Size or Cable for Combi Boiler

[NeilRob]

I had the house rewired about 18 years ago the electrician used 1 mm twin and earth from a 6 amp breaker in the consumer unit to a fused spur with 3 amp fuse for the combi boiler, I am about to have a new boiler installed and want to know if this cable is actually the correct size it has caused no problem but I would have thought 1.5 was more suitable.

 

[Sparkii]

Why 1.5?

 

[Deleted member 26818]

The current Regulations now prohibit the use of 1mm² cables for power.
The minimum CSA is now 1.5mm².
However that not withstanding, 1mm² should be more than adequate for your combi boiler, especially if the rating of the fuse is still at 3A.

 

[Farmelectrics]

not what i would have done but 1mm can take 16a and its fused down anyway to 3a relax its ok

 

[Octopus]

I had the house rewired about 18 years ago the electrician used 1 mm twin and earth from a 6 amp breaker in the consumer unit to a fused spur with 3 amp fuse for the combi boiler, I am about to have a new boiler installed and want to know if this cable is actually the correct size it has caused no problem but I would have thought 1.5 was more suitable.

Are you replacing a boiler or installing a large kettle? 1.0mm is more than sufficient to supply the new boiler!

 

[Danspark]

The current Regulations now prohibit the use of 1mm² cables for power.

Where is this mentioned please ?

 

[Deleted member 26818]

BS7671 Regulation 524.1, Table 52.3, pages 129 and 130.

 

[Silly Sausage]

re 524.1...
Depends on how you interpret that reg (a bit like any other!).
A spur to a combi is hardly a power circuit.

Serious anorak time, this discussion!

 

[Deleted member 26818]

I suppose you can interpret the Reg. however you wish.
How do you interpret the table to mean anything other than what it states?
Lighting 1mm².
Power1.5mm².
Is a combi, some new form of lighting, should I re-lable all the CUs from boiler to lighting?

 

[Badged01]

Have to agree, that would be my interpretation. Min of 1.5mm for basically any circuit other than lighting (or control!)

 

[GLENNSPARK]

well i guess thats all been made easy for us all then.....
the reason they have done this (i suspect)....is to help the clowns that cant/dont work out what size cable to use....lol...

 

[Deleted member 26818]

Now we have to apply a code C3 if the cable is 1mm² even though it satisfies every other Regulation in the book.

 

[Danspark]

No interpretation required.

NeilRob; as your electrical feed for the boiler is existing and you are simply having a replacement boiler, spinlondon correctly stated that it would be "more than adequate" Regulation 524.1 table 52.3 tells us this is nothing more than a deviation from the current regulations; this does not make it unsafe.

If I was the electrical contractor re-supplying the new boiler I would identify it on the certificate as a deviation and label the switched fused isolator as 3A max fuse.

In circumstances where a new feed were required then yes, the cable would be done so in accordance with table 52.3 and fed from a cable with csa no less than 1.5mm.

thanks spinlondon for answering my question.

Dan

 

[Deleted member 26818]

No worries.

 

[Danspark]

A ring final circuit fed at 32 amps, a junction box installed onto one leg of the ring with a 1.5 mm sq cable inserted into the JB feeding a single socket (or switch spur used to feed a boiler)

I was caring out some remedial work after an electrician that had identified it on a periodic inspection report; he was incorrect to do so, but as glenspark says "

clowns that cant/dont work out what size cable to use"

Dan
​

 

[GLENNSPARK]

A ring final circuit fed at 32 amps, a junction box installed onto one leg of the ring with a 1.5 mm sq cable inserted into the JB feeding a single socket (or switch spur used to feed a boiler)

I was caring out some remedial work after an electrician that had identified it on a periodic inspection report; he was incorrect to do so, but as glenspark says "

clowns that cant/dont work out what size cable to use"

Dan
​

and it dont stop there either...lol
sat in the van with my (then) boss....drivin along......then he suddenly throws a PIR sheet into my lap...`ere....`ave a look at this he says......lol...
so a rewireable C/U is a (2) is it?..lol...
and gas+water on one main bonding conductor is a (1) is it?....lolffs...
well, acording to the guy who did the original report it was...lol.....lol....
oh man....

 

[Geoffsd]

Table 52.3 also states 0.75mm flex may be used - if you read it that way.

 

[GLENNSPARK]

its a lot is 1.5 to feed a chuffin boiler....lol...

 

[Octopus]

So its 1.5mm minimum CPC CSA for power circuits from now on.....

I see all the cowboy EICR's now - you need a rewire because your 2.5/1.0mm T&E doesn't comply with regs and is illegal!

 

[Danspark]

So its 1.5mm minimum CPC CSA for power circuits from now on.....

I believe table 52.3 is referring to the line and neutral conductors and not the cpc