Old 'KMF' on EICR

[SimonH2]

One other thing no-one else has yet mentioned - by having those isolators/switches downstream of the corresponding fuses, the fuses could only replaced 'live' (unless there is some way of isolating them upstream of what we have seen) - which would not really be acceptable.

Of questionable risk. You can turn off the isolator so you know you are not changing them "under load", and they are single pole made of non-conducting material so there is just about zero risk of a short to anything (unlike the old cast iron cutouts). So that only leaves the risk of personal contact and/or the fuse holder breaking - but we have unswitched FCUs, and most people used to change fuses (before MCBs) without switching the whole house off.
So I'd not be too concerned about that.

As to making the cupboard a locked "enclosure", that has practical problems - and not just by making the means of isolation inaccessible. Unless the "instructed person(s)" is available any time a meter read is needed, then that's a problem.

 

[JohnW2]

Of questionable risk. You can turn off the isolator so you know you are not changing them "under load", and they are single pole made of non-conducting material so there is just about zero risk of a short to anything (unlike the old cast iron cutouts). So that only leaves the risk of personal contact and/or the fuse holder breaking ...

I largely agree ... but are you suggesting that we should therefore stop 'warning off' (for safety, rather than 'legal', reasons) DIYers from pulling fuses from DNO cutouts, provided that they are plastic?

However, to avoid any concerns/discussions, if one is going to install a separate fuse and isolator, why on earth install the isolator downstream of the fuse?

As to making the cupboard a locked "enclosure", that has practical problems - and not just by making the means of isolation inaccessible. Unless the "instructed person(s)" is available any time a meter read is needed, then that's a problem.

Not a problem if one has a 'smart' meter

Interestingly, in this discussion about "cupboards", I don't think anyone has come up with the "instructed person(s)" thing (i.e. the talk has only been about 'a key', not who has/uses it)! Having said that, I would personally not want any part of the electrical installation in my house (including DNO's/supplier's bits) behind a locked door, even if I had (or was meant to always have!) the key!

Kind Regards, John

 

[SUNRAY]

I largely agree ... but are you suggesting that we should therefore stop 'warning off' (for safety, rather than 'legal', reasons) DIYers from pulling fuses from DNO cutouts, provided that they are plastic?

However, to avoid any concerns/discussions, if one is going to install a separate fuse and isolator, why on earth install the isolator downstream of the fuse?
Not a problem if one has a 'smart' meter

Interestingly, in this discussion about "cupboards", I don't think anyone has come up with the "instructed person(s)" thing (i.e. the talk has only been about 'a key', not who has/uses it)! Having said that, I would personally not want any part of the electrical installation in my house (including DNO's/supplier's bits) behind a locked door, even if I had (or was meant to always have!) the key!

Kind Regards, John

In portable kit the fuse is usually the first thing on the end of the mains lead, It's often built into the IEC plug for example. I realise it's a different situation as there's a preceeding disconnexion point but how many times have we changed such a fuse with the kit still plugged in [apart from the IEC cases]?

 

[JohnW2]

In portable kit the fuse is usually the first thing on the end of the mains lead, It's often built into the IEC plug for example. I realise it's a different situation as there's a preceeding disconnexion point but how many times have we changed such a fuse with the kit still plugged in [apart from the IEC cases]?

Yes, I think that is a pretty different situation.

However, in terms of the actual situation we're looking at, my point/question remains that if one is going to install a fuse and separate isolator in series, why on earth would one even think of putting the isolator downstream of the fuse - am I missing some 'advantage' of doing it that way?

Kind Regards, John

 

[SUNRAY]

Yes, I think that is a pretty different situation.

However, in terms of the actual situation we're looking at, my point/question remains that if one is going to install a fuse and separate isolator in series, why on earth would one even think of putting the isolator downstream of the fuse - am I missing some 'advantage' of doing it that way?

Kind Regards, John

Well the obvious would be having to replace the switch for any reason. I'd say theere's more chance of the switch failing than the fuse holder.

 

[JohnW2]

Well the obvious would be having to replace the switch for any reason. I'd say theere's more chance of the switch failing than the fuse holder.

Hmmm. In the situation we're talking about, provided that the switch was properly installed (without 'loose connections' ) and given that it would (presumably) hardly ever be operated, I wouldn't expect it to need replacing for many decades, would you?

Kind Regards, John

 

[SUNRAY]

Hmmm. In the situation we're talking about, provided that the switch was properly installed (without 'loose connections' ) and given that it would (presumably) hardly ever be operated, I wouldn't expect it to need replacing for many decades, would you?

Kind Regards, John

No but equally we could ask if the fuse is likely to blow...

 

[JohnW2]

No but equally we could ask if the fuse is likely to blow...

In the situation we're talking about, it's obviously very likely that either would happen - but, given that it is solely at the mercy of what happens downstream, I would have thought that it would me much more likely (albeit very unlikley!) that the fuse would blow than than a virtually-never-operated switch would fail (incredibly unlikley).

Would you have advised (or, indeed, would you today advise!) someone to remove/replace a fuse in a Wylex Standard box with the Main Switch 'on'?

Kind Regards, John

 

[SUNRAY]

In the situation we're talking about, it's obviously very likely that either would happen - but, given that it is solely at the mercy of what happens downstream, I would have thought that it would me much more likely (albeit very unlikley!) that the fuse would blow than than a virtually-never-operated switch would fail (incredibly unlikley).

Would you have advised (or, indeed, would you today advise!) someone to remove/replace a fuse in a Wylex Standard box with the Main Switch 'on'?

Kind Regards, John

I'll plead 5th amendment

 

[JohnW2]

I'll plead 5th amendment

We don't have one of those

However, as a general statement (and putting aside your argument that isolators might be more like to fail than fuses are likely to blow!), it is surely the case that one would prefer to have a situation in which a fuse (of any sort) was de-energised before it was pulled/

Despite your 5th Amendment plea (and despite the fact that many of us have probably done both ourselves!), I'm sure we would tell anyone that they shouldn't pull a BS3036 fuse from a Wylex (or whatever) box without switching off the Main Switch, let alone pull a DNO fuse from a plastic cutout, wouldn't we?

Kind Regards, John

 

[SimonH2]

I largely agree ... but are you suggesting that we should therefore stop 'warning off' (for safety, rather than 'legal', reasons) DIYers from pulling fuses from DNO cutouts, provided that they are plastic?

Like many things, IMO that's one best left as the simplistic "don't do it, there are a number of risks". Easier than saying "don't do it unless it's plastic, in good condition, there's an R in the month, and you had Weetabix for breakfast"

However, to avoid any concerns/discussions, if one is going to install a separate fuse and isolator, why on earth install the isolator downstream of the fuse?

I agree.
But then playing devil's advocate, some time ago I vaguely recall asking on here about an FCU a friend had bought, which was a separate switch and fuse holder - pre-configured with the switch after the fuse. Ah, here it is ...
There didn't seem to be much concern about having the fuse first. Obviously there's more scope for touching a live terminal with one of those bigger fuse holders, but that's the only difference I can see.

Not a problem if one has a 'smart' meter

No, but then you have a different problem - but lets not review that discussion again At church I'm back to doing meter readings since the "smart" meters are the old style that go dumb when you switch supplier.

Interestingly, in this discussion about "cupboards", I don't think anyone has come up with the "instructed person(s)" thing (i.e. the talk has only been about 'a key', not who has/uses it)!

Indeed. However, in this case there's nothing the user could touch (less in fact) than they could touch inside pretty well any enclosure ina domestic setting with nothing more than a screwdriver that vaguely fits the cover screws.

Having said that, I would personally not want any part of the electrical installation in my house (including DNO's/supplier's bits) behind a locked door, even if I had (or was meant to always have!) the key!

Ditto
But in our house, there is a small padlock hasp as the meter cupboard is in what was (under previous ownership) the young lad's room - so the parents had it locked to keep inquisitive little fingers out.

 

[JohnW2]

Like many things, IMO that's one best left as the simplistic "don't do it, there are a number of risks". Easier than saying "don't do it unless it's plastic, in good condition, there's an R in the month, and you had Weetabix for breakfast"

What we may do (probably pretty safely) ourselves is one thing, but I really don't think that we would/should tell someone here that it was OK to pull a cutout fuse, even if it were plastic, in good condition, with an R in the month and they had had Weetabix for breakfast.

I agree. But ...

I personally don't see that there is any "but". Even if the risks are minimal, if the situation is such that one is installing a fuse and separate isolator in series, I really see no reason or excuse for ever putting the isolator/switch downstream of the fuse ... and I dismiss the argument that such an arrangement would allow one to replace the isolator/switch by removing the fuse

But in our house, there is a small padlock hasp as the meter cupboard is in what was (under previous ownership) the young lad's room - so the parents had it locked to keep inquisitive little fingers out.

I suppose we are back to 'risk assessments' again - but it doesn't alter the fact that I don't think I would be totally comfortable living in a house in which 'central' parts of the electrical installation could only be accessed by use of a key which I may or may not have immediately to hand if/when I 'needed' it in anger!

Kind Regards, John