Loft - extend 1st floor circuits?

[dhollm]

I'm trying to gauge the potential impact of a loft conversion on our electrics.

At present we have a 6 circuit consumer unit with no spare ways for additional circuits.

The loft is only expected to require normal lights & sockets; ie, no second electric shower or anything like that.

Would it be acceptable to extend second floor socket and lighting ckts to the loft, or would a larger CU be required?

One detail worth noting is that the existing lighting ckts appear to be un-earthed, which I suspect would not be allowed in a new installation like a converted loft. (?)

FYI I *am* planning to bring in an electrician, but at this moment I am just trying to get a better idea of overall complexity to estimate costs.

Thanks!

 

[holmslaw]

..

 

[riveralt]

I'm trying to gauge the potential impact of a loft conversion on our electrics.

At present we have a 6 circuit consumer unit with no spare ways for additional circuits.

The loft is only expected to require normal lights & sockets; ie, no second electric shower or anything like that.

Would it be acceptable to extend second floor socket and lighting ckts to the loft, or would a larger CU be required?

If you have 2 socket circuits and they are small enough then I see no problem in your extending into the loft. The suggested maximum size of a ring final circuit is 100m2 and radials approx 50m2.

One detail worth noting is that the existing lighting ckts appear to be un-earthed, which I suspect would not be allowed in a new installation like a converted loft. (?)

As Holmshaw said you would be unwise to extend your lighting circuit because of the absence of a cpc. I do hope you do not have any metal switches or metal light units.

You have two options. Best is to have the lighting circuits upgraded to include a cpc. This will involve running a cpc from the consumer unit through each ceiling rose and light switch. You could do this just for the upstairs lights and run the loft light from this circuit.
Second option is to extend the current upstairs lighting circuit but run a cpc from the new loft ceiling rose to the consumer unit.

 

[Chri5]

You won't have easy access to the 1st floor ceiling level once the loft is in, I's suggest:-

New sub main for the loft- lights, ring (or radial) for sockets AND a seperate smoke dection circuit- although having them off the lights is considered a good warning indicator (lights failed = knowing smokes have failed- even if battery back up in place).

And renew all 1st floor lighting and drops with 1.0mm or 1.5mm twin with earth (cpc).

10mm earth bonding for water and gas will be required no matter which way you do it.

The more expensive (but more comprehensive) way would be to swing over all existing and new circuits on to a new all in board. That is subject to varification that the old wiring is of a standard to be able to cert to 17th ed.

 

[sparkwright]

As already hinted at, take the opportunity to replace the first floor lighting wiring now, while it's still easy. Obviously check first that there aren't any earth wires in it. Sometimes they are cut off, or twisted together and shoved into the ceiling void.

It sounds like you will never have a chance like this to replace that wiring. Switch drops will probably be in conduits, so you can draw in new cables.

 

[dhollm]

Thanks everyone for the advice. I will definitely plan to address the 1st floor lighting as suggested, and its good to know what some of the other options are.