Ground, Earth, Neutral issue

MaxHeadRoom

Joined Jul 18, 2013
28,617
If it is: how can I test it? How do I test an earth connection?
Do you have a socket close to a metallic water supply pipe?
If so you could measure for any AC voltage between the live conductor and the pipe, if you measure full AC voltage from one conductor, then you COULD have a earth grounded system, if you measure a considerable voltage from both conductors to the pipe, then it would mean you do NOT have a earth grounded supply.
If in doubt, it would pay to get professional confirmation.
Max.
 

Thread Starter

adam555

Joined Aug 17, 2013
858
Yippee Progress :D

That's a very good question.

The plug you showed in post#34 has a sprung metal earth connection, which engages the earth strap shown in post#37.
The plug ditto post#36 does not.

Yes it is entirely possible that conduit has been used as an earth continuity connector.
I do not know if this is accepted practice in Spain or not, it is not used in the UK because corrosion at the joints (or simply the builder's failure to join) can destroy the earth continuity.

I think that link I posted for you from a Spanish based electrician suggests such practice is disallowed in modern Spain.
The reason I didn't even think about the metal casing surrounding the whole is because there are 2 installations at home: the first is the original, with all the sockets well cased into the walls (like the last picture I posted); and then a second installation with additional sockets that are not cased in the wall, but screwed to it; and these last sockets don't make contact or connect to anything that remotely looks like an earth. This last installation is where I have my extension, and all my devices connected.

If the socket casing is really the earth; is there any way to test it?
 

Thread Starter

adam555

Joined Aug 17, 2013
858
Do you have a socket close to a metallic water supply pipe?
If so you could measure for any AC voltage between the live conductor and the pipe, if you measure full AC voltage from one conductor, then you COULD have a earth grounded system, if you measure a considerable voltage from both conductors to the pipe, then it would mean you do NOT have a earth grounded supply.
If in doubt, it would pay to get professional confirmation.
Max.
let me check in the bathroom...
 

Thread Starter

adam555

Joined Aug 17, 2013
858
just checked between a socket and a pipe: got 235VAC from the load to the pipe, and 0VAC from the neutral to the pipe.

So I guess I'll need to the same with the wall casings?
 

Thread Starter

adam555

Joined Aug 17, 2013
858
No, the casing on the wall sockets is not an earth... It's not even conductive; actually, doesn't even seem to be metallic since I can almost pierce it with the probes.
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
just checked between a socket and a pipe: got 235VAC from the load to the pipe, and 0VAC from the neutral to the pipe.

So I guess I'll need to the same with the wall casings?
It is possible wherever your service originates from, one side is taken to Earth ground, just not re-referenced at your service panel.
Not sure if that is customary to do that in Spain though?
Max.
 

Thread Starter

adam555

Joined Aug 17, 2013
858
What about your distribution box ?
It is possible wherever your service originates from, one side is taken to Earth ground, just not re-referenced at your service panel.
Not sure if that is customary to do that in Spain though?
Max.
I don't have a distribution box; just the counter from the electricity supplier, and I can't look inside since it has a seal to avoid tampering. I can only see 4 wires to the counter; which I guess are the load and neutral coming in and out of the home installation.

The break is also sealed and I can't see any wires. But the diagram outside only shows a 2 circuit switch; which I guess are for the load and neutral.
 
Last edited:

Thread Starter

adam555

Joined Aug 17, 2013
858
I checked other sockets around the house... there's no casing on most of them, just holes in the wall and the 2 wires for load and neutral (like in the same picture I posted).
 

studiot

Joined Nov 9, 2007
4,998
Would you like to also discuss the circuits of you power supply?

Where does the lead from the bridge marked negative go to?
 

Thread Starter

adam555

Joined Aug 17, 2013
858
Would you like to also discuss the circuits of you power supply?

Where does the lead from the bridge marked negative go to?
Yes, sure...

It's a dual supply with +12v and -12v, so both the positive and negative go to their respective +12v and -12v regulators... and of course, to the filtering caps... then to the load.

I ended up connecting the 0v (the ground reference of the circuit) to the core of the transformer, the chassis and to the dummy earth (which is only connected on the cable, but not on the wall socket). And now that I separated the devices that seemed to be leaking the most to the earth in the extension where everything was connected (mainly the computer), I don't feel any voltage when I touch the chassis.

... Though, the transformer keeps on humming and vibrating.
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
28,617
The puzzle I had reading the link and watching the video is one point one of the links mentions the neutral not being referenced to earth ground by the service company but carried out at the local panel, but the puzzle is the electrician in the video carried out a Earth Leakage Impedance test, as we once had to do in the UK, but IMO this would require a previous reference to ground somewhere in the system?
I am assuming he was measuring from the ground rod and using the neutral to test the earth impedance.
Max.
 

studiot

Joined Nov 9, 2007
4,998
OK then

Grounding the centre point of the transformer (schematic 2) will provide ±volts (12 is not correct, we can discuss this later) about earth and zero.

You cannot connect the negative to other equipment.

Leaving the supply floating and taking the zero volts from the transformer secondary centre tap. You would then insulate all termianls from the power supply case and have -V --0-- +V. This is the usual for bench or lab power units.
You then have a choice of grounding either the + or the - or the centre zero or stacking this power supply above (in series) another.

Did you understand this?
 

Thread Starter

adam555

Joined Aug 17, 2013
858
OK then

Grounding the centre point of the transformer (schematic 2) will provide ±volts (12 is not correct, we can discuss this later) about earth and zero.
You're right, I just cut and paste the "+12v" and the "-12v" to clearly show where those 2 wires where going. It should read about "+21v" and "-21v" there, and "+12v" and "-12v" after the regulators (which I did not include in the diagram).

You cannot connect then negative to other circuitry.

Leaving the supply floating and taking the zero volts from the transformer secondary centre tap. You would then insulate all termianls from the power supply case and have -V --0-- +V. This is the usual for bench or lab power units.
You then have a choice of grounding either the + or the - or the centre zero or stacking this power supply above (in series) another.

Did you understand this?
At first I had the secondary, power supply and load completely isolated from the chassis, transformer core and earth; and it worked well -that was my original intention. But then I bought the wrong BNC connectors for the output of the circuit (it's a function generator), and those BNC have to be connected to the chassis, therefore, the ground (the 0v) is also connected to the transformer core, chassis, earth... and had to redesign and forget about having the circuit isolated.
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
28,617
You keep mentioning Earth, but apparently you don't have one?
It seems we have not established whether you have access to a definite earth ground, anything so far has just been chassis common to power common so any use of the term 'Ground' just means that a relevant power common is connected to the metallic case of any equipment and if so no safety aspect exists??

http://www.brucearch.com/videos.html#vid2
Max.
 

Thread Starter

adam555

Joined Aug 17, 2013
858
You keep mentioning Earth, but apparently you don't have one?
It seems we have not established whether you have access to a definite earth ground, anything so far has just been chassis common to power common so any use of the term 'Ground' just means that a relevant power common is connected to the metallic case of any equipment and if so no safety aspect exists??

http://www.brucearch.com/videos.html#vid2
Max.
Yes, I'm probably using "earth" in the wrong way; since there really is no earth connection. I guess I keep on using that term to differentiate it from the ground of the circuit (the 0v from the middle terminal of the transformer's secondary).

What I've called earth so far is the 3rd wire in my mains cables and extensions that connect nowhere in the wall sockets, and which is connected to the chassis of all my devices (computer, oscilloscope, etc. since all of them use a 3 wire cable) and to the core of the transformer of the device I'm making.
 
Top