Replacing a fused CU ?



AFAIK the data isnt collected.
NT
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snipped-for-privacy@care2.com wrote:

One can imagine the conversation:
"How effective has Part P been?"
"Oh, I wouldn't know, we only set policy, we don't monitor it!"
"So you can't say whether it has done any good?"
"Of course it's done good, we wouldn't have brought it in, otherwise!".
<groan>
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In article

It's total madness starting to investigate a fault with the power switched on - especially on a strange installation where you've no idea if even the earthing is correctly done.
Most of these sort of faults can be sorted with a simple inspection - loose wires etc - and you don't need the power on for that.
--
*Real women don't have hot flashes, they have power surges.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Yes Dave, and hindsight is a great instructor. At 66 and a lifetime's messing about with electrical installations, this is the first time that's happened to me and although your advice is absolutely correct, worth giving and will I assure you be followed in future, I note with interest that none of those whom I hoped would answer my original post felt it necessary to comment on my possible rashness - one could read in that, that they would have done the same.
Otherwise, thanks guys - the topic will be 'discussed' therefore, rather than 'strongly advised'
Rob
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In article

Should hardly be hindsight, then. After my first electrical shock at a tender age I realised it's dangerous stuff and not to be messed with. I'm genuinely surprised you're still here to post if this is your normal way of working.

I'd be very surprised if they did. Only idiots work on live mains circuits - unless there is no option.

You also have to remember that lots read this group perhaps without contributing. So general advice on best practice is just that and not necessarily aimed at an individual.
--
*If they arrest the Energizer Bunny, would they charge it with battery? *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Just remember the old proverb I was taught as an apprentice " there are old electricians and bold electricians but there are no old bold electricians" Sam
London SW

Yes Dave, and hindsight is a great instructor. At 66 and a lifetime's messing about with electrical installations, this is the first time that's happened to me and although your advice is absolutely correct, worth giving and will I assure you be followed in future, I note with interest that none of those whom I hoped would answer my original post felt it necessary to comment on my possible rashness - one could read in that, that they would have done the same.
Otherwise, thanks guys - the topic will be 'discussed' therefore, rather than 'strongly advised'
Rob
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robgraham wrote:

To endorse what others have said, I don't think you should look at the consumer unit in isolation. If danger lurks it's likely to be out in the installation - as you discovered - and just modernising the overcurrent protection is a bit like adding airbags to a car with no brakes.
I suggest doing, or paying for someone to do, a full PIR first. Then assess what is found and effect appropriate improvements, prioritising according to budget, if that's a constraint.

You did check that the fuse hadn't been replaced by the proverbial 6 inch nail?
If the CU in question is the Wylex standard type, or one of its clones, a worthwhile low-cost upgrade is to replace the rewireable fuses and fuse carriers with HRC cartridge fuses: http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Wylex_Standard_Carriers/index.html

I guess that if you do replace the whole consumer unit now you'd have to follow the 17th edition and provide suitably divided RCD protection for everything. A sensible minimum though might be to just add a single 30 mA RCD (in separate enclosure, after the fuse) for the downstairs ring circuit, thus covering the sockets likely to be used to feed portable equipment outdoors.
--
Andy

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Interesting. Why are non 17th edition CUs so readily available if any replacement must comply?
--
*We waste time, so you don't have to *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Dave Plowman (News) wrote:

You can use them in compliant ways with RCBOs etc. There are also circumstances where you still want non RCD protected ways. Having said that, many people will carry on working to the older standards for a while, and the retailers will be happy to clear old stock. There will also be an ongoing desire to do like for like swaps on damaged kit etc.
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Cheers,

John.

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wrote:

Exactly. A true pro (ie a good DIYer) as opposed to a sparky would buy a CU with a non RCD main switch and use RCBOs instead of MCBs.
The term "17th edition CU" should read "minimum allowed to meet the 17th edition at the lowest cost possible CU"
Adam
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I don't believe building trades people use on-line ordering much. I bought them from trade counters; IIRC, a combination of ERD (who stocked most things but wouldn't order anything else except in box quantities), and Gibbs & Dandy (who didn't stock much of the range, but would order anything even singularly).
The RCBOs you see there are all made up by me from MCBs and RCBO pods. The RCBO pods were under 50 each (might have been more if I was buying just one), and the MCBs well under 10 each (I tend to ignore the price of those).

Because I made them up from separate MCBs and RCBO pods, all the RCBOs in that picture are actually Type B. There would have been no issue with using Type C because by definition they're all RCD protected. If they weren't RCD protected, you'd have to double-check the earth fault loop impedance against more stringent values for Type C to ensure they still meet disconnect times.
The 6A lighting MCBs are all Type C, as is a 20A radial for things I didn't want RCD protected.

