Cables in buried duct - Table 4C3.

I have just had a look at the EIDG example but all I can find is "Four 4-core copper armoured cables are laid in touching ducts beneath a road"... Which to me reads like 4 ducts each containing a single cable, whereas the OP asked for a method for multiple cables in a single duct. Apologies if I've missed it.


Personally I'd treat single cores from the same circuit in one duct the same as the equivalent multicore, since the heat being dissipated is the same. But most of the time BS7671 doesn't give ratings for singles buried in ducts (would that it were) so other methods are needed anyway.


For multiple circuits in a single duct I'd default to table 4C1 row 1 (i.e. bunched and enclosed) if pushed, but for more valuable circuits or for large numbers of simulataneous loads or those close to the calculated rating I might be inclined to check via another method, which might be consultation with a manufacturer or calculation to BS IEC 60287.

I have just had a look at the EIDG example but all I can find is "Four 4-core copper armoured cables are laid in touching ducts beneath a road"... Which to me reads like 4 ducts each containing a single cable, whereas the OP asked for a method for multiple cables in a single duct. Apologies if I've missed it.


Personally I'd treat single cores from the same circuit in one duct the same as the equivalent multicore, since the heat being dissipated is the same. But most of the time BS7671 doesn't give ratings for singles buried in ducts (would that it were) so other methods are needed anyway.


For multiple circuits in a single duct I'd default to table 4C1 row 1 (i.e. bunched and enclosed) if pushed, but for more valuable circuits or for large numbers of simulataneous loads or those close to the calculated rating I might be inclined to check via another method, which might be consultation with a manufacturer or calculation to BS IEC 60287.