Mechanical protection passing electrical cable through Skillion ceiling

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OLeary

2 posts

Wannabe Geek

#306775 20-Aug-2023 17:38

Hi friends!

I’m in an old 1890ish built home with a number of extensions with a skillion/mono-pitch roof covering most of the building. Most wiring in that section is TPS fastened to the walls or ceiling or TRS in conduit pipe (all visible).

I’m looking to replace this with new circuits in the walls (as a home owner it needs to be checked by a sparky and have them connect it to the switchboard). This is all good until I reach an internal wall corner stud which I need to turn at. I believe I can’t use a notch as it will be within 50mm of the wall exterior, so I’d have to go up through the top plate, and through the roof which will also not have clearance. In this case I need to use “mechanical protection”.

The code of practice for home owners section 3.5.2 states I need this where less than 100mm of timber separates the roof and ceiling, and that this can be achieved by installing small sections of pipe where penetrating the timber (common sense for roofing nails). Where I am not penetrating the timber, can I fasten the cable to the middle of the side of the joists/rafters to route around to the other walls top plate? Or would I somehow need to route the cable the whole way in steel pipe from top plate to top plate?

Many thanks for your help.

gregmcc

2147 posts

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#3118316 20-Aug-2023 19:44

I think you may need to re-read ECP 50, page 5 has a bit from the Electricity act, 110 (e) (i) and (ii) - needs to bed tested and certified by an ELECTRICAL INSPECTOR (not an electrician), and connected to a power supply by such an inspector.

The Foreword also says that homeowners are NOT permitted to gain entry in to the back of any switchboard , the cables must be left in the ceiling space in close proximity to the main switchboard, an electrician can do the connection, but as homeowner has done work it requires an inspector to test and certify.

Be careful as the ECP only allows work on TPS cable, so the TRS/conduit is a no go area for home owners.

As these will technically be a new circuit, they will need to now be RCD protected and the start of the new wiring - switchboard.

I would recommend that you engage your electrician as this is sounds like a major project for a homeowner.

OLeary

2 posts

Wannabe Geek

#3118341 20-Aug-2023 23:36

Thank you yes I will not be connecting anything to the switchboard, and as they are new circuits they will need to be inspected by an actual inspector. I would edit my post to clarify the inspector requirement, but I seem to be unable to edit it now after correcting a typo.

The switchboard was already replaced along with some cable at the end of the building which isn’t under a skillion roof for the water heater, a new meter outside with a switch there, and the connection to the house due to cracked insulation. I had asked about a quote to do the work at the time and they suggested to leave it as-is on the walls, but that would prevent us from a lot of renovation work, not to mention a lack of outlets or any heat pump etc. Its also an insurance concern with TRS.

Everything will be checked and will have RCDs on a modern switchboard. Most other details are straightforward, but this one seemed vague. I am only looking to do work allowed for by law in accordance with the homeowners code of conduct.