Discuss wiring in dado trunking in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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nicsin02

hi guys quick question, got sent out to a job today to connect in sockets that are lying on the floor in dado trunking for office computers etc, the whole room is wire in a ring protected by a 32a mcb to 5 seperate 20amp double pole switches, these switches feed about 5 or 6 sockets each on a radial, the electrician in before me wired an extra 16 sockets on to one of these radials meaning the douple pole switch is feeding 22 sockets, is this ok/ they are wired in 2.5mm single cables in trunking which can take 24a according to regs, so would the 20amp double pole switch blow if the radial load exceded more than 20 amps meaning the 24a cable will be protected, just making sure thanks
 
hi
the double pole switch is rated at 20amp not fused, so would overheat not blow i'm afraid. i would consider changing the radial with 22 sockets on it. don't understand why some would wire it that way to be honest
 
I'd be a lot more worried about overloading the RFC at that point as technically there are now 22 spurs!!!!!
 
Surely each 20a double pole switch should be seperately fused when spurred off the ring the way it is now.......

Seems to me a totaly bad install without the extra 16 sockets....the way i read it there's a total of 42+ spurs off a ringmain? (4x 5-6 sockets + 1x22 sockets)
 
Sounds like a right bag of spanners and a fire waiting to happen.
 
Firstly, you are only allowed as many spurs off an RFC as you have sockets on it. Secondly, if I'm reading it correctly, you have several spurs off spurs, which is totally unacceptable unless they are fed from a 13 SFCU from the RFC. This sounds like it needs redesigning asap.
Your question "
so would the 20amp double pole switch blow if the radial load exceeded more than 20 amps meaning the 24a cable will be protected, just making sure thanks" has made me very worried....
 
If you're after a quick fix you could replace the DP switches with FCUs, but ideally it wants redoing properly.
By 'properly' I mean conventionally, not trying to be 'clever'.
 
In your position I'd be thinking about the load and how it could be spread around the RFC and splitting the suite up so it could be better served by more than one circuit.
Either that or, as some of my learned friends have implied, get some fire extinguishers in there:)
 
sounds like a pretty ****ty install, so what does the "20 amps" actually mean on a douple pole switch i would have fought it would stop the cable exceeding 20 amps of current, the sockets only have single earthing aswell!!:banghead:
 
Thats just the maximum rating of the contacts of the switching mechanism. Anymore and they will start to overheat.

so what would u reckon would be the easiest way to fix this i have only an hour in this office 2morrow morning only thing i can think of is replacing swiches with fused spurs any ideas
 
sounds like a pretty ****ty install, so what does the "20 amps" actually mean on a douple pole switch i would have fought it would stop the cable exceeding 20 amps of current, the sockets only have single earthing aswell!!:banghead:

Are you really working on electrical systems without knowing the difference between a switch and circuit protection? Please tell me you are just teasing. :)
 
Are you really working on electrical systems without knowing the difference between a switch and circuit protection? Please tell me you are just teasing. :)

simple mistake:sick: just have to replace with a fused spur and hope they dont exceed their 13 amp allowance
 
so what would u reckon would be the easiest way to fix this i have only an hour in this office 2morrow morning only thing i can think of is replacing swiches with fused spurs any ideas


Tell them what they have is pants and requires quite a bit of work to be put right....more than an hours worth!!!
 
i will put that to them 2morro but i only have an hour to make it as safe

Well that's easy peasy lemon squeezy...

Enter building, inform everyone that you need to switch off offending circuits for a little while, once everything is shut down and safe to isolate, enter consumer unit, identify offending circuits, swicth off, lock off, write down bosses number, give to person in charge and inform them that you have made safe in allocated time and to rectify the situation they need to speak with your boss..... Exit with smile from ear to ear knowing that installation is all safe and prepare yourself for a really sound nights sleep. :77:

:thumbsup
 
Well that's easy peasy lemon squeezy...

Enter building, inform everyone that you need to switch off offending circuits for a little while, once everything is shut down and safe to isolate, enter consumer unit, identify offending circuits, swicth off, lock off, write down bosses number, give to person in charge and inform them that you have made safe in allocated time and to rectify the situation they need to speak with your boss..... Exit with smile from ear to ear knowing that installation is all safe and prepare yourself for a really sound nights sleep. :77:

:thumbsup

i would get sacked for that mate, will just have to stick with 13amp spurs for now, cable wont go on fire so i WILL sleep sound, dont care if 13amps aint enough for their sockets they can deal with my boss about that, as long as it wont burn :cheesy:
 
What concerns me here nicsin02 is your basic lack of understanding to Reg's regarding the several areas mentioned above that you never even touched on yourself, as well as a lack of understanding of the function of a 20amp switch.

I assume its and office with computers and alot of them, so to re-enforce what farmelectrics said you have got a functional earthing system and these radials are unlikely to be set up to allow for this or the ring main in that case.
If the socket circuit isn't under the supervision of an instructed person then RCD cover will also be required and i wouldn't be wiring more than 5 or 6 computers to each circuit unless using a SI unit which allows for an increase in this no'.
Basic understanding of regulations which are clearly shown in picture form in the OSG or Reg's to the allowances for spuring of ring circuits seems to be missing from your knowledge which is of great concern.

What are your qualifications and experience as your post and replies are showing a lack of competence, you shouldn't be undertaking this work if your asking the questions you are and also having other major areas of concern been pointed out to you.

Let me make this clear Nicsin02, if you change, alter or make any addition to this circuit/s then you are responsible for its compliance and it will have to meet 17th addition once you do, the high integrity earthing and the need for it is a great concern in my mind as it is a safety issue if not done correctly.

I hope you can take this as valuable advice and not a dig in any way.
 

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