Discussion:
Repair or discard single pin T12 fixture
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TimR
2014-04-12 18:23:51 UTC
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One room in my shed has an 8 foot T12 single pin fluorescent fixture.

It hasn't worked since we moved in and it didn't matter, that's the side where the lawn tractor sits. I didn't realize it was even there, hung by the back wall; there's a small overhead incandescent that's enough to get tools in and out. there were two fluorescent fixtures, the other one not even wired in.

But I've noticed turning on the light to that side makes the lights in the other side sag badly, and that's how I found the fluorescent fixture. I've never actually seen a single pin tube before, with a spring loaded socket on one end. it's really easy to get the tubes in and out, much easier than with a bipin.

Anyway, it hums like it's trying to start and dips the the lights on another circuit. I swapped tubes with the other one, no change, so i unwired it from the junction box intending to throw it away.

But it's screwed to the rafters from inside, and i couldn't get the cover plate off it. How do you get these apart? It looks like it should snap apart but it won't.

So, are these worth trying to fix? Parts, tubes, ballasts available and reasonable cost? Or am I better off with my original plan of discarding it?

And why are all the fistures I see bipin? The single pins are much easier to change tubes.
m***@att.net
2014-04-12 19:14:16 UTC
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Post by TimR
Anyway, it hums like it's trying to start and dips the the lights on
another circuit. I swapped tubes with the other one, no change, so i
unwired it from the junction box intending to throw it away.
Does it have a starter - a little silver cylinder sticking out of a hole
in the sheet metal somewhere? If so, you might try replacing it. Turn
it 1/4 turn counterclockwise to get it out of its socket, then take it
with you to the store. Make sure the replacement you get is rated to
start two 8' T12 lamps - the ones they will have a bunch of at the store
are for 4' lamps.

If you can get it open, you might check for obvious things, like wires
that have come out of the lamp holders, or gotten pinched on the
housing. Make sure any wire nuts are tight and not full of rust/water,
stuff like that.

If the ballast has puked oil/tar all over the inside of the fixture,
that's a pretty good indication that it's bad. If the sticker on the
ballast is 1) still legible and 2) says "No PCBs" on it, then you can
just toss the ballast if it's bad. If the sticker is gone or if it
doesn't say "No PCBs", then you have to give the dead ballast to your
friendly local household hazardous waste collection program.

If you decide to change the ballast, and if the wiring inside the
fixture looks good otherwise, clip the wires as close to the dead
ballast as you can (after you shut off the power, of course). The new
ballast may or may not have enough wire for an 8' fixture, so leaving
the long wires in the fixture makes your life easier.
Post by TimR
But it's screwed to the rafters from inside, and i couldn't get the
cover plate off it. How do you get these apart? It looks like it
should snap apart but it won't.
Usually there is a screw or a clip near the lamp holders - on an 8'
fixture there may also be one in the middle. Sometimes there are
fasteners at both ends, and sometimes there's only one at one end, and
the other end just slides under a tab on the housing.

Sometimes the clip looks sort of like a wing nut, but you only need to
turn it 1/4 turn to release it. It may or may not be captive to the
cover, so be ready to catch it.

If the roof is less than perfect, or if the fixtures have had a lot of
condensation on them over the years, the cover may be rusted on to the
base...
Post by TimR
So, are these worth trying to fix? Parts, tubes, ballasts available
and reasonable cost?
Tubes are available at Home Depot ($15 or $17 for a two-pack, here).
One of the ballasts they sell (GE 74475, $30 here) should run two 8'
75 W tubes. They may or may not have the right lamp holders and
starters, but a commercial lighting supply probably will.

The 8' tubes seem to come in both 75 W and 110 W versions, but it looks
like the 75 W is single-pin (what you have) and the 110 W has recessed
double-contacts.
Post by TimR
Or am I better off with my original plan of discarding it?
If you can catch a sale, you might be able to get two 4' "shop light"
fixtures for less money than it would take to rebuild one of your 8'
fixtures. You will still have to do a little wiring, because the
cheap shop lights tend to come with 6" cords. You also don't have to
put the two 4' fixtures right next to each other, which may distribute
the light better.

Depending on the space in the shed, it may or may not be easy to
maneuver the 8' tubes; 4' tubes are easier to deal with.

4' tubes are more readily available than 8' ones. The tubes last long
enough that this usually isn't a problem, but if you live where there
is a Wal-Mart and there is not a Home Depot (or equal), 4' tubes might
be a better choice.
Post by TimR
And why are all the fistures I see bipin? The single pins are much easier to change tubes.
I don't know why this is. I tend to associate 8' single-pin tubes with
older commercial installations - perhaps the previous owner of the house
had "access" to tubes at work, so he or she installed matching fixtures
at home.

Matt Roberds
TimR
2014-04-12 19:35:04 UTC
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Part of the reason I wanted to take it out of the circuit was safety. I've seen a couple of ballast fires at work, and a shed tends to have some flammables. With the big sag in current when switched on, I thought something must be wrong.

Then after a few seconds there'd be a click and the other lights would brighten, then another sag.

I don't know if residential fixtures start many fires but now I'm safe.

Part of the reason was i'd use that room more if it had more light, I thought maybe it would be easy to get working, maybe even just new tubes.

