Upgrade of house main fuse

[Bluemotor]

I thought I would share my recent experiences with getting a house supply fuse upgrade, as it might help others faced with the same problem.

Although I already have a 7 KW car charger installed, it was put in some years ago when EVs and chargers were still very new. Nowadays however, the installers are more concerned about whether the total house demand can be met through the house main fuse. So when we recently had our kitchen re- fitted and replaced the gas cooker with an electric one, questions were raised about if our 60A house supply fuse would be sufficient to cover cooker (30A), charger (30A), immersion heater (16A) dish washer (10A), washing machine (10A) and anything else that might be on at the same time.

So I checked my local DNO website (SSEN; this is not the same as you pay the bill to like British Gas, Octopus etc). After some searching it seems I needed to request a Load Check through the website. This was a free and an agent came out after a couple of weeks to review my supply. He took lots of photos of the supply set up and told me he couldn’t just fit a bigger fuse because the holder (‘Cut Out’) wouldn’t take it. Some weeks later I was then send a quote from SSEN for the replacement of the fuse and cut out. Total cost £0.00. I returned the signed quote and another few weeks later some new agents turned up to do the work. This involved removing the old fuse, smashing up the old black cut out with a hammer and large screwdriver (I kid you not!) until just the 2 bare live mains supply cables remained. The new cut out was then attached to the cables and a new 100A fuse fitted, along with replacement wooden back board (see photos). Overall it took them about 30mins.

So after some months, I have a 100A supply and much less risk of blowing the mains supply – all at no cost, but quite a few emails! I wondered if anyone else has faced this problem?

 

[Jomarkh]

You didn't have electric shower listed as the can be 10kW, have you got a combi bolier?
Do you have load management on your EVSE just incase you put the kettle, toaster and microwave on

 

[Bluemotor]

My charger is a 6 year old Podpoint version 1, no load management , no app etc. It just takes the power it wants!

 

[tsedge]

Note for people generally: what is written on the main fuse holder cover may not be the fuse inside. Quite a few old installations say 100A on the cover but there's a 60A or 80A fitted and the only way to know is to open it up, which should be done by the DNO.

 

[Lovemyev]

My charger is a 6 year old Podpoint version 1, no load management , no app etc. It just takes the power it wants!

I had a very similar experience with my local DNO.
Our house was built in 1982 and all the houses on the estate was equipped with a 60 Amp cut out fuse from day one.
Of course, back then this was regarded as plenty, given the loads likely to be pulling on that fuse.
Even with a brief spike demand, the 60 Amp fuse would be able to handle it.
This was okay until items like 12 Kw showers / double ovens / induction hobs and EV’s came along !.
It does not take a lot of effort to get close to that 60 Amp safe working load these days.
With the huge increase in electricity charges, many people with EV’s have found it beneficial to be on a much cheaper off peak over night tariff.
Last year I wanted to try a load shift as much usage as possible into that cheap off peak window of five hours.
However, running a 7 Kw wall box plus an emersion heater ( to heat our domestic hot water / cheaper than gas ) plus the washing machine soon adds up !.
I therefore contacted the DNO and tried requesting a main cut out fuse upgrade.
This was like pulling teeth to be honest.
After a LOT of being messed about, being transferred from department to department, finally I received a call from somebody who was able to understand what I wanted !.
They gave me an appointment and in 20 minutes the job was done.
It was explained to me that a simple upgrade from a 60 Amp to a 80 Amp was a simple five minute job, because the service head for 60 and 80 are the same size.
However, to upgrade to a 100 Amp fuse the service head has to be replaced, as the 100 Amp fuse is physically much larger in its dimensions.
I now have the very same light grey service head as yourself.

 

[Timdevnewbie]

I contact my DNO (UK Power Networks) regarding my setup (6.5kW solar plus electric shower, immersion heater and maybe an EV point in the future, just granny charging for now... ) and they said I needed a new 100A fuse setup and also as I am on a looped supply with my neighbour they need to come along and dig up the road as well. They are booked in to do this in October. I'll let you know how it goes. The guys that came for an initial survey said best to book it in while it's still free as they could definitely see it becoming a paid for service in the future once everyone has EVs and solar..
(I had to jump through a few hoops about size of meter tails etc before they would come out. But we'd had a SMETS2 meter installed only a couple of years back so I knew this should be up to spec. )
Hope this is helpful.
Tim

 

[Susanna]

Just to add to the above, I am also on a looped supply (my property first, then next door but not adjacent). I believe my main fuse to be 80amp, which has not been changed.

My neighbour was contacted about a new supply being laid to their property, but they declined, as they didn’t want the upheaval. I totally understood their point - they were not planning on getting an EV, so the current supply was sufficient for their needs and mine, according to the DNO.

