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On Fri, 19 Nov 2010 09:42:25 -0800 (PST), "hr(bob) "
wrote:
On Nov 19, 8:32 am, al wrote:
On Nov 18, 6:42 am, al wrote:
Some of the outlets in my house stopped working. Outlets on
individual walls in different rooms work while others don't. They are
associated with different fuses, but the fuses are okay. I double
checked them by replacing them anyway and affected outlets still
don't
work. Any idea what would cause this?
Problem solved.
Contractor's estimator checked everything, double-checked the fuses
and discovered a main fuse that was bad. Replaced it and solved the
problem.
My all to obvious error was not checking the main fuses. I just
checked the round screw in fuses. Since moving in here, I've never
touched or even thought of touching those red cylindrical fuses. Now
those fuses aren't the only things that are red.
Anyway, the estimator said as some of you have that the fuse panel
should be replaced with a breaker panel and is preparing an estimate
for that job. Breakers are probably a better option for someone
susceptible to failing to explore all options before raising the alarm
anyway.
Thanks for all the input.
Thanks for your closure to this, we all learned something.
Fuses fail from age/temp cycling. Since the lights SOMETIMES worked,
the fuse was not blown due to a short or overload - the fuse just
"failed"
I don't know how you can say that without examining the fuse close up.
Sounds like it may have crumbled from excessive heating from carrying too
much of a load. Only a hands-on inspection will determine that, and it
would probably mean cutting open the fuse to determine the failure mode.
Don't raise alarms where none are warranted.
Jumpin I would say *exactly* the reverse is true when dealing a lethal
entity like 240VAC where a main fuse has failed and with so many other
unknowns. Not being concerned enough might lead to a similar set of
circumstances where a badly manufactured Chinese replacement fuse FAILS to
blow and there's a meltdown as a result. A blown fuse is a warning that
something's wrong. Assuming it's just a failed fuse and moving on seems to
be bordering on terribly careless. Each to his own, I guess.
FWIW, hearing about a fusebox in a home in this day and age raises an alarm
in my head that there's a potential overload situation. While fuse panels
of 200A certainly exist, every *residential* fuse panel I've ever seen in
the NE USA was a four banger with 15A screw-ins and a 60A total rating. I
realize that experience is terribly limited, but regardless, a blown main
fuse is not something to take lightly.
I don't know what the rules are up in the "Great White Way" or in other
parts of the US, but I assume one of the safety reasons for switching to
breakers is that they are much harder to override with pennies or aluminum
foil. Not sure what the NEC has to say about installing new 200A service
with screw-in fuses in the USA and I certainly know that my limited
experience does not even speak for the USA NE - just the houses whose panels
I have seen. All I know is when a fuse protecting an entire incoming phase
fails, an investigation is warranted to determine the cause. Assuming it's
simply a bad fuse is bad troubleshooting.
In this case, caution is especially called for because we just don't have
the information necessary from the OP to make a good call. We have no
information at all about the daily peak load he's putting on the panel,
either. We don't have a picture of the panel with the cover off, which can
often tell you what kind of workmanship is involved or if the wiring is
shoddy or deteriorating.
I recall seeing one poster here show us a picture of his circuit box with
all of the single wires laid out as neatly as the strings of a harp! I had
never seen and will probably never again see such incredibly precise work -
I wish I could remember the dude's name - when you see workmanship like
that, you can usually discount poor wiring - but I digress.
With all the unknowns, it seems far more prudent to raise a caution flag
than to give him the green light and say "bad fuse, replace and
fuggedaboutit." The part of this that really gives me pause is that he
reported that it's an intermittent fault. Yes, fuses, light bulbs and most
anything electrical can fail that way, but when a safety device fails, it's
far more serious than a light bulb failure. When the fuse protecting an
entire leg fails, I consider that especially serious because it can easily
indicate too much current is flowing through that leg, something that
individual circuit fuses will not catch.
If the box and wiring are in reasonably good shape, and the load is
not over about 80% (70% is better) no problem.
The truth is that we don't know a whit about either of those big IFS in this
case. We don't know how well the loads are balanced in the house - many
times one leg is bearing much more of the load than the other. That can be
simply plugging in space heaters into the "wrong" outlets. In a house with
a bigger circuit panel than the feeders dictate, that can happen easily.
I've seen more than one "heavy up" that didn't include an appropriate
upgrade from the feeder.
All we know here is that one leg of the incoming power lines had an
intermittent, not quite completely failed fuse. We know very little else.
