DNO electrician installed wrong main fuse

[MrBadger]

My concern is that potentially, all my Electrical certificates are wrong now. which in THEORY might lead into some issues if I sell the house, as documents supplemented will not be correct.

Electrical certificates are not retrospective. If they were correct at time of issue then they remain valid.

If however you had further work undertaken, then the new certificates would then be based on the new fuse size.

Likewise any new diversity calculations would be based on new fuse size but also the revised calculation which sounds like it would give a similar result.

 

[Js1977]

My concern is that potentially, all my Electrical certificates are wrong now. which in THEORY might lead into some issues if I sell the house, as documents supplemented will not be correct.

That didn't sound like your concern from the outset of this thread as well as going on about a heat pump you do not have.

 

[arg]

But the point is - why they derating the property when all logic (EVs, heat pumps etc) should be that it should be heading another direction

Because they are reacting to the actual capability of the assets that are installed.

Those cut-outs (and supply cables) were only ever rated for 100A under winter conditions and/or intermittent load. Since there's now significant risk of those conditions being broken, they would rather have an 80A fuse in place so that that any overload results in the fuse blowing (and then a discussion about upgrading the cutout/cable) rather than the cutout overheating/catching fire (and then a discussion about liability).

While it might be nice to go round and proactively upgrade everybody's supply, that's not affordable. This move is a prelude to doing more selective upgrades where proven necessary - either because the fuses pop, or people doing supply assessments and saying that an 80A supply isn't sufficient.

 

[qwickshot]

PS those of you with heat pumps, a 7kw heat pump will at most be drawing 16A and probably more like 10A, even when going full tilt.

Solar will reduce your loading from the grid during daylight hours not the other way round.

So you have a car rated at 32A, a battery storage system (typically 16A, 22A or occasionally 26A), a heat pump pulling at most 20A for a huge 12kw unit going full tilt.

The likelihood all of this going full tilt at the same time as a kettle, induction hob, oven and electric showers is small. Hence the diversity calculation.

My house only had a 32A single ring main when we moved in, it probably had 60A worth of ‘stuff’ plugged into it but it was never overloaded.

 

[phil4]

I'd be thinking of longevity. My 100A fuse blew back in Jan, when cars, batteries etc were all busy charging. HA did note a high draw (~24kW).

Now the reason I think it went was less to do with what I used then, but more that it had been close to the limit night in night out for a while.

So while the 80A may be able to deliver 100A for 4 hours, can it do that every night for years on end? I'm not so convinced.

And no, I don't know if they put a new 100A in or replaced it with an 80.

 

[yessuz]

Because they are reacting to the actual capability of the assets that are installed.

Those cut-outs (and supply cables) were only ever rated for 100A under winter conditions and/or intermittent load. Since there's now significant risk of those conditions being broken, they would rather have an 80A fuse in place so that that any overload results in the fuse blowing (and then a discussion about upgrading the cutout/cable) rather than the cutout overheating/catching fire (and then a discussion about liability).

While it might be nice to go round and proactively upgrade everybody's supply, that's not affordable. This move is a prelude to doing more selective upgrades where proven necessary - either because the fuses pop, or people doing supply assessments and saying that an 80A supply isn't sufficient.

while "upgrades" per se, makes sense, but it does not make any sense to de-rate when it already was a 100A

 

[yessuz]

ok. an update.

been travelling whole week last week.

sent one email to GTC, then next work day follow up on the phone. Got call back from electrician couple of hours later. booked 30 min appointment

He came on Friday, replaced the fuse in ~3 minutes, installed the 100A, no questions asked.

no questions asked by anyone in GTC by the way

 

[thewishy]

Glad it's resolved.

For those concerned about 80/100a fuse limits, and thinking about three phase. Be aware that you can get load aware EV chargers, and I suspect my GivEnergy unit is also load aware, as I don't see any other reason this data would be needed for commissioning. This would mean that, in the unlikely even of your heatpump/immersion/dishwasher/hot tub/powerwall were all to run at the same time, the EV charger would "drop back" on the current available to the EV (So, say you're pulling 90a on a 80a fuse, the EV charger would tell the EV that only 22a is available. The EV will then drop the charging).

It's more generally used for commercial installations or second chargers, but it's an option on at least some chargers.

 

[Astrape]

ok. an update.

been travelling whole week last week.

sent one email to GTC, then next work day follow up on the phone. Got call back from electrician couple of hours later. booked 30 min appointment

He came on Friday, replaced the fuse in ~3 minutes, installed the 100A, no questions asked.

no questions asked by anyone in GTC by the way

Hehehe so much for the rules. Interesting discussion. Like you my charger application was based on 100 amp diversity. 15 kW of night storage heaters and 7 kW of car charger doesnt leave any spare.

Zappi is set to use anything spare from a 98 Amp set limit. Very neat the way it allows me to go in the shower and just downregulates to compensate. But it does make me wonder since my installation is entirely dependant on having a full 100 amps, are they going to give me free three phase if they start to apply this rule rigidly. I don’t really see how they can to be honest, surely they are going to leave some properties as 100A properties because they have been approved that way already.

They came out to physically confirm the fuse was actually 100 amp 18 months ago, and didnt say anything about there being issues with that.

 

[PITA]

If anybody is interested...

We were denied 100 Amp fuses on our 3 Phase installation based on the new National Grid restrictions.

So our 3 Phase setup is 80 Amps per phase... and they won't change it.

But thats still enough for a lot of kit.

 

[ringi]

As a child my parents cooked a meal when they got home after midnight with all the storage heater on. When my dad checked the meter cable had started to melt. He expects the cable screws were not correctly done up in the meter, but could not get the meter after it was replaced to do an investigation and was not at home when it was replaced.

At the time he was in change of metering for different large part of London, he asked his staff why other people did not destroy meters in the same way, they told him it was so common that they would never mention it to someone at his level when they had such callouts!