I was assured that there was no issue with the use of my EVSE, and I frequently time my washer and dishwasher use during my cheaper overnight rate.

Being on a looped supply isn’t necessarily a barrier to having an EVSE installed.

 

[Eclectic]

I asked UK Power networks for an upgrade on the advice of the surveyor who was quoting for solar panels and Powerwall.

The engineer duly turned up and changed the fuse to an 80 amp (I had no problems charging EV etc on the old 60 amp) but said I would need a new holder for 100 amp (physically bigger fuse)

A different engineer turned up for a couple of weeks later, checked that we weren’t on a looped supply, and told me they would have to replace the main cable back to the road outside! He said that they get this a lot now with EVs, and that it would still be free of charge.

I’m just waiting now to be contacted for a date to dig up my drive etc, as it’s about 120 feet from my meter to the road!

 

[johnb80]

You may be surprised to know, a 60 amp fuse running with 100 amps going through it will take 9 minutes to blow. They stand overload for a considerable time, certainly enough to boil the kettle and make the toast!

 

[Lovemyev]

Although the main fuse will be rated at 60 Amps that will be recommended as the max safe continues working load.
However as John correctly points out, the fuse IS capable of safely handling more than 60 Amps for a short period of time, before it will reach the much higher designed in failure point.
A margin is purposely built into the stated load capacity, to accept any short spike's / demands drawn through that cut out fuse.
Remember that an fuse, is deliberately designed to be the weakest failure point.
We used our wall box to charge our first PHEV and then our first BEV for over five years on a 60 Amp main cut out fuse.
With the huge increase in energy prices, anybody on a time of day ( off peak ) tariff, will naturally want to maximise the precious cheaper rates, permitted in the early hours of the morning.
It's all too easy to quickly lose track of how many items ( load ) you are shifting.
A lot of these items are very likely to be high users of electricity ( EV wall boxes / washing machines / emersion heaters / dish washers etc etc.)
All of these items will not be running at the very same time, will they .
However, there will be some overlap if your off peak is only about four / five hours ??.
If we just take a quick "snap shot" of the likely demand on the first three items on that list :-
Wall box 7 Kw's / Washing Machine 3.5 Kws / Emersion Heater 3.5 Kws : Total = 15 Kw's.
15 Kw's = 63.64 Amps.
Already we are starting to push that 60 Amps fuse without including any more items.
Is this likely to be happening on a nightly basis - maybe / unlikely ??????.
This is the point when considering the fuse upgrade, starts to make you scratch your head a little harder .
After discovering a pile of saw dust on my seat about 18 months ago, I decided to contact the DNO to request the 100 Amp fuse upgrade.
Having a wall box that includes load balancing is a great safety feature of course, but remember if you have a lot of other items running at the same time, you could wake up to find your dishes and washing is completed, but your car has not charged to the SOC you expected, as the wall box has been throttled back via the load balancing device.
If you running on a 60 Amp fuse applying a bit of caution is the order of the day here I think.







In the aircraft industry, certain items are tested too twice the safe working limits, but these tests are very tight and restricted in the number of tests permitted !.

 

[johnb80]

If you running on a 60 Amp fuse applying a bit of caution is the order of the day here I think.

I completely agree an upgrade which is usually free is the way to go for sure, the only point I was making is that a momentary excursion above 60 amps isnt an issue. The electrical items you list such as the washing machine and dishwasher dont take their maximum load for very long and most half decent wallboxes do have load management to keep the peaks down.

My system ran on 80 amps fuse for quite some time and we used 25 kW peak consumption (100 amps ish) for several hours on some nights (2 EV's, Home Batteries, Diswasher, Immersion Heater and HeatPumps). No problem, service head didnt even get warm.

In the aircraft industry, certain items are tested too twice the safe working limits, but these tests are very tight and restricted in the number of tests permitted !.

And multiple backup systems too.

 

[Alb]

You may be surprised to know, a 60 amp fuse running with 100 amps going through it will take 9 minutes to blow. They stand overload for a considerable time, certainly enough to boil the kettle and make the toast!

I posted the 1361 curve in another thread:

My HyperVolt Installation (lots of pics)

I went for hypervolt too and a new consumer unit about 6 weeks after getting my 5 EV, so I had plenty of time to experience using fast and rapid charging stations, it does take a bit of getting used to but afte several bad experience with Osprey and Tesco Podpoint (rapid), I quickly discovered...

www.mgevs.com

 

[Hairyfool]

I contacted my DNO because the fuse holder had no label on it so couldn't say if it was good enough or not. I was also unhappy with the Earth rod as the top (which should be inspected every 5 years) was covered by the concrete garage slab.

