Power to Loft (not habitable space)

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Alongside a lot of other (non-electrical) work I'm considering running a spur from a socket in a bedroom into the loft. The spur will power a TV aerial amplifier PSU and be used on rare occasions for loft lighting. A double socket will suffice, or a FCU for the PSU and a single socket for lighting/other stuff whenever it's needed. 'Other stuff' would, most likely, be a cordless drill charger or other power tools if I happen to be doing a bit of work in the loft (unlikely but possible). There's no water up there so no possibility of ever having to thaw frozen pipes.

The loft is non-habitable. Due to its design it will never be habitable. It's floored out for storage only.

The ring main currently serves just under 100 sq.m. Adding the loft (if it's necessary to do that) will take it to about 150 sq. m.

So, if the non-habitable loft is not included in the calculation it's permissible. If it must be included the work is not permissible.

Any thoughts?
 
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The loft is non-habitable. Due to its design it will never be habitable. It's floored out for storage only. The ring main currently serves just under 100 sq.m. Adding the loft (if it's necessary to do that) will take it to about 150 sq. m. So, if the non-habitable loft is not included in the calculation it's permissible. If it must be included the work is not permissible. Any thoughts?
The Wiring Regs (or Part P of the Building Regs) do not generally distinguish between habitable and non-habitable rooms. However, to the best of my knowledge there are no regulations (only recommendations) about the floor area served by a sockets circuit, certainly in an existing building.

Particularly given what you say about indended usage, what you propose sounds fine to me. As you probably know, if it is an 'unfused' spur, you can one have one 'device' connected (one single-socket, one double-socket or one FCU). If you wanted more than one thing, you'd have to install them downstream of an FCU (i.e. a 'fused spur', with maximum total load of 13A or less, depending on the fuse).

Kind Regards, John
 
Historical 100 sq.m was the rule of thumb limit for a ring main but what really limits the size of the ring is volt drop. For lighting circuits 3% for power 5% and clearly one can't just measure the volts as it's all down to load and where the load is placed.

In real terms we can only measure the loop impedance or fault current and calculate the volt drop from this. For these calculations we assume 20A from centre point at 12A even spread so we work on 26A not 32A to work it all out.

Once one starts using fused spurs one has to realise there is a maximum of 13A even less with smaller fuse which also means less volt drop.

Again in real terms I have never bothered working out the lengths of spurs with the main ring it works out at 106 meters. This includes corrections for the fact that your not pulling maximum current.

So rather than work out the exact figures maybe the method should be a risk assessment. I would not expect a problem with a TV amp. Even if it produced interference due to volt drop it would not produce danger. The only real problem is with discharge lighting where too much volt drop may suddenly fail so use tungsten or LED lighting.

So I really see no problem in feeding the loft with a FCU.
 
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That's what I feared, hence the 2nd question.

Those dreadful things are strong enough to hold up the ceilings in the rooms below, and nothing else.
 

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