On 06/26/04 23:06, Trunk-Slammer -Supreme said...
If the breakers are both are in
even numbered slots, move one of them to an odd
numbered slot, if one is odd and one even, move
either one by one slot.
Actually, that's a bit wrong. In most panels, the odds are on the left side and the evens on the right. However, that's not how the 'busses' are configured.
The adjacent left and right slots are on the same phase. For example, 1 (left) and 2 (right) are on 'A' phase, 3 (l) and 4 (r) are on 'B', 5 and 6 on 'A', etc.
To identify phases vs. spaces, go down the panel and count A,B,A,B,etc. Again, the left and right slots on the same horizontal level are the same phase.
That's why a double-pole breaker can be placed anywhere in the panel and pick up power from both phases.Of course, 3-phase panels go A,B,C,A,B,C,etc.
Basically shifting from in phase to out of phase.
One way will eliminate the loop, the other won't.
True that moving a breaker up or down one space will swap which phase it's on.
And right at the moment I can't think of which
way works, and which doesn't, but one or the other
will do it....lol
Same phase should help, but if a swap either way makes a difference, then there's an underlying reason, and it may be something that should be remedied.
There's an old saying among old electricians and technicians: "a ground is a ground is a ground . . . or is it?" Theory and reality don't always agree.
Under normal circumstances, no current flows in an equipment grounding conductor (EGC), so all equipment chassis should be at the same (0v-to-ground) potential.
Most modern electronics have bypass capacitors in them to effectlively-ground induced high-frequency noises. Plus, 60Hz fields are induced everywhere.
Therefore, some current does flow, which means that there are potential voltages, no matter how small, on modern equipment chassis, and each one has its own level.
Normally, shielded cables are used as interconnects, so the chassis are electrically connected. With each power cord that has an ECG comes a parallel path.
Any voltage difference between the chassis results in a current flow in the shield, and this signal is added to the desired signal in the cable, and amplified.
The most sensitive inputs are the most susceptible, and these are the ones in the micro-volt (antenna/cable) and milli-volt (phono and microphone) ranges.
The better electronics have circuitry where the signal ground and chassis ground are not tied together. This and "ground-lift" switches can do a lot to reduce hum.
Some people have success with cutting through the shield at one end of a cable, and cable-TV 'ground-breakers' are usually 1:1 isolation transformers.
This is one application where "balanced" interconnects shine. While the shielding assures induced-noise protection, ground is not used as a signal reference.
"Thus endeth the lesson." . . . for now.
Larry
www.fineelectricco.com