Installing dado ail electrical trunking
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steameraeg
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Installing dado ail electrical trunking

by steameraeg » Fri Nov 18, 2022 5:59 pm

In my home office I have a number of hardware items, each requiring a mains power socket.
At present I use several multiway adaptors which looks untidy and jumbled.
I am considering installing dado rail electrical trunking with numerous sockets to get rid of the multiway adaptors.
My question is: should I use a dado rail electrical trunking as a ‘bridge’ between two wall socket outlets as well as, or instead of, the existing connecting ring main wiring.
That is to say should I have a dado rail electrical trunking in parallel with or in series with(in) the ring main?
Any advice or comments gratefully received.
Cheers
CJ

ericmark
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Re: Installing dado ail electrical trunking

by ericmark » Fri Nov 25, 2022 7:44 am

Always taught not to have loops in a ring final, makes testing near impossible, but as a spur you would need to fuse down, I found the Screwfix grid system was handy as could turn a double socket into a single with a fuse, or two singles allowing the ring final to be split to add more sockets.

The big problem for DIY is to test the ring final, for a MCB/RCBO to trip on overload on the magnetic part of the trip, with a B32 you need 160 amp (5 times thermal rating) to flow, plus 5% margin for safety, so around 1.37 ohms, the cheap plug in testers test down to 1.9 ohms, so no good for a ring final, which means using a proper loop impedance meter, or use existing readings with a low ohm meter.

But the 1.9 ohms is OK for a fused spur, the point is you don't know where the centre of the ring is, so will take the R1 + R2 reading. It is not the doing of the work which is the problem, it is testing the work to ensure it is safe. i.e. will it still trip the MCB/RCBO with a short circuit fault?

An electrician who tests every day gets a feeling for when on the edge, and when well within limits, one looks at the size of house etc, so test when completed when unlikely to exceed limits, for the DIY harder as you have no idea if getting near the 106 meter limit for cable with a ring final, so it needs testing before you start, unless you have a record of the last tests done.

steameraeg
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Re: Installing dado rail electrical trunking

by steameraeg » Fri Dec 02, 2022 12:18 pm

Thank you, ericmark, for your thorough reply.
It looks looks like I'd be better off by not disturbing the cable between the sockets and connecting the dado trunking as a fused spur.
I understand that there is 'no limit' (within reason!) to the number of sockets on a spur and the total proposed power load (mostly computer peripherals) would be well under 13 amps.
Thanks again for your help
Cheers
CJ

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