Is that their function on non-TT installations?
MCB replacement question
- Thread starter LoriT71
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Is this a trick question 
in response to paullegs post dismissing Rcd protection, as being not important, even though a RCD could in some circumstances cut the power faster than a circuit thats not protected, hence reducing something smouldering up and setting fire
in response to paullegs post dismissing Rcd protection, as being not important, even though a RCD could in some circumstances cut the power faster than a circuit thats not protected, hence reducing something smouldering up and setting fire
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I have to agree, if I had that old CU in my garage and a friend showed me a fuse box with live parts showing I would want to swap it ASAP. OK maybe I would suggest they should have RCD protection, but what was fitted in spite of all faults was far better than the original.
For fire protection a 100 mA RCD is ample, and a 100 mA RCD would not trip too often without due cause. However we don't have the readings and I know my daughter had a new consumer unit fitted by my son, but he had to put the sockets on non RCD protection because he could not find the fault. I went up next day after he phoned me to find the error, it did take some time, only a screw which had caught neutral wire but my sons insulation tester had stopped working.
For all we know, it may have poor insulation resistance readings and he may realise it really needs a full rewire and is unwilling to do that for free.
If I was to be given the option of a jobs worth or a old 1980's electrician then 1980's electrician every time. Went to one house, electrician had been and told the lady he could not switch the power back on because regulations required her to have an RCD. Which was wrong it says new install must have an RCD old installs can stay as they are. There are no new circuits, so even following regulations no requirement for a RCD.
She should ask the old guy to swap the MCB for her and ask him why no RCD. He seems a good guy so I am sure he will say why.
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which could be as implying that houses with RCDs do not present any hazard of electrical injury, fatality or a house fire due to an electrical fault. An RCD will reduce the risk but not eliminate it. If the system is without any faults the RCD will never operate.
A fault to Ground from a ciruit protected by a 6 Amps fuse / MCB could pass 5 Amps continuously. 5 amps at 230 V is 1150 Watts of heating at the fault. That amount of heat energy concentrated into a small area around the fault will create temeperatures high enough to ignite timber.
With an RCD fitted the fault to Ground would trip the RCD and stop the heating. If the fault was just below the trip threshold 30 mA at 230 V it would only be 0.69 Watts of heating at the fault which is unlikely to become hot enough to ignite material.
The OP has PME
To be precise the OP has the Earth supplied by the CPC connected to the Neutral. It is only PME where there are Multiple connections between the Network Neutral and true Ground along the distribution network.
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Maybe I worded it a little wrong, I'm not dismissing RCD's in the slightest, but my issue is that some of the comments (in my opinion) could be interpreted by someone non electrically minded to mean that their house is literally minutes away from an inferno, no where did I say RCD's are pointless, but merely stating many houses still remain standing despite an rcd
And as for the moron whos reply was "what is your earth loop impedance"
Really?? I'm sure the OP will be like "hold on, I'll just grab my loop-tester from under the sink, I knew this would come in handy one day..."
It baffles me that this thread is now 4 pages long, when it should of been a simple case of... "No this is not a job for someone with no/very ltitle electrical knowledge, however isnt a very big/expensive job for a professional who can also do the relevant checks/tests at the same time
[/QUOTE]Please don't assume that all electricians have the same low standards as you.[/QUOTE]
And as for this tool, please elaborate, how long would it take you to determine that only the cooker was supplied by this circuit, carry out ins. Res. Test, replace mcb and do a loop test?
And as for the moron whos reply was "what is your earth loop impedance"
Really?? I'm sure the OP will be like "hold on, I'll just grab my loop-tester from under the sink, I knew this would come in handy one day..."
It baffles me that this thread is now 4 pages long, when it should of been a simple case of... "No this is not a job for someone with no/very ltitle electrical knowledge, however isnt a very big/expensive job for a professional who can also do the relevant checks/tests at the same time
[/QUOTE]Please don't assume that all electricians have the same low standards as you.[/QUOTE]
And as for this tool, please elaborate, how long would it take you to determine that only the cooker was supplied by this circuit, carry out ins. Res. Test, replace mcb and do a loop test?
