Hi there,
I had a similar problem in my house, but the lights would dim when any
motor started (furnace blower, fridge, freezer, etc.) The worse effect
was observed when my air compressor started. The symptom I experienced
was that lights on the same phase as the motor dimmed, while lights on
the opposite phase got brighter. I went through many incandescent
lights bulbs as a result. Measurements conducted on the main buss at
the fuse box confirmed that as load was added to one phase, the
voltage rose on the opposite phase, i.e. the neutral wire from the
pole transformer could not handle the current. My house was physically
the farthest away from the pole transformer (i.e. at the end of the
line).
I called the Electricity supplier (in Ontario Canada, its called Hydro
One) and had them come out and make measurements. The technician
measured 4.7 volts of drop between the pole transformer and my fuse
box main buss with a 10.2 amp load. I pointed out to him that my panel
was rated at 100 amps and thus the voltage would be unacceptably low
should I ever draw 100 amps. His reply demonstrated his lack of
knowledge in that he said it would only drop a couple more volts with
a 100 amp load. Guess he never heard of ohm's law.
Anyways, after he left, I called Hydro One and asked to talk to an
Engineer. After 3 call backs from "customer agents", a real network
design engineer returned my call. I explained what his tech had
measured and asked if this was acceptable. His reply was "from the
surface, no, but leave it with me and I will get back to you".
4 days later he knocked on my door and confirmed that all the
distribution wiring out on the street poles was not "up to snuff" and
required replacing. About 3 months later, they began replacing all the
distribution wiring in my neighbourhood (my street was first on the
list!). No more issues since.
It might behove you to try and track down why the dimming is
occurring. The additional load of the air con could possibly cause a
marginal situation to eventually fail. This could possibly get ugly,
depending on what the real problem is and what the resultant failure
turns out to be. I do not regret investing the time I did into
resolving my issue. My neighbours are pleased as well. If you are not
technical, get someone who is to help you. I'm sure a couple of beers
(after the troubleshooting is complete!) as payment is all it would
take to figure out what/where the issue is.
Some possible causes:
1) Pole transformer is over loaded (not very likely as everyone of
your neigbours on the same transformer would be experiencing the same
propblem).
2) Street distribution wiring is too light and cannot handle the
current (as in my case).
3) Bad connection in the distribution wiring (crimp connectors
corroding, meter connection loose, etc.).
4) Bad/loose connection in your mains panel (mains wiring, buss
connection, circuit breaker or fuse connection, etc. -my sister's 100
amp main fuse connection on 1 phase went up in smoke due to poor
torquing of the connections- had to replace the entire panel as parts
for the thing were no longer availible- lots of $$ as a result).
Bad/loose connections will usually generate heat and show a
discolouration as a precursor to the eventual failure. Look for this
symptom.
As a side note, I have converted all lighting in my house to compact
fluorescent. Despite my best efforts, neither my wife or any of my 3
children have learned the fact that a light switch has 2 settings (on
and OFF), not just one (on)!
Cheers for Canada
Bob Morgoch
