Retired
Well-known member
Hi,
I've at last got around to sorting the electrics out on our bungalow; I installed a 6 way Wylex consumer unit over 25 years ago to replace a number of old fuse boxes. This was a simple swap but I never did label up each mcb? When Bron and I moved here there was an old bar type cord activated heater near the bathroom ceiling and I replaced this with a new cord operated fan heater using the original cable connections.
I turned off all the six mcb's and starting with the left hand hand worked through each in turn whilst I did the checks around the bungalow and workshop to see what was powered. This proved very interesting indeed; The bathroom fan heater is connected into the cooker circuit?
I had a few years ago installed a double 13A socket in the hallway beneath my computer desk and as the CU was near connected directly into the spare 16A mcb but now I wanted to sort the hallway sockets because another socket a single in the hallway is on the ring so time to put the computer socket onto the ring but whilst I'm at add another double 13A socket under the desk.
I chopped the hole in the wall and was then ready to sort out the cable and connections; WOW; this makes a change; directly under the floor boards runs the ring cable? This cable disappears out of sight through walls but to be sure I had the power ring I used my digital vernier gauge to measure the cable which read 10.3mm so got everything ready then TURNED ALL THE POWER OFF AT THE CU. I severed the cable leaving plenty length and installed this to the right hand double socket double checking connections and adding the earth sleeving; a short length of new 2.5mm T&E then coupled both sockets and finally I ran new 2.5mm T&E through the wall to the CU at the same point as the original cable; this was so easy I couldn't believe how lucky I had been.
With the end of the new cable swinging in the air I located the 32A mcb for the ring and gave the cables a tug expecting one to pull through the wall freely; well it didn't and as all the cables came through the wall at ceiling height it was difficult to determine which cable was which so I added a junction box clearly marking this; I was now confident at power up all would be as expected until I found the computer was now connected into the lighting circuit? The cable didn't after all go through the wall into the CU but instead disappeared under the workshop ceiling into the front bedroom?
OH dear now I had fun but finally I succeeded and the two double sockets are now safely installed in the power ring; the lighting circuit now boasts an extra junction box.
What did I do wrong? Well I measured the cable and sure enough it was sized over the outer insulation very much like the new 2.5mm T&E but it never occurred to me that stranded conductors have bigger insulation? I've since checked the original 53 year old cables and it appears the power ring cable measures 11.5mm and the lighting cable measures 10.3mm? I've also now measured new T&E cable to find the 2.5mm is 9.4mm over the outer insulation and the 1.5mm is 8.5mm over the outer insulation.
ISOLATE ALL THE POWER BEFORE CUTTING INTO CABLES UNLESS THE CABLE IS DEFINITELY KNOWN TO BE ISOLATED. Fortunately I had isolated the lot at the CU; if I had simply tripped the 32A ring circuit mcb it's scary to think what could have happened had I been a total novice then handled the still live cable which proved to be the lighting circuit.
I've bought a KEWTECH LOOPCHECK 107 socket tester which reads good on the power ring; whilst the computer sockets were installed into the lighting circuit I took the advantage to also check the lighting ring and this too reads good so at least I know the basics are good. I've also bought a cable tracer still awaiting its arrival; I'm fully retired so am turning this into a project and will trace all the cables for future references; I'm used to having vintage radio circuit diagrams to work from so an household wiring diagram could prove useful? I'm not a sparky but I've been around electricity for over 55 years and still have some of the kit I used during my vintage radio restoring days; a couple of DMM's and a nice Evershed & Vignoles 1,000V Megger.
I admit I got caught out regarding cable sizes but I didn't get caught out regarding my personal safety because the THE LOT WAS DEAD BEFORE I EVEN TOUCHED IT. I'm sure every sparky has such stories to tell but this one is mine and was such a near miss worth adding as a warning to those with less experience; I'll never assume anything in future regarding cable size measured over the outer insulation? I hope this is of interest.
