Northern Powergrid will now only supply 80A on a single phase supply. I contacted them recently after buying a house to notify them that there was a heat pump, air con and a hot tub connected to the installation. Along with Solar PV and now an EV charger. The previous owner had just installed what he liked. They came to inspect the main cutout and actually downgraded me from 100A to 80! I wasn't particularly happy and the bloke doing the work even commented that I should have kept quiet. Although 80A is just enough, and the EV charger will ramp down if I get close to it, I thought I'd enquire about 3 phase for the future. They did a desktop survey and came back with a figure of £9k to dig a trench over to the other side of the (quiet) road - about 10m I would guess. So I won't be doing that any time soon.

It's also worth bearing in mind that the onsite guide says it's important to ensure that distribution boards and consumer units are of sufficient rating to take the total load connected without applying diversity.

We used to have a phrase that went ‘Regulation is 2 steps behind the cutting edge of bad practice’ this has never been more true than for PV & Battery installs…

Informative video Joe. Just 1 point to pickup on. Main cut shows 100 amp as a max and not what the fuse inside is rated to. They are meant to put a sticker over the top for the rating of the actual fuse as apparently it is illegal to cut the seals to check the fuse rating.

Interesting that 551.7.2 says you CAN install your genset on the supply side of the overcurrent protective devices. In your example this effectively makes a 116A supply available to your 100A rated CU Main switch before the 100A supply fuse even starts getting warm. Many G99 solar installations are far bigger than 16A...

DNO specification for single-occupied domestic properties specifies an 80A main fuse is fitted to a 100A-rated cut-out AND the maximum continuous load is 20kVA at unity power factor (so 20kW). At a nominal 230V then, the max continuous load is 87A. Add on the potential 16A from your PV system and the total is 103A. I'm not sure when the max continuous load for single-phase supplies increased to 20kW; the breakpoint for upgrading to a 3P+N supply used to be 17kW.

Whilst most configurations are DNO Fuse -> Meter -> Main CU not all of them are. In my own personal property the path is DNO Fuse - Meter - Electronic Isolator / Generator / Battery Backup / switching Interface -> Main CU. This switching interface controls what power comes from where, as well as providing protection from back-feeding the grid during a grid outage. Is this magic box enough to meet the protection required by the regulations and, if so, does it give us a hint of the future by allowing active monitoring and direct control?

Hager were talking about this at their recent tech talk at Elex

It might not be that unlikely to see higher rated consumer panels in the UK at some point. In the USA some years back a few panels started to be offered with a standard 200 Amp main breaker and an upsized 225 Amp bus. I have one of those in my basement that was installed back in 2019. I assumed it was due to solar, but I never saw any marketing material that said so.

Absolutely agree Northern Power downgraded my main fuse without telling me while I had a replacement smart meter fitted (my 3rd in 5yrs) . Previously I had asked 2 years prior to this for upgrade to 100amps which was done no query at all. As you say certainly Northern Power are downgrading every main fuse to 80amps on every visit for any reason and do not tell you.As you say with heat pumps, large arrays, batteries, car chargers and water heaters 80 amps is very minimal. My system trips about once a year and I put that down to load issues.

Thanks for that, interesting video. In the real world, I think the risk is more theoretical than probable. My PV system only delivers full output in high summer, so there is zero chance that I would want another 100 amps of heating load is zero. I doubt if I could get to 100 amps if I turned everything electrical on at the same time, let alone 116 amps. It wouldn't be sustained for any length of time either - the breakers in my consumer unit only add up to 92 amps (I suspect that the ring main breaker would be first to trip, as the lighting circuits are grossly underloaded with the advent of LED lights.

Can you pleae comment on the following please: Let's assume we have a single DB with a 100amp isolator and a 100amp fuse in the cut out. Unless the solar generation is injected upstream of the DB how can any component, including any part of the busbar in the DB exceed 100amp? OR have I misunderstood? As experts in the field, your input to this would be much appreciated.

Gets really fun when you have a 10kW hybrid inverter with 20kWh of storage. It is both a parallel supply and a load.

If you are pulling 100 amps from the grid and the inverter starts up and out puts 16amp of current the installation would be using 84amps from the grid with 16 amps from solar . Even if the system had a battery and you set it to max export ,the export would go to demand in the home .

I'm planning on having our place fitted out with infrared ceiling panels. I'm concerned about how the system will be able to cope if I have about seven or eight IR panels wired in. How do I know a competent sparky to employ? What qualifications or certs should I look for can you tell me please? My only thoughts are recommendations on our local fb group at the moment. Or would I be better off having the panels fitted by the uk company i plan to buy them from? Hoping you dont mind me crashing your video, Joe, I'm only an interested bystander, eager to get things right, proper and safe electrically speaking in my property. Love watching your very informative videos and often try to guess the words in your news reviews, never been right yet!

