Tracing an Earth Cable

[AmateurDIY]

Hello,

I just discovered this Forum, and thought it might be a good place to get some help!

In the loft, I currently have 3 incandescent lights that each have a plastic housing, but I want to replace these with a new metal-framed LED light. Everything is in place, but I am a bit concerned aobut the earth connection in the junction box. This is what it looked like before:

https://www.dropbox.com/s/j58prfjnuku3u0l/001.jpg?dl=0

The three white cables each lead to one of the lights. As they have plastic housings, I assume the previous electrician saw no need for the earth wires, and has trimmed them off. The grey cable at the bottom disappears into the floorboards of the loft, so I cannot see where it goes. I am guessing that this connects power from one of the upstairs lights, and also runs to a switch that is located near the entrance.

I managed to get some slack in the grey wire, and have now exposed the earth wire eough to make a connection in the junction box. This is how I have wired the new LED light:

https://www.dropbox.com/s/7on0x1oz1dd67d2/002.jpg?dl=0

Everything works fine, but it occurs to me that I don't know if the other end of the grey cable has been connected to earth. If not, then I expect this means the frame of the LED light will also be electrified now? The light is at the very apex of the roof, and completely out of reach, but I am still not completely comfortable with the idea of it not being earthed. So, how could I test this grey cable for an earth, if I cannot trace the cable under the floor boards?

I really appreciate any advice you can offer!

Best wishes



Martin

 

[ProDave]

It was wired by a cowboy, not an electrician, so you are right to doubt that he would have bothered to connect the earth at the other end of the cable. Not so easy to check without some proper test kit. the best thing you could do is follow where it goes and visually inspect it to see.

 

[SPECIAL LOCATION]

Hello,

I just discovered this Forum, and thought it might be a good place to get some help!

In the loft, I currently have 3 incandescent lights that each have a plastic housing, but I want to replace these with a new metal-framed LED light. Everything is in place, but I am a bit concerned aobut the earth connection in the junction box. This is what it looked like before:

https://www.dropbox.com/s/j58prfjnuku3u0l/001.jpg?dl=0

The three white cables each lead to one of the lights. As they have plastic housings, I assume the previous electrician saw no need for the earth wires, and has trimmed them off. The grey cable at the bottom disappears into the floorboards of the loft, so I cannot see where it goes. I am guessing that this connects power from one of the upstairs lights, and also runs to a switch that is located near the entrance.

I managed to get some slack in the grey wire, and have now exposed the earth wire eough to make a connection in the junction box. This is how I have wired the new LED light:

https://www.dropbox.com/s/7on0x1oz1dd67d2/002.jpg?dl=0

Everything works fine, but it occurs to me that I don't know if the other end of the grey cable has been connected to earth. If not, then I expect this means the frame of the LED light will also be electrified now? The light is at the very apex of the roof, and completely out of reach, but I am still not completely comfortable with the idea of it not being earthed. So, how could I test this grey cable for an earth, if I cannot trace the cable under the floor boards?

I really appreciate any advice you can offer!

Best wishes



Martin

You are right to be concerned...
basic rule.. Earth conductor continuity should be extended to every accessory position...

If I wanted to verify the earth continuity I would do some dead tests by connecting the live of this circuit at the consumer unit directly to the earth bar...

Then with a suitable continuity tester, measure between live and earth at your junction box and light fittings,
which would confirm that the earth is connected back to the consumer unit...

(Obviously reconnect the live back to the correct circuit afterwards!)

 

[peterspurs]

What the above are saying if you haven’t the proper test equipment you can’t

 

[binky]

You are right to be concerned...
basic rule.. Earth conductor continuity should be extended to every accessory position...

If I wanted to verify the earth continuity I would do some dead tests by connecting the live of this circuit at the consumer unit directly to the earth bar...

Then with a suitable continuity tester, measure between live and earth at your junction box and light fittings,
which would confirm that the earth is connected back to the consumer unit...

(Obviously reconnect the live back to the correct circuit afterwards!)

