Cable sizing

[akist]

I have a single phase 100A supply into my new house. I have ended up having to install cabling around the house. Can you please help me with wiring and sizing?

Lighting circuits = 1.5mm2 mostly in a star wiring
Sockets = 2.5mm2 some with a loop back or in a star
Electric Oven = 6mm2 (distance 4-5m)
Immersion heater = 4mm2 (distance 1-2m)
Washing machine, Dryer, Dishwasher = 2.5mm separately fed
Remote consumer unit = 6mm2 or 10mm2 ( distance 20m )

 

[SUNRAY]

I have a single phase 100A supply into my new house. I have ended up having to install cabling around the house. Can you please help me with wiring and sizing?

Lighting circuits = 1.5mm2 mostly in a star wiring
Sockets = 2.5mm2 some with a loop back or in a star
Electric Oven = 6mm2 (distance 4-5m)
Immersion heater = 4mm2 (distance 1-2m)
Washing machine, Dryer, Dishwasher = 2.5mm separately fed
Remote consumer unit = 6mm2 or 10mm2 ( distance 20m )

Is this a new /self build?

 

[akist]

Yes, everything is new.

 

[SUNRAY]

Yes, everything is new.

In that case my only advice is to ask your electrician what and where he wants you to run.

 

[ericmark]

Immersion heater unlikely to need 4 mm² but the big problem is to get the LABC to accept what your doing.

Does not matter if wired right or wrong, what matters is will the LABC accept what your doing.

 

[akist]

what matters is will the LABC accept what your doing.

I will need to find an electrician to sign it off, or to install consumer units and fuses and then sign it off.

But I wonder, what exactly can the surveyors do?

 

[flameport]

I will need to find an electrician to sign it off,

That won't happen.
It's either electrician installs, certifies and notifies their own work
OR
You install, and have building control inspect/test and do whatever else they decide is necessary. You must find out from BC exactly what they want before you do any work.
It's possible to use a third party building inspector or TP certifier rather than building control, but the same principles apply - you must find out from them what is required before anything is installed.

or to install consumer units and fuses and then sign it off.

That won't happen either, as a consumer unit doesn't have anything to 'sign off' without final circuits attached. Most of the inspection and testing is for those circuits rather than the consumer unit itself.

Wiring a house involves a lot more than just shoving in some cables.
The size of the cables depends on more than just what they are supplying - where and how they are installed makes a big difference.

 

[Taylortwocities]

Whssign

• Taylortwocities
• 16 Jul 2016

What he said

 

[SUNRAY]

Lighting circuits 1.0mm
Oven 4.0mm if on a 32a MCB
Immersion heater usually 2.5mm but 1.5mm OK if on 16a MCB.

There is more to it than simple current carrying capacity.

 

[Taylortwocities]

Lighting circuits 1.0mm
Oven 4.0mm if on a 32a MCB
Immersion heater usually 2.5mm but 1.5mm OK if on 16a MCB.

I don’t like to disagree with you but that does demonstrate your lack of actual practical experience.
For a new circuit I would never install only 4mm² for an oven/cooker. That really limits the future addition of perhaps an induction hob later. Yes I know we must conserve the World’s copper resources blah blah but let’s get real.
And never 1.5mm² for immersion. For more than the average cable run the volt drop will mean it’s not workable. 2.5mm² for the circuit. 1.5mm² flex is ok for the loop ftom the local switch to the immersion.

 

[davelx]

"Sockets = 2.5mm2 some with a loop back or in a star"
2.5mm2 may be ok for your "loop back" - properly called a Ring Final - but it depends on other factors that we cannot know about as mentioned above.
Unlikely 2.5mm2 will do for your "star" - properly called a Radial Final, unless you use an MCB <=25A (generally 20A as 25A are less common). Usually at least 4mm2 for a 32A radial, and even then it depends on other factors.

No-one other than an electrician on site can answer your questions. Find yourself an electrician who is willing to let you do the cable installation, and then install what he specifies the way he tells you to.

 

[Taylortwocities]

Immersion heater = 4mm2 (distance 1-2m)

What? Why? Stop smoking that stuff.

