What would the group rating factor be for more than one layer of many multicore cables laid on a cable ladder system?

Question

Considering many distribution circuits where many multicore cables would be on laid on a cable ladder system all touching with more than one layer, what will the group rating factor be? As per Table 4C4 of BS 7671, I observed that values were given for just single layer of cables up to 9 cables. Please note that some of the cables would be used for intermittent loads and they are not all of the same sizes.

AJJewsbury · Accepted Answer

My guess would be that once you bunch many cables together in many layers the most significant factor in restricting heat loss will be the other cables, and the means of support will matter much less - so maybe go down the table 4C1 (item 1) route. Although I suspect the low factors that yields might suggest that bunching many power cables together isn't an ideal solution anyway. 
 - Andy.

What would the group rating factor be for more than one layer of many multicore cables laid on a cable ladder system?

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