Noob wiring question

[BlkGS]

Hooking up my new electronics for the year. Currently have a 1,2, 1+2 switch. Its connected on the ground side. I was planning to have it hooked to the positive side... but it seems like this will work fine. Any reason not to do this?

 

[jb32566]

ground side connection is correct.
mis-read your question.

 

[Beachbummer]

Can you confirm... Do you mean your battery switch is set up to switch ground instead of positive?

How is the positive hooked up?

I may have misunderstood.

 

[BlkGS]

Yup, its switching ground side. Positive hooks direct to the batteries.

I guess the making I would have to do I make sure the amp ground goes to the switch to make this work

 

[jb32566]

that's wrong. and dangerous.

connect the battery grounds together either directly or with a bus bar
the switch should go to the '+' side of each battery.

sorry i misunderstood earlier.

 

[MidnightRider]

that's wrong. and dangerous.

connect the battery grounds together either directly or with a bus bar
the switch should go to the '+' side of each battery.

sorry i misunderstood earlier.

I understand this is wrong. I'm curious why it's dangerous? What can happen? I always like to learn something new and even though I would never do this, I don't know what bad can happen from doing it.

 

[BlkGS]

What's dangerous about it? Just having wires with 12v looking for ground?

I'm gonna have to do some rewiring, planning to add a dual path switch and acr, but dont have all the pieces in yet.

 

[jb32566]

if you connect the grounds to the switch, anything connected to the batteries still has voltage available but nowhere to go. it's mainly a shock hazard in a normal environment. in a marine environment water can provide a path to ground.

 

[BlkGS]

Gotcha, I'm not super concerned then, 12v doesnt conduct through fresh water anyways.

 

[jb32566]

ok good luck! hopefully you don't ignite any engine vapors with an accidental spark!

 

[jb32566]

your statement had me googling. i hadn't seen this. interesting.

still be sure that the postive terminals are covered to prevent sparking.

 

[BlkGS]

ok good luck! hopefully you don't ignite any engine vapors with an accidental spark!

For sure, I will just have to make sure I vent the vapors really well for the weekend until i get the switch to fix it right.

It hasn't exploded yet, and it's been like this at least since I bought it last year.

 

[Gym]

I don't see any dangerous issue with wiring this backwards as long as nobody with common wiring knowledge does any electrical work on your boat. You can wire your house the same way by switching the common rather than the hot. It will work but no building inspector will pass it.

On my boat I have several factory wires on the negative terminal. I can't imagine running all of these through a switch.

 

[Gym]

your statement had me googling. i hadn't seen this. interesting.

still be sure that the postive terminals are covered to prevent sparking.

Although the guy in this video sounds reasonably intelligent I take issue with several of his comments. Any of us boaters who got their cellphones wet know they were toast because they shorted out due to water intrusion. He also stated putting a lamp in water would short out by ionizing the water??? I believe it would short out because the sink would be grounded and the hot lamp wire would seek ground. Let's see him hold a 110v wire while standing in a puddle while explaining ionization. In this case all 15 Amps of current wouldn't flow through his body due to resistance but probably 8 to 12 amps would. It only takes 20 milliampers to stop the human heart.

Any of you ever get water in your ECU? I can guarantee it was the water shorting between the hot and grounded components that killed the ECU and your motor.

 

[MidnightRider]

if you connect the grounds to the switch, anything connected to the batteries still has voltage available but nowhere to go. it's mainly a shock hazard in a normal environment. in a marine environment water can provide a path to ground.

Hmmmm... this doesn't track for me as an answer. If you were talking AC then this would make sense and I fully understand why you would only switch the hot on an AC circuit and how switching the neutral side could be a very dangerous and bad idea. However on DC, current actually flows from negative to positive and its a closed loop system, no danger of grounding out the system say by standing on the ground and touching positive terminal (unlike AC where you could potentially kill yourself by standing on the ground and touching a hot wire). I was under the impression that putting the switches and load on the positive side in DC applications was really nothing other than a convention that we all agree upon. In fact there are some vehicles that run a "positive ground" system, so all loads and switches are on the negative side. Not saying there isn't a reason why this is bad beyond convention but I've never heard of a reason and this answer doesn't really track for me or satisfy my curiosity - would love to know if there is a reason though.

 

[jb32566]

yah the russians used to do that with tanks. i know the T72 is negative ground. supposedly for oxidation purposes.
my expertise is in embedded systems, not AC so I can't speak to that.

take a look at this.
in the first case, the voltage on the load is 0. It will be pulled to ground.
int the second case, the voltage on the load is whatever the batttery voltage is. any connection to ground will allow current to flow.

 

[MidnightRider]

yah the russians used to do that with tanks. i know the T72 is negative ground. supposedly for oxidation purposes.
my expertise is in embedded systems, not AC so I can't speak to that.

take a look at this.
in the first case, the voltage on the load is 0. It will be pulled to ground.
int the second case, the voltage on the load is whatever the batttery voltage is. any connection to ground will allow current to flow.

View attachment 95051

Huh? Ok, likely my lack of knowledge is just the main hinderance here "getting it". Thanks for trying. I'm shade tree electrician at best, with much more knowledge/experience working with AC, not so much with DC - which is the reason for my curiosity on this subject.

 

[Julian]

Tell the people who get electrocuted at docks that water doesn't conduct electricity!

Electric Shock Drowning (ESD) Explained - BoatUS

Which is why all docks with power to them have warning signs about NO SWIMMING! Idiots on Falls Lake last weekend towed their kids down into our marina on their tube and the kids got off the tube at the dock and swam around. Dangerous as heck, but these people probably had no clue of the danger.

 

[BlkGS]

Tell the people who get electrocuted at docks that water doesn't conduct electricity!

Electric Shock Drowning (ESD) Explained - BoatUS

Which is why all docks with power to them have warning signs about NO SWIMMING! Idiots on Falls Lake last weekend towed their kids down into our marina on their tube and the kids got off the tube at the dock and swam around. Dangerous as heck, but these people probably had no clue of the danger.

Certainly 120V will conduct in water, but low voltages like 12v dont. Unless you have enough conductive materials in it (like saliva does).

 

[MidnightRider]

Certainly 120V will conduct in water, but low voltages like 12v dont. Unless you have enough conductive materials in it (like saliva does).

Yeah 120V AC is a totally different animal than 12v DC