Just to add, a cheap multimeter from the likes of Screwfix would suffice for testing continuity, and could be done via neutral and earth with the board turned off rather than messing around with the board.

 

[Mike P]

Or check phase to earth with a volt meter, confirming the earth is there at every appliance and also polarity and you don’t need to disconnect any connections.

 

[Murdoch]

Ah the good old lighting circuits don’t need continuous earths, a trait of a DIYer, builder or out of date so called sparky

As others have said this really needs to be checked out properly, so maybe get your lighting circuits inspected properly would be my advice.

Sure this will cost but no earth and metal fittings could be deadly

 

[AmateurDIY]

Thank you all so much for the replies!

Yes, it does seem that a cowboy has worked here before! It seems like there are 3 options here, if I want to tackle it myself. Trace the cable manually, and check each connection point, test by switching off the power and then connecting the live to earth at the consumer unit, and then a third suggestion that Mike P made.

I'm not sure if I fully understood that one Mike. Do you mean that I can check for earth at the LED light, without having to disconnect anything? That certainly sounds like the easiest method, if there is a safe way of doing it.

Tracing the cable will be all but impossible, as the loft has chipboard laid down, and is full of storage boxes. I would need to remove everything from the loft and then pull up all the boards to find out where exactly that cable goes!

I do have a multimeter, so I could test at the junction box end, but I will need to examine and photograph the consumer unit first, to learn exactly how to make the right connection. I am expecting that this suggestion looks like this:

 

[Mike P]

I think if you are unsure about this call a professional. Working live is a last resort and really is a job for professionals equipped with the right tools, knowledge and safety protection kit.

 

[binky]

Thank you all so much for the replies!

Yes, it does seem that a cowboy has worked here before! It seems like there are 3 options here, if I want to tackle it myself. Trace the cable manually, and check each connection point, test by switching off the power and then connecting the live to earth at the consumer unit, and then a third suggestion that Mike P made.

I'm not sure if I fully understood that one Mike. Do you mean that I can check for earth at the LED light, without having to disconnect anything? That certainly sounds like the easiest method, if there is a safe way of doing it.

Tracing the cable will be all but impossible, as the loft has chipboard laid down, and is full of storage boxes. I would need to remove everything from the loft and then pull up all the boards to find out where exactly that cable goes!

I do have a multimeter, so I could test at the junction box end, but I will need to examine and photograph the consumer unit first, to learn exactly how to make the right connection. I am expecting that this suggestion looks like this:

just turn off the entire board and test neutral to earth, put a link wire between the neutral and earth bar, there's usually spare terminals. That way you don't have to disturb any of the other connections. Messing with the board is not the best idea if you have no experience of such works.

 

[AmateurDIY]

I think if you are unsure about this call a professional. Working live is a last resort and really is a job for professionals equipped with the right tools, knowledge and safety protection kit.

I understand what you mean about getting a professional. But, it's also difficult to find a professional you can trust.

As you can probably tell, I'm not going to go rushing over to the junction box with my probes! I will definitely do plenty of research first, and make myself aware of all the dangers before attempting anything like this.

So, just exploring your suggestion further, I did some more research. With the power on, I can set my multimeter to AC Volts, and then check the voltage, at the junction box, between live and neutral. This should give around 230V, and then check between live and earth, which should show the same value (if the earth is connected). Is that correct?

My multimeter is nothing special, but I have all different types of probes/connectors for it. I only really use it for low voltages on the car, but apparetnly it can handle this type of voltage too. This is from the manual:
https://www.dropbox.com/s/hs0jk3723iajwjc/Draper.png?dl=0

I will research further, but I am guessing that a safe practice might be to start with power off to the circuit, connect the multimeter securely, using crocodile clips for example. Then lay the multimeter on the floor, and go and switch the circuit on. This way I would not be coming into direct contact with anything while the power is on. I could then just observe the values from afar. This would also rule out an unsteady hand fishing around with probes.

