New CU

bignev · 21 Mar 2004

Hi guys,

please can you help I want to replace my consumer unit. First is this a DIY job (even if I get a real sparky to check it over), if so can you talk me through it. Second I just read in the forum about RCD and RCBO can you explain the difference. I was just about to get a split load board from my local CEF and now I'm not sure what to get. The existing CU is
Cooker
shower
alarm
sockets
sockets
lighting
lighting

I want to put a sockets and lighting in the garage, would you recommend a separate box again RCD RCBO?
Thanks

breezer · 21 Mar 2004

its not a job for the diy person,

rcd is here

mcb is to protect from overload current (short circuit, too much load, etc)

rcbo is if you like, a cross between the two

Millennium_Boy · 21 Mar 2004

Specify either a WYLEX or Crabtree or a MK unit, to whoever does the replacement work - They are amongst the best makes of unit available today.

Big_Spark · 21 Mar 2004

Millennium_Boy said:
Specify either a WYLEX or Crabtree or a MK unit, to whoever does the replacement work - They are amongst the best makes of unit available today.

MK and Crabtree I agree with, but Wylex!! They are pants.

Apart from the first two, the best boards and breakers about are Merlin-Gerin, Hager and MEM.

Bignev, below id the way you want to lay the board out. It is always best to split the kitchen ring from the normal downstairs sockets as the Kitchen needs to be RCBO protected, but your lounge and hallway do not.

Split load boards are old news.

Main Switch: 100A Double Pole Isolator
Cooker RCBO 30mA 40 or 45A...dependant on cooker rating
shower RCBO 30mA 40,45 or 50A dependant on rating and cable size
Kitchren sockets RCBO 100mA 32A
Down sockets Type B MCB 32A
Upstairs Sockets Type B MCB 32A
lighting Type B MCB 6A
lighting Type B MCB 6A
alarm Type B MCB 6A (3A if you can get one)

If you do not have extensive knowledge of Electrical systems and circuits I would not advise you to try this, it would be better to get in a contractor and specify the Consumer unit you want.

Personally, as it is domestic, you would be making a good choice choosing MK Sentry Range..for a start all their kit has a 20 year guarantee.

Yes they are slightly more expensive that the others, with perhaps the exception of Merlin-Gerin, but you get what you pay for.

If you leave it at to the contractor, you could end up with a Wylex, Volex or Square D piece of cr*p.

ban-all-sheds · 21 Mar 2004

You forgot Contactum....

Big_Spark · 21 Mar 2004

ban-all-sheds said:
You forgot Contactum....

I didn't forget, I ignored the rubbish. (If that comment was is response to my post anyway

)

andemz · 22 Mar 2004

FWL_Engineer, you have mentioned in your above post that you would put the Kitchren sockets on RCBO. I then went and had a look at some of the crabtree type A 13 way £109, Type A 9 way crabtree for £79 and the MK insulated 9 way for £59.99. I guess it's a case of what you pay is what you get.

I then saw an RCBO as a stand alone and it didn't state that the consumer unit came with RCBO, am i then correct in saying that an RCBO as to be added to consumer units to protect the kitchen sockets, or have i totally misunderstood it and RCBO's are included on consumer units.

What's the score?

bignev · 22 Mar 2004

Thanks for the quick reply guys, but can you clarify a few points.
FWL you say split the kitchen from the downstairs ring, why + freezer is in kitchen so this would cause problem. Why no RCBO on the rings. I've just read some regs that state all sockets capable of running appliances outside should be protected!!! Please don't think i'm questioning your advice just want to understand more about this subject. I now understand the use of RCBO and will use them instead of a split load board.
Lastly (for now) went into my local Edmondsons. I asked for a price on a Hager board. The guy said Wylex were the dogs B*ll%cks and as good as the Hager board that he also sold. Quote "they are good enough for the council and the MOD" I will be getting a contractor to fit which ever one I get.

ban-all-sheds · 22 Mar 2004

An RCBO protects 1 circuit - it combines the functions of an RCD and an MCB. If you were looking at products that said they were N-way, where N>1, then that would have been a CU, not an RCBO.

FWL will wax lyrical about the advantages of using RCBOs in terms of discrimination and fine grained protection, and he is right, but his solution comes at a high price. Most people are perfectly satisfied with a split-load board, i.e. some circuits protected by an RCD, some not.

And yes, you tend to get what you pay for.

ban-all-sheds · 22 Mar 2004

bignev said:
Thanks for the quick reply guys, but can you clarify a few points.
FWL you say split the kitchen from the downstairs ring, why

Good practice because of the number of heavy loads on a kitchen circuit - WM/TD/DW/Kettle/Toaster. If you have a utility room you should consider having that on its own circuit too...

