Disconnect Switch Wiring ?

Steve09 · 08-08-2011, 10:13 PM

Hello, I couldn't find any answer on which wire Red or White to install my Disconnect Switch on. Some people say it don't matter. I thought the white (ground) so it wouldn't cause any sparks, thanks

Bill_C · 08-08-2011, 10:55 PM

Quote:

Originally Posted by Steve09

Hello, I couldn't find any answer on which wire Red or White to install my Disconnect Switch on. Some people say it don't matter. I thought the white (ground) so it wouldn't cause any sparks, thanks

You thought right !

**KyDan** · 08-09-2011, 08:09 AM

If you're talking about a battery disconnect switch- it should be placed in the
Plus wire.
You can only tell which is the plus wire by tracing it to the battery and visually seeing
which post it connects to. Color might be black, white, red or some other color.
There SHOULD be a standard but there isn't.
You can also tell which is plus by use of a meter. EVERYONE who own an RV needs
a little digital meter for just this kind of thing.

Yes the battery will be disconnected by switching either wire off and on but switches
are normally placed in the positive lead.

dlhoppe · 08-09-2011, 08:52 AM

...and there would be no difference in the possibility of "sparks".

Bill_C · 08-09-2011, 08:55 AM

[QUOTE=KyDan;124059]If you're talking about a battery disconnect switch- it should be placed in the
Plus wire. /QUOTE]

Actually, the negative wire is used for the battery disconnect switch. All disconnect switches in heavy equipment is wired to disconnect the negative wire, not the positive. As the original poster mentioned, this will prevent the contacts in the switch from arcing. Same as disconnecting a cable from your vehicle battery. The negative cable is always the last to connect. Why? If you are connecting your positive post and accidentally touch your wrench to ground you won't get a short while the negative is disconnected. Touch your wrench to ground while connecting the negative terminal (with positive connected) and nothing happens.

jimh · 08-09-2011, 09:18 AM

see if this helps. this is for a cardinal and shows the disconnect on the pos wire. the disconnect separates the converter from the bat.

**KyDan** · 08-09-2011, 09:41 AM

If you're talking about connecting the leads to a battery sure go
ahead and hook up the negative last.

We're talking about RV battery disconnect switches and I stand by my
statement. The battery disconnect switch goes in the positive wire.

Bill_C · 08-09-2011, 09:53 AM

Quote:

Originally Posted by KyDan

If you're talking about connecting the leads to a battery sure go
ahead and hook up the negative last.

We're talking about RV battery disconnect switches and I stand by my
statement. The battery disconnect switch goes in the positive wire.

To each his own. We all have our own reasons "to do, or not to do". However, electricity has no idea which vehicle or unit it is in. It behaves the same.

Goomph · 08-09-2011, 09:58 AM

If I know anything about electric and/or electronics, you install the cut off switch on the positive terminal ...

And having just gone through a similar discussion in another forum which got uglyish, and everyone trying to defend that you cut it off on the negative side, and being adamant about it, I will just watch this from sidelines .....

Yes yes, I know electrons flow from the negative to the positive side ... You still cut it off from the positive side.

I guess my stance is, as long as you do not find your battery dead after a few weeks you will be happy (and so will I for you). I hope you never find out why you should have put the battery cut off switch on the positive side though.

Triguy · 08-09-2011, 10:34 AM

I have a Blue Sea disconnect switch. Blue Sea instructions are to install off of the positive terminal per ABYC standards.

Personally, I have used and seen both neg and pos setups, but the marine ones are always off the positive IIRC.

I have no idea why.

Steve09 · 08-09-2011, 10:39 AM

Thanks alot for all the imput,,,didn't mean to start a fuss,,,lol,,,thanks

VTX Al · 08-09-2011, 10:40 AM

I just followed the instructions that came with the marine battery disconnect switch that I recently purchased. Said to install it on the positive terminal wire. Which, being an electronics tech in my previous life - I would have done anyway. BUT it will function just as well on the neg (ground) side.

....VTX-AL

Steve09 · 08-09-2011, 01:08 PM

ok,,thanks alot,,I was just afraid of sparks .

Goomph · 08-09-2011, 01:14 PM

No fuss, we are gently discussing it

In a very civilized manner too, which pleases me a lot.

Go ahead and install it on the positive side, well negative if you really want to. Just have one though. Nothing is worse then going to your trailer and finding out that the battery is dead. Especially if you really like your power tongue jack like I do ...no, please do not ask me how I know it sucks to have a dead battery

Quote:

Originally Posted by Steve09

ok,,thanks alot,,I was just afraid of sparks .

**KyDan** · 08-09-2011, 01:23 PM

If you cut either battery wire you will shut off the battery system.
No argument there.

Our RVs are pretty much all negative ground.
That simply means pretty much everything in the RV has one lead going
to frame/ground/negative on the battery.

Fuses, switches, 12v circuit breakers that turn things on and off go in the
"hot" lead which in most RVs is gonna be the PLUS side.
(Hot being a wire that will read voltage between itself and ground.)
In my trailer that includes the battery disconnect switch.

brianb · 08-09-2011, 02:22 PM

I've always installed the shutoff as close as possible on the Positive terminal. Usually it was attached to the terminal. Never thought of using the negative side, while it would certainly work that just seems strange and foreign to me. Must be my electrical engineering background...

If I was physically removing the battery I'd do negative then positive to avoid shorting anything with tools. But if it was an attached switch mechanism I just use the hot side.

dlhoppe · 08-09-2011, 02:49 PM

Regarding switch contact arcing when making or breaking the circuit. If there's a load, the switch contacts will still arc regardless of whether you're switching the positive or negative leads. The current potential does not go away.

If you want to test, turn the lights on in your TT and disconnect the negative lead (preferably not at the battery) and touch it a couple of times to make the circuit. You will still have arcing. No way around that.

dlhoppe · 08-09-2011, 02:57 PM

Think of it this way. If you switch the negative, all the circuitry in the TT becomes 12v+ (all the way around to the TT side of the disconnect switch). Is that a problem? Not sure, but I'd rather not do it that way.

jimh · 08-09-2011, 03:37 PM

Quote:

Originally Posted by dlhoppe

Regarding switch contact arcing when making or breaking the circuit. If there's a load, the switch contacts will still arc regardless of whether you're switching the positive or negative leads. The current potential does not go away.

If you want to test, turn the lights on in your TT and disconnect the negative lead (preferably not at the battery) and touch it a couple of times to make the circuit. You will still have arcing. No way around that.

way back in the old days of points in an automobile....they put a condenser (capacitor) across the contacts. that would cushion the interruption. still will get some spark but very little. i'd say try a 0.5uf and see what happens.

jleon01 · 08-09-2011, 04:30 PM

On my tt. I initially tried the switch on the ground wire, had 2 batteries in parallel , but was never able to make the switching work off , so did the positive. My guess is that there must be a frame ground completing the circuit somewhere.

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