Domestic very simple question

[SUNRAY]

The question is simple: what minimum cutout fuse required for 2 family homes with solid fuel heating:

 

[plugwash]

Does the EV charger have a grid limit function? and is there wiring in place to make use of it?

 

[Murdochcat]

100A but maybe 60

 

[flameport]

2x80A
Sling the electric showers away and it can all be done on 1x80A, or even 1x60A

 

[Adam_151]

If as plugwash asks the EVSE has a grid limit function set to whatever the size of the supply fuse is, then that becomes irrelevant as that cant contribute to pushing it over the limit because it'll scale back as far as required to avoid that, so the only real worry left is the showers, if you assume 15 min showers, and the use is somewhat randomised, then perhaps we will assume overlap of use of both of them is not likely to exceed 5mins. A look at the time current curves for BS88 suggests that a load of double its rating will not take it out in that time, so thats 87.5A for the showers and another 32.5A averaged for the domestic loads in both properties (It'll peak above this when the kettle boils - but never for long). I'd reckon the 60A fuse will probably survive for years without trouble, dispite seeing somewhat regular overloads. A 40A one would probably have a supprisingly long lifepan, but will probably get taken out on a cold winter's night when its most inconvieninet.

I can pull about 20kw ~80A here but only for a short duration and only when really trying to, it was a bit of an experiment during a negative pricing period on octopus agile, the dryer was on, missus was using the electric shower, the car was charging, I was vaccuuming it out and I nipped in, pressed the button on the one cup kettle and resumed vacuuming while my cup of tea got boiled and brewed for when I finished the job.

I've seen a whole block of retirement flats, where if you calc'ed diversity as per the OSG, you'd probably need a 1.5Mva Tx on site, but it had a standard CT metered service with 400A head and chamber, a colleague thought it might be fused at the maximum 400A, I kinda thought you'd probably get away with 200 or 250A for a site like that. When DNO came out to isolate for main switchgear change, we found it was on 3x100A fuses, for about 50/60 1 bed apartments, all with electric cooker, some with shower. It had not caused an issue in practice since it was built in the mid 1980s

 

[JohnW2]

I can pull about 20kw ~80A here but only for a short duration and only when really trying to, it was a bit of an experiment during a negative pricing period on octopus agile, the dryer was on, missus was using the electric shower, the car was charging, I was vaccuuming it out and I nipped in, pressed the button on the one cup kettle and resumed vacuuming while my cup of tea got boiled and brewed for when I finished the job.

I recently re-posted (here) data I posted a few years ago relating to the total instantaneous electricity consumption in my (very large) house over a period of about 2.5 years (1.35 million minutes). The bottom-line summary was this:

so, during that period, my total instantaneous consumption was over 40 A for only 6 of the 1,350,00 minutes, and only for 1.58% of the time was the total instantaneous draw more than 20 A.

 

[ericmark]

Like @JohnW2 I also have a large house with flat below it, with a 60 amp DNO fuse, two kitchens, all electric cooking instent electric showers two of them, and the fuse has not blown, but that does not say that's the way it should be done.

 

[SUNRAY]

2x80A
Sling the electric showers away and it can all be done on 1x80A, or even 1x60A

Where will the second fuse go?

 

[SUNRAY]

Customer in garden house, as in the house built for relatives in the garden was cooking lunch and put the kettle on which went bang, no other significant loads. Main house was unoccupied so minimal load. He checked all round with a voltstick and called for EDF then called for sparks in case it wasn't a supply issue.

Second house 20 years old, and power has been good since then, CU upgraded to all RCBO last year due to a tripping issue. EV added couple of years ago and SM couple of months ago.

This was the first time the 40A cutout fuse blew, I'm assuming it was not downrated when SM fitted. Now been upgraded to 60A and waiting to be unlooped.

 

[flameport]

Where will the second fuse go?

In the separate DNO supply that the second dwelling should have had from the beginning.

 

[SUNRAY]

In the separate DNO supply that the second dwelling should have had from the beginning.

Why?

 

[Murdochcat]

Why?

Because the future of homes is electric and 1 x 100A isn’t enough for 2 homes AND it avoids the eternal issues of one home billing for both and having to collect money

 

[SUNRAY]

Because the future of homes is electric and 1 x 100A isn’t enough for 2 homes AND it avoids the eternal issues of one home billing for both and having to collect money

As it happens these 2 homes (being owned by the same family) appear to have worked in perfect harmony on a 40A fuse for 20 years and it was only a broken kettle lead that did the deed.

As to costs involved, sharing a meter saves circa £100 per year. As to cost of getting a new supply laid on was £6K when the house was built
Sharing a fuse is not an uncommon thing: the first 2 which spring to mind

... I didn't mention before C/O is 3ph in a brick built space used for rubbish bins feeding 4 properties...

...I know of a building divided into 3 flats on a looped supply

This pair on the end of the loop even share a cutout fuse

and that building is sporting 3 EV chargers.

and

Oh and I have the same situation at home for previous owners with a Granny Annex (we purchased 2 properties as listed by Land Registry) and we are also looped with a 60A fuse and 10.5KW shower and neighbour has agreement for EV point