Power to the loft direct from CU

[chrisw99]

I am in the middle of a bit of a DIY loft conversion. I have just installed lights up there from the existing lighting circuit, and I'm now thinking of putting a power socket in.

I've added new spurs to ring circuits before, but access to the existing ones in this case is very awkward. However, I have a couple of spare positions on the consumer unit and can easily run a cable from there up to the loft (side by side with the existing cable to the upstairs lighting

The CU is something I've never touched before, so how do I go about connecting up a standard double socket to it?

(On a related note, I have a double socket in the garage which seems to be connected direct to the CU as one of the circuit breakers is labelled "Garage power only". Every other time I use the lawnmower, it trips. Any advice on diagnosing this?)

Thanks
ChrisW

 

[ChrisRogers]

could you take a picture of your CU or tell us what make it is?

Also what rating is this breaker that keeps on tripping?

 

[chrisw99]

As requested, here is a pic...

The one on the left is the spare slot that I would like to add a power socket in the loft to.

I think I know the answer to my lawnmower tripping question, as the garage socket is a 10A MCB and should probably be a 16A.

Running from left to right, I have..

16A - spare
6A - garage light + outside light
10A - garage socket
16A - downstairs sockets
32A - kitchen (new extension) sockets

20A - heating + freezer socket
6A - upstairs lights/downstairs lights/burglar alarm
16A - immersion
32A - upstairs sockets
40A - shower

A couple more questions have arisen now that I've looked at my CU properly for the first time:

1. Is it normal for the upstairs and downstairs light circuits to be on the same MCB? In other threads on here I've always seen them on separate ones? I also seem to have the burglar alarm wired into this one too, even though it's not labelled, as whenever a bulb blows and trips , the alarm goes into tamper mode.

2. downstairs sockets are 16A, upstairs are 32A. Any reason for this?

Thanks for any advice

Chris

 

[plugwash]

looks like a bit of a bodge job

you need to find out what cable stuff is wired in before you even consider uprating breakers

the easiest way for a diyer to size cable is to buy a small length of each size and just compare them to your existing cable i will go through the cuircuits in order you will at the very least need a multimeter (they can be had for about £10) to check that cuircuirts are rings (use the resitance range and check for a ver low value to telly you when things are connected)

ideally you should use breakers of the same brand as your board but failing that take the old breaker with you to compare and get one that matches as well as you can in the position and type of the input terminal on the bottom


6A - garage light + outside light
fine if it's an attached garage but see the comments on the garage sockets secontion if it's detached

10A - garage socket
is this an attached garage or a detached garage
if the garage is attached the cable should be 2.5 T&E or bigger if it is then you can change the breaker to a 16A one if not then you need to replace it first

if it is a detached garage it need to change to armoured cable before going underground and change back to T&E in the garage generally in this case you use a small metal cu in the garage to split out sockets and lighting from a single armoured cable if your garage is detached post it and i can give you more info on how it should be done


16A - downstairs sockets
seems unusually low but you should only uprate it to 32A if either the cuircuit is a ring (2 lives in breaker which when removed from the breaker are still linked to each other (use multimeter to check) and wired in 2.5mm or greater or if it is not a ring the cuircuit is wired in 4mm or greater if the cuircuit is 2.5mm and not a ring you can uprate to 20A but no higher

32A - kitchen (new extension) sockets
this sounds right but i would still check it as for the downstairs sockets

20A - heating + freezer socket
the cable should be at least 2.5mm and the freezer socket if in a position where it is likely to be used outdoors shuold be clearly labled as non rcd and not for powering outdoor equipment

6A - upstairs lights/downstairs lights/burglar alarm
the burgular alarm should not be on a lighting cuircuit since you are short on space in the cu i would put it on the freezer cuircuit but remember to put in a fused connection unit before it if there isn't one already as for the lights this is not against regs but is rather prone to nusence tripping you can uprate to a 10A but if you do so you must replace all swsitches etc with ones that have this rating

16A - immersion
the cable should be at least 2.5mm

32A - upstairs sockets
this sounds right but i would still check it as for the downstairs sockets

40A - shower
would need more info on the size of shower to confirm this rating also the shower should be on the rcd but this raises the issue of the current rating of the rcd if the rcd is rated at 80A or more i would move the shower breaker over to the rcd side and use the spare this would leave on the non rcd side for your loft power which is a perfectly fine location if the rcd is of a lower current rating i would use a seperate rcd with a current rating of 60A or so (so you have some leeway if the shower is uprated in future) in a small enclosure for the shower something like this and this

before opening the cu you should trun off the main switch

inside a split load cu like that you will find a earth bar and 2 neutral bars one for cuircuits on the rcd and one for cuircuits not on the rcd the mcbs will be attached to busbars feeding off the main switch and rcd the terminals bringing the wires in to the main swich should be seperately covered but they are not always so be extremely carefull the first time you open the cu and if they are not covered make a termporary cover and try to get a proper one asap

when connecting a cuircuit you simply conenect the live wire to the mcb the nuetral wire to the appropriate neutral bar and the earth wire (remember to use earth sleeving) to the earth bar if the cuircuit is a ring you will have two cables to connect to each terminal but again you just connect them as above

for the sockets in the loft i would reccomend using a 20A breaker and running in 2.5mm it is perfectly safe to use a 16A though if you have one spare though provided you don't plan to draw huge amounts of power up there

 

[ZenStalinist]

Sure shouldn't the upstairs sockets be on the RCD side also?

