In ,
stan wrote:

On Jun 7, 1:41*pm, (Don Klipstein) wrote:

SNIP to here
* If you replace the ballast, make sure the new ballast and bulbs are
compatible with each other. *There are several different wattages for
4-footers (including U-bent ones 2 feet long). *The 32 watt 1-inch-dia.
and the 40 watt 1.5-inch-dia. bulbs are not electrically interchangeable.

SNIP

Does using an electronic ballast require the use of different tubes
than using old fashioned 'regular' ballasts in good condition?
Reason to ask is that I have a batch of used fluorescent fixtures, in
excellent condition except for a few scratches, from renovations at a
school. (They would have been dumped if had not taken them).
Most, but not all of the tubes were missing/broken so replaced with
same type, which for these fixtures equipped with electonic ballasts,
are the thinner and IIRC are T10 type.

The thinner ones usually used with electronic ballasts are T8.

But experimentally the older fatter 34 or 40 watt tubes will also
work; but might overheat the 'electronic' ballasts????

Check the ballasts - see if they are rated for both 17 and 32 watt
"lamps". (In which case they will be T8.)

If so, then the ballasts are safe to use with T12 40 and 34 watt lamps -
since such T12 lamps have voltage drop between that of 32 and 17 watt T8
lamps.

However, since 40 and 34 watt T12 lamps/bulbs want more current than T8
ones get, the T12's will be underpowered.
When underpowered, "true 40 watt" lamps/bulbs *usually* work OK but
there is a slight chance they will "act cranky" or have shortened life.
34 watt ones may more easily "act cranky" or have shortened life.

One more thing to watch for - using lamps that the ballast is not rated
to work with is "use of electrical equipment other than as directed".
Even when such misuse is safe, your fire insurance company might give you
grief if the misused electrical equipment starts a fire.

If the ballast is rated to run 32 watt lamps but not 17 watt ones, it
will probably still be safe with 40 and 34 watt ones - but this is *not
guaranteed*.

- Don Klipstein )