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I thought there was only one MET in an installation, and everything off that was a Earth marshalling point. (Im talking about a house with individual flats, that share the same supply) Its very common to see an Earthing terminal next to the intake. And from that all the individual Consumer...

I used If = Uo/Zs

OK thanks for the replies. Sorry if I am not using correct terms or being a bit to abbreviatory :) if such a word exists. So the gas pipe enters the flat at first floor level. Connected to that pipe via a BS 591 clamp is the 10mm2 main protective bonding conductor for the gas. That MPB...

This is not a real situation, but based on lots of flats I've seen. This is in London where you have many flats in one house. Pipe work is often not accessible in hallways. Often you can see the gas pipework external to the building and entering at the flat.

If you have a TNCS supply coming into the property In the down stairs meter cupboard you have a switch fuse protecting a 16mm2 T&E cable feeding a CU in an flat in the building. I was just doing some Adiabatic sums on the 6mm2 CPC in the T&E ( Theoretical only, this is not a real example) to...

Thanks John, ELFI and Ericmark. Really appreciate your guidance, some good reading there. Yes I got the R1+R2 from the OSG.

If I wanted to calculate the maximum length of a circuit, in relation to its Zs would the following transposition be correct.. So if it was a 2.5mm2 T&E cable on a 20 amp MCB. I would use 2.19Ω (BS7671) as my Max Zs, as this is at the maximum operating temperature. Not 1.75Ω as in the 80%...

Thanks that make sense, with multiple elements.

10 - C2 (There is a potential danger present and urgent remedial work is required.) So he is concerned about a lack of an RCD in the bathroom judging by the BS7671 reference. Thats a C3 I would have thought. Any note on supplementary bonding in the bathroom

Its just whats been done, habit, lack of understanding, and confidence. Even knowing that the smaller cable size will be adequate, you still go a size up. No big concern, just a realisation , that on a fixed load with a BS3036 you don't apply the factor. Doesn't really matter. Im not doing...

I thought a fixed load was an immersion, and shower, a cooker. Any one appliance that has a maximum load. The cooker and the shower, have a load that can be altered. But are still classed as a fixed load as you can't go over its kW rating? Am I wrong? I ask in relation to the BS3036 fuse. I...

Whats so dangerous about using a socket (Indoors) that has no RCD protection? If the protective device will operate in the correct time. Does it require urgent remedial action. I mean, would you attend an emergency call out because someone said they have no RCD? Doubt it I have no problem with...

C3 yes. But just wondering why it would be elevated to a C2 if all tests well. I presume it has been elevated to a C2 by the comment ' A new CU will be most likely required'

Curious. What code would you give a CU with no RCD protection

With a small pilot drill, I have drilled the back of the back box in line with the lug, threaded the hole, and managed to get a fix.

Just trying to understand the maths behind table 7.1 in the OSG ... Maximum length For a 20A RCBO (Type B) cable 2.5 - 1.5 (T&E) I'm presuming clipped direct as this will give you the longest run The Maximum Length is 42m. Now the volt drop calculation. Using Rated current of...

Apologies for the amount of questions. I would appreciate some thoughts on these please... Grouping factors for cable, and installation methods Grouping... AFAIK they are no they are no distances specified for when a rating factor has to be applied for grouping. So if say three circuits went...

Thank you. I guess my problem is, I don't really understand the design of electrical loads. All I know is that they can pull a current, and some how that current is limited. And I have it deep in my thinking that any electrical circuit can overload, and cause disaster. I blame watching the...

? Yes the MCB will offer fault protection. But it can be rated to high to offer overload protection, The MCB rating has to be less than Iz If you don't have that you don't have overload protection. But if you don't need overload protection, what does the circuit need to satisfy. Fault...