kenwood_nut wrote:
I can't believe how different 12 volt vehicle wiring ... is from house wiring.... |
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I stated this reply after that message. A few delays and a few other replies have crept in.
But FWIW.... (yes, a ramble...)
Well the switching is the same - you only need to switch the one pole.
Hence why you do not need other pole (ground).
But domestic AC usually mandates the switching of the ACTIVE conductor except where BOTH poles are switched (eg double-insulated).
Whereas that - and its logic - may not apply in car etc. A classic example that has recently resurfaced yet again - a "Battery Isolation Switch" that is used in competition etc vehicles to enable isolation of the battery in case of accident etc SHOULD be in the non-HOT circuit - ie, it should disconnect the battery's negative (ground) terminal from the chassis and loads etc. If the switch is next to the battery, it is no big deal. But when regulations require an isolation switch to be on the dash or console, or a rear corner of the vehicle, then isolating the +12V side is suicide! Some argue that in that case, it is safer with NO switch!
Now, do you ground the box etc?
My answer to that is "why create an additional risk?".
But your local regulations will state what is required. Refer to them.
(If your local regulations are a hazard, I empathise....
Been there, Done that!)
It sounds like you have the ever popular M.E.N system. (IE - power station outputs 2 AC lines - aka L1 & L2. They call L1 "Active" and bond L2 to (planet) Earth and call that "Neutral".
The Active L1 is distributed across the country.
Your Active goes via a fuse to your switchboard main switch and thence through fuses to different circuits (lights, power, kitchen, etc).
The Neutral also comes in to the main switch board (aka MSB) where is is bonded (joined) to an Earth Stake, otherwise Earths and Neutrals are kept completely separate in home wiring.
Earths are often literally just that - an Earthed connection meaning to planet Earth. Or yes, also called ground.
The Neutral however is the "return" for the Active circuit.
Power flows out the power station through the active, through the load, and back through the Neutral back to the power station.
That method means that fuses will operate given certain kinds of
faults, and appliances should be at Earth potential so you don't get zapped. (Until lighting hits telephone lines etc... LOL!)
And the above is a simplification. In reality, 3
phases are sent from the power station, not "active and neutral". They are like three L1 lines or "actives" that are 120 degrees apart (aka 3-phase power). And there is no Neutral per se - "neutral" is a mid point between the 3 actives. (Neutral may be "reconstructed" at substations for distribution to consumers.)
But whereas the AC system used to be almost a floating or balanced system - ie, 2 pins and no Earth - the world is standardising on an Earthed distribution system - ie, 3 pins - Active (brown), Neutral (blue) and Earth (green or GREEN/ YELLOW).
Remember - if you touch the Brown, you will s.h.i.t yourself (poo your pants if that gets censored). That's how I remember. We used to have red = active and black = neutral and green = earth. They were easy to remember (red is hot and dangerous).
So back to your question. Do you ground the box?
Well, do you mean ground as in neutral, or ground as in earth?
Our regulations are quite clear - any mains (wall) powered device shall be in an earthed (metal) enclosure EXCEPT where it is a double insulated appliance (only 2 wires; special construction applies).
And earth means earth - the 3rd pin with its GREEN/ YELLOW wire to an "earthed ground stake" - NOT to the neutral pin or circuit.
So, refer to your regulations.
But I am certain that if you did that, you would be replacing your green wires. In most places in the world, that is a serious hazard - an accident waiting to happen.
As to your breaker tripping, as you should be able to appreciate, there is no way that the switch can short so as to cause MORE current to flow through the circuit (light) than the switch itself (ie, a clean contact switch).
So, is it an arc across the contacts that generates noise that trips the breaker?
Or is the breaker an RCD (aka earth or ground switch, aka "Safety
(sic) Switch") that likewise is getting noise and tripping?
Or is the switch "leaking" through you or something and tripping the RCD?
Or is there an insulation breakdown so that when moved, there is leakage through <whatever> which is tripping the RCD?
The latter is often followed by fire.
The latter two are often followed by death, else maybe a cute shock if an RCD is installed AND is working properly (people rarely test them; hence they seize!).
I did write "a cute" shock because of my sick humor, but make that one word if RCDs are not fitted or if you place yourself across the neutral and active (without any earth leakage) as such shocks often are acute.
Forgive my narky attitude, but I no longer suffer Richard Craniums (aka Dik Heds).
And I do laugh - because seeing preventable tragedies is something I also try not to suffer. (Though it was funny seeing that guy on a train light up; fall stiff as aboard to the roof (making a hollow wooden sound as he did); then having spot-fires gradually ignite over his body. 1,500V DC - I'd rather 22,000V AC any day!)
But you may now understand some of my questions....
And you did give the answers I expected.
For some reason, people think switches must be earthed or neutralised. (Yet they know their ignition switch isn't, nor their 2-terminal switches.)
And for some reason, people think that short circuits blow things. [ EG - A common one - you keep blowing light bulbs; people often say "you must have a short". So how do you short a 12V supply into a 12V bulb? Else how does a short ACROSS a bulb blow it (assuming short intermittent shorts so that the fuse doesn't blow)? It's more likely a bad connection that makes & breaks - hence thermal shock etc. ]
Alas it doesn't take much thinking to realise the reality, it's just the we rarely do think...
Yet in retrospect it is all so obvious and easy....