T8 tube spacing?

[BioHazard]

I want to retrofit my 8' T12HO strip lights to use 4' T8s and electronic ballasts. Problem is 2x8' T12HO is the same light output as SIX T8s. To get the same light output I need to replace two rows of tubes with three.

When I remove the giant T12 tubes, there is enough room to mount 3 T8 tubes in the same fixture. Problem is they'd only be about 3/16" apart. Would that be an issue for heat or light output? I'll probably have it on two switches so the center tube isn't always lit.

 

[BioHazard]

Hmmm...I guess they're more like 5/16" apart once I add the sockets:

Is there any reason not to mount the tubes that close to each other? I don't think I've ever seen a commercially made fixture with them that close...

 

[Random Guy]

Should be fine. I saw a 2 lamp fixture in HD the other day that had them closer than that. It may be a bit difficult to get to the center lamp to replace it without removing one of the other two the way you have it set up there, though.

 

[sams]

are you going to electronic ballasts and T8 globes to save power?

having the globes 3/16" apart should not be a problem as there would be enough of a gap there for effective heat disipation. As for lighting efficiency with them like that well thats another story

 

[BioHazard]

are you going to electronic ballasts and T8 globes to save power?

That and my current ballasts are noisy, plus I hate dealing with the 8' tubes. 6x T8 tubes should use around 150w with electronic ballasts...the ones I'm replacing are roughly 220w. (25+ fixtures)

Plus right now I only have two light levels: 1) Cave 2) Walk into the light...
Should be able to save a lot more power with the choice of 1, 2, or 3 tubes lit. Previously it was a paint shop, so it's bright.

 

[sams]

oh right, I was going to say that if it's just a straight swap it's usually a false economy as the minimal extra electricity saved is completely offset by the high cost of conversion and higher maintenance costs. However if you want it for selection of lighting or for other features then I understand.

I did something vaugely simular in that I used twin T8's (56W - 5') and I split the circuits so that I have two switches; one turns on the first globe out of the two and the other well you get the idea.

 

[Atlascycle]

are you going to electronic ballasts and T8 globes to save power?

having the globes 3/16" apart should not be a problem as there would be enough of a gap there for effective heat disipation. As for lighting efficiency with them like that well thats another story

That will not be a problem, he will have to remove all of the bulbs to replace the ballasts before the bulbs actually burn out.

Jason

 

[BioHazard]

That will not be a problem, he will have to remove all of the bulbs to replace the ballasts before the bulbs actually burn out.

LOL, I was just looking at tubes, at 36,000 hour life with 95% lumen maintainence they'd last over 8 years at 12 hours a day, 365 days a year.

By then they will be outdated and if I'm still here I'll probably be putting in something else. These fixtures were only installed in 1997.

 

[Chuckw]

Hi,

Newbie here. Are you mounting these right to your garage ceiling? I'm getting ready to put new lights in my shop and while surfing found this site. Curious about how hot the electronic ballasts get.

Chuck

 

[sams]

electronic ballasts should get no more than just warm

 

[Charles (in GA)]

How do you intend to mount the tubes? Are you cutting notches for the bulb holders? Of course you have to change all the bulb holders, as the 4 ft T8 has two pins vs single pin for the T12HO.

What about in the middle, Have you tried to put the 4 ft T8's end to end with their mounting sockets? I would think they would end up too long for the fixture. I think that is why they stagger the bulbs in the 8 ft long fixtures I've seen with the 4 ft T8's.

Charles

 

[Atlascycle]

LOL, I was just looking at tubes, at 36,000 hour life with 95% lumen maintainence they'd last over 8 years at 12 hours a day, 365 days a year.

By then they will be outdated and if I'm still here I'll probably be putting in something else. These fixtures were only installed in 1997.

Do some research on the T-8 ballasts, the energy savings is there but the maintenance costs are higher. in 2002 where i work the remodeled the offices and changed to all t-8 four bulb fixtures. in the 30 or so fixtures i have only replaced the blubs in one or two fixtures, but i am pretty sure that i have replaced all of the ballasts at least once. some twice.

Jason

 

[BioHazard]

How do you intend to mount the tubes? Are you cutting notches for the bulb holders? Of course you have to change all the bulb holders, as the 4 ft T8 has two pins vs single pin for the T12HO.

What about in the middle, Have you tried to put the 4 ft T8's end to end with their mounting sockets? I would think they would end up too long for the fixture. I think that is why they stagger the bulbs in the 8 ft long fixtures I've seen with the 4 ft T8's.

Charles

Honestly I haven't really looked how I'm going to mount the sockets, but I don't think it will be that hard to come up with something. In the picture there is one of the covers from an older 8' light that I tore down, they're already stamped into 4' sections as if the lights were designed to be used with either 4' or 8' tubes. The 4' cover peice I was using on the floor fits EXACTLY between the sockets.

in 2002 where i work the remodeled the offices and changed to all t-8 four bulb fixtures. in the 30 or so fixtures i have only replaced the blubs in one or two fixtures, but i am pretty sure that i have replaced all of the ballasts at least once. some twice.

Well, not all ballasts are ****. What brand are you using? I plan on using Sylvania "Quicktronic" ballasts, they are extremely efficient and zero flicker in the cold. I do have some older fixtures with these ballasts in them, not sure how old, but they still work...

The fact is the state is paying for most of the conversion, 'cause they want me to save energy. $30 per fixture plus some other bonuses.

 

[Aceman]

Cutting slots on the end to add extra tombstones isn't the right way to do it. Plus there is no center support for the middle tombstones. Anything you do is going to be jerry rigged. Do it right and use 4 lamp T8 strips. Add extra fixtures where you need more light. It doesn't make sense to me to spend all that time modifying old fixtures when you can simply buy new ones.....

 

[BioHazard]

Anything you do is going to be jerry rigged.

Just because I did it myself doesn't mean it is "jerry rigged". It's a ******* sheet metal box...I think I can handle mounting an extra glass tube to it.

It doesn't make sense to me to spend all that time modifying old fixtures when you can simply buy new ones.....

Are you buying? And no, I don't want 4 lamp strips, I want, and need, three.

 

[sams]

I suggest looking at the prices of the ballasts and the tobstones, you likely to find it cheaper to buy new fittings

 

[BioHazard]

I suggest looking at the prices of the ballasts and the tobstones, you likely to find it cheaper to buy new fittings

I already have a big box of ballasts that I got for free, and the tombstones are dirt cheap. The biggest expense for me will actually be the tubes themselves.

I took them apart further tonight and it is quite obvious that these fixtures were designed to be used with either 8' or 4' tubes. The "center support" that is missing is nothing more than a peice of sheet metal, and, there's already slots cut into the fixture to mount one. Where the current HO sockets are the bi-pin tombstones will fit right in with an extra little peice of sheet metal and a small snip for the center tube. EASY to fab up.

 

[sams]

cool, sounds good

show some pics of your work if you can

 

[Chuckw]

Sam"s,

Is your knowledge from experience with electronic ballast?
Chuck

 

[sams]

iron core, but here electronic ballasts cost more than a light fitting complete, go figure that out

I figured that the prices vary all over so I just said to enquire to do a bit of a comparasin