Jeff wrote:
#6 wire has about .00046 ohms/ft. Double that for return and call it 0.001
ohms/ft. Assume 50 ft of wire to subpanel means 0.05 ohms. Thus a 10 A
load would only drop about .5V. To test this get a digital voltmeter and
measure the voltage at a plug of interest. Plug a load like a toaster in
the other plug and see how much drop you get. Do this on both sides of the
240 circuit. If the drop is much more than calculated above then something
is amiss.


wrote in message
...
This winter I installed a 16-circuit subpanel and rewired the second
floor. The sub is fed from the main via a 60A 250v circuit over 6/3.
Everything has been working fine ever since, but I haven't really been
pulling much on these circuits until this week.

Today I'm noticing that when one of my window A/C's compressor kicks
on it is flicking the lights. But these lights are on a different
circuit (same panel). I did not expect this. The A/C is pulling
about 10A (120v) on a 20A dedicated circuit. Other power being drawn
from this panel includes:

-computer: ~5A on a dedicated 20A circuit
-computer and extras: ~5A on a dedicated circuit
-another A/C: ~8A on a dedicated circuit
-lights: ~? (1A maybe) on another circuit

So total I doubt I'm drawing more than 30A of 120V, so I can't be
maxing out the feed, right? That feed should give me 96A of 120V (80%
of 60A at 240V).

So what's the deal? Why would any lights on a different circuit
flicker when the compressor kicks on on another circuit? To be fair,
the flicker is subtle. It's not huge, but it's there.

thanks


Hi,
If you really want to do the test. Ordinary meter is too slow as well as
human eyes. Really oscilloscope is needed or a meter which can read the
instantaneous voltage and freeze the display.