 

[oldbutnotdead]

I have a single phase 100A supply into my new house. I have ended up having to install cabling around the house. Can you please help me with wiring and sizing?

Lighting circuits = 1.5mm2 mostly in a star wiring
Sockets = 2.5mm2 some with a loop back or in a star
Electric Oven = 6mm2 (distance 4-5m)
Immersion heater = 4mm2 (distance 1-2m)
Washing machine, Dryer, Dishwasher = 2.5mm separately fed
Remote consumer unit = 6mm2 or 10mm2 ( distance 20m )

You are coming at this from the wrong direction.
You need to get an electrician on the scheme design before you start throwing cables around- that electrician may be happy for you to do the actual donkey work of installing cables, backboxes etc to your requirements and their specification (which will, or should, take into account 'safe' zones, any thermal insulation, positions of sockets and switches- if this is a new build there are stipulated heights- and many other details) then returning initially to visually check the work and eventually to test, terminate and commission all circuits.
If you really want to do this full install on your own then you can go the building control route- remember you have to notify them BEFORE you start work- but you'll quickly find that for the fees they charge you will almost certainly be better off engaging a self-certifying electrician. Though saying that their fees might not have risen as rapidly as other costs recently so it is an avenue worth investigating.

 

[SUNRAY]

In that case my only advice is to ask your electrician what and where he wants you to run.

Immersion heater unlikely to need 4 mm² but the big problem is to get the LABC to accept what your doing.

Does not matter if wired right or wrong, what matters is will the LABC accept what your doing.

That won't happen.
It's either electrician installs, certifies and notifies their own work

Whssign

• Taylortwocities
• 16 Jul 2016

What he said

There is more to it than simple current carrying capacity.

Lighting circuits 1.0mm
Oven 4.0mm if on a 32a MCB
Immersion heater usually 2.5mm but 1.5mm OK if on 16a MCB.

I don’t like to disagree with you
but that does demonstrate your lack of actual practical experience.
For a new circuit I would never install only 4mm² for an oven/cooker. That really limits the future addition of perhaps an induction hob later. Yes I know we must conserve the World’s copper resources blah blah but let’s get real.
And never 1.5mm² for immersion. For more than the average cable run the volt drop will mean it’s not workable. 2.5mm² for the circuit. 1.5mm² flex is ok for the loop ftom the local switch to the immersion.

No-one other than an electrician on site can answer your questions. Find yourself an electrician who is willing to let you do the cable installation, and then install what he specifies the way he tells you to.

What? Why? Stop smoking that stuff.

You are coming at this from the wrong direction.
You need to get an electrician on the scheme design before you start throwing cables around-

Those are the post giving correct advice. (with apologies for my editing).

Below are the posts giving the wrong advice and would sensibly be ignored.

Lighting circuits 1.0mm
Oven 4.0mm if on a 32a MCB
Immersion heater usually 2.5mm but 1.5mm OK if on 16a MCB.

Immersion heater = 4mm2 (distance 1-2m)

2m is a lot less than the average cable run. Even 1.0mm would probably be OK in this instance.

 

[SUNRAY]

LIAR. My posts are NOT wrong advice.

To elaborate. Lighting circuits only require 1.0mm cable which is rated at 16 amps. Many sparks use oversize cable.

An oven circuit on a 32a MCB only needs 4.0mm cable. Even if an induction hob is added diversity would probably still allow 32a on a 4mm cable. Many sparks use oversize cable.

2m IS a LOT LESS than the average cable run for an immersion and 1.5mm (or even 1.0mm) cable is perfectly OK. No need to use oversize cable.

It is wrong advice.
Did you bother to ask about installation methods, derating factors etc?
Did you bother to ask if it's an oven or a cooker?
Are you seriously suggesting using a 1.0mm² on a 16A OCPD?
Have you ever felt how hot a 1.0mm² gets when running at 13A let alone 16A.
There is no 4.2mm cable that I'm aware of.

As you keep saying the fuse is only there to protect the cable and you are potentially recommending installing unprotected cables. PLEASE STOP before this inexperienced person believes your advice and installs circuits on undersized cable.