RCD's, RCBO's, RCCD's

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Read an interesting post here about RCD's v RCBO's but it was so technical it went way over my head.

When would you only install a consumer unit with RCD's and why?

When would you only install a consumer unit with RCBO's and why?

When would you only install a consumer unit with RCCD's and why?

Can you get a consumer unit with 2 or 3 of the above and would it provide better protection rather than just one option?

I have bought an MK consumer unit with just RCD's. Should I have gone for one of the others? Ideally I am looking for the best protection against all of the risks that I am likely to face in a domestic situation.

Is this an easy question to answer or have I just asked too many questions?
 
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Consumer units with two RCDs and numerous MCBs are usually installed because they are significantly cheaper than other options.

A consumer unit with all RCBOs (combined RCD and MCB) would be installed where the additional cost of doing so was not an issue.

The advantages of all RCBOs is that in the event of a fault, only one circuit is affected, rather than a whole set of circuits.
 
What made you go out and buy a unit without researching first and seeing how little you know do you think you have enough competence to carry out the change ?
 
What made you go out and buy a unit without researching first and seeing how little you know do you think you have enough competence to carry out the change ?
If I've bought the wrong unit I will take it back and buy the right one. I definately won't be doing the work. I have a really old consumer unit with MCB's and I know it is not up to scratch and possibly wrongly thought that RCD's would do the job.

Ideally now that I have asked the question I would like advice about what would be my best option.

Having read a bit more am I correct in thinking that an RCBO is an MCB with an RCD built in so that if a circuit goes it will just trip that RCBO and not the whole board covered by the RCD?

Is there a preferred make? MK, Volex, Crabtree?
 
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MCB - miniature circuit breaker that acts like a fuse
RCD - redidual current breaker
RCBO - MCB and RCD in one
RCCB - RCD which can work in conjunction with one or more MCBs

Split load board - one side without RCCB (generally called an RCD)
one side with RCD
RCBOs can be used on non-protected side as required.

Dual RCD board
one side protected by one RCD
other side protected by another RCD

High integrity board
some unprotected ways for MCBs or RCBOs as required
some ways protected by one RCD
some ways protected by another RCD

Standard board
you can fit either MCBs or RCBOs as required
 
It would be helpful to know what circuits you have, and how your wiring has been done (concealed behind plaster I would guess).

I would say generally the high integrity board is the best option as you will save money on expensive RCBOs, and the 'unprotected' ways (which you can fit RCBOs into) can prove to be versatile for any circuit that has specific needs. ie something like an alarm circuit or a freezer supply.
The idea is that if a fault somewhere trips some of the power in the house, then this circuit should remain on.

Until you tell us a bit more about your circuits, then we can't give you much of an answer.
 
Until you tell us a bit more about your circuits, then we can't give you much of an answer.

I don't have any dedicated circuits like alarm or freezer.

The majority of the wiring is in plaster although there is a real mixture, behind plasterboard, under floors. Seems pretty standard.

At the moment got 8 x MCB's and 100A main switch made up of

GF Power 32A
FF Power 32A

GF Lighting 6A
FF Lighting 6A

Shed 32A (which has its own CU with two MCB's 1 x Power and 1 x Lights which keeps tripping)

Cooker 45A
Central Heating 20A
1 x Blank
 
This is what I have bought. Would I be better off taking it back or wouldit be cheaper to buy individual RCBO's for the circuits I wanted to protect individually?

MK Sentry Dual RCD Board with 2 RCDs & 10 MCBs
16 module, 10 way, populated Dual RCD Consumer Unit.

* Configured as a Dual RCD Board
* Can also be Configured as a High Integrity Board to Accept RCBO's
* Backed Out & Captive Combihead Screws
* No Visible Fixing Screws
* MK Technical Helpline Available

1 x 16 module consumer unit, 1 x 100A switch, 2 x 63A, 30mA RCD and 10MCB.
 
