On Wed, 01 Nov 2006 14:52:57 GMT, "Pete C."
wrote:

" wrote:

The fuse is a 25A "Edison base" fuse in the switchbox on the furnace
itself.

There's no reference to the fuse anywhere in the manual.

I've lived here for 7 years, so the fuse is at least that old. The
house is 12 years old.

So did you replace it, like I said to? What happened?

Sounds like the builder recycled an old fusible disconnect since they
haven't used edison base fuses for quite some time. New ones use
cartridge fuses, or they use small circuit breaker panels.

At any rate a problem might still exist since fuses usually blow as a
result of a problem, not old age. 25A is also a pretty large fuse and an
oddball size as well so it may not be the correct one, 20A or 30A would
be expected.

This is the wire going TO the furnace, right? I recently learned in a
thread here that the wire IN the appliance might have better
insulation and maybe doesnt' have to be as thick a gauge as the wire
from the main box to the appliance.

25 is unusual, and I too would be very reluctant to go to 30. But if
he has been using 25 for 7 years, I'd find myself some 25s. If it
normally uses 22 and once used 27 and blew the fuse, he'll never find
why it once used 27. If it blows the new one, then he may have /
probably has a findable problem.

Of course I agree that a blown fuse represents a bigger problem at
least half the time. Similar to this, a couple days ago, my hot
water limit switch tripped, and I reset it by turning off the breaker,
taking off the cover, pushing the red button, and turning the breaker
on again. It tripped again not long afterwards (don't know when.)

OTOH, in the trash I found a Black and Decker air pump (they call it),
and on the cigarette lighter plug, it said "No user serviceable parts
inside", but they lied. Inside was a glass fuse, and after I drilled
out the rivet, replaced the fuse, and somehow put the plug back
together, the pump has worked fine for a long time. I wonder why it
blew.
You haven't indicated what type of furnace this is yet (oil, gas, etc.)
but most would be expected to be on a 20A circuit since burners and
blowers don't take that much power. Possibly the blower bearing are
going or it's clogged up and is drawing more power than normal?

Possibly a pre-existing condition where someone overfused to 25A to mask
the problem? What size breaker is feeding the furnace from the main
panel? What gauge wire is feeding it if you can see? 12ga would be good
for 20A, 10ga for 30A.

Pete C.