mm wrote:
On Wed, 08 Mar 2006 23:14:52 -0500, mm
wrote:

On 8 Mar 2006 17:46:39 -0800, "volts500" wrote:

This is something that you should try to get the seller to do as a
condition of purchase. Chances are pretty good that if they have the
old 60 Amp "Main, Range and Four" fuse panel that the entire house
probably needs rewired. Usually in houses like that 2 circuits pretty
much run most of the outlets and lights.



This is what the FAQ says about the difference between cb's and fuses:


ubject: Breakers? Can't I use fuses?

Statistics show that fuse panels have a significantly higher
risk of causing a fire than breaker panels. This is usually
due to the fuse being loosely screwed in, or the contacts
corroding and heating up over time, or the wrong size fuse
being installed, or the proverbial "replace the fuse with a
penny" trick.


It would be interesting where the stats came from. I have probably seen
more arcs develop from a plug-in breaker to the bus bar. If using
Fusestats, which are readily available non-interchangable plug fuses,
the wrong size fuse can't be used, nor can the fuse be bypassed with a
penny.

Since breakers are more permanently installed, and have better
connection mechanisms, the risk of fire is considerably less.

Fuses are prone to explode under extremely high overload. When
a fuse explodes, the metallic vapor cloud becomes a conducting
path. Result? From complete meltdown of the electrical panel,
melted service wiring, through fires in the electrical
distribution transformer and having your house burn down.
[This author has seen it happen.] Breakers won't do this.


Fusestats have an interrupt rating of 10,000 Amps, same as residental
CBs (recently some are higher). Cartridge fuses that should be used have
an interrupt rating 100,00A or higher. Breakers won't explode on short
circuits (not a high overload)? How about if it is mechanically slow or
frozen? Anyone still make crappy CBs (ala FPE or Zinsco)?

Many jurisdictions, particularly in Canada, no longer permit
fuse panels in new installations. The NEC does permit new
fuse panels in some rare circumstances (requiring the special
inserts to "key" the fuseholder to specific size fuses)


The "special" inserts to convert to Fusestats aren't particularly
special and often have been installed in old panels.

Some devices, notably certain large air conditioners, require fuse
protection in addition to the breaker at the panel. The fuse
is there to protect the motor windings from overload. Check the
labeling on the unit. This is usually only on large permanently
installed motors. The installation instructions will tell you
if you need one.


The fuse is not there primarily to protect the motor from overload. It
protects the supply wiring from short circuits but gives some protection
to the motor and other equipment in unusual circumstances. That is the
same function the CB provides. I presume the manufacturer likes the
operating characteristic of the fuse better.


I would never ever put a penny in a fusebox, and I wouldn't bother to
change a fusebox to a breaker box unless I was trying to sell the
place, but ymmv.

CBs are a lot more convenient than fuses. However I wonder about 10 year
old panels. It would seem like a breaker could mechanically deteriorate
and freeze or have its operating characteristic change. If a fuse
element deteriorated it should open early. Anyone seen long term
reliability information? Would seem like someone would have run tests.

Like mm, I don't think I would change out a fuse panel if my house had
one, if it was large enough. But I wouldn't install one either. I think
the advantage of CBs, other than convenience, is overstated.

Fused service panels do come in ratings larger than 60A. When I was a
kid the service in my home was replaced with a 100A all fuse service
panel. It was 'main and range' style similar to volts500's description.
A 60A pullout fed 8 branch circuits. There was a 60A pullout for
possible range and I think 1 or 2 30A pullouts. The pullouts were all
service disconnects. (I don't think 'main and range' is allowed for new
installations).

bud--