Upgrading home service from 60Amp to 100Amp

[David.S]

My house was built in the 1930s, The fuse in my service cut out is 60Amp and the wire coming from the street has a 16mm2 copper core(easy to see against the 25mm2 copper tails into the smart meter)

I am ready to install a new 10.8kW Shower, Is a simple fuse change sufficient?

Ive been told by an electrician that the 16mm2 cable coming from the street should be 25mm2 to support a 100A fuse.

I have 6 other people in the house, a 4.2kw oven, and 7kw electric car charger.

Its impractical to take turns in using appliances, on certain days the EV charger, oven, and shower could be in use at once, Along with TV, PlayStation, Kettle, etc also being used.

What would you guys advise?

 

[Andy™]

ask DNO. but since its you wanting additional capacity then expect to pay for it. possibly several thousand depending what needs done. sometimes it may be a new fuse, sometimes a new cable to street. maybe new cables in the street or transformer

most EV chargers can be set to slower charging if overall demand is high, so thats upto 7kw saved during busy times. or fit a lower rating shower too

 

[Geoff1946]

They may be willing to fit an 80amp fuse. Should be adequate and save you a lot of money if the 100amp demands a cable change.
The DNOs have their own rules for cable sizing too.

 

[kerching]

Interested to know how you ascertained it’s a 16mm incomer without physically seeing the copper core? Or did you?
Cable types, insulation and sheath/servings vary from cable to cable so only experience helps if going off external appearances

 

[Andy™]

at a guess he's only looked at the cable between service head and meter compared to meter & consumer unit. actual supply cable size is probably unknown and could be anything

 

[binky]

Your electrician is talking drivel. Most DNO cables are 10mm split concentric. DNOs work to their own rules with regards to cable sizes and I've never seen 25mm on a domestic property Unless you are planning to charge your EV during the day instead of taking advantage of off peak tariffs,I doubt you will have any problems with a 60A main fuse. The fuses used don't just blow at bang on 60 Amps anyway, how quickly they blow depends on how overloaded they are, and that means they can tolerate more than 60A for quite a while sometimes. I would talk to your DNO about possible concerns your main fuse holder is old and therefore potentially dangerous - should get a free upgrade that way.

 

[Murdoch]

You need to talk to the network operator for your area

Out of interest , did you disclose the addition of the EV charger to the network operator ?

 

[ProDave]

Your electrician is talking drivel. Most DNO cables are 10mm split concentric. DNOs work to their own rules with regards to cable sizes and I've never seen 25mm on a domestic property Unless you are planning to charge your EV

Every new build I have worked on here in the last 20 years has a 25mm or sometimes even a 35mm (depending on length) incomer and 25mm tails from supply head to meter.

My own house has 35mm concentric incomer that joins under the street to 95mm for the run up the road to the transformer.

 

[binky]

Every new build I have worked on here in the last 20 years has a 25mm or sometimes even a 35mm (depending on length) incomer and 25mm tails from supply head to meter.

My own house has 35mm concentric incomer that joins under the street to 95mm for the run up the road to the transformer.

you're in Scotty land though. Have to say I rarely work on new build.

 

[Radiotowers]

Every new build I have worked on here in the last 20 years has a 25mm or sometimes even a 35mm (depending on length) incomer and 25mm tails from supply head to meter.

My own house has 35mm concentric incomer that joins under the street to 95mm for the run up the road to the transformer.

Agree
here in central Scotland it was either 16mm copper, lead sheathed or 25mm aluminium concentric underground mains supply.
Wirebacks ( and sometimes incoming overhead) could be old 10mm equivalent VIR with rewirable 30amp fuse carriers but normally 25mm concentric.
The cablehead type is the usual deciding factor, some underground supply cableheads are only rated at 80 or 60 amp ( usually black bakelite) and will normally be marked as such, so an upgrade to 100A could be requested.
I would request the DNO to do a safety check for confirmation.

 

[David.S]

ask DNO. but since its you wanting additional capacity then expect to pay for it. possibly several thousand depending what needs done. sometimes it may be a new fuse, sometimes a new cable to street. maybe new cables in the street or transformer

most EV chargers can be set to slower charging if overall demand is high, so thats upto 7kw saved during busy times. or fit a lower rating shower too

They may be willing to fit an 80amp fuse. Should be adequate and save you a lot of money if the 100amp demands a cable change.
The DNOs have their own rules for cable sizing too.

