way cold in there. In fact there is a furnace that is mounted near ceiling that heats the small area rather well. At the time I installed them it was probably near 85 degrees at the ceiling.

I would maybe try different brand of lamps first and see if that helps. Are the fixture chassis all solidly grounded? As a last resort, I would probably try a different brand of electronic ballast in one of the fixtures.
If that works, then you will probably want talk to your supplier about who’s going to eat the cost of replacing the remaining ballasts or the complete fixtures with a different brand.

8 Foot T8 "Standard Bi-pin" Lamps (430 ma Lamps) are - for lack of a better term - Dogs!
The Capacitive "Cork-Screw" effect will reduce in time, to a point where it is not noticed.

As mentioned, the Swirling Effect is a common phenomena where Lamps are exposed to low Temperatures.
The Lamps, in a way, are suffering from Hypothermia - they cannot produce enough heat to sustain a solid Plasma, so the Plasma does not fill the entire Lamp Envelope.
The Cold Ambient Air surrounding the Lamps draws larger heat quantities away from the Lamps, which directly affects the Illumination Wattage of the Lamps - resulting in lower Light output.

Similar results occur where the Ambient Temperature is hot, only in this case the Lamps absorb heat.

Program-Starting of HO & VHO Lamps - via Hot Cathode Operation, tends to reduce these issues.

Have the Client leave the Lamps operating continuously for at least 8 Hours per day, no less than 5 consecutive days.
If the issue remains unchanged after this period of Lamp Initiation, AND the swirling is a valid issue (read: critical to safety / task, not simply a "Peeve"), consider changing to either 8 Foot T8 HO/VHO Lamp-Ballast setup,
or,
instead of the 8 Foot T8 Lamp, use (2) Four Foot T8 430 ma Lamps with an Instant Start Ballast, in place of (1) Eight Foot T8 430 ma Lamp.

Good luck!

-- Scott

Thanks for the input. At last discussion with the customer, the lamps continue to "corkscrew". It definately is not an issue of being cold. It is actually rather warm at all times in this location. I find it odd that this was never an issue with the T12 fixtures that were previous to the T8's. The customer now states that when the lights are turned off, that now they "arc" in the tube from one end to the other. I am at a loss for answers at this time.

Have YOU actually been there when the lamps are misbehaving? Could something been lost in the relaying of the messages?

Are these fittings using HF ballasts or older type Wire-wound ballasts?

The so-called "arcing" can be put down to the tubes "after-glow" when turned off, this is normal.

Yes I have been there and seen the corkscrewing. I have not seen the arcing yet. These are new Lithonia fixtures that I just installed. I think I will contact my lighting rep today.

I have seen similar effect on 4 foot T8s. New tubes in previously working fixtures will swirl. Sometimes they clear up. Other times the tube gets changed again. I put it down to cheap tubes. Some tubes from the same box are not even the same color.