There was a second probably older fixture behind it. It has screws holding the ballast cover plate on, screws that have obviously been removed a few times, and the lamp holders at the ends are different colors and have different size screws, so I guess it had been repaired a few times.

Of the four tubes available two have definite darkening on one end, two look okay. I've tried swapping without luck.

But here's the other problem. There are only two wires on that circuit, as i found when I got into the junction box. No ground anywhere near. So I dimly remember that rules out many types of fluorescent light, that need a ground to start. Single pins are a different kind of start circuit, if wiki is right.
m***@att.net
2014-04-12 19:59:07 UTC
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Post by TimR
Part of the reason I wanted to take it out of the circuit was safety.
It's probably a good idea to disconnect it if it's acting weird.
Post by TimR
With the big sag in current when switched on, I thought something must
be wrong. Then after a few seconds there'd be a click and the other
lights would brighten, then another sag.
This might be the starter trying to operate a ballast or tubes that
don't want to play along, or it might be some kind of thermal protection
inside the ballast. Either way, it shouldn't be doing that.
Post by TimR
Of the four tubes available two have definite darkening on one end,
two look okay. I've tried swapping without luck.
Sometimes swapping the same tube end-for-end helps a little.
Post by TimR
But here's the other problem. There are only two wires on that
circuit, as i found when I got into the junction box. No ground
anywhere near.
Is it non-metallic cable (Romex), plastic conduit, metal conduit, or
something else? If it's metal conduit, the conduit itself was allowed
to be the ground, until relatively recently.

If it's Romex, take a look at the wall switch box (if any) - is there a
ground in there? You might be able to run a new piece of cable with a
ground wire from the switches up to the fixtures.

If the "shed" has its own electric meter, then there should be ground
available in the shed somewhere. If it runs on a branch circuit from
another building (usually the house), you have to hope that they brought
the ground wire over from the house. Otherwise, if you want ground at
the shed, digging a ditch (or stringing wire overhead) is in your
future...
Post by TimR
So I dimly remember that rules out many types of fluorescent light,
that need a ground to start.
I think they need the lamps next to metal that the ballast housing is
also connected to. In any sane installation, all of that will be
ground, but I don't know if that's strictly *required* for the lamps to
start.

Matt Roberds
Jeff Waymouth
2014-04-13 12:34:34 UTC
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Post by m***@att.net
Post by TimR
Part of the reason I wanted to take it out of the circuit was safety.
It's probably a good idea to disconnect it if it's acting weird.
Post by TimR
With the big sag in current when switched on, I thought something must
be wrong. Then after a few seconds there'd be a click and the other
lights would brighten, then another sag.
This might be the starter trying to operate a ballast or tubes that
don't want to play along, or it might be some kind of thermal protection
inside the ballast. Either way, it shouldn't be doing that.
Post by TimR
Of the four tubes available two have definite darkening on one end,
two look okay. I've tried swapping without luck.
Sometimes swapping the same tube end-for-end helps a little.
Post by TimR
But here's the other problem. There are only two wires on that
circuit, as i found when I got into the junction box. No ground
anywhere near.
Is it non-metallic cable (Romex), plastic conduit, metal conduit, or
something else? If it's metal conduit, the conduit itself was allowed
to be the ground, until relatively recently.
If it's Romex, take a look at the wall switch box (if any) - is there a
ground in there? You might be able to run a new piece of cable with a
ground wire from the switches up to the fixtures.
If the "shed" has its own electric meter, then there should be ground
available in the shed somewhere. If it runs on a branch circuit from
another building (usually the house), you have to hope that they brought
the ground wire over from the house. Otherwise, if you want ground at
the shed, digging a ditch (or stringing wire overhead) is in your
future...
Post by TimR
So I dimly remember that rules out many types of fluorescent light,
that need a ground to start.
I think they need the lamps next to metal that the ballast housing is
also connected to. In any sane installation, all of that will be
ground, but I don't know if that's strictly *required* for the lamps to
start.
Matt Roberds
Single Pin lamps are always instant start. The fixtures have no
starters, nor do they require a ground plane for starting. From the
description these fixtures are probably for F96T12 lamps which were are
included in the energy efficiency rules of the United States and Canada.
This means it will be harder to find full wattage replacement lamps.
Since this shed is probably unheated, an "energy saving" lamp is not the
best alternative since they are sensitive to colder weather. There are
similarly shaped lamps in the T8 family (which means the tube is 1" in
cross section rather than 1.5" for the T12) It is important to note
that T8 lamps are NOT electrically interchangeable with T12 lamps. Your
best alternative at this point is to replace the fixture with a new one
using current technology.

Jeff Waymouth
TimR
2014-04-13 20:59:42 UTC
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On Sunday, April 13, 2014 8:34:34 AM UTC-4, Jeff Waymouth wrote:
Your
Post by Jeff Waymouth
best alternative at this point is to replace the fixture with a new one
using current technology.
Jeff Waymouth
That is my conclusion too, the only thing stopping me is i can't get the cover off. (the metal safety cover over the ballast and wiring area) There are no screws, it just looks like it's crimped on, but I've put a lot of force on it and it doesn't come off. I have the older unit which was also an F96T12 single pin fixture, but it had screws.
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