 

[Richard-the-Ninth]

My multimeter is nothing special..........................but apparetnly it can handle this type of voltage too

I understand what you are saying, but I would not use those small crocodile clips. (They are great on small wires/connecting to wires on bread board) but anything too big and they often jump off, also with nothing special multi meters, they are not designed to contain an explosion (The fuse can explode if there is an error) whereas better quality meters are designed with safety in mind, also the probes are often too long (You hold it on one terminal and it also touches a wire that it shouldn't and........... You would be better off buying a proper recognised tester. I have one (sometimes it better than my expensive kit) I have This one (Click the link) and it even has a continuity tester too.

 

[Mike P]

I understand what you mean about getting a professional. But, it's also difficult to find a professional you can trust.

As you can probably tell, I'm not going to go rushing over to the junction box with my probes! I will definitely do plenty of research first, and make myself aware of all the dangers before attempting anything like this.

So, just exploring your suggestion further, I did some more research. With the power on, I can set my multimeter to AC Volts, and then check the voltage, at the junction box, between live and neutral. This should give around 230V, and then check between live and earth, which should show the same value (if the earth is connected). Is that correct?

My multimeter is nothing special, but I have all different types of probes/connectors for it. I only really use it for low voltages on the car, but apparetnly it can handle this type of voltage too. This is from the manual:
https://www.dropbox.com/s/hs0jk3723iajwjc/Draper.png?dl=0

I will research further, but I am guessing that a safe practice might be to start with power off to the circuit, connect the multimeter securely, using crocodile clips for example. Then lay the multimeter on the floor, and go and switch the circuit on. This way I would not be coming into direct contact with anything while the power is on. I could then just observe the values from afar. This would also rule out an unsteady hand fishing around with probes.

You are right with your theory, but as above “Safety is the key issue here, Working live is normally a last resort and definitely with the correct safety in place and a proper meter with correct test leads and probes.

 

[binky]

I understand what you mean about getting a professional. But, it's also difficult to find a professional you can trust.

As you can probably tell, I'm not going to go rushing over to the junction box with my probes! I will definitely do plenty of research first, and make myself aware of all the dangers before attempting anything like this.

So, just exploring your suggestion further, I did some more research. With the power on, I can set my multimeter to AC Volts, and then check the voltage, at the junction box, between live and neutral. This should give around 230V, and then check between live and earth, which should show the same value (if the earth is connected). Is that correct?

My multimeter is nothing special, but I have all different types of probes/connectors for it. I only really use it for low voltages on the car, but apparetnly it can handle this type of voltage too. This is from the manual:
https://www.dropbox.com/s/hs0jk3723iajwjc/Draper.png?dl=0

I will research further, but I am guessing that a safe practice might be to start with power off to the circuit, connect the multimeter securely, using crocodile clips for example. Then lay the multimeter on the floor, and go and switch the circuit on. This way I would not be coming into direct contact with anything while the power is on. I could then just observe the values from afar. This would also rule out an unsteady hand fishing around with probes.

DEAD TEST only! There's no need to do any live testing to confirm the continuity of the CPC. You want your multimeter set on resistance, you are looking for less than around 7 Ohms on a light cct, with either Line to Earth or Neutral to earth joined at the board.

 

[AmateurDIY]

A friend lent me a tester, just like the one Richard suggested, and I carried out this test today! I have 242V between Live & Neutral, and 242V between Live and Earth. So, in the end I got lucky, and do actually have an earth connection there.

Thank you all for the help here! Just to address a few other points that came up:

I had a look at the consumer unit, and it looks like a sealed unit. I expect that the cover has to come off, before I can start doing anything there. This seemed more intimidating to me, as an amateur, than the live testing did. Mind you, if I was going to go down that road, I suppose I could have done some more research on conusumer units.

I still think my idea of connecting a tester, with the circuit powered down, and then observing the tester from afar is a safe and sensible one. I do have probes and crocodile clips of all different sizes. But to mitigate the clips popping off, perhaps connecting a short wire to each terminal, and then connecting the clips there, rather than to the terminals, could reduce the risk of that.

Merry Christmas to all!