For the outdoor sockets circuit, which is a 20A radial Type C, I used a C20A 10mA RCBO prebuilt. That had to be ordered and didn't arrive until after I took the photo, but it looks exactly the same as the ones I assembled myself. At 60 IIRC, it was the most expensive component. I went for a Type C there because I could imagine it being used for large motor appliances. I went for 10mA because it's generally only used for one or two appliances so cumulative appliance leakage isn't an issue, and earth leakage paths through you outdoors can be subject to additional external resistances which might serve to limit the current below 30mA. That circuit is also TT, where as the rest are all TN-C-S.
Also bear in mind my prices are ~5 years ago.
--
Andrew Gabriel
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Andrew Gabriel coughed up some electrons that declared:

True enough - just price gauging at the moment. My local TLC are very helpful, but not very good at getting unusual kit (eg a Wylex REC2 DP 100A isolator had them flummoxed, but it's the optimum device for running tails in an out of as it's designed to do exactly that, and the load terminals are accessible by a separate cover so it's possible to work on a live but "off" one safely). MEM are "unusual" for them too. I'll give them a chance to source because they are very helpful, but I don't hold too much hope.

Is that ERD in Luton? Found Gibbs and Dandy - branch in Slough. I'm near T Wells in Kent so it's not a million miles and worth knowing they can source stuff. Thanks for that.

Ah. Just looked at memonline.com harder. I found the RCD for DP MCBs, the MR30. Just re-read it and the MR30 pod seems to do SP too - is that the one you used?
That was part of the attraction with MEM - being able to stick in Type B and Type C according to the requirements of each circuit without having to fudge the issue.

Cheers
Tim
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I thought ERD were all over the place (at least in the South East - I think they are also known as Edmundson Electrical), but strangely enough, it was one of the Luton ones, the one on North Luton Industrial Estate. The other Luton one (near Screwfix) specialises in other makes, but has some more common MEM bits. It was also the Luton Gibbs & Dandy.

Yes.
Be careful with the MCBs though. MEM do more than one range and it's easy to get them mixed up. One is for these industrial boards (and has a 10kA breaking capacity) and the other range is for domestic boards and has a lower breaking capacity (probably 6kA). I don't think the pods are intended to fit to the domestic breakers, but I never tried.
--
Andrew Gabriel
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Andrew Gabriel coughed up some electrons that declared:

Well, nadger me doobries - now I have their full name, have located branches in T Wells and Tonbridge. Never noticed them so they must be raund the back of all the places I normal frequent. Thanks - will look in on them.

Cheers - I noticed that too.
Thanks
Tim
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That reminds me -- the RCBOs do get warm, as they contain functional electronics which runs continuously[1]. I rearranged them slightly after that picture was taken so they weren't all next to each other, so they would stay a bit cooler, not that I have any reason to think that might be a problem. Typical life of electronic components does halve which each 10C temperature rise though.
There are also requirements on not putting the more sensitive RCBOs next to high current circuits (40A or above, IIRC) due to magnetic interference.
[1] I wonder if anyone's worked out how many more power stations we'll need to bring all installations up to 17th Ed regs (or later) over the next 30 years or so?
--
Andrew Gabriel
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On 2008-08-02 11:51:18 +0100, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) said:

Is this because of their RCBO properties or through dealing with 10mA detection?

Spacers for this or changing the order?

I suppose if the RCBOs are getting warm to the touch, they are using a couple of watts each?
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It applies to all RCDs. The 10mA rating doesn't make any difference.

I changed the order.
The spacers were only temporary because I didn't have all the components when the photo was taken. I always fill a CU with MCBs even if they aren't all used. They're cheap, and they might no longer be easily obtainable when you want some more later on. (I got caught out with this once in the past when MK stopped doing their original single way RCBOs.)

Probably less than a watt, but when squashed together, there's not a lot of surface area to dissipate that from the middle ones.
I have a couple of spares -- I could rig something up on the bench to measure the power consumption of the RCBOs.
--
Andrew Gabriel
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Yes. The position where the tails came out of the wall was a significant influence on the positioning of the CU. I did move that a couple of inches to make it all line up vertically, which wasn't difficult on a thermal block wall where you can almost use your finger nails to scrape out a larger hole.
--
Andrew Gabriel
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On 1 Aug,

<http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Wylex_Standard_Carriers/index.html
Or even with these? <http://www.tlc-direct.co.uk/Main_Index/Consumer_Units_Index/Wylex_Standard_Range/index.html
--
B Thumbs
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Haven't you replaced that CU yet? I thought I was the one that procrastinated :-)
I bought a split load Wylex CU over a year ago (from Screwfix) and was going to change it myself, but as I had the kitchen re-hashed a bit later and would have to (well, you know!) go some sort of 'official' route I got the leccy who did the kitchen wiring to change the CU.
It all saved going 17th edition... The supply to the fridge/freezer (using the old cooker supply ) is now a non-RCD radial feed (labelled as such).
--
Frank Erskine

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