On 10 Nov 2006 06:52:54 -0800, "Mark" wrote:


w_tom wrote:
Kurt Ullman wrote:
Thanks for the reply. I think the diagnosis will take more time than
replacement, and the string is low enough on the tree that it will only
a minor pain to change it out.

A string of 25 8 watt bulbs would draw less than 2 amps. Two strings
in series would not blow out that 5 amp fuse. Clearly there must be a
short in that string. Load would approach excessive if three strings
were connected through that same 5 amp fuse.

And there is a REAL reason for the fuses. The bulbs are all low
voltage and wired in series and when a single bulb fails open all the
lights would go out EXCEPT they have a special device that when a bulb
fails open the full voltage is applied across the failed bulb and then
it shorts itself. So then that light is off but all the others can
continune to work, with a slightly higher voltage since one bulb has
failed.

So you should be able to see where this is going.. if enough bulbs
fail, they will all begin to fail and when they all short, you will
have one big short, hence you need a fuse that is rated to protect the
wire that the string is made out of, not the 15 or 20 Amps that your
breaker is rated at..

Mark


Hey Mark,
You got this all wrong. You would be correct if this was a string of
mini bulbs, but C9 bulbs are those big outdoor lights bulbs that were
in use before anyone ever made series wired mini lights. Those are in
parallel, and each bulb is rated at 120volts AC.

If you have one of the bulb type night lights in your house, they take
C5 or C7 bulbs (5 or 7 watt). These C9s are the same but larger.

Mark