Replacing fusebox with RCD?

I know that there are pros and cons to replacing a 1980s fuse wire fusebox with a RCD box. I can't help but think that the pros outweigh the cons in terms of safety.
I moved in to a house a few months ago. It has a 1980s wire fusebox. I notice that there is an underground plastic coated cable in the garden going from the house to a shed. I can't find the source of the cable in the house. There are also a couple of outside lights plugged in to sockets inside the house. I've placed plug in RCDs in to them and sure enough they do eventually trip (it may take a few days).
I'm thinking that if I replace the fusebox with a RCD I may end up having lots of problems. I can guess that the outside wiring is going to cause the RCD to trip.
If this was the case would it be better to pay for essential inside appliances like the fridge to be placed on a non RCD circuit or would it be better and cheaper to try to disconnect all of the external wiring and use an extension cable when/if needed?
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Just buy a CU with only a Main Switch installed, then fit RCBO's instead of MCB's/RCD's.
Then, you should have little/no nuisance tripping, and if you do, it would not affect half of the circuits,only the one that is faulty.
Of course, before you connect it up, you'd have tested it anyway to see if there are likely to be any problems.
It'll cost 50-100 more, but worth it IMO.
Alan.
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"A.Lee" wrote in message wrote:

If the possibly nuisance wiring is connected as a spur to the main circuit then I guess I will just have to pay to have the faulty wiring disconnected.
I think outside wiring is a recipe for disaster unless it has its own separate protection.
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lives saved per year by RCDs and MCBs: zero or very close. So not a very useful exercise.

its common to need to sort out wiring issues and sometimes replace an appliance to get everything to work with an RCD

if it already does trip an rcd, then yes

more reliable

or convert it to 24v


To be honest, this is the sort of thing often undertaken but achieving close to nothing. If you've got 100-200 to play with, you'd get about 100x as much safety benefit by fitting a second stair rail.
NT
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On 13/03/2011 17:18, Tabby wrote:

As regular readers will be aware, I disagree strongly with NT when he makes glib statements of this nature.
While I am happy to accept that a CU swap in itself is not necessarily going to improve safety, there are some aspects of it that can make a significant impact. One of these is including RCD protection where none was present before.
Over the years, the wiring regulations have required ever more integration of RCDs into circuit protection. And generally, the (already very low in the UK) death rate from electrocution has fallen along with these and other enhancements. There are some points to note however; the initial use of "whole house" RCD protection resulted in fewer electrical injuries but a rise in injuries from trips and falls - presumably resulted from unexpected loss of lighting. Also the introduction of part P would also seem to correlate with a reversal in the fall in injury rate.
However deaths are only one aspect of electrical injury. There are vastly more people hurt each year from electrical shocks. Mostly from using or abusing (sometimes faulty) electrical appliances. There are also a significant number of house fires, the cause attributed to faulty wiring. RCDs can and do mitigate the effects of these dramatically. It can be the difference between "ouch that hurt", and a trip to A&E to address a burn or cardiac arrhythmia.
Hence, as with many black and white statements of "fact", there are actually large areas of grey that are dependent on the circumstances. A couple living in a first floor flat with no garden, and no kids, would probably have very little to gain from RCD protection for their sockets. A house with a garden, a full compliment of electric garden tools, and inquisitive kids that like "experimenting", and unearthed lighting circuits would be strongly advised to install RCD protection as a matter of some urgency.
A summary of pros and cons for CU upgrades:
http://wiki.diyfaq.org.uk/index.php?title=Changing_a_consumer_unit#Reasons_to_change

Which is generally a good thing. Wiring issues include things like borrowed neutrals and neutral to earth shorts, which can place maintainers of the electrical system at a risk of shock.
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Cheers,

John.

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I may as well expand a little on my pov on this. The basic issue is that the number of deaths from electrocution is tiny, in comparison to numerous other risks we face daily that are 100x or 1000x larger, such as stair falls. If one has curious children, there are far better uses for the money than an RCD. Electrocution just isnt what endangers people to a large enough extent to be worth the cost of what the OP intends.
For every cause of death, there are many more cases of injury of various sorts. We compare deaths because they're generally firm & known figures. I'm not saying RCDs wont prevent death & injury, they will, but there is a wide range of things one can spend the same money and derive *far* greater safety benefit. Survival is an important life skill, and maximising one's odds is achieved by knowing the big risks and directing time/energy/money into improving those, rather than using it for a relatively tiny benefit.
NT
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On 13/03/2011 21:51, Tabby wrote:

You seem fixated on fatalities - most electric shocks don't result in a fatality. There are a significantly larger number of people hospitalised than those actually being killed (some 200,000/year or over 750/day on average[1]).
Then an even greater number injured but not requiring hospital treatment (1.2m/year). After that an even grater number hurt but not actually injured.