(Since writing this, the OP has added a post indicating that he's got 200A
circuit panel but we don't know if it's really 200A service or a 200A box
sitting on 60A feeder lines.) With no ability to go onsite, we've got a
barrel full of IFs that raise the caution flag.
Yes, I agree with you that fuses do fail from inherent vice but IMHO *every*
fuse failure or circuit breaker pop warrants an investigation to find out
what popped it. In this case, I would be looking at the total KWh's used
monthly in relation to the size of the panel and also whether the panel was
properly balanced with each leg carrying as close to half the load as
possible. I'd turn everything in the house on and get out my tong meter to
see what branch circuits were carrying in terms of load. I'd visually
inspect the outside feeders to make sure they were sized for 200A and not 60
or 100.
IIRC, the panel should be sized so that even if every device in the house is
running, the main fuse won't blow. I am not sure that's the case here. We
also know fuses fail in multiple ways: in addition to failing
intermittently or "popping" correctly in an overload, they can also fail to
blow and thus not protect the wiring. That's an extremely hazardous
situation.
If the two fuses for each leg are of the same vintage, I would replace both
of them if I wasn't going to heavy up the panel and the load appeared to be
well-balanced. My best guess, from the limited facts we've been presented,
is that the load is too great for the panel and that one leg was carrying a
heavier share of the load than the other, causing the fuse on that leg to
deteriorate and partially fail.
But in reality, we don't even really know whether the fuse was bad.
Replacing a fuse in a loose fuse holder could jiggle bad electrical
connections just enough so that the intermittent disappears for a while. We
can't know that unless somebody actually checks the dead fuse with an
ohmmeter and carefully inspects the connections coming from the pole.
Running a cartridge fuse hot for a long enough time could easily cause
serious deterioration. If that leg's overloaded, simply replacing the fuse
could lead to tragedy, especially if the bad fuse is replaced with one that
doesn't operate at its rated load, but higher than rated. And before you
say that's unlikely, consider that you're the one saying we're dealing with
a bad fuse to begin with. (-: Who's to say, without an examination, whether
that intermittent fuse *should* have opened completely but didn't?
I've seen people ask very "shocking" questions, that indicate a lack of
knowledge about electrical work. My favorite is whether it's OK to use a
ground as a neutral. These kinds of comments lead me to almost always err
on the side of caution when giving advice on the net, especially with things
that have the lethality potential of possibly overloaded circuit panel.
There's almost *never* enough information given by the OP to make a clear
call. That's just the nature of Usenet.
In my limited experience, it's far too common for people to add circuits
without thinking about the total load. I'm partially guilty of that crime.
I've added the skinny "two in one" breakers to my house that have the
potential to overload the main fuse if I run every circuit to capacity. I
definitely should have heavied up the incoming feeders to meet code but I
added the new circuits not to draw more juice, but to replace the old cloth
covered circuits one-by-one with 12/2 romex w/ground and GFCI protection.
I left the all the old circuits in place because they serve porch and
overhead lights that would have required major demolition to replace. Now,
almost all the large loads like space heaters and window ACs run off 20A
grounded circuits. I've got sensors on the incoming feeders that connect to
my HomeVision controller to let me know the overall current draw on each
phase. I used that information to switch circuits around until they were
balanced, at least for the static large loads. I monitor it periodically to
ensure the loads have stayed balanced.
I have a lot more breakers than I should, but the overall load has not
changed - it's just been redistributed and rebalanced so each leg shares the
load as well as I could balance it. The only difference in the overall load
occurs at peak cooking times. One of the reasons for the rewire was to add
an XTB coupler/repeater/amp for my X-10 stuff, and more importantly, to be
able to use the microwave, the toaster oven and the refrigerator in this 70
year old house without blowing a breaker. That's not going to put a strain
on the main fuses for each incoming leg because the kitchen outlets are
served by different phases, a trick I learned right here in AHR.
Unfortunately, that's not the case in many other installations where there
are too many circuits drawing from one phase and overloading it. I don't
think replacing a fuse is going to get the OP off the hook. It could still
be something like a bad connection to the main feeder in the circuit panel
that's heating up and heating the fuse, too. Again, only an on-site
inspection will reveal things like that.
I hope the OP continues to post his progress in running the problem to
ground. (Electrical pun!) My money's on something other than the fuse being
defective. There's something rotten in Denmark (do we even know where the
OP lives, BTW?).
--
Bobby G.