Need some advice and to introduce myself

[NellyManjaro]

Hey everyone,

I'm new to this forum so don't know what to do exactly but I'm sure I'll figure it out and help people where I can.

As for now it is me that needs the advice and it may sound a bit stupid...

Now doing a CU upgrade in an old terraced so if my training was correct I need to do an electrical installation certificate?? Now it's a refurb so I've been in and done done work on sockets etc for kitchen and also they want a gas hob and a plumbed in thermostatic shower (something the company i work for do) So I've disconnected the 6mm cables that used to supply the existing electrical ones and pulled the cables out.

What I am left with is a lighting circuit and a ring circuit... am I right in thinking that I can install a garage unit?? With a 63A main RCD switch??

I've never actually come across this option before hence my uncertainty

Any help would be greatly appreciated



Also while I'm asking I've just been to a job part way through writing this with mcb trippig that has a 10 way split RCD unit with just 1 lighting circuit and 1 Ring main BUT there is an electric hob on a plug top... where the plug is welded to the socket. I'm 6ft 4 and pretty damn strong but it will not budge even for me lol so going to have to run a new 6mm cable in for that one again something I've never seen... told many people when they've asked me I've told them they need a separate circuit for it etc so never actually had one plugged in before

Sorry for waffling... many thanks

 

[ferg]

You could fit a garage unit but that would not leave any extra ways for future works.

I'd be tempted to fit a 6 outgoing way main switch board and use RCBO's.

Yes you need to issue an EIC and notify.

Separate circuit for the hob.

EIC for that too.

 

[NellyManjaro]

Thank you for the quick reply

I did consider this but the available space I have to work with is very limited so smallest unit possible is what I think I will need to go for.

But I can issue an EIC for this... as in there is nothing against me using this garage unit as the CU for the house?? I can't find anything to say I can't it just has to be RCD protected right?? So I can sign it off without any problems??

 

[ferg]

Nothing to stop you using it just because it's called a garage unit.

 

[I2C]

Hi there and welcome to the forum!

Having a separate distribution board in the garage is common, in fact I did a job recently as part of a full re-wire to install one. The hob is also common but a little different so I'll explain both below:

Garage DB (Distribution Board)
- I'd install an RCBO in the main-incoming CU to protect against both short-circuit/over-currents & earth-faults regarding the supply-cable from the main-incoming CU to the garage DB.
- The RCBO's current-rating should be sized for the current-capacity of the supply cable to the garage DB
- The RCBO should also have adequate discrimination regarding earth-faults, compared to the RCD/RCBO installed inside the garage DB under (531.2.9, page 142, BS7671).
- There should be an RCD/RCBO rated 30mA for additional protection in the Garage DB (411.3.3, Page 56, Bs7671).
- When sizing the conductor between the garage DB and main-incoming CU, make sure the voltage-drop is acceptable (Appendix 4, page 328, BS7671)
- A separate electrical-installation-certificate should be provided for the Garage DB.

Kitchen Hob:
- Find out it's design current or calculate it using the power-consumption as advised by the manufacturer.
- If the Ib (design current) is less than 13A and supplied with a plug, check the fuse is adequate and install a socket with a FCU (fused-connection unit) for proper isolation.
- If the Ib is more than 13A and/or without a plug, use a suitably rated switched-FCU for connection.
- Often, the cable-CSA is large for cookers and hobs, given their large power-consumption and amount of time they are used for. The manufacturer often recommends a CSA so double-check the manual.

 

[Wilko]

Hi NM !
Personally I would go one up from a garage unit.

 

[Octopus]

Forgive me if I've misread this BUT are you saying that you have a 10 way CU but only 2 circuits?

And you want to replace said 10 way unit with a 2 way CU?

If so this will not meet the regs minimising inconvienience, nor does it allow for future expansion of the installation.