My take on all this is that perhaps the 'electrician' thought he would change the consumer unit to simply replace the one with the switch surround missing - even though that part could be simply replaced with one that no doubt could be obtained on E-bay.
The new consumer unit is, in essence, a like-for-like replacement, in that there are still no RCDs - yet this is unacceptable in reality. One could say it was a quick, cheap favour - better than nothing, etc - but this is NOT the way to replace a consumer unit.
Using different branded MCBs - no excuse. Wylex is readily available - even on a Sunday in B&Queue.
Using a 6 amp MCB for a cooker circuit. Could this be a stupid mistake - getting muddled with 6mm2 cable and 6 amps?
My biggest concern, however, is the connections he has made. The wires going into the terminals don't look as good as they should be.
Is his eye sight failing?
We are not there to see if the connections are sound - but they don't look all that marvellous - some look worse than others.
It's odd - we often hear about retired electricians - so you tend to expect really good, old school quality work - and more often all you get is rubbish.
Some of these retired electricians, sadly, seem to think they can do good work without really trying any more.
But they can't.
Get a recommended electrician round to check all his work, and consider RCD protection.
Though a bit expensive, you could replace some or all of those MCBs for RCBOs.
An RCBO is a cross between an RCD and a MCB.
The new consumer unit is, in essence, a like-for-like replacement, in that there are still no RCDs - yet this is unacceptable in reality. One could say it was a quick, cheap favour - better than nothing, etc - but this is NOT the way to replace a consumer unit.
Using different branded MCBs - no excuse. Wylex is readily available - even on a Sunday in B&Queue.
Using a 6 amp MCB for a cooker circuit. Could this be a stupid mistake - getting muddled with 6mm2 cable and 6 amps?
My biggest concern, however, is the connections he has made. The wires going into the terminals don't look as good as they should be.
Is his eye sight failing?
We are not there to see if the connections are sound - but they don't look all that marvellous - some look worse than others.
It's odd - we often hear about retired electricians - so you tend to expect really good, old school quality work - and more often all you get is rubbish.
Some of these retired electricians, sadly, seem to think they can do good work without really trying any more.
But they can't.
Get a recommended electrician round to check all his work, and consider RCD protection.
Though a bit expensive, you could replace some or all of those MCBs for RCBOs.
An RCBO is a cross between an RCD and a MCB.
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No - only by someone seriously hard of thinking.
Oh - let's see - who was it who decided that the comments could be so interpreted?
I am sorry.
I keep forgetting that DIYers are exempt from the laws of physics, and that if they fit an MCB it will of course work just fine no matter what the loop impedance is, and that it is only when professional electricians get involved that they won't work properly if the impedance is too high.
I expect an awful lot baffles you. I would have thought you'd be used to it by now.
Stop digging and proving him correct.
Do you have a lot of experience in this field?
@paulieg1988 I think that you have entirely missed the ethos of this forum.
It is not a help forum for DIYers. It is basically a competition between contributors who have differing opinions, and also an opportunity to put to public ridicule anybody who so much as puts an apostrophe in the wrong place.
Once you take that on board then it is not as awful as it might appear.
And PS, there's a handy 'ignore' button should one of the 'experts' be more caustic than you might like!
It is not a help forum for DIYers. It is basically a competition between contributors who have differing opinions, and also an opportunity to put to public ridicule anybody who so much as puts an apostrophe in the wrong place.
Once you take that on board then it is not as awful as it might appear.
And PS, there's a handy 'ignore' button should one of the 'experts' be more caustic than you might like!
Taylortwocities, I kinda love you a little right now. Your dryer-than-dry humour is right up my street, and I actually had a "laugh out loud" moment reading your comments. And after the last couple of days of worrying that the headmaster is going to walk in and demand "Who started this?!" (and everyone points in my direction), your post seems like oil on troubled waters (or at least, an amusing distraction). I hope everyone else sees it exactly like that too.
Thanks again to everyone who has been so helpful with my current CU troubles. I appreciate all the replies - from the simple ones to the technical ones (even if they sometimes stretched my brain a little).
Lori
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