+ freezer is in kitchen so this would cause problem.

I would advise not having the F/F on an RCD or RCBO protected circuit.

Why no RCBO on the rings. I've just read some regs that state all sockets capable of running appliances outside should be protected!!!

They should - not sure I'm happy with the advice to have the downstairs sockets not on RCD/RCBO...

Please don't think i'm questioning your advice just want to understand more about this subject. I now understand the use of RCBO and will use them instead of a split load board.

Expensive...

Lastly (for now) went into my local Edmondsons. I asked for a price on a Hager board. The guy said Wylex were the dogs B*ll%cks and as good as the Hager board that he also sold. Quote "they are good enough for the council and the MOD"

Both organisations are of course well known to anybody who sells to them as having a money-no-object approach to purchasing

I will be getting a contractor to fit which ever one I get.

Let him supply it then.

BR · 22 Mar 2004

FWL_Engineer said:
It is always best to split the kitchen ring from the normal downstairs sockets as the Kitchen needs to be RCBO protected, but your lounge and hallway do not.

Split load boards are old news.

Main Switch: 100A Double Pole Isolator
Cooker RCBO 30mA 40 or 45A...dependant on cooker rating
shower RCBO 30mA 40,45 or 50A dependant on rating and cable size
Kitchren sockets RCBO 100mA 32A
Down sockets Type B MCB 32A
Upstairs Sockets Type B MCB 32A
lighting Type B MCB 6A
lighting Type B MCB 6A
alarm Type B MCB 6A (3A if you can get one)

I agree with splitting the kitchen ring from the remainder of the house, and as ban said would add an extra circuit for utility (and also sitting room). However for somebody who quotes 16th edition to the letter, i am suprised at FWL's comments in respect to RCD protecting sockets.

Kitchen sockets should be protected by a 30Ma RCD (not 100Ma)
All other sockets (with the possible exception of the freezer socket) should be RCD protected

As you can imagine, using RCBO's here (although preferable to a split load board) is going to become very expensive.
Personally I feel a split load board is the way to go here, but if you are determined to use RCBO's you could omit the Cooker circuit from RCD protection as (in my opinion) it is not really required

bignev · 22 Mar 2004

ban-all-sheds said:
Good practice because of the number of heavy loads on a kitchen circuit - WM/TD/DW/Kettle/Toaster. If you have a utility room you should consider having that on its own circuit too...

Indeed I do have a utility room. So is there an easy way to create its own ring, eg separate the two from the main downstairs ring then use junction boxes to create their own send and return cable (this may not be the correct term but i'm sure you know what I mean)

As to let the contractor supply unit. I have trade account for self build extension so get the CU at a good price

Oh yeh and its just taken me all this time to figure out how to do the "quote" thing

breezer · 22 Mar 2004

bignev said:
Oh yeh and its just taken me all this time to figure out how to do the "quote" thing

you may also find this useful

Big_Spark · 22 Mar 2004

BR said:
I agree with splitting the kitchen ring from the remainder of the house, and as ban said would add an extra circuit for utility (and also sitting room). However for somebody who quotes 16th edition to the letter, i am suprised at FWL's comments in respect to RCD protecting sockets.

Kitchen sockets should be protected by a 30Ma RCD (not 100Ma)
All other sockets (with the possible exception of the freezer socket) should be RCD protected

As you can imagine, using RCBO's here (although preferable to a split load board) is going to become very expensive.
Personally I feel a split load board is the way to go here, but if you are determined to use RCBO's you could omit the Cooker circuit from RCD protection as (in my opinion) it is not really required

BR..PLEASE quote the regulation that states all sockets need to be protected by an RCD?? Oh you can't, there isn't one.

As for 30mA in the kitchen...hello, harmonics on the neutral from inductive loads will likely trip a 30mA RCBO, remember that RCBO's are DC sensing and they will trip if you have enough inductive appliances in your kitchen..such as electronically controlled washers, dryers, fridges and freezers.

You bang on about sockets being RCD protected then you make that comment about not protecting what is likely the largest drawing device in the house..the cooker.

Did you know that 80% of electric shocks in domestic premises arise from Cookers and hobs!!

bignev · 22 Mar 2004

Thanks breezer
_______________________________________________________

Sorry to interrupt the debate chaps but i'm now confused again. I understand the theory in splitting the kitchen, but RCD/RCBO on the downstairs or upstairs ring yes/no and WHY.

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