New Consumer Unit versus Plug In MCB's?

[macman81]

My mum has a 1960's fusebox (don't think they were called consumer units back then). Last summer she managed to cut her power cable while mowing the lawn (she survived)...but it got me thinking about the overall safety of the system. I am thinking of either buying some plug in MCB's to fit onto the existing board, or should I get it replaced with a modern consumer unit with built in MCB's? Obviously the latter will cost much more, but from the safety and cut-out aspect, are the plug ins as good?
The rest of the system does not seem too bad, as it has been renewed in part over the years, and the board is not overloaded with lots of modern appliances, so it's the speed of the cut out should something go wrong that concerns me.

 

[Adam_151]

A MCB provides overcurrent protection a like a fuse does, granted it does it much better than the old semi enclosed re-wireable fuses and is resetable, but essentially it does the same job.

An RCD on the other hand trips out on earth leakage; if there is a circuit through anything other than live and neutral, eg. a person getting a shock because he is stood on the soil and touching a live wire, then it'll trip out. The current edition of BS7671 (the IEE wireing regulations) requires 30ma RCD protection on all socket outlets which may reasonably be expected to supply portable equipment outside the equipotential zone (outside of the house to you), as supplimentary protection against direct contact (direct contact is touching something thats supposed to live... like a wire that has got cut somehow)

Its RCD protection you want, adding plug in MCBs won't add this, a new board is the best way to add this, and the most common way of meeting the regs is a 'split load board' its a board that has one RCD and that protects the circuits on one side of the board, but not the other, each circuit still has its own MCB on its correct side of the board (sockets and showers on the RCD, lights, alarms, smoke detectors on non RCD)

There is actually in many cases to RCD protect the upstairs sockets, but I beleive its good practice to (and the next version of the regulations will probably ask for it)

The other thing to say, is you can get things called RCBOs which are MCBS with built in RCDs, they are expensive though (around £40) and you can't get them for your old board, you'd still need a new board (though it wouldn't be a split load board in this case). the advantace of them is if the RCD trips (and sometimes they can be very sensitive) you don't loose all the circuits

 

[sm1thson]

my opinion (Im not a spark)

first thing to realize is to protect her from electric shock she needs an RCD you can buy one that plugs in, I suggest you do before she mows the lawn again. Shocks out doors are much more likely to kill (and more likely to occur in the first place) which is why it’s a regulation now that socket that can reasonably be expected to supply something outdoors must be RCD protected. A plug in one may do for now, but in time will get lost.

-if you replace the fuses for MCB’s it just means that it saves hassle of rewiring a fuse when they blow, but they shouldn’t be blowing. MCBs are a bit quicker I think but not significantly. You could change sockets near doorways to RCD ones (they are expensive) to give RCD protection.

-if you replace the fusebox with a modern CU it will (should) have an RCD of some sort so sockets are RCD protected.

-it is likely that other things need looking at namely
-Earthing?
-Main Bonding?
-Supplementary Bonding?
-Earth present in lighting circuit?
-wiring over 30 years old and needing replacement?

 

[JohnD]

Plug-in MCBs are very handy, and if your mother has one of the typical "Wylex Standard" units then the MCBs are readily available and easy to fit. They retail at about £7 but you may be able to get used ones for about £2.50. In this case make sure you get the matching coloured plastic shields since they are sized to fit and not interchangeable.

However, their biggest contribution to safety is that users are not tempted to replace burnt out fusewire with a thicker grade, or a nail. They are also much quicker and easier to reset.

If you are thinking of safety improvements, look for some new sockets incorporating RCD protection, and use them to replace (at least) the sockets which can reasonably be expected to supply equipment used outdoors, and preferably also any which may be used for watery appliances like kettles and washing machines.

RCD sockets are superior to RCD adaptors, because when an adaptor trips, people are inclined to remove it and plug the (faulty) kettle straight into the mains.

 

[macman81]

Thanks for the various advice. Is it possible to get a stand-alone RCD protection device (presumably this would fit between the consumer unit and the meter) to protect the whole system, and then I would probably upgrade the old fuses to MCB's? As opposed to replacing the whole consumer unit with a new one incorporating RCD protection?
This is also relevant to my own house, where I have a modern (about 6 years old) Wylex consumer unit with MCB's, but no RCD protection. I would like to fit RCD protection but don't really want to have to replace such a new unit).

