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Topic Title: Siemens consumer unit
Topic Summary:
Created On: 30 September 2017 01:18 PM
Status: Read Only
Linear : Threading : Single : Branch
 Siemens consumer unit   - Clintrose1 - 30 September 2017 01:18 PM  
 Siemens consumer unit   - SKElectrical - 01 October 2017 09:22 PM  
 Siemens consumer unit   - Electutor - 02 October 2017 07:35 PM  
 Siemens consumer unit   - Clintrose1 - 07 October 2017 02:14 PM  
 Siemens consumer unit   - Clintrose1 - 07 October 2017 03:55 PM  
 Siemens consumer unit   - geoffsd - 07 October 2017 04:40 PM  
 Siemens consumer unit   - Clintrose1 - 07 October 2017 05:13 PM  
 Siemens consumer unit   - geoffsd - 07 October 2017 05:21 PM  
 Siemens consumer unit   - Clintrose1 - 07 October 2017 06:20 PM  
 Siemens consumer unit   - geoffsd - 07 October 2017 07:02 PM  
 Siemens consumer unit   - WiredScience - 07 October 2017 08:44 PM  
 Siemens consumer unit   - Clintrose1 - 08 October 2017 10:59 AM  
 Siemens consumer unit   - OlympusMons - 08 October 2017 11:21 AM  
 Siemens consumer unit   - Clintrose1 - 08 October 2017 03:04 PM  
 Siemens consumer unit   - geoffsd - 08 October 2017 04:03 PM  
 Siemens consumer unit   - Clintrose1 - 08 October 2017 04:39 PM  
 Siemens consumer unit   - geoffsd - 08 October 2017 04:44 PM  
 Siemens consumer unit   - AJJewsbury - 08 October 2017 06:46 PM  
 Siemens consumer unit   - geoffsd - 08 October 2017 07:22 PM  
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 30 September 2017 01:18 PM
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Clintrose1

Posts: 46
Joined: 10 November 2016

I am fitting a new induction hob and it requires new 6mm feed, my problems lies with the consumer unit. It is about 30 year old, Siemens model. The breakers which are in the board are the Siemens 5SX21 models. It isn't rcd protected and to save money and time by not installing a mini enclosure with a rcd next to it for my induction. Does anyone know of a rcbo which I can fit into these boards?

Thanks
 01 October 2017 09:22 PM
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SKElectrical

Posts: 1124
Joined: 01 February 2009

No. Take one out and to local wholesaler. I'm certain that a haer DSmith Proteus will fit.
Proteus do a nice compact RCBO which helps in small CUs.
 02 October 2017 07:35 PM
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Electutor

Posts: 37
Joined: 24 October 2016

Yes there is an rcbo for the Siemens 5SX21 but it takes up two ways of your consumer unit. These guys may have them http://circuitbreakerspecialis...o.uk/index.php?cPath=8
 07 October 2017 02:14 PM
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Clintrose1

Posts: 46
Joined: 10 November 2016

Just an update, I have bought a RCBO which takes 2 wAys in the board, Siemens 5 SU 3 RCBO.. It arrived today and I couldn't help but notice one terminal on the top of rcbo and the 2 on the bottom; which I believe is for the load side!! How the hell is this going to work? With the busbar being at the bottom of a consumer unit! Have to complete this job on Monday and this has put a spanner in everything .
 07 October 2017 03:55 PM
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Clintrose1

Posts: 46
Joined: 10 November 2016

I'm thinking linking from the main switch to have this work? Would this need a 25mm tail? It would a 6mm be okay for this with it only being a 32A rcbo?

Edited: 07 October 2017 at 07:53 PM by Clintrose1
 07 October 2017 04:40 PM
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geoffsd

Posts: 1786
Joined: 15 June 2010

Originally posted by: Clintrose1

I'm thinking linking from the main switch to have this work? Would this need a 25mm tail? It would a 6mm be okay for this with it only being a 32A rcbo?

