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Discuss Boiler circuit? in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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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.
 
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Spudnik

  • Thread Starter Thread Starter
  • #2
16A 2.5 radial fine with a 3 amp fused spur at the end of it.

Horizontal runs are also perfectly acceptable.
 
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craig2210

  • Thread Starter Thread Starter
  • #5
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.
 
Last edited by a moderator:
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joe kane

  • Thread Starter Thread Starter
  • #6
Keep it 2.5 if they say it would do no harm
 
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barx

  • Thread Starter Thread Starter
  • #7
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.
 
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Guest123

  • Thread Starter Thread Starter
  • #8
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.:)
 
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Scott F

  • Thread Starter Thread Starter
  • #9
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
 
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ezzzekiel

  • Thread Starter Thread Starter
  • #10
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
 
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Spudnik

  • Thread Starter Thread Starter
  • #11
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

Scott
What, 500mm from ffl??:D
 

sparks1234

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Arms
Some of the condensing boilers need a start up current around 10 amps so watch out for 3 amp fuses, so best go for the 2-5. room for expansion
 
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Spudnik

  • Thread Starter Thread Starter
  • #14
Some of the condensing boilers need a start up current around 10 amps so watch out for 3 amp fuses, so best go for the 2-5. room for expansion
Didnt know that.

Must admit i have always put 3 amp in and as far as im aware never had any probs.
 

sparks1234

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Arms
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
 
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