1st install job advice please

[telectrix]

Come on then, read the Table, and tell us your interpretation of it.

my interpretation is that as the fan is supplied from the lighting circuit, the cable spec. is that for.............





wait for it....................








............................................................................a lighting circuit.

 

[longboat]

Got myself one of these from ebay. the missus loves drying her hair in the bathroom. I wired it in 2.5 T&E to be on the safe side.

 

[micknew]

Got myself one of these from ebay. the missus loves drying her hair in the bathroom. I wired it in 2.5 T&E to be on the safe side. View attachment 20614

Well done.

 

[longboat]

Thank you micknew. A picture speaks a thousand words as they say.

 

[nickblake]

those enviro fans are well good if you installed the fan the wrong way round there would be no need for the hair dryer , back to the bathroom issue , installation methods are required to select your cable size , insulation clipped direct etc personally I would only use 1.5mm , fused spur fan isolator , junction box on down lighters etc and bonding is required if even if you do have RCD protection unless install is plastic a 1 meter length of pipe in some circumstance could be an extraneous part so the pipe work should be checked supply supplementary bonding can be omitted if all circuits are RCD protected and bondings in place etc

 

[alanl]

Hi alani, the average bathroom fan (15W) consumes about 0.06A.
There is no way I would feel you must use 1.5mm.

Yes, I know that, but it is there in the Regs.
I asked the query on the IET site, and the answers there are indeterminate.
Smokes could be included in Note 1, but there is no definition of a power or lighting circuit in BS7671.
How about a single socket outlet, protected by a 6A CB supplying a TV only, less than a metre from the CU?
That would run fine on a 1mm T+E cable, but it wouldnt comply with Table 52.3, yet in all other respects would comply.

Yes, I know in the real world such situations dont often arise, but the original poster should think about this before installing a low wattage fan on a 1mm conductor.

 

[Andy78]

Yes, I know that, but it is there in the Regs.
I asked the query on the IET site, and the answers there are indeterminate.
Smokes could be included in Note 1, but there is no definition of a power or lighting circuit in BS7671.
How about a single socket outlet, protected by a 6A CB supplying a TV only, less than a metre from the CU?
That would run fine on a 1mm T+E cable, but it wouldnt comply with Table 52.3, yet in all other respects would comply.

Yes, I know in the real world such situations dont often arise, but the original poster should think about this before installing a low wattage fan on a 1mm conductor.

How would installing a socket circuit that can take a 13A fuse in a plug top, protected by a 6A MCB comply with regs ?

 

[Engineer54]

That would run fine on a 1mm T+E cable, but it wouldnt comply with Table 52.3, yet in all other respects would comply.

So the cable complies in all other respects except for an arbitrary table, relating to undefined power circuits. So when is a power circuit not a power circuit then??

So what you're saying is, a 1.5mm cable needs to be installed from the CU to the bathroom to cater for a 15/20W extract fan, because the existing lighting circuit is 1mm?? Jesus, are you completely off your rocker or what??

 

[alanl]

It's all down to design considerations.
If we had every appliance working on a RFC, it would (probably) overload that circuit.
The Designer will take that into account, and make the assumption that all appliances will most likely not be all on at the same time, so gives it a 32A CB, which is enough for maybe half of the appliances to run together.
The same is true of a socket outlet behind a TV, it is marked as 'For use of wall TV only'.
If situated at the top of a wall, behind a TV, it is very unlikely to be used for general use, and if marked correctly, it will comply.
To be sure that it doesnt get used for other things, a 5A socket outlet and plug could be used, or even a FCU, but most people are sensible, so would not use it for anything else.

 

[alanl]

So the cable complies in all other respects except for an arbitrary table, relating to undefined power circuits. So when is a power circuit not a power circuit then??

So what you're saying is, a 1.5mm cable needs to be installed from the CU to the bathroom to cater for a 15/20W extract fan, because the existing lighting circuit is 1mm?? Jesus, are you completely off your rocker or what??

It isnt what I am saying, it is in the Regs.
It isnt an arbitary table is it? It is there on page 130, with Reg 524.1 pointing to that table.

The argument is, what is a power circuit?
Is it a fan, or, can a fan be spurred off a lighting circuit in 1mm, and still comply?
There are no definitions, the closest I can think of are the difference in voltage drop between lighting and 'other uses'.

Why have a rant, without explaining what you think?

 

[Engineer54]

It isnt what I am saying, it is in the Regs.
It isnt an arbitary table is it? It is there on page 130, with Reg 524.1 pointing to that table.

The argument is, what is a power circuit?
Is it a fan, or, can a fan be spurred off a lighting circuit in 1mm, and still comply?
There are no definitions, the closest I can think of are the difference in voltage drop between lighting and 'other uses'.

Why have a rant, without explaining what you think?

That's exactly what i said, you're taking notice of a table that has no definition as to what constitutes a ''power circuit''!! If a circuit electrically/mechanically complies with all the relevant criteria, then a non descriptive table can be kicked into touch as far as i'm concerned!! As usual in these situations, applying a little commonsense will show you the way!!