 

[bernardgreen]

Plug-in MCBs are very handy, and if your mother has one of the typical "Wylex Standard" units then the MCBs are readily available and easy to fit. They retail at about £7 but you may be able to get used ones for about £2.50. In this case make sure you get the matching coloured plastic shields since they are sized to fit and not interchangeable.
.

Used ones may be for sale as they were replaced as they were defective or they may be counterfeit devices of dubious quality.

Life is worth more than £5 saving. Buy new.......

 

[Steve]

Thanks for the various advice. Is it possible to get a stand-alone RCD protection device (presumably this would fit between the consumer unit and the meter) to protect the whole system, and then I would probably upgrade the old fuses to MCB's? As opposed to replacing the whole consumer unit with a new one incorporating RCD protection?
This is also relevant to my own house, where I have a modern (about 6 years old) Wylex consumer unit with MCB's, but no RCD protection. I would like to fit RCD protection but don't really want to have to replace such a new unit).

An RCD to protect the whole system would go between the meter and the fusebox, yes. But then you get problems whereby if something goes wrong, it takes the whole house out, and you have no 'lectric. Not Good.

Your Wylex CU probably is a normal consumer unit, which will take RCBOs, or it you have sufficient space, an RCD to give a split load or fully protected configuration. Again, an overall RCD has the same problems as above, but is compliant. A split load is slightly better, and RCBOs are the best

 

[macman81]

Sorry, what is RCBO (residual current ? ?). The Wylex CU is an 11 way box with only 8 in use at present. So to have a split load configuration, do I have to replace all the existing MCB's with RCBO's, or does the RCBO just fit in one of the unused slots?

 

[Steve]

An RCBO is a single-width module that provides individual circuit RCD protection and MCB protection in one. It is therefore slightly higher, but the height is behind the CU cover, so you dont notice it. They are about £35-40 each, and are the creme-de-la-creme of electrical protection. You'd need one for each circuit you want protecting. Despite the cost, they are probably the easiest to retrofit into an existing board.

A split load config involves splitting the circuits onto 2 busbars (you might need new busbar), and putting an RCD on one busbar. This would therefore be more time consuming and complicated to do, as the circuits would need re-arranging on the CU.

Overall RCD protection is the easiest of the lot - just replace the mainswitch with an RCD!

 

[plugwash]

An RCBO is a single-width module that provides individual circuit RCD protection and MCB protection in one. It is therefore slightly higher, but the height is behind the CU cover, so you dont notice it. They are about £35-40 each, and are the creme-de-la-creme of electrical protection.

personally I think it is better to have the RCD protection as local to the load as possible, a RCBO per ring is better than a split load but not by much.

Your Wylex CU probably is a standard unit, which will take RCBOs, or it you have sufficient space, an RCD to give a split load or fully protected configuration. Again, an overall RCD has the same problems as above, but is compliant. A split load is slightly better, and RCBOs are the best

A wylex standard CU (the type that uses plug in breakers) which is what the original poster appears to have WILL NOT take RCBOs. Nor can you just replace the mainswitch with an RCD.

 

[Steve]

Your Wylex CU probably is a standard unit, which will take RCBOs, or it you have sufficient space, an RCD to give a split load or fully protected configuration. Again, an overall RCD has the same problems as above, but is compliant. A split load is slightly better, and RCBOs are the best

A wylex standard CU (the type that uses plug in breakers) which is what the original poster appears to have WILL NOT take RCBOs. Nor can you just replace the mainswitch with an RCD.

nonono, the OP's MOTHER has a standard fusebox. The OP IIRC has a Wylex consumer unit fitted 5 years ago.

 

[JohnD]

Your Wylex CU probably is a standard unit, which will take RCBOs, or it you have sufficient space, an RCD to

misleading use of the words "Wylex" and "Standard" in the same sentence

 

[JohnD]

btw, did you know Marianne Faithfull used to be Mick Jagger's girlfriend?


That's the only time you'll find the words "Mick Jagger" "Girlfriend" and "Faithfull" in the same sentence

 

[Steve]

Apologies JohnD, i didn't look at it like that. I'll go back and fix my balls-up

 

[RF Lighting]

I'll go back and fix my balls-up

Fix them up where?




fnarff fnarff