It is fairly noticeable that those posting electrical questions here;
a) Often do not provide sufficient 'background' info.
And b) Do not respond, or respond incompletely to questions (or the
'what ifs') by those posting to try and help them!
This leads to to a lot of speculation and comments that begin with
comments "If the AC was part of the original installation ...........
etc. The waste of a lot of time and maybe further confusion for the
original poster; some of whom shouldn't be 'at' electrics at all. I
have a neighbour like that who could be dangerous!
A recent example here has been that 90 amp breaker question!
We still don't know whether the AC breaker worked fine for years and
then started to trip? Is the AC unit itself working OK anyway, what
other load is on that breaker panel etc. etc.
In other words incomplete information. No specifications or conditions
under which things are being used.
Often when investigating electrical problems 'unusual' things have
been found that threw a whole new light on the problem as originally
1) 3 way switches wired up for years so that "Oh yes both switches
have to be on for the light to come on!!!!!". Someone had replaced one
of the switches incorrectly.
2) A 230 volt motor hooked up to 115 volts! Didn't work well; got got
and occasionally stalled!
3) An outlet on a computer desk designed for a light load or minor
computer accessory into which some had plugged an extension cord for a
kettle (1300 watts) and a toaster (1200) watts; all on one phase of a
3 phase supply. Which finally blew, when the computer area had to be
powered by a 3 phase battery fed inverter not the mains supply! The
massive unbalance shut down the whole thing and destroyed computer
controlled telephone services for quite a while!
4) A grossly overloaded 230 b volt 3 phase delta supply, where someone
had provided a centre tap on one of the phases of the supply
transformer in order to get a zero voltage neutral; sort of.
The voltage from that centre tap to the 3rd (other) phase was really
While the above are generally some of the more unusual we had the same
weirdness when one side of a neighbours 115-0-115 garage supply went
open (outside) but their house was OK. Nobody could understand why
they were getting c voltage on both 'sides' but the 230 volt stuff in
the garage would not work. Answer switch off everything; but the
handle of the main switch was broken off ............... and test the
incoming voltages! So we actually had 115-0-nil! Better than a broken
Anyway gotta go. Neighbour has problem with electrical brake switch of
his transport truck's air brakes! We think we've got it narrowed down
but the most likely faulty switch is above and behind a hot Cummins