The engineer that came out removed the fuse holder but still couldn't read the fuse. New terminal, 100A fuse and supply line earth.

They did a resistance check on the earth rod<0.2ohm so OK to leave the house on it until I could move over to the new earth.

 

[Richard P]

I thought my upgrade would be free too but our DNO charged over £100 simply to switch the existing 60A fuse for a 100A one, which took less than 5 minutes

 

[KT23]

Just to add to the above, I am also on a looped supply (my property first, then next door but not adjacent). I believe my main fuse to be 80amp, which has not been changed.

My neighbour was contacted about a new supply being laid to their property, but they declined, as they didn’t want the upheaval. I totally understood their point - they were not planning on getting an EV, so the current supply was sufficient for their needs and mine, according to the DNO.

I was assured that there was no issue with the use of my EVSE, and I frequently time my washer and dishwasher use during my cheaper overnight rate.

Being on a looped supply isn’t necessarily a barrier to having an EVSE installed.

I too was 'looped' (my house first then adjacent neighbour) and they turned up to de-loop us. The original plan to dig up verges and drives was changed due to the neighbour on the other side moving in and needing drive access.

What they did was to dig down next to the external electric box, remove the loop to the neighbour and instead fit a junction box in the ground between us. This means that we are both being supplied by the original single cable in the ground and rather than 'from me to them' it splits in the ground.

Not sure why this is better than looped as all electricity still flows through that single cable - but it ticks the boxes!!

 

[DBedford]

I thought my upgrade would be free too but our DNO charged over £100 simply to switch the existing 60A fuse for a 100A one, which took less than 5 minutes

It’s not the time it took which cost you, it’s the training and skill of the technician your paying for.

You may be surprised to know, a 60 amp fuse running with 100 amps going through it will take 9 minutes to blow. They stand overload for a considerable time, certainly enough to boil the kettle and make the toast!

But if you don’t want it to blow with 100amps flowing, get the correct fuse. Timing a 60amp on overload could be a dangerous game to play!

 

[Gadget Geek]

It’s not the time it took which cost you, it’s the training and skill of the technician your paying for.

It makes you wonder what you pay the standing charge for. . . Oh, yes, it's to cover the cost of being connected to the network. Surely a main fuse is part of that connection.

 

[ETLINLT]

Yes, I too found the local network provider (UK Power networks in my case) very helpful, quick and free .... until they discovered my house shares a supply with neighbour.

The contractor sent to check my fuse (it said 60/80 on the cover) missed this on first visit as I have only the one cable as I am second on line and my neighbour not in to check their wiring.

'Issue' discovered when 'back office' checked their documentation (preparing to despatch another contractor who could change the fuse to 100 - the first one not having the correct bits) ., something I would have hoped they would have done before sending a contractor out.

After another very prompt site visit to locate the underground supply cables., I am. 4 months later, still waiting for a date when they can send a team to dig up footpaths and give me a separate supply.

LESSON LEARNT - I knew there was a risk of my type of property having a 'shared supply' - however embarrasingly., I thought if I had the problem, there would have been two cables (one in and one out)., never struck me that only two if you are first on the chain.

You may find getting a charger fitted takes longer than waiting for car delivery ! Lack of destination or indeed any type of public charger here in the South East is dreadful and will be a major hold up for many people moving to EVs in next few years.

On the plus side - my granny charger is doing a sterling job., however I don't use car every day.

 

[johnb80]

But if you don’t want it to blow with 100amps flowing, get the correct fuse.

I never suggested not getting the appropriate fuse fitted, merely pointed out that a 60 amp fuse wont blow immediately with even quite a large overload.

Timing a 60amp on overload could be a dangerous game to play!

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

 

[Hairyfool]

.
Not sure why this is better than looped as all electricity still flows through that single cable - but it ticks the boxes!!

The underground cable will be considerably higher a rating than your cable but while looped the single lower rated cable to your house will also carry the current to his house as well. If both houses are fused a 60A then the cable from the network to your fuse block is expected to cope with 120A. Un-looping means you still have that (minimum) 120A cable even though you are no longer feeding the neighbour.

One of the problems with more houses having EVs is the underground cable. The original spec will include expected max load. As a very simplified example consider 10 houses on a single feed, all 10 houses have a 60A fuse giving a theoretical max of 600A. However the spec will take into account that the likelihood of all 10 houses drawing 60A is very low so they may only install a 4-500A cable.

EVs cause two problems. 1st they need an uprated 80A feed instead of 60, more important though is the High current draw is probably going to be running for much longer. Cooking the family Sunday lunch may be a similar draw but only for a few hours and the load will rises and fall with the thermostat. The EV may take a similar load but it will be continuous and potentially for much longer.

In my little 17 house cul-de-sac three of us next door to each other have EVs and one has two.