Ah, that's better. You have successfully unconfused me, and I now understand (I hope) what you really did meanFor example, a double socket in a lounge behind a TV is unlikely to be overloaded.
APOLOGIES: OMITTED WORDS ADDED.
Kind Regards, John.
Multiple FCUs
- Thread starter JohnW2
- Start date
Kind Regards, John.
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Yes.
Unbelievable.
And stupidly irresponsible.
You hadn't said that, hence my question to you.
But now you have:
No - what I reacted with was perfectly justified anger at the outrageous way John behaved because when he introduced a new design and asked me to comment I expressed a new concern.
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Only "probably"?
Do you still think that it might be compliant?
1) It is neither unrealistic nor unreasonable.
2) Without it there is a breach of the Wiring Regulations.
3) It is therefore absolutely necessary.
Were that a requirement then ring finals would be banned, for a start.
If you really don't think that changing an MCB is in principle no different from changing a fuse in an FCU then it's pointless trying to discuss this with you.
If you don't think that but are arguing for the sake of it then it's pointless trying to discuss this with you.
What's the Iz of the cable?
According to my copy of BS 7671, code 4 includes "This does not imply that the electrical installation inspected is unsafe."
I believe it would be, so I'd give it a Code 2.
You have to remember what "unsafe" means. It does not mean that something bad is guaranteed to happen". If you ride a motorcycle without a crash helmet and leathers you will probably not smash open your head and rip your skin off, but that does not mean that it was not unsafe.
It's hard to come up with a logical reason for choosing to contravene BS 7671.
How would you suggest he could be sure that he had done that if he just did what he fancied ot guessed would be OK, with no observation of any recognised formal standards?
And the relevance of that to
is what?
What's the Iz of the cable?
P
Paul_C
Fair enough - After catching up on all the confusion & "de-confusion" that occurred after I called it a night, I see that you recognize the concerns about the possibility of two heavy loads being connected to a double socket, and so would not install one on a non-fused spur. There was no intent to grill you about it as such, just to make the comparison between the two scenarios of a double socket on an unfused spur and multiple FCU's at the end of an unfused spur. So I can see your consistency in documenting the potential for a problem to arise if somebody changes the loads in the future against your policy of not putting a double socket on an unfused spur, even though permitted by the regs.
I think it's clear though that many who would flag up the multiple-FCU situation proposed by John would not have a problem with installing a double socket on an unfused spur, and that's where inconsistency of approach arises, since for a danger to arise in the former case requires somebody to physically hard-wire new loads into the FCU's and change the fuses, whereas for a danger to arise in the latter case requires only that somebody plugs two 3kW appliances into the socket.
But I still think that in the multiple-FCU scenario the responsibility for making sure that the existing arrangements are suitable for the new loads rests with whoever makes those changes at that future time.
Was that an 11kV-415V transformer feeding a local neighborhood, or an HV-HV unit further back along the chain?
Perhaps the answer is for the fuse holders in FCUs to be re-designed such that the rating of the fuse is determined by the holder. This would require that there was also a range of matching fuses where the mechanical size was related to the fuse's rating making it impossible to fit a 13 amp fuse into an FCU protecting a 3 amp circuit.
That won't of course prevent the determined, un-informed and thoughtless person changing the FCU at a later date.
That won't of course prevent the determined, un-informed and thoughtless person changing the FCU at a later date.
P
Paul_C
Why? Have I at any point suggested that the person fitting the new appliance should not check that the existing circuit is suitable?
This line started from the issue of a homeowner changing the load connected to an FCU, and a comparison with changing an oven. You asked for thoughts on whether such a change needed the issue of a BS7671 certificate (and seemed to be implying that you thought it unnecessary), to which I replied that I thought it would be justified if the work was being done by somebody who was working to BS7671. Others have said the same.
You asked how the average homeowner was supposed to complete such a certificate, to which I replied that he had no need to because he has no specific requirement to be following BS7671 to the last detail.
Does every homeowner who changes a light fitting, replaces a stove etc. have sufficient knowledge to follow all the details of BS7671, or any other formal standard? No. Hence why I said there's no need to follow any formal standard specifically. That doesn't mean that the person making the replacement shouldn't make sure the circuit is suitable for the replacement item.
I think John accepted that it is not compliant with BS7671 several pages ago. The question is whether somebody inspecting the installation is going to try and flag it up as being "unsatisfactory."
But as you are fully aware, those wiring regulations are not mandatory.
So if ring finals have not been banned because it's not considered essential to safeguard against what Mr. Homeowner might change incompetently in the future, why do you consider there to be a need to make provision for what incompetent changes he might make to John's FCU proposal?
It's not just about changing a fuse in an FCU. It's about changing the fuse and hard-wiring a new load to that FCU. Both that and changing an MCB require alterations to the fixed installation.
It depends on how it's installed obviously, but the regs. you are quoting as if they are the be-all and end-all of electrical installations permit it to be less than the total load which could be connected to a double socket.
No, but neither does mean that everything should be considered potentially unsafe because of what incompetent changes somebody might make in the future. Somebody might add half a dozen 500W floodlights to an existing lighting circuit wired in 1.00 sq. mm conductors and then change the fuse protecting that circuit to 15A. Does that mean that a perfectly safe 5A lighting circuit should be condemned as "potentially unsafe" because of that possibility? Or we're back to the replacement shower scenario again: Should you condemn a perfectly acceptable shower circuit wired in 6 sq. mm cable because somebody might change the shower and MCB later?
I never suggested guessing or anything like that.
The comparisons which have been made over the last several pages.
As above.
The point I was making is that some of those who would condemn John's FCU proposal because it doesn't comply with BS7671 would not have any such problem with a double socket on an unfused spur, even when the cable was run in such a way as to have a rating below the total load which could be connected to the sockets.
If you're going to argue that it's reasonable and realistic to put a 13A fuse upstream of the spur to the three FCU's, then it should, logically, be just as reasonable and realistic (more so in fact) to expect similar fuse protection for the spur feeding a double socket. (As in fact SecureSpark had indicated he provides for by using fused triple sockets on a spur but not doubles.)
As I've said, less than 26A, unless the cable is 'clipped direct' for its entire length.
Kind Regards, John.
That was, indeed, my initial question, and it has been well answered - there clearly are people who 'could have a problem'. Thank you, gentlemen.
The jury is out. The answer to that question depends entirely upon the extent to which a designer is allowed to determine/specify the 'design current' of a circuit supplying a fixed load.
Your view (and that of some others) is that the design current has to be based on what might happen if someone makes fundamental changes to the circuit (including changing to a much heavier hard-wired load) in the future. I'm far from convinced that has to be the case, and think that a designer probably is allowed more latitude/ discretion/ professional judgement than that - but I know you disagree with that.
Kind Regards, John.
It wasn't a 'new concern' which arose of out of any 'new design'. The single feed from the ring had been there all along, so you had had ample previous opportunities to express any concerns you may have had about the point loading of the ring. However, you didn't express any such concerns, the only concern you expressed relating to the CCC of the cable. When I suggested removing that concern for you, by increasing cable CSA (but changing nothing else) you obviously couldn't continue to use your previous argument, so raised the 'new concern' which you hadn't previously mentioned.
... and, regardless of the technical issues, your 'reaction' was quite unacceptable by any standards - and I see that the mods agreed with me about that.
Kind Regards, John.
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