F32T8 bulbs in F40T12 fluorescent fixtures

[mc]

We have a kitchen illuminated by 48-inch fluorescent lights above a
translucent suspended ceiling. We are slowly upgrading them to electronic
ballasts and F32T8 bulbs.

In the meantime, here's tonight's discovery:

F32T8 bulbs work fine in F40T12 fixtures. In fact, they even work in
fixtures that are finicky with F40T12 bulbs (presumably because the ballasts
are getting old).

Have others had the same experience? Am I shortening the bulb life, or
anything, by running an F32T8 bulb on a ballast designed for an F40T12? I
know that *theoretically* I may be putting more current through it... in
practice, does it make a difference?

[t***@sbcglobal.net]

Post by mc
We have a kitchen illuminated by 48-inch fluorescent lights above a
translucent suspended ceiling. We are slowly upgrading them to electronic
ballasts and F32T8 bulbs.
F32T8 bulbs work fine in F40T12 fixtures. In fact, they even work in
fixtures that are finicky with F40T12 bulbs (presumably because the ballasts
are getting old).
Have others had the same experience? Am I shortening the bulb life, or
anything, by running an F32T8 bulb on a ballast designed for an F40T12? I
know that *theoretically* I may be putting more current through it... in
practice, does it make a difference?

t8s will not work in t12 fixtures. They need a electronic ballasts. I
replaces all my t12s with t8 and new fixtues. The t8s stay brighter
longer and use less power for the same amout of light as the t12.

what i like about the t8s is no humming sound and saves power.

[mc]

Post by t***@sbcglobal.net

Post by mc
F32T8 bulbs work fine in F40T12 fixtures. In fact, they even work in
fixtures that are finicky with F40T12 bulbs (presumably because the
ballasts are getting old).
Have others had the same experience? Am I shortening the bulb life, or
anything, by running an F32T8 bulb on a ballast designed for an F40T12?
I know that *theoretically* I may be putting more current through it...
in practice, does it make a difference?

t8s will not work in t12 fixtures. They need a electronic ballasts. I
replaces all my t12s with t8 and new fixtues. The t8s stay brighter longer
and use less power for the same amout of light as the t12.

Should I disbelieve my eyes, then? Read what I said.

[sylvan butler]

Post by t***@sbcglobal.net

Post by mc
F32T8 bulbs work fine in F40T12 fixtures. In fact, they even work in
fixtures that are finicky with F40T12 bulbs (presumably because the ballasts
are getting old).
Have others had the same experience? Am I shortening the bulb life, or

Yup, don't know. I don't do it because I suspect the ballast overheats.

Post by t***@sbcglobal.net
t8s will not work in t12 fixtures. They need a electronic ballasts. I

Did you even READ the original post? THEY WORK.

Post by t***@sbcglobal.net
what i like about the t8s is no humming sound and saves power.

The "no humming" is because of the electronic ballast and is also
achievable with good quality magnetic ballasts.

sdb

[TKM]

Post by mc
We have a kitchen illuminated by 48-inch fluorescent lights above a
translucent suspended ceiling. We are slowly upgrading them to electronic
ballasts and F32T8 bulbs.
F32T8 bulbs work fine in F40T12 fixtures. In fact, they even work in
fixtures that are finicky with F40T12 bulbs (presumably because the
ballasts are getting old).
Have others had the same experience? Am I shortening the bulb life, or
anything, by running an F32T8 bulb on a ballast designed for an F40T12? I
know that *theoretically* I may be putting more current through it... in
practice, does it make a difference?

If your existing fixture does indeed have an electgromagnetic ballast
designed for the F40T12 lamp, then the following applies:

The major difference between an F40T12 fluorescent tube and an F32T8 tube is
the current rating. The F40 is rated for 0.430 amps; the F32 is rated for
0.265 amps. Once a fluorescent lamp has started, the ballast acts like a
current source and drives the lamp according to the load current rating of
the ballast.

