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Hi everyone, just a couple of quick questions. I'm currently working on a new build site (my 1st as I'm a relative novice) and there are some conflicting ideas.

Would a dedicated boiler radial requiring a 3A fused spur require 2.5 t&e and a 16A MCB as specified by one of the guys on site - it seems a little excessive? I would have gone for 1 or 1.5 and a 6A MCB but I'm just the boy so I'm keeping quiet for the moment!

Also due to some difficult rsj locations the ring circuit in a couple of rooms runs vertically but has to loop under the rsj - when it was suggested that the sockets were linked horizontally at 450mm it was rejected as being poor practice. I had a look in the onsite guide and although it clearly shows horizontal lighting circuit runs it does not show the ring.

Just thought I'd run these by you sensible types as te guys on site can't seem to agree on either of these issues.

Thanks.
 
There is no problem running a 1.0 or 1.5 radial on a 6amp mcb for a boiler and then fitting a fcu to fuse this down further to 3amp. The 2.5mm t&e radial is just common practise as many older heating systems were current intensive but with modern boilers consuming hardly anything it is getting common to find more 6amp radials. At the end of the day you install a circuit with the correct sized cable and fuse for the load its intended to supply, like an immersion circuit for instance, so your right in saying that it can now be seen as excessive. The same goes for burgler alarm systems too. As for horizontal cable running, this is fine as long as it's ran in the appropiate zones.
 
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Many contractor/client specs still say 2.5mm radials on a 16A MCB for heating. Guess it just gives a bit redundancy for future use should it be required. Also, many see horizontal runs >500mm bad practice. Although regs say its fine. If its their job, you do it their way. Many jobs in this trade tend to end up as 'do as your told, not as you please' (so long as its safe and meets regs). After all, client is paying for it.
 
Personally I always go down the 2.5, 16A route, habbit more than anything.

Whilst the regs say it's fine, I never do the horizontal thing it just doesn't sit right in my fried mind.:)
 
As Barx said 2.5mm on 16 amp then fused down to 3a gives you options for further use at a later date ie if they wanted to upgrade
Not likely, but.
Unfortunately when your young and work for someone else a lot of the time you just have to bite your tongue.
I think we have all been there.
End of the day if the regs say ok then show them .Still will not change their minds
With horizontal wiring I know where Lennys coming from,you have to protect the cables from someone who may move in a put a picture up etc,etc
However in the kitchen when your not sure of measurements for kitchen cupboards going across with cables your less likely to get a screw through .some of these fitted kitchens have no scope for adjustment of fixings.
Also if the socket is close go across or if a void you have no other option .
Like anything with time and experience you will find your own way.
Scott
 
you tend to find all things are pretty much standard in house circuits, apart from the diy crew, BUT your the electrician and are trained to calculate requirements for any any circuit
 
Yes, some of them are beasts, they are able to have much longer exhaust flues and I guess the fans are heavier to get the air flow
 
running cables horizontally, if you look in the regs or on-site guide it deffinetly shows safe zones for routing cables. vertically and horizontally.

Dave
 

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