i am thinking along the lines off the practice off not insulating below cold water tanks in the attic often above the hot water tank to help prevent freezing also iff old pipe runs arnt fully closed or insulation sorted as required cold air may circulate
Possible Airing cupboard heater
- Thread starter mprice109
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Looks alright.
That is not a spur off a spur; it is a radial circuit.
That is not a spur off a spur; it is a radial circuit.
Correct - a "Spur" is not the accessory containing the fuse , it is correctlly called a Switched Fused Connection Unit.
A "Spur" is a short branch off a larger circuit (imagine railway lines) although the SFCU or its non switched brother (FCU) is often used in a spur from a ring or radial circuit, tha`s why it is often (incorrectly) reffered to as a Spur.
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I had understood that a spur was, as you say, a short single cable connection off a larger circuit, but that applied only to a spur from a ring final circuit.
For radial final circuits there isn’t a term.
Consider a regular loop-in lighting circuit. There is usually one cable to the first light (or switch), then there’s a myriad of connections to further lights and switches. These are never considered as “spurs” or even branches. They are just part of a radial circuit.
Taylor2C My understanding is not just a Ring Final Circiit but also a Radial, probably a 2.5 T & E radial with 15/16/20 amp opd but also say a 4.0 radilal with a 2.5 spur too.
PS branches - probably not usually a spur but very short ones maybe/maybe not. When branches become "Trees" especially ?
PS branches - probably not usually a spur but very short ones maybe/maybe not. When branches become "Trees" especially ?
I don't disagree with much of that, except that, in the case of radials, I don't think things are well enough defined to say that any terminology is 'correct' or 'incorrect'.
I don't know if (m)any others think similarly, but I seem to have evolved my own convention as regards radials....
A radial can branch as much as one wants and if the cable is all of the same CSA (adequately protected by the circuit#s upstream OPD), then I see no reason to call them anything other than 'branches'.
However, if something 'branching off' from a radial is wired in cable of lower CSA, which is not adequately protected by the circuit's upstream OPD (either supplying one socket, hence adequate downstream protection for the cable from plug fuse(s), or supplying multiple sockets via an FCU) that is much more like a 'spur' from a ring final, and I am hence much more inclined to call it 'a spur'.
Kind Regards, John
Yes John I think I pretty much agree with what you`ve just said there.
Can we define branch or log on a radial with same csa branch I am not sure either way.
If it is substantially shorter than the others then maybe just about (perhaps)?
Can we define branch or log on a radial with same csa branch I am not sure either way.
If it is substantially shorter than the others then maybe just about (perhaps)?
Glad you agree!
As I said,if it were of a CSA which could be adequately protected by the circuits's upstream OPD (alone), I would call it 'a branch' - in all other situations, I would be more inclined to call it a 'spur'.
Kind Regards,John
I don't disagree with John's thinking but as the BS7671 definition is:
Spur. A branch from a ring or radial final circuit.
Whatever we think will be just that and we cannot expect others to know what we are talking about - especially as most of them would be thinking of an FCU.
Spur. A branch from a ring or radial final circuit.
Whatever we think will be just that and we cannot expect others to know what we are talking about - especially as most of them would be thinking of an FCU.
Glad you agree!
As I said,if it were of a CSA which could be adequately protected by the circuits's upstream OPD (alone), I would call it 'a branch' - in all other situations, I would be more inclined to call it a 'spur'.
Kind Regards,John
Sorry I said "log" when I meant "spur" . I got trees and branches in mee heed! 
It is, but, in the case of a radial circuit, that's a 'silly'definition ....
In the simplest situation, if a radial 'splits into two' (i.e. a "Y-shaped circuit"), then, beyond that 'split', which of the cables is "the radial circuit" and which is the "spur from it"?
Kind Regards, John
I assumed that, and therefore didn't even bother to comment!Sorry I said "log" when I meant "spur" . I got trees and branches in mee heed!
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