upgrade meter tails, or downgrade main incoming fuse??

[martinsayer81]

hi guys

hoping you could give me your thoughts,

i am pricing for a consumer unit change, its an old fuseboard with re-wireables.
it has 16mm meter tails, but it has a fairly new looking 100A main fuse.

its a small-ish house..... 2 ring mains, 2 lighting radials, a couple of sockets in the garage, and an immersion heater radial,

i was wondering whether or not i could just down-grade the main fuse to a 60A and keep the existing 16mm tails( no damage, or signs of overheating or burning)
or whether i have to leave the fuse at 100A and fit 25mm tails?

there's no electric shower or oven,

i would appreciate your advice

many thanks

 

[Knobhead]

:s every new property has this as standard so copper prices are not the issue , the guys asked for advice put in 25mm and allow for growth of the electrical system

Planet Spongle I think.

What groth of the electrical system, it's a house for gods sake!

 

[SLSpark]

Planet Spongle I think.

What groth of the electrical system, it's a house for gods sake!

Yes a house with no electric shower electric cooker ,pv system outbuilding supplys etc etc etc.

if the fuse is sealed and there is local isolation how do you know what size the fuse is ,only indication it the 100a sticker on cable head fuse.

still cant see the big fuss about fitting 25mm tails while changing a DB

:s

 

[SYKRAPS]

Its the weekend, everyone should be smiling and playing nicely

 

[imago]

Regulations, guidance notes, DNO requirements, actual demand figures, and fuse sizes. To be honest the main reason I upgrade to 25mm tails is for an easy/quiet life.

I could demonstrate by readings and/or calculations that 16mm would be more than adequate. The thing is though, it's easier, cheaper, and quicker just to swap the tails out, so I do. The same goes for 10mm to 16mm main earth and 6mm to 10mm bonding in a lot of cases too.

 

[SLSpark]

Regulations, guidance notes, DNO requirements, actual demand figures, and fuse sizes. To be honest the main reason I upgrade to 25mm tails is for an easy/quiet life.

I could demonstrate by readings and/or calculations that 16mm would be more than adequate. The thing is though, it's easier, cheaper, and quicker just to swap the tails out, so I do. The same goes for 10mm to 16mm main earth and 6mm to 10mm bonding in a lot of cases too.

my point exactly ,i also upgrade the main earth to 16mm,
no ones said 16mm mains tails isnt adequate but good practice to upgrade while changing DB.

 

[GLENNSPARK]

Planet Spongle I think.

What groth of the electrical system, it's a house for gods sake!

i think he might mean growers tony.....

 

[Engineer54]

Regulations, guidance notes, DNO requirements, actual demand figures, and fuse sizes. To be honest the main reason I upgrade to 25mm tails is for an easy/quiet life.

I could demonstrate by readings and/or calculations that 16mm would be more than adequate. The thing is though, it's easier, cheaper, and quicker just to swap the tails out, so I do. The same goes for 10mm to 16mm main earth and 6mm to 10mm bonding in a lot of cases too.

What's easy about dressing and connecting 25mm tails into tight CU enclosures, when in most circumstances isn't actually required anyway?? I maybe missing something here, but how is it ''easier, quicker and cheaper'' to swap out, the existing correctly sized tails for unnecessary 25mm tails??

 

[SLSpark]

What's easy about dressing and connecting 25mm tails into tight CU enclosures, when in most circumstances isn't actually required anyway?? I maybe missing something here, but how is it ''easier, quicker and cheaper'' to swap out, the existing correctly sized tails for unnecessary 25mm tails??

I personally don't find it a challenge to connect 25mm tails into any db I have fitted terminals are more than adequately sized and easy enough to "dress" the 3 meters max of cable

 

[imago]

What's easy about dressing and connecting 25mm tails into tight CU enclosures, when in most circumstances isn't actually required anyway?? I maybe missing something here, but how is it ''easier, quicker and cheaper'' to swap out, the existing correctly sized tails for unnecessary 25mm tails??

They're not too bad to do into a Hager board which is what I use 99% of the time, but I take your point. A 'typical' CU change for me will be on a three bed house built from the '30s to the '70s. A lot of them will have vastly increased loads from the original or even the rewired in the '70s or '80s installation. You are quite right that they're still nowhere near the 100 or even 80 amp draw though. I find customers fall into two categories mostly: 1) Don't care what you need to do, just get on with it. and 2) Read up a bit, or had another 'electrician' in to quote. The larger group is 2). So for me to take time explaining why the 'advice' they've found on the internet, or the "You've got to upgrade the tails." statement by previous sparks isn't necessarily the case takes too long for the additional few quid difference in replacing the tails. If you vary too far from the majority 'opinion' in a lot of cases it can give the impression you're cutting corners.

 

[Engineer54]

I personally don't find it a challenge to connect 25mm tails into any db I have fitted terminals are more than adequately sized and easy enough to "dress" the 3 meters max of cable

Just not necessary in the majority of cases!!

I was talking about within the CU, not outside of it. Wasn't saying that terminals weren't adequately sized either. But your not telling me that 25mm tails in a CU, aren't more of a challenge to dress than 16mm. Most UK CU's, don't give you much room for any wiring, some are a real challenge space wise, to fit RCBOS . ..lol!!!

 

[Knobhead]

i think he might mean growers tony.....


View attachment 15772

Special regulations apply there Glenn, you need the 17[SUP]th[/SUP] edition of the Hydroponics Wiring Regulations.

 

[danf1966]

OSG .....2.2.3 minimum tail csa should be 25mm

 

[imago]

OSG .....2.2.3 minimum tail csa should be 25mm

OSG On Site Guide

 

[GLENNSPARK]

OSG .....2.2.3 minimum tail csa should be 25mm

aye and it also shows a nice diagram of a TT system with 16mm CSA main earthing....lol....

 

[GLENNSPARK]

Special regulations apply there Glenn, you need the 17[SUP]th[/SUP] edition of the Hydroponics Wiring Regulations.

the `happy funny farm` eh...lol...:rolleyes4: