T
trev
Funny you should mention that, I did an EICR on a dog grooming place the other week, 8.5k shower fed in 4mm, no MCB, supply to it shoved in with the tails then through an 80 amp RCD
K
Knobhead
Nick, just admit, you’re milking this job by adding totally unnecessary work.
Someone had to say it, it may as well be a grumpy git like me.
Someone had to say it, it may as well be a grumpy git like me.
L
Leesparkykent
I see something similar in a kebab shop for the fryers once, ironically the place was called blaze kebabs lol.
N
NickD
If I was going to milk the job, I would have just got on and milked it without asking about it. Actually I just want to do an engineeringly-correct job, if that's a word. If it suits you to believe that milking it is my motivation then that's your prerogative. I could think of a darn sight more lucrative ways to milk this job than bunging in an OCPD, if that was my inclination.
K
Knobhead
O
Octopus
N
NickD
Client at a job the other day had agreed a board change in order to extend the socket ring circuit. However with the fusebox cover off it became apparent that the standalone RCD next to it was protecting the socket circuit in question, not the shower circuit as advised. RCD was in good order and so was the socket ring circuit. Did I milk it by proceeding with the board change? No.
N
NickD
Forget any arguments you think I'm making then and please just answer my question; do you consider it is entirely justified and good engineering practice to rely on the present rating of the DNO's fuse to protect the consumer's tails?
O
Octopus
Im not getting why you ask a question, then argue to ---- about the replies.
In this situation it really does seem that Tony has hit the nail on the head. Its as if you want someone to justify your point of view. If there is no evidence that the current tails are under any pressure, why don't you leave them be, or when you ask for an isolator to be put in in order to change the consumer unit, ask the engineer to add a 60/80 and not the standard 100A they always seem to put in.
Don't ask questions if your point of view is set in stone...
In this situation it really does seem that Tony has hit the nail on the head. Its as if you want someone to justify your point of view. If there is no evidence that the current tails are under any pressure, why don't you leave them be, or when you ask for an isolator to be put in in order to change the consumer unit, ask the engineer to add a 60/80 and not the standard 100A they always seem to put in.
Don't ask questions if your point of view is set in stone...
K
Knobhead
One of the first questions you were asked was “what size is the DNO fuse?”
You don’t know.
Will the DNO suddenly decide to up the fuse?
You don’t know.
Will the load dramatically increase?
You don’t know.
About the only thing you do know is that there has been no problem to date.
N
NickD
No, absolutely not, not at all. I don't actually have a point of view on the answer to this. I would be very happy indeed to walk away from this confident that leaving the 16mm tails in situ, relying long-term on the rating of the DNO fuse for their protection, was a totally reasonable and defensible engineering proposition.
Let's try again...
The stated purpose of the DNO fuse is to protect the DNO's cable upstream of it, and any protection it gives to the consumer's system downstream of it is mere happy accident. It is unclear (to me, anyway) what the duty of care of the DNO is if it goes to uprate the fuse when the consumer's system in fact relies on the present rating of the fuse for its safety. The DNO is a large complex organisation with which I am not particularly familiar. I can have no real control over what it does with the fuse in the future, and I would be kidding myself if I were to make blanket assumptions about the DNO's operational processes and practices (including about them complying with what may appear to me to be common sense).
However, what makes it legitimate and reasonable for me to rely on the present rating of the DNO fuse to protect the consumer's tails for the long term, is the following: _____________
Please fill in the blank. Thanks.
PS If you believe "The tails have been OK up to now" is a good answer then with respect I think you've missed my point.
Last edited by a moderator:
D
dcelectrical
am I being thick here, I have never known the DNO to come in and change fuses, they generally ask us to change them when a builder pops them and nicks the one from the flat next door before walking away whistling the tune of rawhide.
K
Knobhead
N
NickD
- May 6, 2008
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The problem we have here is this quote from the opening post
quote
Ordinarily I would upgrade the tails & EC to 25/16 as a matter of course
The post then goes on to describe the difficulty in routing the proposed tails
I may be wrong but it seems to me that the question of the supplier fuse (given the above quote)is never taken into account and it is only now mentioned because of routing problems for those tails
It is for this reason that I think the post is looking for justification of the change ( when he knows full well its not required) and he is unfortunately clutching at straws to allay the criticism that has been given
quote
Ordinarily I would upgrade the tails & EC to 25/16 as a matter of course
The post then goes on to describe the difficulty in routing the proposed tails
I may be wrong but it seems to me that the question of the supplier fuse (given the above quote)is never taken into account and it is only now mentioned because of routing problems for those tails
It is for this reason that I think the post is looking for justification of the change ( when he knows full well its not required) and he is unfortunately clutching at straws to allay the criticism that has been given
N
NickD
If you want to think that, that is of course your prerogative; and it would seem the logical next step is to blow me out of the water by filling in the blank with a great answer, which totally convinces with reason and evidence why the tails can be left as they are as long as the present DNO rating protects them.
Alternatively, if I have no such agenda and am genuinely asking the question, the logical next step is to fill in the blank with a great answer, which totally convinces with reason and evidence why the tails can be left as they are as long as the present DNO rating protects them.
K
Knobhead
The service fuse will be a BS88, about a subtle as a brick under O/L. It won’t limit the fault current.
If you consider that in urban areas the feeder cables may be protected by 400A or even 630A fuses a 35mm[SUP]2[/SUP] concentric doesn’t stand a chance.
That weakness is part of the protection. A fault on a small service cable the cable will act as the fuse and blow the fault clear.
It’s as rough as the proverbial badgers arse, but it works.
N
NickD
I bow to your superior knowledge. Could you be so kind as to deploy it in the direction of answering my question?
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