"Pete C." wrote in message
ster.com...
stuff snipped
The only thing good about fuses is that they prevent people from
using
them
improperly as ON/OFF switches the way too many people do with circuit
breakers. You can, of course, unscrew the fuse if you want to use it
as a
switch, but that's not potentially destructive to the safety
capabilty of
the fuse. At least not the way using a circuit breaker as a switch
is.
Well, there were LOTS of 200 amp fuse panels installed, and I have a
100 amp fuse panel innmy house.
Fuses are a lot more reliable than breakers. Fewer "nuisance trips",
although fuses can fail from age/heat cycling/fatigue - and virtually
no chance of "sticking" and failing to trip when required. They are a
nuiscnae when they do blow - you need to have the right value fuse
within ready reach, and a flashlight next to the panel is always a
good idea.- Hide quoted text -
- Show quoted text -
We rented a condo down in miami a few times and they left instructions
to flip the breakers on for the hot water and the hvac when you
arrived and flip them off when you left. I thought about telling them
that was going to bite them but most people really don't like
unsolicited advice.
"It looks like a switch, so it *must* be a switch" is the attitude a lot
of
people take when using a breaker as a switch but it's really not a good
idea.
A lot of circuit breakers are specifically rated for switching duty, and
it is very common in industrial facilities like warehouses for the
circuit breakers to double as the light switches.
Well, when I start posting in Alt.Industrial.Repair I'll keep that in mind.
(-:
I still think it's a bad idea for homeowners to use circuit breakers as
switches because of even the small possibility that they are using older
breakers that are not rated for switch duty.
Citing the existence of industrial breakers that can operate as switches
probably isn't helpful for the majority of homeowners, because it gives
someone who's probably got no way to determine whether his breaker is
switch-rated a potentially false sense of security. While technically
correct and even germane to the issue, I think its not quite right to
compare an industrial circuit panel to a consumer panel. Given that houses
often change owners quite a few times, it's likely the panel's original
receipts and manuals are long gone. I am sure no one wants to do the home
repair community a disservice by pointing out an exception that's mostly
related to commercial wiring and could be very dangerous in a non-industrial
setting.
I just looked at my 30+ year old breaker box and there are no external
markings indicating any of the breakers is switch-rated. I'm betting that
when I look through the pile of old breakers I pulled there will be no
indication whatsoever regarding "switch ratings." It's why I'll reiterate
that using a safety device as a control device is not a good thing to do.
I'll add a caveat that "unless you are sure it is switch rated." I will
also have to add that "The likelihood is that you'll actually have to pull
the breaker and confirm it by model number and manufacturer's specs or by
looking for the rating stamped somewhere on the device." That puts
likelihood of proper confirmation of the breaker rating way outside the
skill set of most condo renters who are told to "just flip the breaker."
Besides, I think it's *damn* good practice to actually *install* a switch if
you need a switch, and to keep people out of circuit boxes as a general
rule.
The bottom line is that it's probably NOT helpful to suggest that a person
switching off the AC or the water heater via a breaker in their rented condo
may be in the right because some industrial panels have breakers that can
and do serve as switches.
Breakers not rated for switch use edge closer to failure the more often they
are used as switches because they are subjected to wear they were not
designed to bear. I'm certain of this because when Dad retired from the
Navy's Material Science Division he went to work as a forensic engineer.
The annals of fire litigation are filled with failed breakers, stuck
Klixon's and any number of failed, bypassed or misused safety devices.
Somewhere I have pictures from his old cases about breakers and Klixon's
recovered from fire scenes that were part of the circuit that should have
tripped but didn't, leaving wires and electric furnace cores to overheat and
burn. While this was twenty years ago, I recall clearly safety experts
citing breakers being more likely to fail if they were also being used as
switches. It sounds like in recognition of this constant misuse of a safety
device that breaker makers changed their design to allow them to be used as
control devices.
http://www.hq.nasa.gov/alsj/alsj-CBsVsSwitches.html
In August 2005, Journal Contributor Mike Polizsuk, who works for the U.S.
Navy as a civilian engineer, most recently for the Naval Air Systems Command
at Pax River in the Program Office for the F/A-18 Hornet fighter jet where
he was responsible for engineering oversight of the Hornet's structural and
mechanical systems, wrote:
One thing I note continuously throughout Apollo is the way they cycled
circuit breakers, often as a matter of routine operations. In my experience
with aircraft systems, circuit breakers are considered as protective devices
that should not be used as a switch to turn systems on and off. While it may
be acceptable for maintainers to open breakers to make a system safe for
maintenance, it is not standard practice for pilots to cycle breakers. We
would only put it into a checklist reluctantly, and only if no other way
exists to turn off a system. Since the circuit breaker plunger is held in
mechanically, repeatedly cycling it can wear it out. For a system or
component that is required to be turned on and off, a Power switch should be
used, with a circuit breaker also in the circuit for protection."
Amen.
--
Bobby G.