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Cable in Buried Conduit

Nick Smith
Hi folks

I'm having a bit of a discussion about what type of cable is suitable to be buried in ducts. My reading of the BS7671 is that only multicore armoured cable should be direct buried or buried in ducts based on Table 4A2 (p390) and the fact that there are no current ratings for installation method D for anything except multicore armoured.


But Table C1 of the on site guide states that twin and earth is "For use underground in conduits or pipes".


My actual problem is being asked to comment on a design where 1c XLPE/AWA cables have been direct buried and also H1Z2Z2 singles have been installed in underground ducts. The H1Z2Z2 data sheet states that it can be installed in ducts, but I am taking that to mean ducts that are not buried, so I am almost sure that this is not acceptable.


Any comments appreciated.


Thanks

Nick
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  • 0
    I not not particularly concerned about the installation method of the AWA cable. It is not ideal that it is flooded, but as has been pointed out, there are a lot of buried armoured cables out there. I would like more information on the voltage rating as it runs between the DC Connector Box and the Inverter, an ungrounded circuit that should be rated at 1500V. The inverter provides ground fault monitoring, although not when the PV array is in operation. There is also BS6724 SWA AC direct buried cable between the inverter and the switchboard in the same sort of ground conditions. Again, not ideal but in practice it should be ok.


    The solar cables are double insulated, rated at 1.5kV (up to 1.8kV unloaded) and buried in ducts. The site has some very wet places which would mean the ground around the duct would be waterlogged. I know there have been problems on other sites with earth faults in the DC array cables which were flooded.


    Thanks for everyone's help. I think I have a clear way forward now and know what information I should be asking for.
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  • 0
    I not not particularly concerned about the installation method of the AWA cable. It is not ideal that it is flooded, but as has been pointed out, there are a lot of buried armoured cables out there. I would like more information on the voltage rating as it runs between the DC Connector Box and the Inverter, an ungrounded circuit that should be rated at 1500V. The inverter provides ground fault monitoring, although not when the PV array is in operation. There is also BS6724 SWA AC direct buried cable between the inverter and the switchboard in the same sort of ground conditions. Again, not ideal but in practice it should be ok.


    The solar cables are double insulated, rated at 1.5kV (up to 1.8kV unloaded) and buried in ducts. The site has some very wet places which would mean the ground around the duct would be waterlogged. I know there have been problems on other sites with earth faults in the DC array cables which were flooded.


    Thanks for everyone's help. I think I have a clear way forward now and know what information I should be asking for.
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