4 sq.mm. would be alright for 32A if the PSCC can be handled - but I would use 10 sq.mm. as it will contact better.
 07 October 2017 05:13 PM
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Clintrose1

Posts: 46
Joined: 10 November 2016

Thanks for the reply Geoff, can I just use brown conductor from 10mm t&e? Or do I need something better?
 07 October 2017 05:21 PM
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geoffsd

Posts: 1786
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That will be fine inside the CU.
 07 October 2017 06:20 PM
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Clintrose1

Posts: 46
Joined: 10 November 2016

Great. Do you know of any alternative rcbo which would fit in this kind of board? Something I can pick up from a wholesale on Monday?
 07 October 2017 07:02 PM
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geoffsd

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Not off hand, sorry.
 07 October 2017 08:44 PM
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WiredScience

Posts: 323
Joined: 25 January 2012

Originally posted by: Clintrose1

I am fitting a new induction hob and it requires new 6mm feed, my problems lies with the consumer unit. It is about 30 year old, Siemens model. The breakers which are in the board are the Siemens 5SX21 models. It isn't rcd protected and to save money and time by not installing a mini enclosure with a rcd next to it for my induction. Does anyone know of a rcbo which I can fit into these boards?



Thanks


By the time you've waited for ebay (or wherever) to deliver a second hand RCBO of unknown provenance (do you have a suitable RCD tester?), you could have installed a brand new RCD in a separate enclosure.

Buying from the DIYer's favourite place that's sells screws and fixings it would cost less than £30 for the bits. And you get a warranty.
 08 October 2017 10:59 AM
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Clintrose1

Posts: 46
Joined: 10 November 2016

Yeah I've now decided to opt for a mini cu, I can pick one up for £29.99, 40A rcd for main switch. Along with 32A mcb. Now am I okay to take a link from the main switch in the main CU? To this mini cu which is going right next to this. If allowed, what size would you recommend?
 08 October 2017 11:21 AM
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OlympusMons

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Joined: 05 February 2016

Why do you need RCD protection for a hob?
 08 October 2017 03:04 PM
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Clintrose1

Posts: 46
Joined: 10 November 2016

I believe everything is to be RCD protected?

Can you please shed a light on me of what is a must for RCD protection in domestic and what you can get away with not having on an RCD. Is it just sockets? What about hobs? Cookers? Lights?

I apologise if this comes across like a rookie question. I just want to be clear, as I normally try get everything I install rcd protection.. Which like in this case can cause problems for what should be little jobs
 08 October 2017 04:03 PM
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geoffsd

Posts: 1786
Joined: 15 June 2010

There are plans to have every circuit protected by RCDs.

Appliances don't require RCD protection although it obviously works out the same.


At the moment, if the circuit is not new (or is new but otherwise protected) then you don't have to fit an RCD, except for sockets (unless you do a risk assessment).
 08 October 2017 04:39 PM
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Clintrose1

Posts: 46
Joined: 10 November 2016

Cheers for the reply Geoff .

It's good to know, I've spent the best part of my weekend trying for an rcbo/rcd protection when I can get away with it. If I installed a cable which is 50mm depth in wall, does it still need additional protection?

Clint
 08 October 2017 04:44 PM
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geoffsd

Posts: 1786
Joined: 15 June 2010

Less than 50mm. and unprotected by earthed sleeving/conduit, it does.

That doesn't mean go deeper than 50mm. as that will contravene the Building Regulations in 'normal' walls.
 08 October 2017 06:46 PM
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AJJewsbury

Posts: 16108
Joined: 13 August 2003

There are plans to have every circuit protected by RCDs.

I hope not - there will be a lot of very looking silly distribution circuits if there are. The 18th DPC did mention adding domestic lighting circuits to the list things that need 30mA RCD protection (probably no bad idea given the accessible live parts on BC and ES lampholders) but that's still a long way from even every final circuit - cookers, immersion heaters, alarm panels, high earth leakage IT equipment and so on (soft sheathed cabled concealed unprotected in walls notwithstanding).

Presuming the OP's using T&E chased into a wall in the normal manner, and is going for an extra enclosure anyway, I'd suggest keeping it simple and just put an RCCB in the extra box - fed from the MCB in the original CU. That way you've no worries about small conductors protected only by the DNO's fuse or confusion from multiple main switches.

- Andy.
 08 October 2017 07:22 PM
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geoffsd

Posts: 1786
Joined: 15 June 2010

I'm glad to stand corrected if it is not the case. I only meant NEW work, of course.
I do tend to forget about commercial work when replying about domestic work.

However, if there are no plans for all RCD circuits in dwellings, why the proposal for the removal of excepted sockets and why introduce it for lighting circuits?
Should people not be taught not to poke their fingers in lamp holders?

I'm surprised stairs are still allowed, aren't lavatories dangerous?
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