Western power are fitting 80A cutout fuses as standard according to there engineers when i've needed an upgraded supply

does an MCB in a consumer unit used for solar power have to be bi-directional and double pole?

I read something about some sparkies upgrading the main fuse, - we will see more sub-mains going bang! ....the only thing more spectacular is an exploding sewage cover ....looool...

Ah, i think I get it now. The supply potential is considered to be upped to 116a if solar is installed. Does this increase if a battery storage unit is also fitted? An extra 20 amps can be provided by those.

I haven't done any PV installs but are people connecting them directly into the DB through a breaker like that? The only ones I've looked at are connected into something like the Hendy blocks with the mains which then feeds into the DB. This way isolation is still through the 100A isolator in the board, just make sure the tails are rated properly. Also the DB is completely dead when the isolator is off rather than having a second supply into it. Anyone out there who does PV want to chip in with how they do it?

It must have been another quiet day in the regulations office when they came up with that nonsense reg. They can add it to all the other nonsense regs that no one takes any notice of! 🤦‍♂️

Why not connect the PV invertor output to the supply side of the consumer unit main fuse?

One thing worth noting is this video is the first place I've heard about the 16A export limitation for domestic solar PV installations. Thinking of the number of people I've heard going on about filling whole tracts of land they don't use with PV arrays for the *$£€s* I can see a lot of unqualified PV planners becoming rather disappointed! 😥🌦😉 As for me? I live in a home that faces north, where PV panels would be about as much use as a fuse in a teacup. Who needs a 16A export limitation? I'd be lucky if I ever produced 16 *mA!* 🤣

Where boards permit, fit an 80A double pole MCB as the main switch, instead of a main switch. Would always seem sensible anyway, less chance of popping the main fuse, ever.

You mention the 100A main fuse, but what if the main switch in the CU itself is rated 63A. That would mean 63+16=79 so ok then?

Would it not be sensible to have all sources of power (including solar inverter, battery storage and future V2G equipment) to first come together with the meter tails before they go into the consumer unit? Obviously each unit would then need its own protection devices. I'm thinking that added cost, number of enclosures and time of installation would be considerations but since I'm not a qualified person, just an average member of the public, can someone enlighten me as to where my thinking is wrong. Cheers.

However, the regulation is clear that Ig(s) is the rated output current of the generating set or sets, NOT the rating of whatever overcurrent protection that is installed on the generating set or sets. Which means, the PV fuse is not what sets the limit, but what the PV set is capable of outputting if no fuse were to be installed and any current settings are set to unlimited. Ergo, the output rating of the inverter and/or the solar panels. Meaning, that if you install a "beefier" inverter and/or solar panels to cope with periods of low sun, and then set the inverter to never output more than 16 A, and then install a 16 A fuse, then you would fall short of this regulation if the generating set are *capable* of outputting more than 20 A if the incoming fuse supply is 80 A (even if this would trip the PV fuse or generator fuse). I guess its a fault of the wording of the regulation, and it should have said something in the like: Ig(s) is the rated output current of the generating set/sets, or the rated current/current setting of the generator circuit overcurrent protective device either incororated within the low voltage switchgear and controlgear or upstream of it, whichever is lowest.

So someone else made a good comment about maybe coming off henly blocks to its own cu. Good subject

Two CUs is a perfectly valid installation process.

The 100A cut out would normally protect the consumer unit where it to take more than 100A if everything was turned on at once which is possible but unlikely. Adding 16A from PV and bypassing the cut out is only a 16% difference which even if it was passing through the 100A cut out would not cause it ti blow anyway - so every CU can exceed 100A by 16A even without PV just by turning lots of things on. It'll be well within the design envelope. It's not a practical concern just a pedantic regulation point. People install 10kW showers on 32A breakers with 43A going through which don't trip and when the regulations allow diversity they are acknowledging probability - how long is this 16% theoretical overload going to last?

Hi there. I designed, built and opened a zero-emission B&B down here in Rye, East Sussex. Along with a 34-panel solar array, 12kw ASHP, Smart Mixergy Tanks, 10x Air to Air Heat Pumps, underfloor heating and heater skirting boards, 4x 7kw EV chargers (and more)...and you're invited to come and stay with us :-) Hope you catch this comment....and keep up the good work! Javed, Magnolia House Rye

I have a 125a three phase dB in my house kindly source from work

Great

Take into account weather conditions, when the sun shines you don’t use a lot of power

How many installations have you ever seen drawing the 100A - 23kw ?? - that would be costing £6.90 hour £165.60 day £1159.20 per week ? Yet again the regulatory framework continuues its never ending upward spiral - the regulations will shortly look like the old Encylopia Brittanica full set. The lunatics have left the assylum and are currently housed at the NICEIC headquarters with "jobs for life" and "gold plated pensions".

