Thoughts on overloaded radial?

[JohnS888]

Hi all

Pretty new to working for self. Got call out yesterday for a ring circuit that kept tripping rcd. I identified the faulty cable which had low 0.05 IR reading L to N. I followed this to where next point should be but on opening circuit found only one cable...not good. On closer inspection of sockets I found that most of them had c.p.c's cut out. I can only imagine previous spark had thought this good idea as a previous earth fault had been tripping rcd. Why he cut them right out though so they are impossible to extend I don't know. Anyhow now having disconnected faulty cable decided best thing I could do to make 2.5 not overloaded was to change 32amp mcb for 20amp problem being the washing machine, boiler and oven all on this circuit I did expect this would trip out but thought at least I've give them some power back temporalily which had been without for 3 days and protected cable from overheating. I advised at time although cooker had no rating on it this is likely to cause trouble with circuit and really needs own circuit and is likely to trip out and that ring really needs to be rewired with at very least a new leg from board. What has surprised me is landlord has phoned me since and rather than mcb tripping what's happening is when the various appliances are on other appliances lose power. Ie washine machine on and boiler stops working, cooker on washine machine stops working. Why would this be the case rather than mcb trip out? Thanks

 

[Pete999]

Are you saying that the RFC you were called out to investigate a fault, has no CPC? and yet you left it connected?
Did you carry out any of the testing that is required for RFCs, if so what were the results? would be interesting to see them.
'

 

[Strima]

What's the R1+R2 for the circuit? Possibly volt drop causing undervoltage.

 

[snowhead]

If it was all O.K before then I'd say either a bad connection at the New MCB / neutral or at one of the sockets you've been in.

 

[DPG]

What was the cause of the low L-N IR reading?

 

[JohnS888]

Are you saying that the RFC you were called out to investigate a fault, has no CPC? and yet you left it connected?
Did you carry out any of the testing that is required for RFCs, if so what were the results? would be interesting to see them.
'

Pete
I have previously been in this situation and others have advised that no c.p.cs at sockets/appliances is not reason enough to not reenergise circuit. If advised client, noted this clearly on cert and put sticker on DB are you saying I shouldn't of done this and walked away from job without reenegising? Thanks

 

[DPG]

Pete
I have previously been in this situation and others have advised that no c.p.cs at sockets/appliances is not reason enough to not reenergise circuit. If advised client, noted this clearly on cert and put sticker on DB are you saying I shouldn't of done this and walked away from job without reenegising? Thanks

Are you sure that advice wasn't for a lighting circuit? An RFC without a CPC is a lot more dangerous.

 

[Midwest]

Are you sure that advice wasn't for a lighting circuit? An RFC without a CPC is a lot more dangerous.

I would go as far as to say its pretty lethal.

 

[MJPD29]

Pete
I have previously been in this situation and others have advised that no c.p.cs at sockets/appliances is not reason enough to not reenergise circuit. If advised client, noted this clearly on cert and put sticker on DB are you saying I shouldn't of done this and walked away from job without reenegising? Thanks

I have never heard that advice and personally I don't think I would have re-energised sockets with no CPC. Possibly leave them some temporary power or try and connect whichevet socket have an earth as I would consider having no earth dangerous.

 

[JohnS888]

Are you sure that advice wasn't for a lighting circuit? An RFC without a CPC is a lot more dangerous.

Complete fail then? I should of walked away?

 

[Midwest]

Complete fail then? I should of walked away?

So are you saying this circuit that powers socket outlets, has no earthing?

 

[Pete999]

Pete
I have previously been in this situation and others have advised that no c.p.cs at sockets/appliances is not reason enough to not reenergise circuit. If advised client, noted this clearly on cert and put sticker on DB are you saying I shouldn't of done this and walked away from job without reenegising? Thanks

Yes I am

 

[JohnS888]

Yes I am

Ok thanks I'll call her and send email confirming this circuit should be powered off an not reenergised until all earthing has been rectified

 

[Risteard]

Scary stuff. It should be obvious to any competent Electrician that unearthed socket-outlets are completely unacceptable.

 

[Pete999]

Ok thanks I'll call her and send email confirming this circuit should be powered off an not reenergised until all earthing has been rectified

Go there yourself, disconnect all the RFC conductors at the CU and lock off the CB that was feeding the RFC asking your customer to switch it off is hardly a professional approach, It's your neck on the line mate, make sure 100% all RFC conductors are ditched from the CU.

 

[westward10]

You don't really have the authority to disconnect the circuit unless the client is happy with this. What you need to do is put in writing the possible consequences of the situation and get the client to sign it, then it is up to them. Unfortunately you have now altered the circuit when what you should have done, hindsight is a great thing, is left it as it was and notify the client. As it was it posed no threat as the rcbo was tripping but you have now reintroduced the hazard.

