Are T5's, T8's & T12's interchangeable?

[Paul Mc]

I have three fixtures in my basement greenhouse that currently use T12 bulbs. I needed another light as my tropical collection has expanded and we need more room. Unfortunately, I did not realize that I was buying a T5 fixture until I tried to put T12 bulbs in them.

After researching, I found that T5 bulbs are probably better for the higher light orchids and tropicals that I keep in the basement.

So, my question is the following: Is it possible to replace the T12 bulbs with T5's in my old lighting fixtures? I know the new light I just bought will not fit 2 T12 bulbs, so that's not possible.

[Ray]

Different holders and a different ballast would be necessary. You'd probably be better off replacing the fixtures.

On that subject - as a Hydrofarm reseller who discounts their prices (most don't), if you want to check out the fixtures on their website, I'd be happy to quote you on anything. They ship from all around the country, so the shipping costs are minimal.

[silken]

Paul Mc, supposedly T12 fixtures are being pulled off the North American market at the end of this year. I am no authority on that statement but when I was buying replacement bulbs for our society, several lighting companies told me that and I have Googled and found the same info. So you might want to look into that before buying more T12 fixtures or ballasts.

I had old T12 fixtures in a T12 metal canopy and just screwed in the smaller slim T5 fixtures and now I have a nice reflective canopy for my T5's. The places where the T12 bulbs were inserted just remain empty.

[Paul]

Originally Posted by silken

Paul Mc, supposedly T12 fixtures are being pulled off the North American market at the end of this year. I am no authority on that statement but when I was buying replacement bulbs for our society, several lighting companies told me that and I have Googled and found the same info. So you might want to look into that before buying more T12 fixtures or ballasts.

I had not heard that! Well that really blows. How come?

Hmmm, will T8's fit in the T12 fixtures? I really would prefer not buying a bunch of new fixtures

[silken]

Answers.com - Will a T8 fluorescent bulb work in a T12 fluorescent ballast

Answers.com - Is it true that T12 bulbs are being discontinued and must be replaced with T8

Here are two links with answers to your question about T8's and about T12's being discontinued. (They use more power). I have no idea how reliable this site is (Answers.com) but I have heard about the T12's being discontinued from every place I went in our city in Canada. I was sourcing out bulbs for our society so I was quite a few places! The T8's and fixtures here were a fairly inexpensive way to go compared to T5's. but I bet Ray from First Rays could give you some info as to what is best.

[Paul Mc]

Thank you everyone.

Ray, I will keep your offer in mind. We are going to attempt to replace our T12's this weekend with 2 T8's (they are close to a table filled with plants) and more T5 fixture as it is in the ceiling.

So this raises another question. Normal florescent bulbs are T12's aren't they? I'm asking because we had several lights added in the basement and we have not needed to replace the bulbs yet. But one of those lights we use as the grow light (the one in the ceiling). I guess I should have an electrician come back out and replace that one?

[Paul Mc]

Oh, and they are hardwired in, turned on by light switches. That's why I'm terrified to replace them myself. I don't play with electricity, was almost electicuted when messing with it a few years back and have been gun shy ever since.

[silken]

I was told the T12 bulbs will be available for a while longer but then discontinued. Same goes for the ballasts. They are being pulled at some point too but not sure when. Guess they are of no use without anything else! I notice lots of ads for good deals on T-12's. Guess businesses are trying to unload them to unsuspecting customers. I would check with a government agency to get the real facts.

We have lots of T-12's in our kitchen too and they will need to be replaced at some point. Luckily my husband is handy and will do it. Likely t8's or re-do the ceiling and get pot lights. More money on reno's and less for orchids

[Ray]

I cannot claim to be an expert, but if I am recalling correctly (questionable as i get older), a 4' T8 is a 34W bulb, while a T12 is 40W. Putting a lower-watt bulb in an incandescent fixture is fine, as it will only draw what it is designed for, but with fluorescents, the ballast acts like a current-limiting device, which is why they are matched. A T8 ballast limits the bulb to 34W, so putting that bulb on a T12 ballast "pushes" it to 40W, which will likely just make them live shorter lives.

You will get more light from the T8's, even with the proper ballast. There is some variability, but here's some "typical" values:

T12- 60 lumens per watt x 40W = 2400 lumens
T8- 90 lumens per watt x 34W = 3060
T5- 85 lumens per watt x 54W = 4590

Lastly Paul, no matter which you go with, the distance from a ceiling fixture to a tabletop-grown plant means the light intensity will be minimal. Fluorescents are preferred lighting for plants precisely since they can be brought close enough for proper intensity without overheating them.

[flhiker]

Ray is correct. I'll will add that the type of bulb (cool white, daylight, aquarium/plant bulbs will omit different a spectrum and brightness, which some may be better then others. I don't grow under lights so I don't know whats best but I do work with fluorescent's often.