Rewiring plan

[VogonPoet]

Hi, I'm planning on rewiring my house in the near future. As I'm not certified I'll be getting building control to inspect and sign off on the installation. Before I send in the BC notice I was hoping that some of the experienced people here could run an eye over my initial plans to see if there are any obvious errors or omissions.

The house is a small three bed semi, with one bathroom upstairs. Downstairs there is a kitchen, lounge, utility room/toilet and an attached shed/store. It appears the house was last rewired in the late 80s with the old red/black style twin and earth.

My plan is to replace the old CU with a MK Sentry unit (this one: http://www.screwfix.com/p/mk-sentry-12-module-6-way-populated-main-switch-consumer-unit/8318p), run new cable and convert everything to run on RCBOs. That unit comes prepopulated with a number of RCBOs which I was planning on assigning to the circuits as follows:

6A Radial 1.5mm - Downstairs lights (3 x ceiling roses, 9 x led downlighters)

6A Radial 1.5mm - Upstairs lights (4 x ceiling roses) + bathroom (3 x led downlighters, extractor fan, shaver socket)

16A Radial 2.5mm - combi-boiler

32A Ring final 2.5mm - lounge sockets (5 x doubles) + understairs cupboard double socket (used to run some computer equipment)

32A Ring final 2.5mm - upstairs sockets (around 10 x doubles spread throught the bedrooms)

40A Radial 6mm - run to isolation switch for cooker/hob - 4mm runs from there to separate oven and hob.

I'd also add some more RCBOs:

6A Radial 1.5mm - "external" lights (wall mounted security lights + a light in the attached shed/store)

6A Radial 2.5mm - alarm system

32A Ring final 2.5mm - kitchen sockets (4 doubles + 1 single) + double socket in utility room for washing machine + double external socket

Notes:

My burglar alarm runs the smoke/heat alarms in the house, hence no separate mains smoke alarm circuit. It has a 24hour battery backup built in.

I'm wondering whether it'd be a good idea to use the last space to add a separate circuit for the fridge-freezer? Maybe 16A Radial in 2.5mm? Or I could just leave it free for future expansion.

Have I made any glaring errors? Is the MK consumer unit one to avoid? Any feedback would be much appreciated.

 

[deadshort]

Don't use MK ! Hager, or BG, If on a budget.

You don't need 2.5mm for your boiler or alarm
The separate circuit for the freezer is a good idea.
Install 2 single sockets instead of a double if you have a TD and WM in the same location.
If the external socket is fed from ring, add a DP switch which can isolate it if water gets in !

And always leave spare ways !

Regards,

DS

 

[ericmark]

The error is the LABC, you have a problem, if they will not accept your signature on the installation certificate, then you need to employ some one who's signature they will accept on an electrical installation condition report, likely they have a list of electrical firms they will accept the form from.

This means added cost, every time you want to switch on a section, which in real terms means you can't live in the house while doing the work. In real terms the LABC route is for electricians who are not scheme members, it was never designed for DIY.

 

[JohnW2]

The separate circuit for the freezer is a good idea.

Opinions vary. I wouldn't personally put a freezer on a dedicated circuit unless I had a (temperature-sensing) freezer alarm, particularly if the freezer circuit was RCD/RCBO protected.

Kind Regards, John

 

[EFLImpudence]

1mm² is more than adequate for 6A circuits.
4mm² 32A radial will likely be more appropriate for the kitchen - and possibly the other 'rings' (unless they are actually 'rings').

 

[ericmark]

Opinions vary. I wouldn't personally put a freezer on a dedicated circuit unless I had a (temperature-sensing) freezer alarm, particularly if the freezer circuit was RCD/RCBO protected.

Kind Regards, John

Ask one question, how often do you look at the freezer alls well light or other display? I rarely look, if my emergency light above stairs is lit, I note it straight away, and go and reset the RCD. Having an emergency torch on the freezer supply then yes you may notice, but lack of lights don't alert in the same way as a light coming on. I know on a power failure my freezer flashed the highest temperature it went to before supply was restored, until you open and close door. But that only works once power is restored.

 

[JohnW2]

Ask one question, how often do you look at the freezer alls well light or other display?

Exactly my point. Our main (chest) freezer is in the cellar, and it's not all that unusual for us not to look at it for a few days, by which time it might well be "too late". That's why I would have a freezer on a dedicated circuit, particularly if RCD/RCBO protected, only if I had a (battery operated - or, at least, battery backed-up) audible (in the house!) freezer alarm.

Similarly with 'dedicated' RCD/RCBO-protected alarm circuits (smoke or whatever). Again, I would want a battery (or battery backed-up) audible alarm to indicate power loss on such circuit(s).

Kind Regards, John

 

[crystal ball]

Ring finals ?? why not 20 amp radials?

 

[flameport]

Lights can both be 1.0mm
No point having the boiler on it's own, just add it to one of the other circuits. Same with the alarm.
A lounge and cupboard does not require a 32A circuit.
Neither do the sockets upstairs.
Cooker circuit oversized, 32A will be ample.
There may be a case for a 32A ring in the kitchen, but that could probably be altered to avoid one.

I'm wondering whether it'd be a good idea to use the last space to add a separate circuit for the fridge-freezer?

No, complete waste of time. No benefit at all. Unknown why so many people suggest such a thing.

 

[JohnW2]

Ring finals ?? why not 20 amp radials?

I have absolutely no problems with radials but, as I often say, I have my reservations about 20A circuits, particularly when serving areas like kitchens, utility rooms and workshops etc. After all, one can theoretically 'overload' such a circuit with just what can be plugged into one double socket.

4mm²/32A radials are fine in such situations.

Kind Regards, John

 

[securespark]

Having suffered twice in my life with an rcd trip causing defrosting while away, I would always put them on a separate 20A radial.

 

[JohnW2]

Having suffered twice in my life with an rcd trip causing defrosting while away, I would always put them on a separate 20A radial.

I imagine that makes you pretty unlucky. However, if (as seemingly will soon be required by regs, unless you hard-wire the freezer) that dedicated circuit is RCD protected then, if you're one of those people who suffers from 'nuisance trips' then, as I said, I would only put it on a dedicated circuit if I had a freezer alarm (or, I suppose, a power-failure alarm, but that won't necessarily detect a freezer fault). Of course, even that won't help if the house is empty, but I don't think there's much one can do about that!

For what it's worth, in nearly 50 years of living with freezers, the only 'spoilt food' I've ever personally experienced/witnessed was (and just the once) due to a freezer failure that did not result in any protective device operating.

Kind Regards, John

 

[winston1]

Ring finals ?? why not 20 amp radials?

Nothing wrong with ring finals. They have been around 70 odd years and proved themselves successful.

With 20 amp radials you need twice as many RCBOs with no real benefit.

 

[winston1]

I imagine that makes you pretty unlucky. However, if (as seemingly will soon be required by regs, unless you hard-wire the freezer) that dedicated circuit is RCD protected then, if you're one of those people who suffers from 'nuisance trips' then, as I said, I would only put it on a dedicated circuit if I had a freezer alarm

Do it now then before the new regs. Because they won't be retrospective.

 

[JohnD]

Nothing wrong with ring finals.

I've always liked RFCs, but even I can't deny that in the event of a break in one, two, or even three conductors, the user will be unaware of any problem in daily use, and even if he pokes a DIY circuit tester into a socket.

This will cause some or all of the circuit to be a radial fused at 32A but run in 2.5mm cable.