Upgrade of house main fuse

[DBedford]

Sound, all good until you want to start cooking at mid-night, while using the washing machine, EV charger and tumble dryer, rare occurrence I guess

 

[Brian0]

The EV charger should have a setting to limit the power taken, monitored by the CT on the incoming mains cable. If the total load would exceed the fused supply (in your case 60A) it should reduce the charging rate accordingly. I had to have this (Zappi) until the DNO came and changed the incomer. New fuse block and 100A fuse, to replace the old (and broken by EdF) 60 A one.

 

[Rolfe]

Sound, all good until you want to start cooking at mid-night, while using the washing machine, EV charger and tumble dryer, rare occurrence I guess

I have every intention of doing that tonight, while the home battery is charging too. We'll see what happens!

 

[Susanna]

I had no issues with charging the car and using the washing machine and dishwasher at night in the cheap rate period with my existing 60amp fuse, and I am on a looped supply.

The DNO said it was fine (my neighbour didn’t want to have their driveway dug up for a separate supply), but ultimately National Grid came out and upgraded both our cut outs to 80amps.

According to my electrician, my neighbour wouldn't now be permitted to have an EVSE unless the supply was unlooped.

 

[Lovemyev]

Although the main cut out fuse maybe rated at 60 amp load, but the actual fail point of that fuse, will be a lot higher than 60 amps.
Older type properties are commonly protected by 60 amp main fuse protection, but the newer type properties, tend to be covered by a 100 amp fuse.
60 amp fuses had no problem satisfying the electrical demands only a few years ago, we never had the volume of high load appliances like induction hobs and EV wall boxes etc that are available today.
Reaching the 60 amps threshold is much easier today than it once was of course.
If you consider that when using a wall box / tumble dryer or washing machine and maybe an immersion heater for your domestic hot water, then you are close to the 60 Amp rating ( 13 kW = 59 amps).
Naturally anybody on a cheaper off peak electricity tariff, wants to maximise all of those benefits.
But a little common sense is advisable.

 

[johnb80]

Although the main cut out fuse maybe rated at 60 amp load, but the actual fail point of that fuse, will be a lot higher than 60 amps.

The fail point is a combination of time and over current.

A 60 amp fuse for example wouldnt blow with a load of over 90 amps (21 kW) for 6 hours.

60 amp fuses had no problem satisfying the electrical demands only a few years ago, we never had the volume of high load appliances like induction hobs and EV wall boxes etc that are available today.

Very true but not really a major problem, I regularly max out our 100 amp feed, my record was 24.9 kW (105 amps) and it's never been a cause for concern, the overload condition only lasts for about 15 minutes during very cold spells, I could program my way out of it but theres no need.

Reaching the 60 amps threshold is much easier today than it once was of course.
If you consider that when using a wall box / tumble dryer or washing machine and maybe an immersion heater for your domestic hot water, then you are close to the 60 Amp rating ( 13 kW = 59 amps).

Most decent Wallboxes have the ability to throttle the charging if max supply current is reached. It may well be worth setting this just as a precaution in case the above scenario arises.

Naturally anybody on a cheaper off peak electricity tariff, wants to maximise all of those benefits.

Indeed we do, make hay while sun shines, my average energy cost is currently 5.3p kWh!

But a little common sense is advisable.

Agreed, nothing to panic about if you go a couple amps over but planning to avoid massive overloads is wise.

 

[Lovemyev]

Our wall box is a dumb unit and offers no load management via an amp clamp.
Our DNO responded to my request to upgrade the service head, in order to accommodate a 100 Amp main fuse.
We had been running on the 60 Amp original fuse for about 4 years prior without any problems.
But when the unit price of my gas tripled, I decide that it was cheaper to heat my hot water via electric on our off peak tariff.
The upgrade to the cut out fuse was merely to ensure that the original 60 Amp fuse never became threatened by the extra demands.
It was a free upgrade so why not .

 

[DixieTGS]

A 60 amp fuse for example wouldnt blow with a load of over 90 amps (21 kW) for 6 hours.

Did you mean 600s / 10 minutes?

 

[Everest]

Did you mean 600s / 10 minutes?

Neither....

Unless it's my poor eyesight, I see the 60A fuse line crossing the 90A current line (x-axis) at 2000s (y-axis). So I make that 33 minutes and 20s.

Edited to add: most of these graphs also assume heat dissipation at nominal 20 degrees C, so a fuse will blow quicker (or an MCB trip quicker) in (for example) a heatwave in the summer vs. in the cold winter if your fuse is not in a heated part of the house.

 

[DixieTGS]

Ooh, very sloppy. I just looked up the easy to follow 100A line as being near enough . But with the max time on the graph being less than 3 hours, I knew something was wrong with the 6 hour value.

I see you went for the 2000 second line instead of 3000 line even though it is closer - I presume you're good at interpolating log scales correctly by eye .

 

[johnb80]

Neither....

Unless it's my poor eyesight, I see the 60A fuse line crossing the 90A current line (x-axis) at 2000s (y-axis). So I make that 33 minutes and 20s.

View attachment 34567


Edited to add: most of these graphs also assume heat dissipation at nominal 20 degrees C, so a fuse will blow quicker (or an MCB trip quicker) in (for example) a heatwave in the summer vs. in the cold winter if your fuse is not in a heated part of the house.

Yes youre right, early mornings dosed up on flu meds and becoming senile in my old age

Looking at it again, 3600 seconds or thereabouts at 90 amps therefore 1 hour at 150% rated load.

 

[OzricEV]

We're waiting on the DNO to unloop our supply and upgrade our fuse.

Saying that, we have a peak load well in excess of 135amp and the 60amp fuse hasn't popped yet.

 

[Rolfe]

I have every intention of doing that tonight, while the home battery is charging too. We'll see what happens!

I realised I don't need the car today, and tomorrow's trip has been postponed till next week, and I got home on 40% anyway, so I decided not to charge after all. Another time...

 

[Everest]

Saying that, we have a peak load well in excess of 135amp and the 60amp fuse hasn't popped yet.

 

[securespark]

In what way is it dangerous? Thats what the fuse is there for.

Retired now, but been to many installations where the intake fuse had blown due to being constantly overloaded, if only by a small margin, but eventually, the fuse has failed. It's not dangerous, but it is damn inconvenient!

Norweb (to become United Utilities, then Electricity North West Limited) allowed me to unseal the main fuses so I could replace consumer units. Some older fuse holders were not labelled with a rating, but those that stated 100A did by no means always contain a 100A fuse. 60 and 80A were common.

And in older intake fuse holders, 40A was common. I have even found 30A fuse wire in a kosher DNO-sealed cutout!

Older houses have (by today's standards) smaller sized cables feeding them whereas today the modern cables are either 16 or 25mm² for 80 or 100A supplies.

When we got our MG4, our meter was swapped for a smart one, but the old one was rated at 40A!

As for charging the car, my Octopus tariff used to do it religiously overnight but now will work out when it can charge whatever time of day it is.

The system balances loads too.

 

[Everest]

Not sure what you point is, but any fuse is just there to protect the downstream wiring and equipment. i.e. so the fuse blows before the wires get damaged or overheat.