how do i detect electrics in wall?? please help!!

[rachaelinnc]

hello all... i am in the middle of the easy task of putting up shelves in my kitchen..... however i am scared of electrocuting myself ... i am using a detector to try and find wires and pipes but it does not seem all that accurate..... what can i do????
any tips would be much appreciated!

 

[JohnD]

How old a house is it, and what is your opinion on the quality and professionalism of the electrical and plumbing installation? (this will give some clues)

 

[rachaelinnc]

the house was built in 1920s.... i think the previous owner did quite a lot of her own diy badly... including electrics.....

 

[andy]

hello all... i am in the middle of the easy task of putting up shelves in my kitchen..... however i am scared of electrocuting myself ... i am using a detector to try and find wires and pipes but it does not seem all that accurate..... what can i do????
any tips would be much appreciated!

you should be safe to drill. drills (most anyway) are double insulated, so providing you dont touch the metal drill bit (i doubt you would anyway when its in use), the worst thatll happen is the cable will go bang, probably be a spark and the circuit will go dead. then you have the job of repairing the cable...

 

[JohnD]

If it was built in the 1920s, it will have ben rewired. If it was done by a not very good amateur, they may not have run the cables vertically and horizontally from the fittings (this is the approved method so you can look at a switch or socket and predict where the cable will be).

However - an advantage of clumsy workmanship is that the chases in the plaster, where the cables went, have probably been replastered imperfectly. So you will often be able to feel a ridge with your fingertips. And if you are redecorating, and take the wallpaper off, you will se the repairs to the plaster where the cables were run.

Light switches almost always have the cables running vertically up to the ceiling. Sockets usually have the cables running vertically down to the floor (or up to the ceiling if the floor is concrete). but if you see several sockets, switches, cooker outlets or fan on a wall, the cables may run between them in unpredictable paths. However, if you are using a double-insulated (plastic bodied) drill you won't electrocute yourself. If you go through a cable the drill will feel as if it has found a gap in the wall.

Sadly everyone drills, nails or screws through a pipe and a cable at least once in their lives.

 

[swelec]

you could decrease the possibilty of drilling through cables by NOT drilling in a line drawn perpendicular to or horizontal to any sockets or switches

you could also swich off the electric supply to the house and use a battery powered drill - the bang would then happen when you switch the power back on

if in doubt wear rubber gloves and wellies - that is a joke only

 

[swelec]

too slow

 

[plugwash]

not if you only hit one conductor it won't!

then you will have reduced the CSA of the cable possiblly leading to later overheating but you won't blow anything immediately. Further if its the live conductor you hit it could potentially make your screw live as well.

best bet is to try and map out the installation, this will require a multimeter, a length of wire to extend one of the multimeters leads and quite some time in daylight (you probablly wan't the main switch off if its an install your in any way unsure of) also you wan't to prove dead EVEN IF THE MAIN SWITCH IS OFF. its not unheared of for people to say take a power feed from a street light or from hidden wiring in the back of the service fuse holder (so it can only be seen if the holder is opened, not just the fuse removed) to reduce thier leccy bill.

 

[andy]

you could also swich off the electric supply to the house and use a battery powered drill - the bang would then happen when you switch the power back on

good idea. now, which of those 204 screws i put in the wall is the culprit...

 

[Adam_151]

There are what are called the prescribed zones, where cables can be run without mechanical protection, these run horzontally and vertically from all electricial accessories, and the 150mm around the edge of the wall IIRC (so a column at each corner, and a row near the top), If you want to drill outside of a presibed zone, cables will be mechanically protected or more than 50mm deep in the wall, if you want to drill in a prescribed zone, you have to establish that it is free from cables by doing such things as opening electricial accesories and checking which direction cables run.

If you do hit a cable, then as per andy's post, there will just be a bang and you'll have to call in a spark to repair it

 

[andy]

there will just be a bang and you'll have to call in a spark to repair it

unless there competent enough to do the repair themselves

 

[swelec]

you could also swich off the electric supply to the house and use a battery powered drill - the bang would then happen when you switch the power back on

good idea. now, which of those 204 screws i put in the wall is the culprit...

the one with a chunk of plaster missing and a black scorch mark around it

 

[rachaelinnc]

thanks for all the tips.... will get started first thing in the morning.... and may post in the diy disasters forum in the evening