Battery Disconnect

[PerryB]

Originally Posted by Bob Landry

The positive or negative location of battery switches has been argued on many forums ad nauseum. I work in the marine industry and have never seen a battery switch installed anywhere but on the positive side. I have also never seen one OEM installed anywhere else on a RV. I grew weary of being constantly argued down about it by the armchair electricians and finally decided that it wasn't my problem.
The reason for putting it on the positive side is that both 12V ground and AC ground are tied together. It's possible for a 12V device to pick up enough of a ground to create a parasitic drain while not actually enabling the 12V device to work. By breaking the 12V source there is no question that 12V has been removed from everything.
There will still be those who insist on doing it their way. Good luck with that, but that is the rationale behind it.

Thanks, Bob.
That actually makes perfect sense. Of course not knowing this I have long since installed my master disconnect on the ground side. In my case I have always pulled the main A/C breaker prior to disconnecting shore power and it remains off when in storage so I've unwittingly eliminated the potential for parasitic return. Now that I've read this I'll install my next one on the hot side.
My other "excuse" is that I've installed master disconnects on my farm equipment for years (all on the ground side), since most of it does a lot of sitting and the switches prevent discharge through the various keep -alive circuits and of course the dual system/common ground issue doesn't come into play here.

[Pmedic4]

Originally Posted by Javi

Sorry, I grew up in a time where the 120 AC didn't have a ground wire.. only a neutral. In which case it didn't matter which side you interrupted the current flow on..

That's really not true. Even prior to having the ground wire, there was a 'hot' and a 'neutral'. If you only switch the neutral, you have have power at an outlet or light, and someone only needs to supply a ground. The bare ground wire you mention is not the only way to complete a ground. When the hot wire is switched, there is 'technically', no potential for the getting power through the neutral line.