I seem to find for any given pipe and cable combo there is a critical distance up to which it is a piece of cake, beyond which it rapidly gets hard and then   much beyond 1.5 times that it becomes essentially impossible. Clever use of lubricant and draw tape with wheels etc helps change that distance, but there is still remarkably hard cut-off when the only method it to have mid-point access. But in general flexibles do go quite a bit further for the same nominal sizes.

Mike.

mapj1 said:

But in general flexibles do go quite a bit further for the same nominal sizes.

Agreed, I think that's the issue ... unless, of course, the live conductors are 6181Y (insulated and sheathed), there's plenty of space in there for thermal and space to bend/twist.

Looking at how much spare space there might be with the max diameters of cables and max thickness of conduit walls (assuming plastic, as the wall thickness is a little more), if you get one bend after another, it's not going to be easy due to the rigidity of the 16 mm² 7-strand:

It is going to have to be Plan B. As Graham's diagrams show, the insulated cables appear to have plenty of room. OSG is not explicit, but perhaps it does allow for the thicker walls of (some) PVC conduit.

Here is my effort: with 3 x 16 mm² cables, they might be expected to fall under gravity into one of the two positions below. Vertical runs will slump together to some extent.

If we substitute 3 x 6 mm² for the live conductors, there still seems to be plenty of room and the 7 strands of the 16 mm² conductor have now become 21. Granted the bends tend to be squashed a little, but the smaller cables should be able to fit around the larger one more easily.

I think that I have got the scale correct, but just in case, here is some real conduit and cable.

I can probably manage with 2 x 6 mm² for the live conductors. Table 4D1A gives 41 A for each, but multiply by a factor of 0.8 per Table 4C1 and that gives 65.6 A, which is fine on a 63 A MCB.

Frankly, I don't intend to get anywhere near 63 A, whcih would cost about £4.50/hour or £110 per day!!!

It is going to have to be Plan B. As Graham's diagrams show, the insulated cables appear to have plenty of room. OSG is not explicit, but perhaps it does allow for the thicker walls of (some) PVC conduit.

Here is my effort: with 3 x 16 mm² cables, they might be expected to fall under gravity into one of the two positions below. Vertical runs will slump together to some extent.

If we substitute 3 x 6 mm² for the live conductors, there still seems to be plenty of room and the 7 strands of the 16 mm² conductor have now become 21. Granted the bends tend to be squashed a little, but the smaller cables should be able to fit around the larger one more easily.

I think that I have got the scale correct, but just in case, here is some real conduit and cable.

I can probably manage with 2 x 6 mm² for the live conductors. Table 4D1A gives 41 A for each, but multiply by a factor of 0.8 per Table 4C1 and that gives 65.6 A, which is fine on a 63 A MCB.

Frankly, I don't intend to get anywhere near 63 A, whcih would cost about £4.50/hour or £110 per day!!!