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Leakage from underfloor steel conduit trench

K Samoei

I recently inspected an old building whose wiring is drawn in underfloor steel conduits in a trench openable from the floors above (1st and 2nd floor)., and branching of to lighting and power points.  Despite the rust as shown here, the installation is in ‘working condition’.  However, there are two concerns. 

First, water ingress from cleaning is staining the soffit/ceiling under and it's a nuisance to users. Second, the old wiring used the steel conduit system as a CPC and rust could have reduced it's effectiveness.

I have thought of covering/encasing the trench permanently but two issues arise. How to deal with draw-off points at corners and at 10m interval; and the possibility that rewiring may be rendered impossible in the future.

I would appreciate any comment from anyone who has had to reckon with this such a challenge and how they approached it.

6ef10e5c47824bb2036fbbbdb1293ace-huge-img20210927120405-1.jpg
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    As I see it there are 2 problems - the water and the corrosion.

    how are these trenches supposed to drain - that needs fixing first. Foam fill may actually make it worse if water is then trapped and can only escape via light fittings etc.

    It is hard to be sure in the pic, but that conduit looks quite far gone, or it may be rubbish or brown leaves.. To stay in service needs enough metal not only to carry the amps of a full fault to blow a fuse or whatever but also to fulfil the conduit's other purpose - of mechanical protection

    If it is still OK and could be brushed clean and painted with kurust or hamerite, then it may go for a bit longer, but the water ingress needs solving, and that is  not really an electrical issue.

    If you do rewire, some or parts, could you use SWA, or even plastic conduit. In either case joins need  to be submersible if that water ingress is not solved first.

    Mike

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  • 0

    As I see it there are 2 problems - the water and the corrosion.

    how are these trenches supposed to drain - that needs fixing first. Foam fill may actually make it worse if water is then trapped and can only escape via light fittings etc.

    It is hard to be sure in the pic, but that conduit looks quite far gone, or it may be rubbish or brown leaves.. To stay in service needs enough metal not only to carry the amps of a full fault to blow a fuse or whatever but also to fulfil the conduit's other purpose - of mechanical protection

    If it is still OK and could be brushed clean and painted with kurust or hamerite, then it may go for a bit longer, but the water ingress needs solving, and that is  not really an electrical issue.

    If you do rewire, some or parts, could you use SWA, or even plastic conduit. In either case joins need  to be submersible if that water ingress is not solved first.

    Mike

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