how to detect easily damaged cable under floorboards

[nk1255]

hello

theres a damaged cable under floor boards in either the living room, hallway or dining room.

the 'downstairs sockets' mcb type b in consumer unit trips as soon as i flick it back up, so the problem is in one of the rooms above.

how do i detect which cable under the floorboards it is without having to remove carpets and dining room tiles, as that's a big job and costly.

are there any qualified electricians on this forum that can help with how to identify the problem from the consumer unit?

i was told that you can check from the consumer unit ( from the mcb type b that has tripped) or from the ring main.
apparantly you can use a multimeter(?) to check which cable from the ring main (tripped mcb type b) has dropped voltage/amps.
also can check the cables in each socket which is affected with a multimeter.

how can a megger ( insulation meter) be used to check which cable is damaged?

thanks

​

 

[Dave OCD]

To be honest you'd be better employing a good electrician with the right test gear , that way the fault could be identified and fixed pretty quickly and you then know the circuit is safe for continued use.
Many small jobs can be done safely by a competent DIYer but this needs knowledge and experience of fault finding.

 

[IAmSparkytus!]

You pick up the multimeter, turn it to the off setting and put it down. Next you pick up your phone and call an electrician ?

Seriously though... fault findings an art (not a recognised one) and if you've never used a multimeter or megger before let alone done any fault finding, you'll struggle and we would be backwards and forwards forever trying to explain to you how to use it, what the readings mean etc etc

 

[Dave OCD]

Just what I said,but differently. ?

 

[IAmSparkytus!]

Just what I said,but differently. ?

Sorry, Dave! Must have been typing as you were typing and gotten pipped to the post ?

 

[littlespark]

You may find the fault is just a loose wire behind a socket and not an inaccessible damaged cable. Rule that out first.

Power off, unscrew the sockets from the wall and have a look.
This is the first part of any testing.

“Visual inspection”

 

[Petej999]

hello

theres a damaged cable under floor boards in either the living room, hallway or dining room.

the 'downstairs sockets' mcb type b in consumer unit trips as soon as i flick it back up, so the problem is in one of the rooms above.

how do i detect which cable under the floorboards it is without having to remove carpets and dining room tiles, as that's a big job and costly.

are there any qualified electricians on this forum that can help with how to identify the problem from the consumer unit?

i was told that you can check from the consumer unit ( from the mcb type b that has tripped) or from the ring main.
apparantly you can use a multimeter(?) to check which cable from the ring main (tripped mcb type b) has dropped voltage/amps.
also can check the cables in each socket which is affected with a multimeter.

how can a megger ( insulation meter) be used to check which cable is damaged?

thanks

​

Where are you situated?

 

[nk1255]

thanks everyone

im not going to find the fault myself! im not an electrician!

i want to know how to identify the problem step by step
step 1 what to check
step 2 what to check
etc
also what equipment is needed

then i can call an electrician to check
if i know what checks are to be done, then ill know if the electrician is ripping me off or not!

 

[nk1255]

Where are you situated?

london, wembley

 

[7029 dave]

thanks everyone

im not going to find the fault myself! im not an electrician!

i want to know how to identify the problem step by step
step 1 what to check
step 2 what to check
etc
also what equipment is needed

then i can call an electrician to check
if i know what checks are to be done, then ill know if the electrician is ripping me off or not!

I dont ask my Dentist for step by step info on how to do his job or what equipment is needed.

 

[Dave OCD]

thanks everyone

im not going to find the fault myself! im not an electrician!

i want to know how to identify the problem step by step
step 1 what to check
step 2 what to check
etc
also what equipment is needed

then i can call an electrician to check
if i know what checks are to be done, then ill know if the electrician is ripping me off or not!

Rather than all this just get some recommendations from family. friends or colleagues , we're not all rip off merchants !

 

[plugsandsparks]

thanks everyone

im not going to find the fault myself! im not an electrician!

i want to know how to identify the problem step by step
step 1 what to check
step 2 what to check
etc
also what equipment is needed

then i can call an electrician to check
if i know what checks are to be done, then ill know if the electrician is ripping me off or not!

He could do all the necessary checks and still Rip you off. If, as you say its a persistent trip then at least he/she should get good consistent readings. From then on its a bit of common sense and a small dose of the "force".

If he/she can detect the fault from the CU, then easiest to break the cct roughly half way and follow your nose. Sometimes you can be lucky and find it within minutes as the giveaway is a newly painted wall or sometimes you can be there a couple of days as i found out in a commercial office a few years ago.

 

[nicebutdim]

Thomas Nagy seems to have a decent reputation and Wembley is practically on his door step.

 

[Lister1987]

Thomas Nagy seems to have a decent reputation and Wembley is practically on his door step.

He's getting out of domestic work and onto Highways, believe he's stopped taking on domestic work, aside from any of his long serving customers

 

[Electrics]

Whether you know what he's going to do or not, if he's gonna rip you off he can just make up some complicated sounding problem and do a load of unnecessary work and charge you a bomb for it.

Sounds to me like you're wanting to try and tackle it yourself. No offence but the old 'i'm going to get an electrician i just want to know exactly step by step how to do it first so i don't get ripped off' is the oldest trick in the book.

 

[pc1966]

As already mentioned, start by ruling out the accessible stuff by checking all of the socket outlets fed from that MCB.

Obviously you have to make absolutely sure the power is off to the sockets being checked, simplest DIY option is a socket tester (having proved it works in a working socket, e.g. upstairs) on each and every downstairs socket before you open it up. Never assume they are all on the same supply, someone might just have done something really dumb... Or if you can (daytime, enough light, etc) just put off the main CU switch.

If you can rule out a fault at the socket backs (e.g. cable cut on back box as no grommet, etc) then it could well be a cable fault under the floor, or some hidden junction box, but identifying that location is much harder. Generally UK sockets tend to be wired in a "ring final circuit" (though they might be radial) and if you have a suitable insulation tester you can disconnect the CU end, split the ring at a known location such as furthest socket, and then see which of the halves has the fault. Then proceed to divide and conquer until you have found the faulty link.

However, messing around with the CU is really not to be suggested as a DIY activity as there is a real and serious risk of if going badly wrong. Also you need to be aware that a multimeter is not very good at fining cable faults as they only test at a couple of volts max, and if you ever do plan on using a multimeter on mains cable always make sure it is CAT-III or CAT-IV rated! Some cheap or old meters have little protection against a high energy fault and sadly folk have died from the resulting explosion/burns before, so it is not something to ignore.

Measurement category - Wikipedia

en.wikipedia.org

Typically an electrician would have a Multi Function Tester (MFT) that includes insulation resistance at 250V or 500V, though some prefer a stand alone IR tester (often known as "megger" in the same way we refer to hoovering the floor, first big brand name). Not only are they ideal for cable fault testing, they are also designed to be safe if accidentally testing a live circuit.

Which we all know should not happen as we all follow safe isolation procedures, don't we? But sometimes in life sh*t happens and you really don't want your day to get any worse due to inadequate instrument safety.

 

[littlespark]

We’re not actually allowed on the forum to give “step by step” instructions…. Even for educational purposes.

 

[Petej999]

london, wembley

BIT to far for me was going to try and help out by a visit just a thought ,sorry no can do, good luck with it anyway.

 

[Dustydazzler]

Give Delroy a call , he loves fault diagnostics

Home - Eastway Electrical

www.eastwayelectrical.com

 

[IAmSparkytus!]

Give Delroy a call , he loves fault diagnostics

Home - Eastway Electrical

www.eastwayelectrical.com

Delroy, is that you??