Buss Bar near the compass?

[Mack]

I have my battery located right under the companionway and am about to start doing a complete rewire of my boat, a CP16.  I had intended to put a bus bar right behind the battery and run everything to it.  (I was looking at the Blue Sea Systems Dual Busbar: #200599).  I have standard lights and a trolling motor.    However, the compass is mounted near where I was intending to put the buss bar.    The compass is located on the bottom part of the cockpit vertical wall.  I would post a picture but I haven't figured out how to do it yet. 

Am I going to have issues with this?  I don't want to affect the compass by running juice 6" away from it. 

[Bob23]

Hi Mack:
   I wouldn't place a compass that close. I think I remember that anything that could possibly affect the compass shouldn't be any closer than 24" but I could be wrong. It is your  basic navigational tool so why take the chance on introducing error?
Bob23

[skip1930]

Move the Buss bar away. Far away from the compass.
Any + or - wires passing near the compass ought to be twisted up together in a drill motor with one end of the wires in a vice.
That makes a nice neat wiring loom. And the twist cancels out the influence on the compass.
Even if it's just a red light on the compass, twist the wires.

skip.

[Craig]

Good advice! Those wires carrying DC will affect the compass any time current is flowing.

[MacGyver]

As much as I thought that it was a issue, turns out it isn't as big a issue as one thinks.
Several boats having compasses here have gobs of rats nest wiring right behind them and instruments within 4 inches...........NO ISSUES.......

That being said, I'm not saying to do it. But be mindful. IMO the 2 wires to the light in it are no big deal.........also the affects by my understanding come from large amperage. Not small amperage

If that small light affects it.......why have it on it?

At any rate, rule of thumb is to mount the instruments about 6 to 9 inches away from the compass. They never say anything about the wiring.............

Mac

[nies]

It has always been my understanding to make sure the pairs of wirers are twisted around each other in any run and a min. of 6 inchs from a compass........nies

[Harrier]

A "rats nest of wires" can be ok for the same reason as mentioned about twisting the wires - the electromagnetic fields cancel each other.  Its when you have nicely organized wires running straight that you introduce the potential for a problem.  The trolling motor might be enough of a draw to cause some issues.  Easy way to find out is to test it.  Temporarily run the line past the compass on a constant heading and see if/when the compass swings.

On a side note.  I was hunting with my father about twenty years ago and we parked his truck underneath some high tension powerlines.  When we returned a couple hours later we found the entire truck was vibrating and audibly humming at what I assume was ~60hz.  Needless to say I wished my father good luck and stood back 50 yards while he started the truck.  The truck started fine but that moment gave me a new appreciation for electromagnetic fields.  Pretty cool stuff...

[skip1930]

In Canada the high tension wires that run cross country and hung way up there high have to be painted in an Electrodeposition Tank [e-coated] as the alternating currant of electrons running back and forth over the wires tend to scrape off molecules of copper which fall to the ground and kill off the vegetation leaving brown streaks on the ground under the wires. Cool hey?

skip.