 

[plugwash]

the only sockets that have to be on rcd by regs are those which could feasiblly supply portable equipment outside the main equipotential zone

so upstairs sockets are fine on non rcd

plus his board has a lot of ways on the non rcd side so unless he is planning on a cu replacement he has to keep some stuff on that side

 

[chrisw99]

Thanks for the detailed response plugwash.

The garage is attached, and the cable is 2.5 T&E, so I should be ok to replace the 10A with a 16A to stop the lawnmower causing a trip.

As for my loft, I was exploring last night and I'd overlooked the upstairs landing socket which I can easily run a spur from up to the loft.

This leaves me still with the 6A spare breaker. I was thinking of just moving the burglar alarm from being on the lighting circuits to the spare one.

If you look at the pic, the burglar alarm is the white cable going into the CU, all the others are grey. As I said before, the CU is a bit of a mystery to me, but it seems to me to make this move is it simply disconnecting the live from the burglar alarm cable from its current position with the light circuits, into the spare one, leaving the N and E as they are?


I'm a bit puzzled as to why the alarm is in with the lighting circuits, the alarm is a lot more recent than the CU, so the installer had a spare to use if he wanted but must have picked the lighting circuit for a reason known only to himself

 

[plugwash]

still the shower rcd issue to consider....

you should either put it on a the rcd side of the CU or give it is own rcd as mentioned

however you should not put it on the rcd side of the CU if the rcd in the cu is anything less than 80A rated

 

[Big_Spark]

I agree with Plugwash, the whole thing looks like a complete bodge-up.

Personally I would advise you get a full Periodic Test and Inspect done on the whole installation to confirm it's integrity and conformity before going messing about with.

To comment on your last post, you stated you could take the power for the loft off a spured socket upstairs, sorry, you cannot do this.

 

[plugwash]

if the landing socket is on the ring (you should make totally usre of this first) then there shuldn't be a problem with running one socket on a spur from it

if you wan't more sockets up there ir of the landing socket is on a spur already you must use a 13A fused fcu at the start of the spur

 

[chrisw99]

Thanks for your input FWL, although I don't believe I said the landing socket was a spur, I said I could take a spur from this (it is definately on a ring).

plugwash - the RCD is 63A. The shower is 10.8kw.

I'm intrigued how you both call it a bodge up. To my laymans eye, everything is cabled correctly as it should be, connections are sound, everything is clearly labelled so I can see what is going on in one glance. Admitedly, there are one or two funnies as mentioned in the posts above, but "complete bodge up" is going a bit far isn't it? Can you give me a list of items as to why you believe this to be the case?

 

[plugwash]

ok maybe that was a bit of an exageration

but if there are visible oddities in an install then it probablly means the system has been worked on by less thant fully competent people which could mean there are other hidden issues

i wouldn't put the shower on the main rcd if it's of such a lot rating as it wouldn't take much over the load of the shower to be voerloading the rcd

i suggest fitment of a seperate rcd for the shower as mentioned before

 

[chrisw99]

It probably won't surprise you all to learn that the previous owner of the house had his occupation listed as "electrician" !!

That in itself probably means I should get a PIR done soon

A couple of other points I've just discovered. The spare 6A breaker appears to be dead. When the power is on, there is no juice at all from its live terminal (and its not my tester as the 6A breaker next to it "garage lights" is live).

I tried moving the alarm connection from the light circuit to the garage light circuit (RCD side), and it immediately trips the RCD. It appears the alarm trips the RCD whatever it is connected to, hence the reaon the installer must have connected it to the lights, as it is the only 6A breaker on the non RCD side.

Would you still recommend moving the alarm to the heating + freezer 20A slot? Why not the 16A immersion one, as to be honest I never use the immersion so this is almost a spare in itself and is the least likely to trip or need to be turned off? The alarm itself is behind a 3A FCU btw.

 

[plugwash]

imersion heaters cuircuits should be dedicated so no

did you remember to move the neutral to the right bar when you moved the alarm?

also if you have a dead mcb just replace it

 

[Big_Spark]

Chris, many apologies, brain working faster than fingers earlier and I mistyped my comments about the spured socket.

It should have said

To comment on your last post, you stated you could take the power for the loft off a spured socket upstairs,fine if only one socket, but if multiple sockets, sorry, you cannot do this. without the inclusion of a fused spur.

Sorry for any confusion my cocked up post created!