So a 5 way unit, with RCBO's for the existing circuits and some blanks is the way to go IMHO

Plus you need to ensure earthing and bonding is up to spec

Then

EIC
Part P notification

 

[NellyManjaro]

No I have a 4 way unit with 're wireable fuses lights sockets shower cooker... but the shower and cooker cables have been taken out because they want gas hob and thermostatic shower (great water pressure and new combi boiler installed) so I'm left with 2 circuits... I have very limited space... the old unit was very tight and new units are generally bigger with the rcds etc requires more space so what I wanted to know was can I upgrade that to a garage unit? I know it doesn't allow for further installation something I will always make sure to leave for people but this time I have no space... Will get a garage unit in but nothing else hence the question.

Basically is there anything stopping me installing 1... it's the only CU in the house no garage etc small terraced house so is it acceptable to install 63A RCD garage unit as the CU effectively and will I be able to sign it off with no issues??

Many thanks for the replys guys much appreciated

 

[Octopus]

5 way rcbo board then

 

[telectrix]

as above ^^^^^. a RCBO board takes up far less width because you don't have those 2 module RCDs taking up space. i did a 8 way this week. only 11" wide. as opposed to 14" for a dual RCD board.
(yes murdoch, it was a Control Gear, following your recommend. 6 ways used and 2 spare).

 

[NellyManjaro]

If I can change the location of the CU say if the customer is fine with taller boxing... is it better to get say an 8 way dual RCD or the rcbo boards?? Never actually used the rcbos before

 

[NellyManjaro]

They are open to moving the unit up a bit to allow more space as long as it's boxed in which it will be.

I mentioned the rcbo board and was honest saying I've never fitted them before but alot of people won't fit anything else but alot of people don't fit them etc either or is up to regs etc that sort of stuff.

So what are the pros and cons of rcbo boards to the usual dual RCD ones?? They seem to be more expensive... and as I recall to my college days they effectively do the same job as an RCD but only trip the 1 circuit rather than the whole side the RCD is protecting?? So when it says you have to have RCD protection on sockets etc and RCBO is just that?? I'm just a little confused as never done one but remember you need to disconnect flying leads for IR test.... sounds like I have free reign to choose whichever I want so which would you guys fit if given the choice?? There's only a lighting and a ring main now anyway

Thanks in advance

 

[SJD]

Sort of repeating what has already been said:

You shouldn't put both circuits on the one RCD, and you don't have space for a board with 2 RCDs. This rules out a so-called "garage" CU.

Therefore fit a board with a main switch and 2 RCBOs. They are not that expensive, check RCBO prices before deciding on the brand.

And leave at least 1 and preferably 2 or more spare ways.

So what Murdoch said some posts ago is probably your answer, it if will fit in. Again, check brands, some housings are wider than others for the same number of ways.

 

[NellyManjaro]

Yes but they said I can move the unit up meaning I can get a split board anyway so it will fit in if I move the unit... what I want to know is given the choice what would other people use... I've never considered rcbos because last time I looked I was looking at around 100 extra for about 4/5 circuits i think it was which is the only time ive looked because in my eyes it wasn't worth the extra

Bare in mind I have 2 circuits so a split board will have them on separate rcds anyway

 

[kingeri]

I don't fit split load boards any more, never liked them. In this case, you're talking about only two circuits, so two RCBOs won't break the bank.

 

[telectrix]

Yes but they said I can move the unit up meaning I can get a split board anyway so it will fit in if I move the unit... what I want to know is given the choice what would other people use... I've never considered rcbos because last time I looked I was looking at around 100 extra for about 4/5 circuits i think it was which is the only time ive looked because in my eyes it wasn't worth the extra

Bare in mind I have 2 circuits so a split board will have them on separate rcds anyway

Control,Gear 8 way RCBO board c/w main switch and 6 RCBOs is £109 inc. VAT. no functional earth leads with this model.a doddle to fit.loads of space above RCBOs.no brainer.

only fault i could see was no round K/Os, you need to drill them if required.

 

[NellyManjaro]

So 1 last question all be it a stupid 1 to you guys... do the rcbo boards need any RCD protection?? Are they classed as RCD in themselves?? I really know naff all about rcbos sorry

 

[telectrix]

a RCBO is a MCB and RCD combined in 1 MCB sized unit, so no additional RCD is required. the only drawback is that the RCD part is not double pole, so will not isolate a N-E fault.

 

[telectrix]