Kind regards, Col.
I've at last got around to sorting the electrics out on our bungalow; I installed a 6 way Wylex consumer unit over 25 years ago to replace a number of old fuse boxes. This was a simple swap but I never did label up each mcb? When Bron and I moved here there was an old bar type cord activated heater near the bathroom ceiling and I replaced this with a new cord operated fan heater using the original cable connections.
I turned off all the six mcb's and starting with the left hand hand worked through each in turn whilst I did the checks around the bungalow and workshop to see what was powered. This proved very interesting indeed; The bathroom fan heater is connected into the cooker circuit?
I had a few years ago installed a double 13A socket in the hallway beneath my computer desk and as the CU was near connected directly into the spare 16A mcb but now I wanted to sort the hallway sockets because another socket a single in the hallway is on the ring so time to put the computer socket onto the ring but whilst I'm at add another double 13A socket under the desk.
I chopped the hole in the wall and was then ready to sort out the cable and connections; WOW; this makes a change; directly under the floor boards runs the ring cable? This cable disappears out of sight through walls but to be sure I had the power ring I used my digital vernier gauge to measure the cable which read 10.3mm so got everything ready then TURNED ALL THE POWER OFF AT THE CU. I severed the cable leaving plenty length and installed this to the right hand double socket double checking connections and adding the earth sleeving; a short length of new 2.5mm T&E then coupled both sockets and finally I ran new 2.5mm T&E through the wall to the CU at the same point as the original cable; this was so easy I couldn't believe how lucky I had been.
With the end of the new cable swinging in the air I located the 32A mcb for the ring and gave the cables a tug expecting one to pull through the wall freely; well it didn't and as all the cables came through the wall at ceiling height it was difficult to determine which cable was which so I added a junction box clearly marking this; I was now confident at power up all would be as expected until I found the computer was now connected into the lighting circuit? The cable didn't after all go through the wall into the CU but instead disappeared under the workshop ceiling into the front bedroom?
OH dear now I had fun but finally I succeeded and the two double sockets are now safely installed in the power ring; the lighting circuit now boasts an extra junction box.
What did I do wrong? Well I measured the cable and sure enough it was sized over the outer insulation very much like the new 2.5mm T&E but it never occurred to me that stranded conductors have bigger insulation? I've since checked the original 53 year old cables and it appears the power ring cable measures 11.5mm and the lighting cable measures 10.3mm? I've also now measured new T&E cable to find the 2.5mm is 9.4mm over the outer insulation and the 1.5mm is 8.5mm over the outer insulation.
ISOLATE ALL THE POWER BEFORE CUTTING INTO CABLES UNLESS THE CABLE IS DEFINITELY KNOWN TO BE ISOLATED. Fortunately I had isolated the lot at the CU; if I had simply tripped the 32A ring circuit mcb it's scary to think what could have happened had I been a total novice then handled the still live cable which proved to be the lighting circuit.
I've bought a KEWTECH LOOPCHECK 107 socket tester which reads good on the power ring; whilst the computer sockets were installed into the lighting circuit I took the advantage to also check the lighting ring and this too reads good so at least I know the basics are good. I've also bought a cable tracer still awaiting its arrival; I'm fully retired so am turning this into a project and will trace all the cables for future references; I'm used to having vintage radio circuit diagrams to work from so an household wiring diagram could prove useful? I'm not a sparky but I've been around electricity for over 55 years and still have some of the kit I used during my vintage radio restoring days; a couple of DMM's and a nice Evershed & Vignoles 1,000V Megger.
I admit I got caught out regarding cable sizes but I didn't get caught out regarding my personal safety because the THE LOT WAS DEAD BEFORE I EVEN TOUCHED IT. I'm sure every sparky has such stories to tell but this one is mine and was such a near miss worth adding as a warning to those with less experience; I'll never assume anything in future regarding cable size measured over the outer insulation? I hope this is of interest.
Kind regards, Col.
