Supply cable upgrade

[CheeryChappie]

Hi,
I've recently bought a two story house I am preparing to let out. The electrics generally test ok but the supply cables to the meter and distribution boards are a bit "light" and I'd appreciate any comment on possible improvements.

Existing - a good sized (modern looking) cable arriving at main fuse from supplier - main fuse 60A - 16mm tails to meter - two sets of cables leaving meter; 1st set 25mm tails going to consumer unit with 80A rcd (not split load) feeding el shower(32), el cooker(32), 3Xsocket circuits(2 rings)(32,32,16), lights(6), smoke alarms(6), combi boiler(6).
2nd cable leaving meter is 10mm t+e going upstairs to another consumer unit with 80A rcd (not split load) feeding shower(32), 2 socket circuits(rings)(32), lights(6), smoke alarms(6).

My conclusion is the 16mm tails to the meter are too small and the 10mm t+e is way too small.

My thoughts for improving it are to discuss with the electricity supply company getting the fuse uprated to 80A. Uprating the 16mm tails to the meter to 25mm, and uprate the 10mm t+e to the upstairs consumer unit to 25mm also (with a 16mm earth). (I know having everything on RCDs is not ideal but in time I will look at fitting split load units.)

Any thoughts or help would be appreciated, thanks.

 

[plugwash]

16mm tails are fine on a 60A or 80A service fuse you only need 25mm for 100A or over and even on 100A 25mm is only slightly overloaded

i still reccomend using 25mm for new installs though in case of future supply upgrades and because its generally only a short distance anyway

as for the 10mm ganged onto the meter that is as dodgy as hell meters are only supposed to have one set of outgoing cables and furthermore i cant see how you can terminate T&E to a meter without leaving single insulated cores exposed

if both showers are running at once you will either overload or be very close to overloading the service fuse (what power rating are theese showers anyway) but it may be impossible to run both at once anyway due to them cutting out from inadequate water pressure

do you plan to let out the 2 floors seperately?

 

[CheeryChappie]

I'm not sure what size the showers are, they are a few years old so are likely lower than todays 9.5+ KW.
It's going to be let on an HMO basis, 1 bathroom, 1 shower room, 1 kitchen, 1 lounge, 5 bedrooms.
So the 16mm to the meter is ok but I should fit proper connectors and replace the 10mm t+e with 16mm to the upstairs consumer unit.

 

[plugwash]

you shouldn't run connections for more than a short distance without your own isolation/overcurrent protection

also you should design yoru system in such a way that it can be upgraded to 100A total if the need arises

finally you should have one main point of isolation

personally i would fit a small CU with a 100A switch incomer and connect this to the meter with 25mm tails

in this i would fit 2 63A mcbs and then run 16mm twin and earth from theese to the 2 existing CUs

the upstairs CU should be clearly labeled as being a SUB board so that people don't get the idea it isolates the whole house

http://www.tlc-direct.co.uk/Products/CMM4N.html
http://www.tlc-direct.co.uk/Products/CM9063B.html
http://www.tlc-direct.co.uk/Products/CA16.html

ideally you should get the rec out to connect and disconnect but if you do decide to pull the service fuse yourself take great care not to touch any metal parts when pulling it and make sure no current is flowing by turning off CU main switches

 

[securespark]

meters are only supposed to have one set of outgoing cables

Tell that to Norweb/Whoever they are now!

On several occasions, I have come across several pairs (up to 5 in one case) of tails in a meter. Even some where neutral has been placed in incoming terminal instead of outgoing (does not really matter as they are linked, but all the same....)

 

[plugwash]

ok its possible to do it but in a lot of cases the only way to do so is to leave single insulated cores which is dodgy

 

[supersparks]

personally i would fit a small CU with a 100A switch incomer and connect this to the meter with 25mm tails

that fettish for small CUs is arising again......

 

[plugwash]

got any better ideas?

you are supposed to have a single point of isolation by the iee regs
a lot of recs require your won overcurrent protection on runs over a certain length

the small CU covers both issues

 

[supersparks]

got any better ideas?

you are supposed to have a single point of isolation by the iee regs
a lot of recs require your won overcurrent protection on runs over a certain length

the small CU covers both issues

yes i do, its called a switch fuse

Recs will only be bothered if it is a run of 5meters +

ive seen people get away with 8
even though the rec say 4(my area)

switchfuse would be the norm