There are so many computers and air purifiers and television equipment
hooked up It's surprising my breakers aren't blowing all the time but...
why would the main breaker blow? Seems like the individual breakers would go
first. A new AC compressor was just installed and there is something weird
because one of the other breakers for "lights" or something stops the AC
when it is tripped. The actual AC breakers trip the AC too.
Tia, : -)
It's quite possible the total load is now greater than the panel
capacity even though no individual circuit is overloaded.
If the breaker that you mention that stops the AC does something other
than the inside air handler, you definitely have a problem.
Sounds like time for an electrician for some diagnostics and maybe the
AC guys back to figure out whether there's something amiss w/ the wiring
Is it possible that the *control* for the A/C is on a lighting branch
It is possible, especially if you have a lot of breakers, that if the
A/C goes on it might be pulling only 30A on a 40A breaker but the
cumulative load of everything in the house would be over 150A or
whatever your main breaker is...
Hardly. Any central A/C would require 240 and 30A+ and I've never seen
that kind of a lighting circuit in a residence. Unless, of course, some
_real_ doofus mixed stuff all up and has multiple wires connected to a
breaker or some other really, really weird stuff. But, even then, any
lighting circuit would normally be only 15A or 20A max, not enough to
keep from tripping...
That's certainly possible, and I'm guessing the new A/C was the straw
that the camel wasn't happy to see...
I'm also guessing there's something else not right and OP needs a pro to
evaluate what's what...
Bad main breaker is what the guys who installed the compressor are saying.
Is it a difficult or dangerous thing to change? The breaker has pigtails the
need to be unscrewed and it isn't clear how to shut off power between the
main breaker and the feed. It doesn't seem right that 'standing or a board'
would take care of it, insulation wise, as one guy told me.
It seems like replacing the main breaker might be cheaper and have a good
chance of success instead of calling an electrical expert out to test the
You don't need to test the lines, but an ammeter will tell you if the main
is tripping prematurely. They do go bad, but it's certainly not the first
thing I'd be looking at, and definitely not guessing at
On Mon, 18 Jun 2007 22:47:27 +0000, email@example.com wrote:
Knowledgeable person = electrician or equivalent.
Yes the electric service provider must be notified. Around here they frown
upon breaking their seal. Probably holds true with most.
I agree. The OP doesn't know how, he needs to find someone with experience.
I had a stint as a commercial A/C installer (electrical) some years back.
I know what it takes to be successful and stay alive at the same time :)
well I like working on electrcal but am not a electrician, but know
how to safely pull a meter.
there are times it must be done, like a fuse breaking off in a fuse
box. that happened to a friend, I pulled the meter and notified the
power company on monday, fuse broke off saturday morning...
power company said they didnt care provided they were notified.
might be a bad main breaker or more likely a unbalanced load. my
neighbor had that problem with christmas lights, he lit up the
neighborhood, after a quick check we re balanced his legs and all was
I fix office machines for a living but could of been a electrician, I
wierdly enjoy the challenge of snaking lines and thru walls.
this reminds me I had some stuff fall over in the basement and destroy
the plastic seal on the water meter. need to call them so they can
occasionally do jobs for friends always for free, I like being useful:)
On Tue, 19 Jun 2007 01:12:34 +0000, firstname.lastname@example.org wrote:
Personally I think the OPs mains breaker is weak if it trips more than
once which should be a vary rare occurrence if at all. I did some work
with an electrician years ago in my late teens. Learned and retained a lot
from that years worth of experience. He did new home installs only so I
didn't get any renovation/troubleshooting skills, those came later on in
life. Recently I upgraded my girl's service from 60 amp fuses to 100 amp
breakers. I'll have to call a friend to do the room by room rewire, I'm
getting too old for that crap :)
The "lights" breaker shouldn't affect a central AC system, unless it's a
main breaker for a sub section of your panel, and the AC breakers are
located in that sub section. If your service is too small for the loads in
it, the main will trip. you need to get someone with an ammeter and take
readings while switching on the circuits
Sounds like you guys kind of agree. It not apparent to me, though, why there
is any case that the regular breakers would not trip before the main. Maybe
it's beyond someone so ignorant of the way this kind of thing works.
On Mon, 18 Jun 2007 23:38:39 -0700, "AKA gray asphalt"
If you have a 200amp main breaker, with 20 20-amp breakers and 15 amps
flowing through each of the 20 circuits, that's 300 amps total.
Which breaker will trip?
You can assume everything is working well.
If one breaker is getting weak, it might trip no matter what other
breakers do, and no matter what the current.
Why not turn off the AC for a couple days and see if anything trips.
Probably not since the AC was just added. Then you will have an idea
of where the additional current is being used. Probably the AC is the
culprit, but it's probably not using more than it should.
Then you can turn off everythign but the AC and see if the AC by
itself trips the main breaker. Probably not, especially since it
doesn't trip the individual breaker. but these tests interest me. If
you get results that I or the others don't expect, you'll have a big
clue as to the problem.
Or you could just take their suggested advice. They have more
experience than I and they're probably right.
As a couple of people said, you can install loads that are all smaller
than the breaker they are connected to. But when you add up all the
loads it can be larger than the main breaker.
Your original post said "a new compressor was just installed"
If that means A/C was just installed when there was none before, or a
larger A/C was installed, the total electrical load may now exceed the
main breaker. This is easy to do with smaller services like 100A or
less. In that case you need to increase the service size (relatively
costly) or don't run major loads at the same time as the A/C. Major
loads include electric drier, electric stove, electric water heater.
When an electrician adds a major load they should determine if the
existing service is large enough and at least warn you if it is not (it
is a code violation if the NEC covers your area).
Else what is "new compressor"?
The furnace normally includes the thermostat and control circuit for the
A/C. As several people said, if the furnace is on the lightning circuit
you talk about, turning it off will also kill the A/C.
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