Known figures perhaps - but only a part of the story. The old lady falling down the stairs in the dark as a result of having no lights after a rewireable fuse blew which she could not repair, won't be counted as an electricity related statistic. The incidental cases of death after a shock (where shock was the initiator but not the actual cause of the fatality) is something over three times the actual direct death rate.
Most fires resulting from electrical origins are caused by misuse of appliances, or people placing things to close to heaters etc, however there are still getting on for 8000/year caused by electrical faults.
A DTI report in 1997 estimated that 20% of electrical fires would be prevented by a RCD.
Nearly half the dwellings in this country do not have RCD protection at the consumer unit.
[1] http://www.esc.org.uk/industry/policies-and-research/statistics /
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John.

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People compare death rates because theyre a much bigger problem than just a trip to A&E, and because death figures are collected on more things, and generally are firmer.

the same is true for all other causes of death too

that's not an RCD issue though. In fact RCDs make that one worse, not safer.

yes, as with other causes of death

Informative statistics. One can estimate from these that: - about 50 people a year die in electrically caused domestic fires - RCDs would prevent about 10 deaths per year in electrical fires, as well as a similar number from electrocution.
NT
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On 16/03/2011 23:09, Tabby wrote:

Agreed, however I was not advocating that he fit RCDs so as to prevent death. Yes, if he is unlucky enough to be subjected to a potentially fatal shock there is a pretty good chance they will save him[1], but chances are he won't suffer a shock of that lethality.
[1] When you think of all the stories of death from electrocution that we have discussed here in recent years, some would have been prevented by adequate equipotential bonding, and most would have been prevented by a suitable RCD.

Yup. So lets look at what can be done to reduce the accidents requiring hospitalisation, and then decide if the cost is worth it.
Say the chances of you being electrocuted (i.e. fatally) in any given year are 1 in 3.2M. Even if you are in the place for ten years that's still 1 in 320,000, or 1 in 100,000 ish for someone out of a family of three. Is it worth spending 150 as a one off payment to avoid death at those odds? Many would justifiably say probably not.
Now lets say the chances of you getting a sufficiently serious injury from an electric shock that will land you in hospital are 1 in 325 for any given year. That comes down to 1 in 32 if you live in a place for 10 years, and that's just you. Say you're talking about a family of 3, you are now at 1 in 10 for someone in the family to be injured. Now the question then becomes would you pay 150 as a one off cost to prevent that?
(and don't forget the NHS probably kill more people each year than road accidents, so just being a patient is a risk in itself!)

With an installation to current standards a RCD will not make that one worse. However I picked on that point more as an illustration to why one might consider a CU upgrade even in cases were there are no special concerns regarding shock risk. e.g. situations where the inhabitants either won't be able to rewire a fuse if they needed to, or would be likely to do it dangerously if they did.

Indeed - you can go update all those bits in the wiki where you mention there are "n thousand house fires a year in the uk, how many of these are due to electrical faults is unknown" now, since now we know ;-)

And more importantly they would prevent 1,600 house fires / year.
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Cheers,

John.

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I've addressed the key issue later in the thread
NT
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On Sun, 13 Mar 2011 21:26:50 +0000, John Rumm wrote:

Even nowadays most CUs on offer still have either 1 30mA RCD or, if split, 2 30mA RCDs. About 20 years ago the local council rewired their houses (ours was still council-owned then) and I had a chat with the council's engineer who was going round to do the specs. My Father wasn't too steady on his feet and I was worried about sudden loss of light. The result was that the split CU has 1 RCD at 100mA with lights and other non-critical circuits on it and 1 at 30mA with everything else. I also managed to get switches (lights and sockets) with concave rockers fitted - much easier than flat rockers for aged fingers.
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Peter.
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One of the problems with counting injuries and lives saved by RCDs is that people do not realise that they have just had a close call. All they know is that the RCD tripped. Considering the massive numbers of electric gardening tools that are now in use compared to 20 years ago when RCDs became common place then they probably save more injuries than they are given credit for.