Until you tell us a bit more about your circuits, then we can't give you much of an answer.

I don't have any dedicated circuits like alarm or freezer.

The majority of the wiring is in plaster although there is a real mixture, behind plasterboard, under floors. Seems pretty standard.

At the moment got 8 x MCB's and 100A main switch made up of

GF Power 32A
FF Power 32A

GF Lighting 6A
FF Lighting 6A

Shed 32A (which has its own CU with two MCB's 1 x Power and 1 x Lights which keeps tripping)

Cooker 45A
Central Heating 20A
1 x Blank

Has the shed currently got an RCD?
Why does it trip?
Would be sensible to find out why and repair ir.

A high integrity board could accomodate the shed on the unprotected side. You could fit an RCBO here, or possibly an RCD in the shed.
A neutral-earth fault on the shed would prevent other circuits tripping out.
 
Are you planning on installing this yourself??
I don't have any intention of installing this myself. I will need to get someone competent in. Is this notifiable?

Has the shed currently got an RCD?
Why does it trip?
Would be sensible to find out why and repair ir.

A high integrity board could accomodate the shed on the unprotected side. You could fit an RCBO here, or possibly an RCD in the shed.
A neutral-earth fault on the shed would prevent other circuits tripping out.
No RCD on shed, just MCB's
Don't know why it trips lthough I was going to get this looked at at the same time as the new CU being fitted.

What is a High Integrity Board?
 
This is notifiable work.
If you actually find an electrician willing to fit the consumer unit you have purchased, please don't use them.

Your best option is to return the board you have purchased, and get some quotes from electricians to supply and install a new consumer unit.
 
In this country most consumer units have single width RBCO's which only switch the line feed and not the neutral so they can only really be used with a TN system.

The quality and type of RCD can make a huge difference and just the RCD can vary in price from a few pounds to around £350 for auto resetting and testing type. Some also give a warning of impending problems with LED's and as with most things you get what you pay for.

With a house where there has been no RCD protection it is likely there will be some faults which have gone un-detected for years and one of the biggest problems when consumer units are changed is to find out what is causing the problem.

The more RCD's that are used the easier it is to fault find. And if one can use RCBO's then that is the better option. At least with that system if a circuit is a problem then a MCB can be used until the problem is cured. With the twin RCD unit there is no real way to revert back to non RCD while the faults are found.

Forgetting the law and Part P there are still a lot of problems in fitting a consumer unit not least how to isolate while you fit it. But electricians have a set of meters that can send 500v into the wires to find faults so can normally isolate the problems. The DIY guy is normally at best armed with a multi-meter which is unlikely to find many of the faults. The electrician will normally have a favourite make of consumer unit and will carry spares for that make and not only have a RCD tester but can test by substitution. To buy the consumer unit and then present it to an electrician means he may not have spares to hand to be able to fault find using all options so one could find it costs more in his time to get everything up and running. Also of course if there were to be any recall for anything you had bought you would not likely be informed. So it is better to let the electrician doing the job select the consumer unit.

If we consider DIY then not only will you need to pay the LABC £100+ to register the work but even to hire the test equipment will cost around £80 per week and to buy around £750. In real terms the only people who would DIY fitting a consumer unit would be electricians who have not become a member of a scheme and not Joe public.

As I have said the meters use 500v to test with and also do live tests which if not done correctly could present danger so even if one did have access to the testers then unless trained in their use you still would be better not to DIY.

Years ago there was an attitude "I know what I am doing I don't need to test" but there were also quite a number of accidents as a result. Not always due to guy doing job but due to mistakes of those who went before him. Thankfully those days are behind us and all electricians not only test their work but also produce a record of their results. This protects them so if some one latter fiddles with their work they can show there have been changes. One hopes one never has to refer back to test results but soon the Part P regulations will have been in for 10 years and then since all installations should be tested every 10 years you will need to be able to produce results for any domestic installation and lack of these results will place the blame for any accident on the owner.
 

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