I notice that some - but not all -electronic ballasts specifically mention
"1 or 2" bulb operation.
Since I have 2 single bulbs fixtures that will need new ballasts and I
happened to have on hand 2 "2 bulb" electronic ballasts of more than
sufficient wattage, any electrical reason why I could not make use of these?
Thanks for any comments or wiring suggestions.


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"John Keiser" wrote in message
news:aPidnUviOuk2XMPUnZ2dnUVZ_v3inZ2d@hawaiiantel. net...
I notice that some - but not all -electronic ballasts specifically mention
"1 or 2" bulb operation.
Since I have 2 single bulbs fixtures that will need new ballasts and I
happened to have on hand 2 "2 bulb" electronic ballasts of more than
sufficient wattage, any electrical reason why I could not make use of
these?
Thanks for any comments or wiring suggestions.


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AFAIK, this 'problem' was originally one that was associated with
non-electronic ballasts i.e. ones that were a pure line frequency
transformer. To have the voltage at the output anything like the specified
value, the load had to be known, and it was always recommended that if a
bulb failed, it should be replaced ASAP, as the output voltage would
increase with the reduced load, over-volting the remaining bulb(s). It's
also important of course, not to overload such a device with too many bulbs,
hence the wattage rating on it.

It's a little different with the electronic ballasts in that they are
fundamentally a switch mode power supply, so in theory, you would expect
them to give a reasonably stable output whatever the load, up to some
specified maximum amount, where you would start to overload it. However, all
the ones that I've seen, this side of the pond at least, only nod in the
direction of a 'proper' switcher. The output is a high frequency square
wave, modulated at line frequency, due to the fact that that there are no
primary or secondary-side filter caps. There is also no kind of regulation
applied to the design. So, the short answer to your question is that I think
the only way that you will see if the ballasts that you have are suitable
for continuous driving of a reduced load, is to stick a 'scope across the
output, then load it with first one bulb, and then two, and see if there is
any significant change to the output waveform, or brightness of the first
bulb, when the second one is connected.

Arfa

On Fri, 2 Jan 2009 15:38:49 -1000, "John Keiser"
wrote:

I notice that some - but not all -electronic ballasts specifically mention
"1 or 2" bulb operation.
Since I have 2 single bulbs fixtures that will need new ballasts and I
happened to have on hand 2 "2 bulb" electronic ballasts of


more than sufficient wattage

Uh, the *same* wattage...


, any electrical reason why I could not make use of these?
Thanks for any comments or wiring suggestions.

Actually, I though "sufficient" was the right word. I assumed that a
ballast could be damaged if it was incapable of supplying sufficient
current. If the ballast can supply more current, what is the harm?

[I glean that maximizing bulb life is an issue for precisely matrching
ballasts in commercial applications but a minor concern in my house.]

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"John Keiser" wrote in message
news:Re2dnaCB4fpkQsLUnZ2dnUVZ_sbinZ2d@hawaiiantel. net...
Actually, I though "sufficient" was the right word. I assumed that a
ballast could be damaged if it was incapable of supplying sufficient
current. If the ballast can supply more current, what is the harm?

[I glean that maximizing bulb life is an issue for precisely matrching
ballasts in commercial applications but a minor concern in my house.]

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Well, it might not be such a minor issue if you actually do it. Over-volting
a 12v halogen by as little as 10% can significantly shorten its life, and
when you start having difficulty getting them in a couple of years after the
eco-bollox merchants have had the manufacture of them banned totally
world-wide ...

If the ballast is rated to supply more current than is actually required,
there is no harm going to come to the ballast itself. However, if there is
no regulation of the output voltage other than by load and the ballast's
output impedance, then you could significantly shorten the bulbs' service
life, by having insufficient load.

Arfa

These are 4 foot T12 bulbs.


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"John Keiser" wrote in message
news5OdnZv264uh0fzUnZ2dnUVZ_oPinZ2d@hawaiiantel. net...
These are 4 foot T12 bulbs.


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Ah, flourescent tubes then ? That's a different matter altogether ... ;~}

Arfa

In article ,
"John Keiser" wrote:

These are 4 foot T12 bulbs.

John-

I admit I don't know much about the use of electronic ballasts. It was
my understanding that T12 bulbs were meant to be used with a magnetic
ballast, either with or without a starter. For an electronic ballast,
the bulbs are T8.

Is it also possible to use T12 bulbs with an electronic ballast? If
not, you should be able to use your electronic ballast in the fixture by
getting the correct bulbs. People in the electrical department of a
Home Depot or Lowes type of store should be able to advise you.

Fred

The ballasts I have are labled for "T12" so that's OK. They work swell for
2 bulbs. I wired one as a test for a single bulb and it seems OK as well.

I also have some electronic ballast for "T8" and did on test on a "T12"
bulb. Also seemed to work fine.

Apart from wattage/current capacity, why would a T8 ballast differ from a
T12?




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In article ,
Fred McKenzie wrote:
I admit I don't know much about the use of electronic ballasts. It was
my understanding that T12 bulbs were meant to be used with a magnetic
ballast, either with or without a starter. For an electronic ballast,
the bulbs are T8.

You can get electronic ballasts for virtually any type of tube. I have
tri-phosphor T8 types lighting the worktops in my kitchen driven off Osram
dimmable electronic ballasts. They are more efficient than conventional
ballasts therefore producing less heat and allow extremely long tube life.
The dimming is achieved by a simple pot working in a low voltage circuit.
Good starting characteristics too - near instant. Other benefit is some
dislike the mains frequency flicker produced by some fluorescent lights.
These ballasts run at approx 30kHz so no visible flicker or audible hum.
They are expensive, however.

http://www.bltdirect.com/products.php?cat=499

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