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RossT
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12-05-2017, 11:23 PM
21

Re: Circuit breakers

Originally Posted by Judd ->
Consumer units installed after 1985 should have an RCD to protect the socket circuits as standard. If you can see a big on/off switch on your fuse box with a small test button on it, that's your RCD. That button needs to be pressed at regular intervals to make sure it works.
Could there be one possible instance of confusion here between there being an RCD on the consumer unit and one of the older and less safe ‘Earth Leakage Circuit Breakers’ (ELCB) ? The ELCB’s have a big on/off switch and a test button so are similar to an RCD unit and were fitted to some houses (like mine) built in the 60’s. However, they don’t offer the same degree of personal protection as a more modern RCD. Having a ELCB is not illegal, but I think that a professional electrician who was asked to carry out any work on such a consumer unit now would be legally required to replace the ELCB with an RCD to meet current safety codes?

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13-05-2017, 06:49 AM
22

Re: Circuit breakers

Originally Posted by Judd ->
If your fusebox is made by Wylex, you can buy plug-in MCBs (circuit breakers) that replace the standard fuse-wire type. See photo - this is recommended for your 5amp lighting fuses. Less hassle
Thanks, Judd, not sure of the make - will go and look. It would make life a lot easier as cards of fuse wire are hard to find these days.
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13-05-2017, 07:48 AM
23

Re: Circuit breakers

Always a good idea to use an RCD outdoors, if your ( electric ) lawnmower cuts the cable there's a chance that the wire is still live, as the grass could be damp it could be ( and has been) potentially lethal an RCD will cut the power in milliseconds
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13-05-2017, 01:27 PM
24

Re: Circuit breakers

Posted by Ross T

"Could there be one possible instance of confusion here between there being an RCD on the consumer unit and one of the older and less safe ‘Earth Leakage Circuit Breakers’ (ELCB) ? The ELCB’s have a big on/off switch and a test button so are similar to an RCD unit and were fitted to some houses (like mine) built in the 60’s. However, they don’t offer the same degree of personal protection as a more modern RCD."

The name ELCB is a generic name that includes Voltage operated types and the current operated RCD, RCCBOs, the current operated types are designed to trip if a fault current of over 30mA is detected.

In the past, Voltage operated types were prevalent especially in farming areas and rural locations that provided their own earthing system in the form of a copper rod or in some circumstances, the use of a water pipe. The danger with these specifically in farms is the relatively high voltage required to flow to earth before they tripped and there are many instances where farm animals have been electrocuted as a consequence. If they didn't trip at all, the voltage could travel up a next door neighbours earth-rod and trip their breaker off. I once had to check an entire caravan site because a group of caravans' electrical supply was being tripped off. The fault was eventually traced to a fault on a neighbours caravan and a V-op ELCB that hadn't operated.

Having a ELCB is not illegal, but I think that a professional electrician who was asked to carry out any work on such a consumer unit now would be legally required to replace the ELCB with an RCD to meet current safety codes?"

It's not a legal requirement to upgrade any installation to current standards provided that the installation complied with the regulations in force at the time when installed. Electricians can only advise a course of action and it's up to the homeowner to act on that advice or not. You'd be surprised at how many householders think electricians are trying to con them out of a few quid when in point of fact we're trying to stop them being electrocuted or being burned to death in their sleep. In your case, because of it's age, the ELCB (BS:4293?) should have the trip-time checked, and it should operate in under 200mS at a 30mA test current (ELCB should be 30mA type) and under 40mS at 150mA test current. Modern RCDs allow a 300mS trip time. If it doesn't trip within the required time that's when to get it changed. I would be surprised if a sparky would add any extra wiring to an ELCB of that age without testing its operation first but even then, I would put a new RCD in just for the new wiring as it has to comply with the latest Regs.
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13-05-2017, 02:04 PM
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Re: Circuit breakers

Originally Posted by Judd ->
Best not to use a plug-in type RCD adapter if the consumer unit has its own RCD as it can interfere with the main RCD. If the main RCD doesn't work then that's a different story, one of those could be used as a stop-gap until the main RCD is sorted.
That's interesting Judd. I have a plug in RCD for my pond pump and UV light. The cable is about 10 metres long. I did quite a bit of research and all said I needed the extra RCD despite having it on my C Unit. So is it best to ditch the plug in one? We had a power cut the other day and it had to be reset, so I know it works.
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13-05-2017, 02:47 PM
26

Re: Circuit breakers

I personally wouldn't put an RCD adapter `up stream` of the main RCD in the consumer unit because there should be no need for one providing that your main RCD(s) still functions - you do press the Test button occasionally don't you. If you press the test button on your extension, does it also trip the main RCD off?

