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Discuss RCD RCBO over current in the Electrical Forum area at ElectriciansForums.net

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Hi,

I know the basic differences between MCB, RCD and RCBO.

I was wandering what happens to a RCD if the current reaches the RCD's limit?
Why do RCDs have got ampere rating if they don't protect against over current?

In case of RCBO, how do I know at how much ampere they shut down?
Is it the ampere rating or is it the Short circuit level/Breaking Capacity?

I am planning on buying a new consumer unit or ask somebody to build a custom one and have it installed by an electrician.

If I buy/have build one that doesn't have MCBs but RCBOs only do I need RCD as well?

I know MCB + RCD could be cheaper but I don't mind spening some extra money if the result is better. Is it better?
 
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davesparks

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Mentor
Arms
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You need to speak to the electrician who will be doing the job, they will be able to assess the existing installation then discuss the options and advise of the best consumer unit to have fitted.

An RCD has A current rating which is the maximum it is designed to carry and switch safely, this is effectively the same as the current rating for any switch, it just tells you the normal working current it is designed for.
 

Wilko

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Arms
Esteemed
The RCD will have a "safe for use" certified current rating, like 80A say. If current greater than 80A is passed through the device it may not operate as intended or may be damaged internally due to conductor size or insufficient switching capacity.
 
D

Deleted member 26818

It’s quite simple really.
Light switches are rated at 10A and the light circuit is protected by a 6A MCB.
Socket-outlets are rated at 20A - 26A and the socket circuit is protected by a 32A MCB.
 

GBDamo

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Supporter
Briefly, RCBO offer dual protection, Overcurrent (or Overload) Protection offered by an MCB or fuse and Additional Protection against Earth faults offered by an RCD.

Stone Age option.

MCB range in price from £3.00 - £10.00 depending on brand and supplier, will need one or two RCDs at £20-£50 and a mains switch at £10-£30.However a pre-populated split consumer unit(CU) with ten MCBs and Two RCDs should cost between £100 -£150 depending on brand.

Hager VML916RKO 16 Way Fully Loaded Dual 100 amp RCD Metal Consumer Unit - https://www.consumerunitworld.co.uk/hager-vml916curk-16-way-high-integrity-fully-loaded-dual-100amp-rcd-metal-consumer-unit-3567-p.asp

Welcome to the 21st century option.

RCBOs range in price from £15.00 - £50.00 depending on brand and supplier and will need a mains switch at £10-£30. These don't tend to come pre-populated but the CU below is £30.00.

18th Edition Hager 10 Way RCBO Consumer Unit VML110. - https://www.consumerunitworld.co.uk/hager-vml110-10-way-rcbo-metal-consumer-unit-1796-p.asp

Hager ADA310G Small RCBO B Type 10 Amp 30mA 6kA Din Rail Mount Consumer Units - https://www.consumerunitworld.co.uk/hager-ada310g-small-rcbo-b-type-10-amp-30ma-6ka-3115-p.asp

So to build a ten RCBOs CU will set yo back £280.00 ish.

There are other considerations that your electrician will need to consider such as the requirement for SPDs and/or AFDDs (cop out) but this should give you an idea of where to start.
 
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