Cable in Buried Conduit

At the risk of sounding a bit obvious, the exam question should be "Is the cable adequately protected against the likely environmental influences ?"


Do not assume that the annex of suggested cable ratings is some sort of list of approved installation methods from which you cannot deviate - you can very much roll your own,  but then  you are on your own to work out what the current ratings and so forth should be.


So, as an extreme example of something  not in the annex to BS7671, a bit of arctic flex cable under a concrete path  in a bit of old hosepipe, it could be argued, is probably safe from damage by gardening tools, but it may flood,  so we then  ask  is the cable OK if it gets wet. Usually PVC is fine, but rubber insulations are better if long term immersion is expected.  Now that example would be dog rough, but not immediately dangerous. Under a flower bed unsuitable, and unwise for new installation in all cases. Considering that BS7671 has a scope that includes doorbells running at 8V on one hand and 3 phase bare overhead supplies at the other,  and you may see that some adjustment with  the application is required. (for example I'd be OK with the flex feeding a doorbell, less so for mains..)


So what are the killer factors here ?

What is the particular aspect of these buried ducts, as opposed to say similar ducts on the surface,  that worries you - will  it be waterlogged, will there be rats, will there be other cables pulled in beside it to do damage ? If yes to any of the above, then you are right to flag it up.

Actually the  XPLE AWA is probably OK  against those, being quite tough,  but the H1Z2Z2  - you do not say the size, but I imagine this is  like the singles used for connecting solar panel hookups, about 3/8"  in diameter with a thin reinforced insulation ?  This could be damaged by drag- but it all depends how it is/was installed. I note the datasheet linked above says OK for direct burial...

Mike.

At the risk of sounding a bit obvious, the exam question should be "Is the cable adequately protected against the likely environmental influences ?"


Do not assume that the annex of suggested cable ratings is some sort of list of approved installation methods from which you cannot deviate - you can very much roll your own,  but then  you are on your own to work out what the current ratings and so forth should be.


So, as an extreme example of something  not in the annex to BS7671, a bit of arctic flex cable under a concrete path  in a bit of old hosepipe, it could be argued, is probably safe from damage by gardening tools, but it may flood,  so we then  ask  is the cable OK if it gets wet. Usually PVC is fine, but rubber insulations are better if long term immersion is expected.  Now that example would be dog rough, but not immediately dangerous. Under a flower bed unsuitable, and unwise for new installation in all cases. Considering that BS7671 has a scope that includes doorbells running at 8V on one hand and 3 phase bare overhead supplies at the other,  and you may see that some adjustment with  the application is required. (for example I'd be OK with the flex feeding a doorbell, less so for mains..)


So what are the killer factors here ?

What is the particular aspect of these buried ducts, as opposed to say similar ducts on the surface,  that worries you - will  it be waterlogged, will there be rats, will there be other cables pulled in beside it to do damage ? If yes to any of the above, then you are right to flag it up.

Actually the  XPLE AWA is probably OK  against those, being quite tough,  but the H1Z2Z2  - you do not say the size, but I imagine this is  like the singles used for connecting solar panel hookups, about 3/8"  in diameter with a thin reinforced insulation ?  This could be damaged by drag- but it all depends how it is/was installed. I note the datasheet linked above says OK for direct burial...

Mike.