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Site fabricated wooden trunking/capping
Former Community Member
Saw this in a wooden summerhouse, the owner has created his own wooden capping to conceal the cables of a ring final circuit. I was wondering if this might create a safe zone issue where it runs along the bottom edge of the room. The cable is obviously not "buried in a wall at a depth < 50mm but could somebody inadvertently screw something to it. Is it concealed wiring or wooden trunking? Would it get a code if doing a EICR?
The real reason I raised the question about 4D5 was not to question whether a B32 is OK for this circuit or not - simply that I come across a lot of applications in which T&E is used, that aren't covered in 4D5 - causing a lot of debate about what to do next, or which method or other table is easier to use.
And of course I see training materials from different organisations with different approaches to that problem too ... so for example if one organisation chooses to well over-engineer and select Method 103 (13.5 A for 2.5/1.5 cable), they will get a vastly different answer to someone using Method 102 (21 A for 2.5/1.5 cable).
In reality, I think this is probably nearer to Method B as Andy alluded to.
However, how valid is it to use another table like Andy did? Let's have a look (apologies if this is teaching people to suck eggs, just thought it would be useful to readers in the future) ...
csa
Current carrying capacity
Ref Method C
Ref Method A
2.5 mm2 Table 4D2A
27.0 A
18.5 A
2.5 mm2 Table 4D5
27.0 A
20.0 A
In the table above, we see that clipped direct (Method C), both the 4D5 and 4D2A show the same current carrying capacity. However, when enclosed in a conduit in a thermally insulated wall (Method A), 4D2A round cable has a 7.5 % lower current carrying capacity than 4D5 T&E. This is because it's radiating surface area is less for the round cable.
So, Andy's approach of using 4D2A is no less safe than using 4D5 - it certainly errs on the side of caution, as the table above demonstrates ... but it's taken an extra couple of steps to see that.
The real reason I raised the question about 4D5 was not to question whether a B32 is OK for this circuit or not - simply that I come across a lot of applications in which T&E is used, that aren't covered in 4D5 - causing a lot of debate about what to do next, or which method or other table is easier to use.
And of course I see training materials from different organisations with different approaches to that problem too ... so for example if one organisation chooses to well over-engineer and select Method 103 (13.5 A for 2.5/1.5 cable), they will get a vastly different answer to someone using Method 102 (21 A for 2.5/1.5 cable).
In reality, I think this is probably nearer to Method B as Andy alluded to.
However, how valid is it to use another table like Andy did? Let's have a look (apologies if this is teaching people to suck eggs, just thought it would be useful to readers in the future) ...
csa
Current carrying capacity
Ref Method C
Ref Method A
2.5 mm2 Table 4D2A
27.0 A
18.5 A
2.5 mm2 Table 4D5
27.0 A
20.0 A
In the table above, we see that clipped direct (Method C), both the 4D5 and 4D2A show the same current carrying capacity. However, when enclosed in a conduit in a thermally insulated wall (Method A), 4D2A round cable has a 7.5 % lower current carrying capacity than 4D5 T&E. This is because it's radiating surface area is less for the round cable.
So, Andy's approach of using 4D2A is no less safe than using 4D5 - it certainly errs on the side of caution, as the table above demonstrates ... but it's taken an extra couple of steps to see that.
