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The regs state The CSA of a protective conductor can be selected by calculation [543-01-03] or selection [543-01-04] (table 54G) My point is if the cable is selected from the OSG then neither of the above have been directly conformed to. However, the OSG cable charts will have been...

From a design point of view, how can it , as you don't know what the PFC will be. This is really my point, as if the max permissible Zs (1.5ohm) of the circuit is used to evaluate the value for I then a very small CPC will be calculated, and if a very low Zs is used, 1.5mm could be calculated to...

I know that the CSA of a protective conductor can be selected by calculation [543-01-03] or selection [543-01-04] As selection uses table 54G, the CPC for typical domestic circuits would be the same size as the phase conductor. As this is not usually the case for T&E wiring, e.g 2.5/1.5, what...

No water pipe ! :) What I find interesting :oops: is that if I treat the steelwork as an extraneous conductive part then I must connect it to the house earthing system by means of a bonding conductor. If I treat the steelwork as an electrode for a TT system, then I must isolate it from...

Armour completely not connected, i.e. coiled up ! It does seem low, but as I said theres a big cage of steel in the ground over an area of a double garage of say 5x8M, surrounded by damp sand of the bedding for the block paving which abutts its front and side.

Initially I used an analogue multimeter which showed pretty much zero resistance. I then used a fluke 1653. I used the R lo setting, zero'd leads, and measured from the earth pin of an extension socket (plugged into the house) and a bolt head on the steelwork in the garage...and also...

Yes, its a low figure, and thats with the suppy from the house isolated. I think its because the base of the garage is a concrete/steel cage raft, and the steel framework of the garage is in contact with the steel of the raft, and must therefore be providing a good earth. And yes, further...

Thanks for reply, Nozspark, I did consider the TT option, my understanding is that in this case I would not be able to take the CPC off the distribution circuit from the house, therefore I would need an RCCB in the garage to provide the RCD protection. As it stands its a fairly basic DP switch...

Having determined that the steel structure of a detached concrete sectional garage is an extraneous conductive part (0.34 ohms when measured between the CPC on the house downstairs ring final and the steelwork ), I know that I have to provide main bonding to the steel work from the MET ...

Found it! http://www2.theiet.org/publish/wireregs/wiringmatters/documents/Issue16/2005_16_autumn_wiring_matters_electrical_installations_outdoors.pdf

I saw recently a link to a technical pdf guide from the niceic on detatched garage electrics, has anyone got the link or a copy ?

It was in fact a fuse (tucked away behind the entry keypad )as rightly pointed out, many thanks.

I have extended 2 pir cables by using chock blocks and rewiring sensors as they were previously (six wire). I cannot set the alarm now, All of the zone lights are lit but it just beeps quietl and doesn't go into "set". I did this while the system was still powered up :oops: I have checked...

Thannks EdwardCurrent. Does that mean my calcs are OK? What should the MCB be ?

Looking at the curve for a 40A mcb, it wont trip at 55A for over 10,000 seconds!

The route for the cable from the CU is up into the loft thru plaster, along into above kitchen then down in the plaster to CCU.

I have to install a cooker (3.5kw) and ceramic hob in a kitchen. The hob rating is a total of 6.4 Kw (thats 4 x 1.6kw for each plate) There is an existing supply in approx 10M of 6sq mm T&E. Currently this terminates onto a ccu with socket. Assuming I replace the ccu for one without a socket...

Unfortunately cant change the existing OPD as its an old wylex board which has had the rewiarbles replaced with mcbs, as far as i'm aware they dont make rcbo's for them. Also, 40A is I believe the maximum that the board is designed to take.The position and situation of the board and supply does...

There currently is a 40A MCB on a 6mm circuit clipped direct for a shower circuit in a CU without RCD protection. I wish to provide for a new shower (9KW) a small CU unit housing an a 40A RCBO. Can I simply install this in the adjacent airing cupboard downstream of the 40A MCB ? i.e. 40A...

That blank plate would like real nice behind the curtain rail.... :lol: If he can get the cable to connect in a choc block, then it should reach into a crimp, why the need for slack !?