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Re: [APD] 55 watt bulb for 65 watt ballast? -- Generally yes, but . . .

I'm very sorry, Byron, tht I did not speak more clearly.

I meant to say that you probably *could* (not *should*) use
square pin bulbs on a ballast meant for straight pin bulbs
and vice versa. I don't know that I would try to do it
since there are so many bulbs of both types available that
is shouldn't be too hard to find the ones that match best.
Also, sometimes when a "maker" of a lamp gets a bulb
manufacturer to make a run of bulbs for them, they might
specify slightly nonstandard characteristics.

Interchanging 65W and 55W with the same pin arrangement is
virtually inconsequential. 

Bulbs with diff pin arrangements can be swapped and
probably will work on an elecronic ballast, which are
somewhat flexible, but not on magnetic ballasts.

Electrically the square and straight pin bulbs are similar,
but not the same. Generally, the square pin bulb has a
slightly higher lamp voltage and slightly different
starting requirements but it is close enough for electronic
ballast handle the difference. Magnetic ballast may have
problem operating both lamps due to different lamp starting

Here are two examples of bulbs sold by Hellolights.com and
I believe they are typical bulbs:

55w straight pin: 
Nominal Rated Lamp Voltage: 100V 
Nominal Rated Lamp Current: 550mA 

55w square pin: 
Nominal Rated Lamp Voltage: 110V 
Nominal Rated Lamp Current: 670mA 

At 60Hz. 

These would probably work on the same electronic ballast.

The electronic ballast manufacturer, Fulham, for one
example, recommends a different wiring between the ballast
and the 55w square pin bulb and the 55w straight pin bulb,
to accomdoate the diff voltage and current requirements.

I think my personal recommendation is that you look for a
bulb with the same pin arrangemement, but don't be
concerned about whether it's is rated 65w or 55w.

Alternatively, if you can find out the starting voltage,
running voltage, and running current for a bulb, you can
surely swap for any other bulb that has requirements very
close to those, within, say, about 5%.

Suppose you go a hold of a half dozen diff models of
electronic ballasts that are rated for, say, a 55w straight
pin bulb and hooked each one up, one at a time, to the same
55w bulb. In each case, the actual voltage, current,
brightness, and heat, would probably be a little diff.
Luckily exact matches between bulbs and ballasts are
necessary -- although close matches generally are.

If a ballast runs a bulb a little harder, it will be a
litle brighter and hotter and the life might be a little
shorter. If it runs a bulb and little softer, then it will
be a little dimmer, cooler, and the life might be slightly
longer. But the diff in bulb life from any one bulb to the
next, even in the same production run will vary -- that's
to be expected

Most folks are not going to have operating characteristics
data redily available nor test equipment to obtain the data
by trial. So, ask the bulb vendor if the bulb will work on
your ballast/lamp. If the vendor says it will, the vendor
will probably support you if, perhance,  the bulb doesn't
work out. If the vendor doesn't want to risk it, then you
probably shouldn't either.

I hope this time I have been clearer even if I haven't made
your choices much easier.

Good luck, good safety, good fun,
Scott H.
--- "Byron J. Yu" <sixty9 at gmail_com> wrote:

> Are you saying that i can't just wire square pin end caps
> to my
> ballast (which is currently wired with straight pin end
> caps--coralife)?
> WIll it work? What are the consequences?

Still some time left to get the 65% discount hotel rate.

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