When I recently had the cutout fuse at my house replaced by UKPN due to the holder being damaged, they replaced the original 100A cut out fuse with an 80A one. Since I have a PV installation your video suggests the reason why they did that.

So hundreds if not thousands of legacy PV installs that were done in the days of the feed-in-tariff up until they conjured up this reg are technically non-compliant much like all those that don’t have type A RCDs because it wasn’t a “thing” 10 years ago? 🤔🙄 I see the logic but in practical terms it’s creating a solution for a very unlikely problem

I don't understand this - what happened to diversity? I have a twin stacked main CU - on the lower busbar there are 6 circuits that, if you just blindly added all the CB ratings together, comes to a total of 176 amps. Great Scott, I could melt the house with that and worse, this busbar 'only' has a 63 amp RCD on it - begad! The upper busbar has my lights/smoke/alarm circuits on a 63 amp RCD plus a 32 amp RCBO for the garage sockets and (gulp) the dreaded PV circuit feed that can shift 32 amps / 8 kWh when sunny. Quick maths when I have somehow loaded the lighting, smoke detectors and alarm circuits all to 6 amps each = 54 + 32 + 32 = 118 amps! Clearly I can melt the house, or something. Think of the children. Meanwhile, all my circuits are protected at the correct value, no busbar is overloaded and the DNO 100 amp fuse is untroubled. The maximum load I have ever pulled from the grid for all the domestic circuits is 32A / 8kWh (multiple ovens etc, near to Christmas). To that I could add 8kWh from my inverter to potentially add up to 64 amps but that would still be split across the 2 busbars and, in this example, would be the PV/Battery doing all the work and not the grid. I guess I could charge the battery from the grid (at 5kWh) plus do multiple ovens etc, to pull 13kWh / 53 amps from the grid but again, this troubles nothing. Oh and since when did we add incoming amps to outgoing amps? We used to think of current flow. Yes, you could transfix yourself with the idea that 100 amps incoming when combined with 16 amps of solar could enable a household to exceed the 100 amp rated limit of their CU. But guess what, you can do that right now as the 100 amp fuse will quite happily supply you with 116 or even 132 amps for a very very long time... This is all a distraction as the main issues we face with domestic electrics are poor workmanship or undetected failures. We are way past the era of simple circuits on aluminium wiring feeding multiple 3-bar fires under the glow of multiple 60 or 100 watt bulbs. We live in an era of LED lights, efficient heating systems and a plethora of low-current devices spread liberally around the house. Our real-world issues involve things like switch-mode power supplies, DC leakage, nuisance tripping et al. When you see how much current an illegal grow-house can pull without anyone noticing I doubt this PV concern is of any actual concern.

British installations are so far behind. Where I'm living we all have 3 phase supply with 35A main fuses and it works without any problems and you are not overloading the switchboard. And yes 35A main fuse sounds small but you don't need 32A in front of your sockets.

V2G is going to be a problem then.

An inverter is not a generator. An inverter is an inverter. The regs just don’t meet with reality.

The elephant in the room that no-one is talking about: PV inverters export by generating a voltage about 5V higher than the incoming mains and can go as high as 265Vac. So what happens to the property voltage if the mains is already the maximum tolerance of 253Vac? What happens if two neighbouring properties export at the same time? Has anybody thought this through?

Good video but thats not how its done in the real world. 551 who actually know this as all.mcs installers have not got a clue lol. Thousands of systems have been fitted. So now they should not really be fitting solar to certain properties no

Seems to me you need a current limiting device on the solar to stop it ramping up under full load conditions in the installation. Or obviously down grading the main fuse to take account off the additional supply but I’m sure there’s lots of installs out there that are not compliant. It’s not good enough to hide this in BS7671 waffle well done for highlighting this!🥵

Sounds like something else to put in the pile of reasons to try and justify a whole new set of books.

Fit your own garage board every time with a 40amp mcb ready for a ev charger problem solved,but as usual can whoever dreamt this up while they had nothing else better to do explain how a energy supply from solar generation #clue right there becomes a load oh unless it’s the 4w standby overnight usage while on standby,so on that logic the 60/80/100 amp supply should be a load too.