I personally think the main question (in addition to cost) about AFDDs in domestic installations is whether they are in any sensible sense 'needed', on any circuit (not just 6A ones)!
Kind Regards, John
Circuit tripping VO ELCB
- Thread starter Corjj
- Start date
Kind Regards, John
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They are an IET recommendation, therefore a client should be advised of that, so that they can make their informed decision. If the client asked me, would I have them in my house, the answer would be no.
I have copied and pasted my comment from another post
-This thread has reminded of a problem I encountered many years ago. I had to force a spur cable through a very small gap and had to form a very tight right angle. A few months later the cable failed, and I found the cable was badly burnt at the tight right angle. At the time I had no idea what had caused the burning. But it seems this must have been due to series arcing caused by my mistreatment of the cable.
On the few occasions when I have run a 2.5 through a box I have always had to force it into the corners of the box using a hammer shaft or other blunt instrument. Seems to me forcing the cable into a box is creating the perfect conditions for series arcing - and possible fire.
Don't do it.-
That is the only occasion in many years of work that an affd might have tripped due to a fault created by me. A fault that could have had extremely serious consequences.
I have copied and pasted my comment from another post
-This thread has reminded of a problem I encountered many years ago. I had to force a spur cable through a very small gap and had to form a very tight right angle. A few months later the cable failed, and I found the cable was badly burnt at the tight right angle. At the time I had no idea what had caused the burning. But it seems this must have been due to series arcing caused by my mistreatment of the cable.
On the few occasions when I have run a 2.5 through a box I have always had to force it into the corners of the box using a hammer shaft or other blunt instrument. Seems to me forcing the cable into a box is creating the perfect conditions for series arcing - and possible fire.
Don't do it.-
That is the only occasion in many years of work that an affd might have tripped due to a fault created by me. A fault that could have had extremely serious consequences.
Does you mean AFDD and not AFFD
In case he hasn't explained about Arc Fault Detection Devices ( AFDD ).....
https://www.electriciancourses4u.co...know-about-arc-fault-detection-devices-afdds/
Maybe, but I would personally think that such would be an extremely rare type of fault, and an even more extremely rare cause of "extremely serious consequences". Apart from anything else, a cable fault which resulted in series arcing would presumably usually become rapidly apparent due to malfunction of the circuit. So, like you, I personally would certainly not perceive a need for AFDDs in my own home!
In any event, I would have thought that thermal damage to cables, and even consequent fires, behind accessories would be far more commonly due to poor connections - which do not necessarily result in arcing that would be detected by an AFDD.
However, as you say, I suppose it's appropriate to make clients aware of 'recommendations', whatever one's personal views may be!
Kind Regards, John
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Yeah we discussed SPDs and agreed they would be fitted. The fusebox one does have one fitted and believe it also has a dedicated MCB for the SPD. I will check about circuit checks, his T&Cs do say:
Where work is to extend or modify existing circuits, costs quoted assume that the existing installation is in adequate condition and complies with minimum current regulations. Any works found required to bring the necessary parts of the existing installation up to standard will be at additional cost.
Seems fair and appears to be from a standard T&C pack.
I was also going to check whether I should get the DP versions as they are £4 more each and help with full circuit isolation I guess without having to use the main isolator?
Wow that would soon add up! Seem good though.
I think that's unfair for a CU replacement, he has to fully test as part of those works. But if he tests before he starts it makes any faults found more manageable to rectify. Of course you will have to pay extra, but its better than him completing the replacement and finding for example the lighting rcbo keep tripping due to a borrowed neutral (very common fault) and you're standing in the dark. Doing the full test first means he would only need to do a couple of spot checks when he's complete.
Let’s just remind ourselves the whole point of this thread.
The voleb was tripping
So let’s assume one circuit has a fault and needs investigating (first ideally)
The voleb was tripping
So let’s assume one circuit has a fault and needs investigating (first ideally)
Make sure they're Type A and not crappy Type AC also.
Yeah saw they are only a little bit more for A which seems worth it.
We haven't fitted Type AC for many years now. Frankly they should be banned in this day and age.
So I asked the electrician whether testing of circuits will be done before the installation and he said normally he doesn't, only once CU is installed.
Also when checking that the spec of the RCBOs was OK as he specified trip curve and sizes, I put "I assume Type A, DP ones are preferable?" response came back "no you need type B".
I know from the thread and research that the best option is trip curve B, type A DP so will order based on that, but not fully reassured by responses. It also does make me wonder what type he used when doing a CU replacement at my other place follow an EICR failing it.
At the end of the day as long as I have a compliant, certificated and safely installed CU to replace existing I'm happy - I know from my background as an engineer I maybe get involved in the details too much at times and like to ask questions.
Also when checking that the spec of the RCBOs was OK as he specified trip curve and sizes, I put "I assume Type A, DP ones are preferable?" response came back "no you need type B".
I know from the thread and research that the best option is trip curve B, type A DP so will order based on that, but not fully reassured by responses. It also does make me wonder what type he used when doing a CU replacement at my other place follow an EICR failing it.
At the end of the day as long as I have a compliant, certificated and safely installed CU to replace existing I'm happy - I know from my background as an engineer I maybe get involved in the details too much at times and like to ask questions.
He's referring to the overcurrent characteristics of the circuit breaker. Type B in RCD terms is completely different (allowing substantial DC currents not to blind the device), but are generally prohibitively expensive.
I think there are a fare few sparks out there (in UK) who don't know what a type AC or A RCD is.
And even if he does, he may not expect a layman to know.
Type A RCD were only mentioned in a recent regulations update AFAIK, and even then not mandatary.
It should be noted wylex RCBO's (and therefore crabtree and volex etc) have been Type A for decades, as well as the older MK
And even if he does, he may not expect a layman to know.
Type A RCD were only mentioned in a recent regulations update AFAIK, and even then not mandatary.
It should be noted wylex RCBO's (and therefore crabtree and volex etc) have been Type A for decades, as well as the older MK
Quite so - and whoever started this practice/fashion of using "Type" to refer to two totally different characteristics of an RCD/RCBO (which results in total ambiguity with "Type B") probably deserves to be shot!
Kind Regards, John
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