 

[Pete999]

You don't really have the authority to disconnect the circuit unless the client is happy with this. What you need to do is put in writing the possible consequences of the situation and get the client to sign it, then it is up to them. Unfortunately you have now altered the circuit when what you should have done, hindsight is a great thing, is left it as it was and notify the client. As it was it posed no threat as the rcbo was tripping but you have now reintroduced the hazard.

As a professional Electrician you should not leave some dangerous and as the client switch it off, sorry Westy, that's a lame excuse Mate. Would hate to think what would happen if the OP had left it was and Mr or Mrs Client had got a whack from something that wasn't Earthed and didn't do anything about it, think the Judge would have differing views to yours.

 

[westward10]

The worst thing he did was to alter it and get the circuit active again so at the moment he is now responsible for it. What I am saying is you put it in writing to the client and for them to sign it, leave the circuit as you found it which was tripping anyway and walk away.

 

[Pete999]

The worst thing he did was to alter it and get the circuit active again so at the moment he is now responsible for it. What I am saying is you put it in writing to the client and for them to sign it, leave the circuit as you found it which was tripping anyway and walk away.

That's one way I suppose!! So you have come across something that is potentially lethal and you walk away, what happened to the duty of care to your customer, out the window I presume? sorry Mate can't agree with your reasoning, flawed somewhat.

 

[westward10]

That's one way I suppose!!

It is the best way unfortunately for the OP he has now put the onus upon himself by altering it to make it live again.

 

[Pete999]

It is the best way unfortunately for the OP he has now put the onus upon himself by altering it to make it live again.

Which is why I suggested he go back and disconnect!!!! or at the least make safe, don't you think? probably not.

 

[Midwest]

I think in fairness to @JohnS888, he has tried to rectify a fault on an RFC by disconnecting the offending leg, reducing the size of the ocpd on the existing leg. Thats all good so far. What I can't understand exactly, is how there are no cpc's at the sockets?

As far as the appliances 'loosing power', I'm not quite sure what the landlord means by this. If @JohnS888 acknowledges he's dropped a bit of a clanger (every day is a school day), 'we' might be able to advise in a more helpful way.

 

[Baddegg]

OP....I think if you contact the client and explain the situation and tell em you’ll be round sharpish to sort it (it really is your problem now) I’m sure any sane person would take your advise and not use or even switch of the circuit breaker......and if you can do this in writing (text/email) as well all the better, live and learn mate just get back sharpish and sort it and then chalk it up and move on ?

 

[TJ Anderson]

Hi OP. The 0.05M/Ohm between L&N won't be the cause of your RCD tripping mate. Are you 100% sure you disconnected all the loads? Did you do any other tests?

 

[davesparks]

Go there yourself, disconnect all the RFC conductors at the CU and lock off the CB that was feeding the RFC asking your customer to switch it off is hardly a professional approach, It's your neck on the line mate, make sure 100% all RFC conductors are ditched from the CU.

Disconnecting the circuit until it is repaired properly is the best course of action yes, however it relies on the landlord and tenant giving permission for this to happen.

If the OP was to go to the property and disconnect the circuit without permission then they could be guilty of other offences.

As it is a rented property they cannot make an alteration to the installation without the landlord's permission and they cannot enter the property without the tenant's permission.
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Got call out yesterday for a ring circuit that kept tripping rcd. I identified the faulty cable which had low 0.05 IR reading L to N. I followed this to where next point should be but on opening circuit found only one cable...not good. On closer inspection of sockets I found that most of them had c.p.c's cut out. I can only imagine previous spark had thought this good idea as a previous earth fault had been tripping rcd.

. What has surprised me is landlord has phoned me since and rather than mcb tripping what's happening is when the various appliances are on other appliances lose power. Ie washine machine on and boiler stops working, cooker on washine machine stops working. Why would this be the case rather than mcb trip out? Thanks

Assuming that is supposed to be 0.05megohms L-N then that will be passing a current of around 5mA.
So there's two problems with suggesting that this is responsible for the RCD tripping, it's not enough current to trip an RCD and RCDs don't operate on L-N faults.

I doubt that it was an electrician who disconnected the CPCs, it is more likely a diyer. It could be the tenant or landlord attempting to solve a problem themselves.

If this loss of power was not happening before you worked in the circuit then it is likely that it is caused by something you have done, this could indicate a high resistance joint somewhere.
A possibke cause of this is incorrect fitting of the MCB so that the busbar prong is behind the moving part of the terminal and not clamped within it.