In this case, it's a little surprising that the F32T8 lamp starts, but that
can happen -- especially when the lamp is new. However, the lamp is being
overdriven by about 60%. Fluorescent lamps can be overdriven by 10% or so
without major problems, but you are likely overheating the cathodes and
driving the lamp quickly toward end-of-life due to cathode deterioration.

Putting an F40T12 lamp on an F32T8 ballast is less destructive since the F40
will be under driven. It will be low in light output, but it will start and
likely last for its rated life.

TKM

[mc]

Thanks for the very informative reply! The bulbs have lasted a couple of
years already.

Post by TKM

Post by mc
We have a kitchen illuminated by 48-inch fluorescent lights above a
translucent suspended ceiling. We are slowly upgrading them to
electronic ballasts and F32T8 bulbs.
F32T8 bulbs work fine in F40T12 fixtures. In fact, they even work in
fixtures that are finicky with F40T12 bulbs (presumably because the
ballasts are getting old).
Have others had the same experience? Am I shortening the bulb life, or
anything, by running an F32T8 bulb on a ballast designed for an F40T12?
I know that *theoretically* I may be putting more current through it...
in practice, does it make a difference?

If your existing fixture does indeed have an electgromagnetic ballast
The major difference between an F40T12 fluorescent tube and an F32T8 tube
is the current rating. The F40 is rated for 0.430 amps; the F32 is rated
for 0.265 amps. Once a fluorescent lamp has started, the ballast acts
like a current source and drives the lamp according to the load current
rating of the ballast.
In this case, it's a little surprising that the F32T8 lamp starts, but
that can happen -- especially when the lamp is new. However, the lamp is
being overdriven by about 60%. Fluorescent lamps can be overdriven by 10%
or so without major problems, but you are likely overheating the cathodes
and driving the lamp quickly toward end-of-life due to cathode
deterioration.
Putting an F40T12 lamp on an F32T8 ballast is less destructive since the
F40 will be under driven. It will be low in light output, but it will
start and likely last for its rated life.
TKM

[a***@gmail.com]

How long does a normal F40T12 will last?

I am facing the same situation here:
I have some F40T12 with Robertson electronic Ballaster "RSW234T12120".
The RSW234T12120 claims to work on Both F40T12 and F36T8 lamps. Today I visited Lowes, and got some F40T8 lamp. I put it in where the F40T12 was installed, it works. But I don't know how long it will work on the lamp and ballast.

The RSW234T12120 is a normal power factor electronic preheat (Rapid) start Ballast.

I measured the temperature near the end of the tube:
T12: 35~40C
T8: 50~57C
Room Temperature: 19~20C.
MIke D.

Post by mc
Thanks for the very informative reply! The bulbs have lasted a couple of
years already.

Post by TKM

Post by mc
We have a kitchen illuminated by 48-inch fluorescent lights above a
translucent suspended ceiling. We are slowly upgrading them to
electronic ballasts and F32T8 bulbs.
F32T8 bulbs work fine in F40T12 fixtures. In fact, they even work in
fixtures that are finicky with F40T12 bulbs (presumably because the
ballasts are getting old).
Have others had the same experience? Am I shortening the bulb life, or
anything, by running an F32T8 bulb on a ballast designed for an F40T12?
I know that *theoretically* I may be putting more current through it...
in practice, does it make a difference?

If your existing fixture does indeed have an electgromagnetic ballast
The major difference between an F40T12 fluorescent tube and an F32T8 tube
is the current rating. The F40 is rated for 0.430 amps; the F32 is rated
for 0.265 amps. Once a fluorescent lamp has started, the ballast acts
like a current source and drives the lamp according to the load current
rating of the ballast.
In this case, it's a little surprising that the F32T8 lamp starts, but
that can happen -- especially when the lamp is new. However, the lamp is
being overdriven by about 60%. Fluorescent lamps can be overdriven by 10%
or so without major problems, but you are likely overheating the cathodes
and driving the lamp quickly toward end-of-life due to cathode
deterioration.
Putting an F40T12 lamp on an F32T8 ballast is less destructive since the
F40 will be under driven. It will be low in light output, but it will
start and likely last for its rated life.
TKM