Lifesaver question on earthing

[Klimon]

When wiring up an amp, I connect all conductive parts that can be touched (pio caps, trafo's etc., my chassises are in wood) to the earthing pin of the power chord socket... To me atleast this sounds sane, but when the power outlet on the wall hasn't got an earth connection, and one of the touchable metal parts would carry a high voltage due to contact with a loose HT wire inside the amp, I think I'ld be fried after all.... What the solution? Connecting the earth-pin to one of the two phases?

Thanks Simon

[Kent Smith]

Good question! There is a low and a high side, but even the low side has some voltage on it. But outlets are not always wired consistantly. I would not want to ground to that. I have seen adapters that have a wire with a lug to connect to a screw on the outlet, but even that may not be grounded, especially in older homes. You may have to take your chances....

[Eli Duttman]

Simon,

Check a cold water pipe physically close to the place the equipment will be situated for continuity to ground. If all is well and continuity to ground is present, use the pipe for the safety ground connection.

Cold water pipe grounding is an old crystal radio trick.

[Klimon]

I'm afraid there's no cold water pipe in the vicinity of my listening spot.... although I could predict my wife's reaction to me wiring up water pipes...

How are production tube-amps wired (or any other HT carrying device for that matter)? If chassis is simply connected to earth-pin the risk is equally great when a HT wire would get loose and touch the chassis

You may have to take your chances....

I'm in the situation you describe: old house without earthing connections. I just hope there a way in between the water pipes and taking the risk (for the sake of the other people living here)

Thanks for thinking along! -- Simon

[kevinkr]

A large isolation transformer in this situation should make it safe should one or the other side of line become connected to chassis or some other metal part you can touch.

One other thought might be to use ground fault circuit interruptors they work by measuring the current in both legs and if they don't match closely they disconnect the power. I suspect versions exist for 230V operation. (They do in the USA - used in hot tubs, spas, and swimming pool filtration systems. Anything used in the EU should have the CE mark though.)

I take it this is rental property and there is no possibility of getting an electrician in to upgrade the wiring to the receptacles powering the hifi system?

No grounds on kitchen receptacles?

[Klimon]

I take it this is rental property and there is no possibility of getting an electrician in to upgrade the wiring to the receptacles powering the hifi system?

You got it (even no grounds on kitchen receptacles)

I'll look into the options you mentioned

Thanks!! Simon

[kevinkr]

Well on the bright side you don't have to deal with the weird grounding arrangement used in buildings built after 1960. I spent the later part of my teen years in Brussels where most of the grounded outlets I encountered had that funky ground pin sticking out, others were like the ones used in Germany.

You'd think after all these years they would have tried to harmonize the wall sockets in EU countries..

I take it yours are the generic two prong type.. I think a gfci that interupts both sides of the line would be a worthwhile safety enhancement, and since you can't ground things I would recommend you not bus ground together at the receptacles. This should be less expensive than the isolation transformer approach, otoh given the probable state of the wiring in your place the additional isolation a transformer would provide might not be a bad idea.

I've had unapproved power switches that developed internal shorts to the bat, and this made the chassis hot. Make sure any switch you use has a vde, cebec or similar (semko, demko, nemko) and/or CE mark on it. Should reasonably assure that these sorts of failures don't happen.. Same for fuse holder.

High voltages on the secondary side of your power transformer are not an issue as long as all external connections are solidly connected to the chassis of the equipment in question through the star ground. It is particularly important to make sure that the 0 ohm end of the secondary of your output transformer is connected to chassis in case the interwinding insulation ever fails.

[martin clark]

Check a cold water pipe physically close to the place the equipment will be situated for continuity to ground. If all is well and continuity to ground is present, use the pipe for the safety ground connection.

While that's often probablyOK, it's a practice frowned on in Europe and absolutely discouraged. Much water distribution / connection to mains supply is now via HDPE pipe, meaning that connecting your water system to a live chassis might make for a much bigger problem, not a smaller one...

To answer the original question - I think I'd simply use mains connectors that demand a mains earth connection.

[DigitalJunkie]

Same thing here in the US,I think they now frown upon the cold water pipe grounding scheme because of the increased use of plastic pipes.

Although the CATV and phone company guys apparently haven't noticed,they're still grounding the CATV/phone feeds to the outdoor water faucets which are fed by plastic pipes. Doh!?

[Klimon]

that funky ground pin sticking out,

That's the generic type here ... they should make it worldwide standard (along with 230V)