Thanks, Both of these are good options to think about.

Every new build I have worked on here in the last 20 years has a 25mm or sometimes even a 35mm (depending on length) incomer and 25mm tails from supply head to meter.

My own house has 35mm concentric incomer that joins under the street to 95mm for the run up the road to the transformer.

What core size would the live and neutral be on a 35mm concentric incomer?

Interested to know how you ascertained it’s a 16mm incomer without physically seeing the copper core? Or did you?
Cable types, insulation and sheath/servings vary from cable to cable so only experience helps if going off external appearances

Your electrician is talking drivel. Most DNO cables are 10mm split concentric. DNOs work to their own rules with regards to cable sizes and I've never seen 25mm on a domestic property Unless you are planning to charge your EV during the day instead of taking advantage of off peak tariffs,I doubt you will have any problems with a 60A main fuse. The fuses used don't just blow at bang on 60 Amps anyway, how quickly they blow depends on how overloaded they are, and that means they can tolerate more than 60A for quite a while sometimes. I would talk to your DNO about possible concerns your main fuse holder is old and therefore potentially dangerous - should get a free upgrade that way.

Actual photo from my property. - Live incoming identical to neutral in pic, The cutout has no metal ferrule crimps preventing cover removal.

You need to talk to the network operator for your area

Out of interest , did you disclose the addition of the EV charger to the network operator ?

Yes it was disclosed two years ago

 

[ProDave]

What core size would the live and neutral be on a 35mm concentric incomer?

35mm

 

[Andy™]

What core size would the live and neutral be on a 35mm concentric incomer?

er.. 35?

 

[SPECIAL LOCATION]

I am ready to install a new 10.8kW Shower, Is a simple fuse change sufficient?

What would you guys advise?

If you are aware that the incoming supply has limitations why even consider a 10.8kW shower??

Dropping the rating a bit is probably a useful improvement with minimal loss of actual perceivable performance..
and less hassle than faffing around with upgrading cut-out fuse.

 

[David.S]

35mm

Is that the most common setup in scotland? Thats a big difference.

er.. 35?

Wasn't sure if the 35mm included outer casing

If you are aware that the incoming supply has limitations why even consider a 10.8kW shower??

Dropping the rating a bit is probably a useful improvement with minimal loss of actual perceivable performance..
and less hassle than faffing around with upgrading cut-out fuse.

I wasnt aware until after electrician attended.
if fuse can be upgraded from 60A to 80A then its not faffing around.

 

[johnb2713]

Your electrician is talking drivel. Most DNO cables are 10mm split concentric. DNOs work to their own rules with regards to cable sizes and I've never seen 25mm on a domestic property Unless you are planning to charge your EV during the day instead of taking advantage of off peak tariffs,I doubt you will have any problems with a 60A main fuse. The fuses used don't just blow at bang on 60 Amps anyway, how quickly they blow depends on how overloaded they are, and that means they can tolerate more than 60A for quite a while sometimes. I would talk to your DNO about possible concerns your main fuse holder is old and therefore potentially dangerous - should get a free upgrade that way.

60 amp fuse takes 10 minutes to blow with 100 amps going through it !



Im not suggesting it should be a regular practice but a momentary overload is easily tolerated.

 

[Geoff1946]

As it was once explained to me, "fuses are for short circuit protection, circuit breakers give overload protection".
An over simplification, I know, but true.

 

[Radiotowers]

35mm

correct

 

[apprentice87]

Is that the most common setup in scotland? Thats a big difference.



Wasn't sure if the 35mm included outer casing



I wasnt aware until after electrician attended.
if fuse can be upgraded from 60A to 80A then its not faffing around.

It is 35mm2 cross sectional AREA. NOT NOT NOT the diameter of the cable...

john..

 

[apprentice87]

The currently used DNO service cables are either 25 or 35mm CNE "hybrid" cables. The inner core is aluminium, just under 7mm DIAMETER, and the entire cable outer diameter is about 1/2" diameter.. [for a 25mm] the 35mm being slightly more..

Here are the single phase and three phase versions.

john.