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Hi, could anyone explain why in a TT system, if the consumer unit has Single Pole RCBO's that it's also necessary to fit a 100ma TD RCD as a main incomer. Sorry but I can't get my head around this one! Thanks

Hi, been to a house today and customer complains that the RCD trips SOMETIMES when she uses the iron and almost always when she uses the hob. The RCD will not reset unless all the breakers are first switched off. Apparently it's been like this for some years. Looks like the place was rewired...

Hi, just installed a new CU for someone. ELI, IR, ZS etc for every circuit are fine. They only have one ring for the whole house and I've protected this with a 30ma RCBO. The 2 lighting circuits and cooker circuit are also protected by RCBO's. When I check the RCBO for the ring circuit it's...

Hi, I've been to look at a job today (wiring an extension bedroom) and noticed that the meter tails are 10metres (yes 10!) long. Local DNO will only allow max of 5metres. Not been in the trade long and so not come across this problem before but was planning to install a 100a switch fuse next to...

Hi, what would be the possible causes of an RCD failing the "half" test? Tested a 30ma RCD today after installing a new wylex split load board. It trips at 24ms on 1X test; 8ms on 5x test but fails the half test. There are 3 rings and 4 lighting circuits on the CU, I tested the RCD on each...

Hi I’ve been asked to fit some downlights to a very large kitchen/diner and adjoining conservatory. In total there will be 35 lights. Allowing 100w per outlet this is around 15amps. As I see it there are 3 options: 1) Split the lights between 3 standard 6A circuits using 1.5mm T&E...

Hi Folks, I need to fit 4 240v downlighters, I've not fiited any before so sorry if this is a dumb question. Can I use 1.5mm T&E to connect to the connecting block on the light or do I need heat resitant flex (and then connect via a junction box to 1.5mm T&E) as I know there are some issues...

Hi, just out of curiosity is there a reg which states that upstairs and downstairs socket circuits should be on separate MCB's/fuses? My place has one ring for the kitchen and one ring for the rest of the house. I know it's good practice to keep them separate but is there any reg?

Hi, I looked at a friends new kitchen today who had a bit of a nightmare with the sparky who wired it. Sockets weren't straight or in line; some "only work if you bang the plug" cables were cut too short and joined with tape etc etc. He's also used 0.5mm 2 CORE FLEX from the consumer unit to...

Hi, this is probably a daft question but is it safe to use a dimmer to switch a metal (class 1) light fitting? Just curious as I was talking to a sparky today who said it was unsafe. I've not heard this before so would welcome your thoughts! Cheers

Hi, anyone got any ideas about this; a friend of mine has an electric shower which sometimes trips the RCD when he switches it OFF at the double pole pull cord switch (after first switching off at the shower)! The RCD resets without any problem. He reckons it does it may be once or twice a...

Hi Folks Is the difference in the r1 and r2 readings of stranded 2.5mm T&E the same as for solid T&E; i.e the resistance of r2 is about 1.67 greater? Just done a test on a ring circuit cabled with stranded and get 0.12ohms for phase and neutral and 0.3ohms for earth (this was after I...

Hi, this may sound like a dumb question but as the name suggests I'm still learning! Part 3 on a Minor Works Certificate asks for the IR results. Is this the IR results for the complete installation or just for the circuit that's been altered/added to?? Thanks

Just been looking at the nice diagram in the OSG that shows bonding in a bathroom. Question is in practice, in an existing installation, how do you discreetly run the cables say from a shower to a cold water pipe or from a shaver unit to a cold water pipe without ripping up floor/wall coverings...

A relative of mine has just discovered that the house they've been living in for 7 years doesn't have an Earth! It seems that whoever rewired the place last connected the main earth cable into the cutout of a TNS system but there was no actual link from the incoming armour of the cable to the...

Hi Folks I've just moved house and would like to fit a new CU at some point in the future once I'm qualified. At the moment we have an old MEM fuse box on a TT system. There's a PME connection available but not a Main Earth Terminal that I could connect to. i.e the main fuse would need to...

Hi folks I was doing and Insulation Resistance check on a ring circuit at home today and got the following result: P-N >299MOhm N-E > 299MOhm All was fine until I tested between Phase and Earth. The initial reading was 185MOhm this then increased up to about 275MOhms...

Hi Folks I'm part way through my studies and we've just been learning about ELI. I thought I was begining to understand it until I did a test on my own installation today. The problem is, is that my ZE reading is HIGHER than ZS. If I'm right ZS=ZE + (R1 + R2). I'm on a TT system and got...