By your description, the type you have is the non-latching type - if the power goes off, you have to physically reset it when the power comes back on whereas a standard RCD doesn't. The non-latching type were and are more prevalent in petrol stations where the RCDs have to be reset using a key. This type is recommended where there is machinery being used as it can be dangerous for machines to fire up again.
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13-05-2017, 03:19 PM
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Re: Circuit breakers

Originally Posted by Judd ->
I personally wouldn't put an RCD adapter `up stream` of the main RCD in the consumer unit because there should be no need for one providing that your main RCD(s) still functions - you do press the Test button occasionally don't you. If you press the test button on your extension, does it also trip the main RCD off?

By your description, the type you have is the non-latching type - if the power goes off, you have to physically reset it when the power comes back on whereas a standard RCD doesn't. The non-latching type were and are more prevalent in petrol stations where the RCDs have to be reset using a key. This type is recommended where there is machinery being used as it can be dangerous for machines to fire up again.
Hi Judd

If I press the test button on the extension, it does not trip the main but if I press the test button on the main, it trips the extension, which I then have to reset manually. The cable is 1.5mm rubberised and run in trunking.
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13-05-2017, 03:24 PM
28

Re: Circuit breakers

@ Judd re post#24

Thanks for those comments. The reason I have delved in to this area was that some time ago, I was thinking of renting out this house (though it never happened) and so started to think about what might need doing to make sure that the electrics would be ok. It was then that I realised I didn't have an RCD but just the old ELCB. I'd had a new Wylex consumer unit installed when I first moved in (1993) and so thought everything was "up to code"...but not so. I'm out in the sticks so the house as its own earth spike (TT supply?) and that's probably not up to code (needs heavier connecting cable) and the connection between the consumer unit and the water supply probably needs heavier cabling also. I gather that changing consumer units now must be done by a "top level" electrician and he has to report the work to the local council, or if a lesser electrician does the work, I have to pay the council to come and check it out? Is that right? We live in "highly specified" times!
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13-05-2017, 04:24 PM
29

Re: Circuit breakers

Originally Posted by RossT ->
@ Judd re post#24

Thanks for those comments. The reason I have delved in to this area was that some time ago, I was thinking of renting out this house (though it never happened) and so started to think about what might need doing to make sure that the electrics would be ok. It was then that I realised I didn't have an RCD but just the old ELCB. I'd had a new Wylex consumer unit installed when I first moved in (1993) and so thought everything was "up to code"...but not so. I'm out in the sticks so the house as its own earth spike (TT supply?) and that's probably not up to code (needs heavier connecting cable) and the connection between the consumer unit and the water supply probably needs heavier cabling also. I gather that changing consumer units now must be done by a "top level" electrician and he has to report the work to the local council, or if a lesser electrician does the work, I have to pay the council to come and check it out? Is that right? We live in "highly specified" times!
Your earthing cable going to the `spike` needs to be at least 6mm, same with main bonding going to water and gas pipes. Anything less than this should have been sorted when the new consumer unit was installed. If this was as recent as 1993 this should have been a plastic `split` design model, i.e. sockets, showers and outdoors equipment on the 30mA RCD side, all the rest on the main switch side. As this is a TT supply, that main switch should have been a time delayed 100mA S type RCD so as to give the 30mA trip time to operate. The existing ELCB should have been removed.

These days of course everything has altered. On new installations, the main earthing lead to the spike should be 16mm and the bonding to water and gas should be 10mm. Another thing now is that consumer units are mainly metal to prevent any loose connections causing a fire. In the `old days` metal CUs would not be allowed on TT systems as there would have been a risk of electric shock on the unit itself. This has now been addressed by the use of a stuffing gland which has a thick rubber grommet within it with three pre-drilled holes one for each 25mm meter tail and one for the 16mm earthing lead. When installed and tightened up, the tails and earth lead are gripped tightly to prevent them moving. Each circuit would then have (preferably) its own RCCBO (RCD and MCB combined) but dual RCD split load CUs are still okay.

You are correct in saying that an electrician has to be registered with the ECA, NICEIC or some such other governing body to do the work or they can notify your local council's building control department before the work commences and after the work is finished. This is an expensive route to take because most councils are robbing b******s and for the most part send people out to inspect the work who don't know their arses from their elbows. A mate of mine used to take this route and they used to send a joiner out to look at the job!

Thankfully, all that BS is behind me now - we can't seem to go a month without some changes or modifications to the Regulations.
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13-05-2017, 04:31 PM
30

Re: Circuit breakers

Originally Posted by Longdogs ->
Hi Judd

If I press the test button on the extension, it does not trip the main but if I press the test button on the main, it trips the extension, which I then have to reset manually. The cable is 1.5mm rubberised and run in trunking.

That's not a bad sign then. There should be `discrimination` between the two devices, i.e. the tripping of the downstream protection device, fuse or RCD, shouldn't affect the main safety device.

As a side note - those of you who have bought `anti-surge` sockets to prevent damage to PCs, TVs etc should not be using more than two at any one time if you have RCDs fitted in your consumer unit. These have a designed leakage current built into them and if using too many that leakage current could trip your RCDs off.
 
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