A 1980s installation is probably lacking in the correct main bonding and possibly a borrowed neutral on the upstairs downstairs lights. 1980s installs usually pass all the insulation tests.

They are the sort of things that should be sorted out with or without an RCD CU.
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Adam



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"Gareth" wrote in message

Now I'm really confused.
I don't have much money but what I do have I need to spend sensibly. I have a 2 year old, a small garden and outdoor wiring including wiring to a shed and a small child's play house. Plug in RCDs do trip when connected to the outside wiring (outside lights).
Should I invest the little money I have in consumer unit based RCD protection (with possible re-wiring costs)?
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On 16/03/11 00:22, Gareth wrote:

you could add a all house RCD before the old fuse unit, maybe add another rcd circuit for outside so it doesnt trip everything else, and get some emergency lights for the stairs,
http://cpc.farnell.com/pro-elec/lfac502a/bulkhead-maintained/dp/LA03293 ? [g]
[g]
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Yes RCD's are rather useful when you do find you or yours accidentally connected to the mains.
Been there and -just- survived. !...
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Tony Sayer


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On 16/03/2011 09:05, tony sayer wrote:

I imagine most of us posting to this group have had our share of 240v tickles.
My worst one was when I had a part-time job as a student in Edinburgh, at a Hi-Fi repair shop.
Many people handed in their crap with the plug removed (yes, really! ) because they thought we might steal the plug!
So the workshop has RS 'Safeblocks', things that you opened up to reveal spring-loaded connectors for connecting bare wires to. Flapping the box shut turned it on.
I'd finished working on some piece of crap , and was replacing it in it's housing. The safeblock was open. I had the crapware in both hands. A manual fell from a shelf, whacking the safeblock closed. I got the the full 240 from 1 hand to the other, causing me to grasp the whole thing tighter to myself. I was well aware of my electrocution, and was fully conscious. I jumped up and down causing the item to drop from my grasp to the floor, releasing me from the current.
The other guy in the workshop hadn't noticed, and wondered why i'd dropped the thing.
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R




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Thats the sort of thing I suppose you have to take into account when designing Nuclear plants;)..

Lucky you .. I couldn't even move at all;!..

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On 16/03/2011 00:22, Gareth wrote:

As a minimum it seems you need to sort the fault with the exterior electrics, and use a plug in RCD for any activity that requires power outside.
Personally I would install RCDs / RCBOs at the CU since it eliminates the possibility of forgetting, or when someone gets a shock in an unexpected situation etc. However I can do the work myself, so its a cheap job.
As to spending more, then that us your call. One way to assess the risk is to compare it to other common risks. e.g. The number of accidents requiring hospital treatment from electrical shock per year are about 4/5ths of the number of casualties caused by road traffic accidents per year in the uk. The death rate however is much smaller (i.e. < 30 rather than < 3,500).
Part of the difficulty is that the human as a species is spectacularly bad at assessing anything other than short term immediate danger risks. A rock flying towards you - no problem, our primitive brain is hard wired to duck!
Risks in the future however we rationalise and downplay. As do ones where we feel we have control over them. Risks from common events frighten us far less than ones from rare events.
Hence why we fear serial killers and not obesity, planes and not cars, and leaks from nuclear power stations and not smoking.
So electricity in the home we are complacent about - its common, we feel we control it, and the chances are harm will occur to someone else a long way into the future.
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Cheers,

John.

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Well you do need to get the outside lights sorted.
Was the fusebox swap intended to be a DIY job as can be a big job if you are not experienced with electrics.
You do not have to rush into anything at the moment.
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Adam



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..
Good question. Opinions here differ, so its going to be your choice. As John pointed out, we tend not to assess risk rationally. A really good tool here is published death statistics. Google top 10 causes of death for various tables on this - they're intentionally simple & easy to understand. Some of these tables are divided into age bands, some apply to one country, some are worldwide etc.
One thing stands out immediately from these: the major risks to life are massively greater than any risk posed by electrical faults. If you had 1000 to spend, and apportioned the spend according to the relative number of deaths from various causes, the allotted spend on electrical issues would be in the region of 1. Yes, electrical incidents kill, but others kill a good 1000x more in all age groups, and those are where the money is better spent.
For each major risk area there are organisations that give out recommendations as to how to minimise these dangers.
There are some options for dealing with the faulty outdoor lights, but fitting a new CU with RCDs and MCBs wont fix them.
NT
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