Earth & neutral connections

  • #26
Averagesupernova
Science Advisor
Gold Member
3,624
627
Supposed to be connected at the panel. But, I have found this to NOT be the case on more than one occasion. Have seen up to 3 volt or so potential difference between neutral and local ground. This is a simple and useful check to make rather than committing to an unproven assumption.

Assuming the above, and you connect the right wires, the system will operate fine. Not necessarily best practice, but will not negatively affect system operation.
Just because you have a difference of up to 3 volts at the outlet does not mean they are not connected to the same place in the panel.
 
  • #27
35
0
European plugs and difference between neutral and ground

I recall in some Eastern European countries, there is no ground wire and the two prongs are of equal length (interchangeable.) Can somebody explain why?
 
  • #28
stewartcs
Science Advisor
2,177
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I recall in some Eastern European countries, there is no ground wire and the two prongs are of equal length (interchangeable.) Can somebody explain why?
The different sized prongs are for polarized receptacles. It ensures the equipment does not have any voltage applied to it once the switch for the equipment is turned off. This is for electrical safety reasons. The type you are describing (equal width prongs) is non-polarized and has the potential for a shock hazard even when the switch for the equipment is off (this assumes the equipment has its on/off switch on the neutral leg).

Those plugs are probably just outdated and have never been replaced to meet current electrical code. Alternately, being in Eastern Europe, their code may not require this.

CS
 
  • #29
100
2
If you had non-polarized plugs, and connected the casing ground to neutral (or just had a fault), then plugged in backwards, you now have a hot case. That's why the switchover to polarized plugs came about.
 
  • #30
156
0
Necrothread.
IIRC, in Europe, the Blue is hot and Brown is neutral.
No it's not, unless they've changed the regs without me noticing*...

For domestic wiring (i.e. not 3 phase) the wire colours are: Brown Live, Blue Neutral, Green/Yellow stripe Earth/Gnd.

Earth & Neutral may well be connected together, exactly where depends on how it was wired up...

The Neutral & Live wires will go through the RCD (GCI), so connecting the earth & neutral together at the mains socket will trip the RCD.


*(The 3 phase wiring colours have indeed changed in the UK recently, in an effort to maximise danger...).
 
  • #31
NoTime
Science Advisor
Homework Helper
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For domestic wiring (i.e. not 3 phase) the wire colours are: Brown Live, Blue Neutral, Green/Yellow stripe Earth/Gnd.
Thanks for clearing that up.

*(The 3 phase wiring colours have indeed changed in the UK recently, in an effort to maximise danger...).
:rofl: But as I pointed out before, I've seen it done wrong far to often to actually trust the colors to be right.
 
  • #32
359
0
In Britain and most countries neutral is the centre point of a 3 phase transformer.,. 120 deg phase between the 3 'lives' which are fed to alternate houses. We had the situation a year ago where we had power but some of the neighbours hadn't. One of the phases was missing.

In the USA and some other countries it is usually to have 2 lives, 180 deg between them entering the house.. Small apliances being connected between one live and neutral 110 V... Large items are connected across the 2 lives = 220 Volts.

The earth will be connected to the neutral at some point, at the transfomer OR where the supply enters the house and even points in between. Shorting earth to neutral may cause an RCD (Earth Leakage) breaker to trip out because it no longer senses the same current flowing in the live and neutral.. Some will travel through the earth wire and by-pass the RCD.
 
  • #33
33
9
Just thought id mention that some appliances require earthing for more than one purpose as an example some electronic devices like computers,require an earth mainly for safety to protect from electric shock and also to dump 'noise' generated by the electronics if you dont properly earth the computer it may have a harmful potential on any metal surfaces as well as creating interferance and operational issues.
 
  • #34
33
9
the phases on the step down transformer are all used and not wasted as you seem to think in domestic supplies 1 phase might do 1 street the others might do another street etc with balanced loading in mind each house on a street might be alternately connected to a phase as you the supply cable is run eg; house (a) phase 1, house (b) phase 2, house (c) phase 3 then back to phase 1 for house (d) etc etc with the center tap of the transformer the common neutral for all the houses.
 

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