Neutral and Earth

[chris ma]

Hi,
I have a little concern with my current project regarding the mains connection. The power supply that I am building using a single pole power switch. It means the neutral wire and the earth wire are always connected to the house circuit except the live wire control by the switch. This kind of connection is at the mercy of assuming the house mains outlet connected correctly by the builder or someone, isn't it? The only fuse I have is in-line with the live wire. My question here is at power off position why I can still sense something on the heat sink. I do not know how to describe this sensation on my fingers that when I touched the heat sink and slide/rub lightly on its surface you get that sensation that you know there are something electrical on the piece of equipment; like sliding your finger on the surface of a tone arm when it is on you know the power is on.

But the power switch is off and I still have this sensation. What if the house wiring is incorrect this means I would have a live heatsink waiting to kill someone?

If this is the case why there is no general practice or warning for diyers that we must use 2 pole switches?


Regards,
Chris

[li_gangyi]

Make sure you plug cannot be reveresed...and test your socket if the live and neutral are on the correct places...maybe the sensation you felt wasn't even electricity...

[Christer]

There is a simple test for the wiring. Measure the voltage
between earth and neutral with a voltmeter. It should be zero
or near zero if correctly wired.

It is a very good practice to always use two-pole mains switches.

[chris ma]

Originally posted by li_gangyi
Make sure you plug cannot be reveresed...and test your socket if the live and neutral are on the correct places...maybe the sensation you felt wasn't even electricity...

I am pretty sure it is related to the wall circuit, there is nothing to feel when the cord is disconnected from the wall.

Chris

[SimontY]

Hi,

I had this funny sensation from my cd player, so I earthed the chassis. The sensation is gone, and I have had no problems from earthing it.

Someone told me in another thread that this sensation comes from 'capacitive-coupling' between the transformer and the metal chassis. Reversing mains polarity may help cure this, but don't ask me about safety - I don't know anything! (that's a warning!)

I guess if you earth it well (low resistance, good connections etc) then it ought to be safe. (but like I said, I'm not qualified)


-Simon

[AudioFreak]

Single pole switches should never be used for mains power devices for the reasons outlined in the previous posts

[li_gangyi]

Originally posted by AudioFreak
Single pole switches should never be used for mains power devices for the reasons outlined in the previous posts

Yeah..so go and get a double pole one~!!!...it's almost the same price anyway...and double the safety...

[roddyama]

Chris,

You can pick up an elecrical outlet analyzer from most any hardware store for a few $$. All you have to do is plug it in and it will let you know if your outlet is wired correctly. Look for something like this.

[li_gangyi]

Yeah...but still go get the double pole switch ok???

[chris ma]

Thanks Rodd,
I have seen those detector in Home Depot..

Originally posted by li_gangyi
Yeah...but still go get the double pole switch ok???

I bought these single pole switches a year ago for I like the fact that it has a build in light and rated at 16A from RS component UK. Luckily I have bought four of them so I will have to add the other 2 for the Neutral wires, mono blocks; just the pain to undo everything and redo the mounting plate...

I just have to push 2 switches each time to power up/down....

Chris