Hi - I am in the throws of planning the install of a dedicated radial for my Naim rig.
I have seen various posts…I intend to do use a separate dedicated consumer uint with an earth leakage trip and a mechanical circuit breaker. This will be connected using a Henley block and associated new 100a tails.
Now when I get to the business end - I want to have 2 x double unswitched socket outlets
Question 1. I intend to use 10mm2 cable … how do I terminate and connect the 2 x double socket outlets??? Is it possible to get 2x10mm into the socket/screw terminator … or do I have to use another Henley block to split 10mm supply out to the sockets…
Question 2. 10mm cable is rated at 40amps … but the sockets are 13a … do I have to install a 10amp MCB … or am I allowed to install 32amp - as a std ring main would have.
I am pulling all my cables and doing much of the install myself … my local electrician is doing the tails and testing the circuits. I am used to wiring - I wired my whole house in 2012 - and had the electrician install tails and test circuits to comply with the then 17th edition. (I am using the same electrician now)
To prove a point, I managed to squeeze two 10mm cables into a terminal on an MK socket. So it can be done, but it’s a tight fit. Perhaps more concerning is that you then need to squash those stiff 10mm cables into the back box. After discussing this with my electrician, we decided against it. We went with his suggestion, which was to run a single cable to a point just short of the sockets, and split it into 2 with a Henley block, as there was space under the floorboards to do this. An alternative was to run 2 cables from 2 ways on the consumer unit.
I used a 32 Amp MCB, as recommended by Steve Hopkins at Naim. You may find that the new regs are stricter, especially wrt the use of MCBs instead of RCDs, but I’m sure your electrician will know the rules.
@Richieroo, if this was possible (under the floorboards) then a meter or two to the sockets may be beneficial to put some wire distance between the sockets. Some of the benefit of a mains block may come from the 2m lead to the block. Cumulatively with poweramp on the wall 2m leads gives 6m between poweramp and pre. Alternatively a second radial.
Make sure you have a really good earth as well. Not sure PME is particularly clean being shared with everyone else.
Phil
Regarding the Earth, run the wire from the hifi CU direct to the meter cupboard to keep it separate from the rest of the house. One option is to just have a double socket and use a mains block.
I’m using 6mm2 cable to MK unswitched sockets and a star earthing arrangement. You can pair 6mm2 cable in and out of one socket but it’s about seating the wall sockets in the back-plate without stressing the cables too much. This was hard with 6mm2 but it must be nightmare with 10mm2?
I recently tried one of the new Musicworks blocks (with sparkly base) to see if there was any benefit using just one wall socket directly to a mains block. I’m sorry to report that I much preferred my wall sockets. Another example of OMMV!
You really need to be using the 18th edition for your design.
This is what concerns (latest 18th edition) me … I think that means using a 30ma earth trip and probably 32amp MCB and a metal consumer unit. I talked to my brother about it who is a qualified sparks … he believes the issue will be getting 10mm cable into the socket - and then having enough flex to allow the socket to fix back to the face plate. His words were…10mm is about as flexible as welding rod! and this could be perceived as unsafe as the socket assembly and back box were never intended to accommodate this gauge of cable. He reckoned that the only way to do it safely would be to take the 10mm as close as possible to the socket then use Henley blocks … to then take 6mm to the socket. This re iterates some of the installations mentioned above.
As Chris mentions, a single run of 10mm2 T&E will fit fine into a standard double socket. Use a deep back box and form the individual conductors before making the connection to the screw terminals. This will minimise stress on the socket terminals when the socket is screwed down to the back box.
Cookers use 10mm, or even 16mm cable, sometimes into a single back box, and electricians will be used to doing that, so getting it into a larger double box is certainly possible, and many here will have had exactly that done on their dedicated mains. Sure, a standard socket will have been designed with 2x2.5mm T&E in mind as this is what most ring mains use, but there are plenty of us whose electricians have been happy to use 10mm, and sign it off under the regs.
Ok … yeah I will use a deep back box … I will feed back again once I have my cables pulled.
I look forward to your reaction when you first switch on. One of the best improvements I’ve ever made to my system was a dedicated mains and I’m only using 6mm2.
10mm2 into one socket and then daisy-chained into a second one is the best solution. It can be done, but it’s very tight and the stiff cables make it very difficult in the back box. Take your time, use a deep box and it will go safely. Squeezing the wires with pliers and careful moulding helps. Avoid as many cuts in the line as you can, so a henley block just before the sockets is not a good idea.
Ok … what concerns me is that I will do all that … then the electrician will insist on unscrewing socket to check wiring which be pretty darn tight…
My view is that although it is possible to get 2 x 10mm cables into a double socket, the strain on them is considerable, and I’m not at all comfortable with the strain you out on the whole thing by pushing it onto the back box. If your wall permits it, you could consider fabricating an oversized back box which would make the whole thing a lot easier to instal without putting a lot of force on the socket.
I wonder if any of those audiophile sockets are any better in this respect. Maybe MCRU or Furutech?
I think if I use a sunken 32 box and then put a 37mm surface extender on …that will give me a 69mm deep back box…which might be possible.
When I had my wiring done some time ago, I considered having twin sockets fed by 10mm multi-stranded cooker cable but my sparks wouldn’t run it in & out of the socket terminals (at best a very tight fit), as he considered this dangerous over time, as the copper cabling and the sheathing tends to harden.
Instead, I went with radial feeds from a dedicated CU - although this does mean there is a plug-in order per the order on the bus-bar. A dealer has suggested I try a mains block fed from one radial, so as to remove the potential effects of the bus-bar et al but I’m not convinced on this.
The hi-fi CU takes the better feed from a Henley block which splits the property feed between the house & hi-fi CU’s. The hi-fi circuit also has dedicated earthing - all done via sparky.
I’ve no idea whether this all makes a big difference. It was done alongside a rewire of the house - I think so.
The deepest standard back box is 47mm, so I would go for that, as you’ll need all the space you can get. Get some extra long screws for the socket, and you may be able to recess it deeper into the wall if space permits.
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