Nowty Towers Vs UK Grid Storage

[Tinbum]

I much prefer gas for cooking (hob) and electric oven, hate electric hobs. We have a gas main in the road outside the house but we use a small propane bottle for the hob which lasts ages.

I used to think that. Electric had much less power and took a long time to react (eg if a pot was boiling over you'd turn it down and it'd continue heating the pan for a while). However modern induction hobs are a whole other KoF. Loads of power, all of it goes into the pan, reacts instantly, looks good easy to clean, etc...

I'm not keen on induction, my mother used to have them when they very first came out many years ago and continued with them. I found they were easy to turn on by accident and that the surface stayed hot but you couldn't see it was hot. I can see they do have advantages though- cleaning especially.

[nowty]

I still haven't experimented with an induction hob yet so not going to happen just yet but my gas usage for cooking is less than 1kWh per day so its not material compared with the thousands of kWh's, used to heat the house and hot water and the vast majority of it in only 3 or 4 months of of the year. So its not a relevant argument in this case, no point trying to save 250 kWh of gas for cooking if I'm still burning 5000+ kWh of gas heating the house.

I doubt I could not heat the house through a cold winter with just my small heatpump and 2 storage heaters unless it was very mild, so I'm not having it cut off just yet. My target of not to exceed 2000 kWh of gas in a 12 month period is a wet finger in the air guess and I think it will be tough. My previous low record of 4009 kWh of gas was with a lot of heatpump and storage heater boost but it was more expensive that gas, hence the last 12 months its increased to over 5000 kWh of gas.

I have said many times gas was too cheap to drive the right behaviours, but now I see a tipping point with the recent price increases and the TOU tariffs, coupled with plenty of battery storage.

A secondary air to air heatpump is on my project list but I doubt it will happen this year.

[nowty]

This weekend is a real test of my almost non gas use, gas boiler is still switched off, house still very warm 23 degrees in lounge / kitchen. Outside is only 3 degrees and blowing hard, tomorrow might only be 2 degrees. Solar generation is very poor today and tomorrow.

My heat pump usually only comes on 50 % of the time, but today, the heat pump has been on constantly and looks to remain that way all day, radiators around 38 degrees. Home battery level around 70% SOC so should make it through the day. SWMBO isn't helping though insisting on two washing loads today.

Its now getting really tough to keep a level import rate during my cheap rate leccy 6 hour slot. Quite a bit of thought has to go into what will go on and when in order not to allow any peaks much above 15kW, but still absorb enough power in the 6 hour slot so I can avoid any peak rate import.

[Stinsy]

Why are you limited to 15kW? Surely 20kW is comfortably within the capabilities of a 100A supply?

[nowty]

Why are you limited to 15kW? Surely 20kW is comfortably within the capabilities of a 100A supply?

My main grid fuse and tails (16mm2) to / from the import meter get warm at 13kW, very warm at 15kW and uncomfortably hot at 18kW+ so I try and keep to 15kW as a general rule.

It does take a couple of hours of constant load to get to uncomfortable temperatures so I don't mind up to 18kW for short periods.

So I would not want to do something like,

2 x car chargers on max 14kW
Heatpump 2kW
Storage heater boost 2.5kW
Home battery charger 6kW
Heated Floor 1kW
Hot water immersion boost 3kW
Other stuff 0.5kW
Total 29kW

So typically only one car charged per day or both at reduced rates.
Hot water immersion boost only after heatpump has switched off.
Home battery charger set to only what is required but at the moment that needs to be the max 6kW.
Heated floor during last hour of cheap rate after car chargers have completed.

[Stinsy]

This is something I’m very interested in. I currently see transient loads of 10kW during the off-peak period but 5-7kW is typical. However when the BEV arrives I’ll be adding 7.4kW to that. My tails are 25mm but they are longer than the recommended 3m.

• BEV charging: 7.4kW

• Battery charging: 3.4kW

• Storage heater: 1kW

• Baseload: 0.5kW

• TOTAL: 12.3kW

Those will be the constant off-peak loads.

Transitory loads include:

• Small oil filled, 500W x2: 1kW

• Large oil filled: 2.2kW

• Washing machine: 3kW

• Dishwasher: 3kW

The oil-filled heaters are thermostatically controlled so come on and off, the washing machine and dishwasher only draw full power for a very small part of their cycle.

[nowty]

My battery is now down to about 35% SOC so I've only got about 9kWh's left in the tank, heat pumps been on all day.

I've managed to tweak the settings on my Octopus Intelligent APP to give me an extra hour of cheap rate from 10:30pm to 11:30pm so that extra hour will hopefully save my bacon because I have two more freezing days to get through and that heat pump is not going to stop.

[Oldgreybeard]

How have you handled the DNO, with regard to them authorising over the max of 13.8 kVA long duration load from a nominal 100 A supply?

When I made the (mandatory) notification of our heat pump installation, and the (mandatory) notification of the installation of my EV charger, the DNO requested a maximum demand assessment and issued me with a prohibition notice that I wasn't to use the charger until they had accepted it. We have a 100 A main fuse fitted, so the supply is rated at the normal maximum of 13.8 kVA (because the fuse rating is just for cable protection, so isn't the supply current rating).

I had (naively) assumed that having a 100 A fuse meant we had a 23 kVA supply, but they sent me a copy of the regulations they work to (standard apparently, for all DNOs) that made it clear that they were only required to supply a maximum continuous power of 13.8 kVA (60 A at 230 V) to any domestic installation. They did warn that we must not exceed 60 A continuously, and that if we did I would need to request a three phase supply, with it's maximum total rating of 41.4 kVA (assuming they would allow 3 x 100 A, which is really 3 x 60A).

The DNO weren't happy with my initial load assessment, so insisted I measure the max current over a period of a few days, with a peak-reading clamp meter logger (I hired one). They did accept that I was OK to continue to use the EV charge point once I sent them evidence of the logged current over a week (we topped out at about 56 A for a couple of hours) and they had approved the EV charger installation.

[Andy]

That's interesting. I just upgraded from 60A to 80A with no issues at all. They would have offered me 100A if I was willing to pay for upgrades. I do wonder how it will work for all three houses on our local transformer. It is only 15kva so am being a good neighbour and using load curtailment.

I wonder if they just had too much load in your area. I found this

https://electrical.theiet.org/bs-7671/f ... c-webinar/

If there is a large uptake in EV charging in a particular area will the DNO refuse a supply upgrade to a specific household to accommodate EV charging?
We understand that DNOs have committed to upgrade dwellings to 100 A per phase. Above this, that would be a question for individual DNOs.

Any installation whose demand exceeds 13.8 kVA requires notification to the DNO prior to installation of the equipment.

[Andy]

I had (naively) assumed that having a 100 A fuse meant we had a 23 kVA supply, but they sent me a copy of the regulations they work to (standard apparently, for all DNOs) that made it clear that they were only required to supply a maximum continuous power of 13.8 kVA (60 A at 230 V) to any domestic installation. They did warn that we must not exceed 60 A continuously, and that if we did I would need to request a three phase supply, with it's maximum total rating of 41.4 kVA (assuming they would allow 3 x 100 A, which is really 3 x 60A).

I would question this. You have to pay extra at install for 100A. A friend was building a new property on plot of three and they only had 60A each because it would have cost more to have 100A. If you are in fact being limited to 60A then may be you should have some money back.