Spud312r Posted October 20, 2022 Share Posted October 20, 2022 Hi all We are about to demolish a small bungalow and build a new 2 storey home for my disabled wife with PV/Storage and ASHP etc Currently we have single phase 100A supply and would expect to be limited to the normal PV export limit of 3.6kW from our DNO UKPN Looking at the substation/transformer and UKPN Mapping I can see its a HV Transformer High Voltage 1kV -> 22kV Control Zone = 11kV Chelmsford South Voltage = 11kV The power supply will be repositioned and terminated in a new GRP during the demolition/groundworks phase and our neighbours power line will be moved from going over our land to under it . How can I check if the transformer is capable of 2 phase supply as that would give us a better PV export limit and what. kind of cost would I expect. We had a UKPN survey to talk about relocating our neighbours powerline and I asked about 2 phase supply and he just mentioned the transformer would have to be upgraded/replaced ? When I see 2 powerlines coming to the transformer does that indicate possible 2 phase supply ?? Link to comment Share on other sites More sharing options...
ProDave Posted October 20, 2022 Share Posted October 20, 2022 Definitely single phase, only 2 HV cables to the pole. Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 20, 2022 Share Posted October 20, 2022 Ask them if they can provide you with 2x 1ph connections off that tranny, or whether it would need to be upgraded to glean the 3rd connection. I've seen this practiced in a good few places where the original connection had been exhausted and a second ( same ) phase ( or L2 ) added. You just have a 3ph head and L1 and L2 are off the same 11kV tranny, so you get 2 lots of 80a or 100a off L1 to play with. Usually one will go to the domestic CU for all the normal stuff, and then the second goes to EV, or even 2x 7kW EV chargers. As you already have a 100a connection the house CU could still take one 7kW EV charger, ( the rest of the UK are having these routinely retrospectively fitted so should not be an issue, your DNO only care right now as it is a new connection / service alteration! ), so you could link that to the PV for use in Eco mode for trickle charging, and then swap the car to the second phase for faster charging or to charge EV#2 etc, on the basis that it would never have any meaningful input from PV anyways, so you can strategize the bulk EV charging that way. Just means adding a second EV charger. It depends on the loading of your ASHP, as the DNO's still shit the bed when you mention one.......even though a big electric shower is a far worse enemy in terms of shunt resistance / constant power consumption. Most modern ( inverter driven ) ASHP's are soft start, and then modulate down significantly after start up. That's dependant on the type of dwelling you construct, and the types of heating emitters you're intending to use. Ask for a second same phase and see what they say. A few years back I did a big system overhaul on a 5/6 bed house with 3 electric showers and all electric cooking, in the main house, and also all electric cooking in the granny annex in the apex roof of the large detached garage. All of that was running off one 60a 1ph connection. Two of the showers were 8.5kW, and the one in the en-suite was 10.5kW!! The 60a fuse survived on diversity and that everything was never actually on at exactly the same time. I then had 5kW of PV installed and the DNO didn't bat an eyelid, approval was instant, but I had deleted 2 of the 3 electric showers for a wet system by then. DNO didn't know about that, or care, as it was retrospective. For some reason they go nuts when it's new works...... Link to comment Share on other sites More sharing options...
SteamyTea Posted October 20, 2022 Share Posted October 20, 2022 35 minutes ago, Nickfromwales said: Two of the showers were 8.5kW, and the one in the en-suite was 10.5kW So all 3 were rubbish. 35 minutes ago, Nickfromwales said: deleted 2 of the 3 electric showers Why stop at 2. Link to comment Share on other sites More sharing options...
Spud312r Posted October 20, 2022 Author Share Posted October 20, 2022 1 hour ago, ProDave said: Definitely single phase, only 2 HV cables to the pole. Thanks but possible to have 2 phase (2 x single phase )?? Link to comment Share on other sites More sharing options...
Spud312r Posted October 20, 2022 Author Share Posted October 20, 2022 1 hour ago, Nickfromwales said: Ask them if they can provide you with 2x 1ph connections off that tranny, or whether it would need to be upgraded to glean the 3rd connection. I've seen this practiced in a good few places where the original connection had been exhausted and a second ( same ) phase ( or L2 ) added. You just have a 3ph head and L1 and L2 are off the same 11kV tranny, so you get 2 lots of 80a or 100a off L1 to play with. Usually one will go to the domestic CU for all the normal stuff, and then the second goes to EV, or even 2x 7kW EV chargers. As you already have a 100a connection the house CU could still take one 7kW EV charger, ( the rest of the UK are having these routinely retrospectively fitted so should not be an issue, your DNO only care right now as it is a new connection / service alteration! ), so you could link that to the PV for use in Eco mode for trickle charging, and then swap the car to the second phase for faster charging or to charge EV#2 etc, on the basis that it would never have any meaningful input from PV anyways, so you can strategize the bulk EV charging that way. Just means adding a second EV charger. It depends on the loading of your ASHP, as the DNO's still shit the bed when you mention one.......even though a big electric shower is a far worse enemy in terms of shunt resistance / constant power consumption. Most modern ( inverter driven ) ASHP's are soft start, and then modulate down significantly after start up. That's dependant on the type of dwelling you construct, and the types of heating emitters you're intending to use. Ask for a second same phase and see what they say. A few years back I did a big system overhaul on a 5/6 bed house with 3 electric showers and all electric cooking, in the main house, and also all electric cooking in the granny annex in the apex roof of the large detached garage. All of that was running off one 60a 1ph connection. Two of the showers were 8.5kW, and the one in the en-suite was 10.5kW!! The 60a fuse survived on diversity and that everything was never actually on at exactly the same time. I then had 5kW of PV installed and the DNO didn't bat an eyelid, approval was instant, but I had deleted 2 of the 3 electric showers for a wet system by then. DNO didn't know about that, or care, as it was retrospective. For some reason they go nuts when it's new works...... Thanks for that . I will ask if dual (2 x single phase) could be provided , will that allow me 2 x 7kW EV inverters or a single 15kW EV inverter with and export limiter set for 14kW spread over L1/L2 I am not really bothered about exporting back to the grid, but it all helps, its the grid backup that's important with max PV/Storage size that I need, required to power house/heating/water and medical equipment and the ASHP (Stiebel Eltron WPL 25 AS - SCOP (EN 14825): 4.39) As my wife is disabled and the house just being electric, the idea is to have a EV/inverter setup and large battery storage in case we have power failure as she needs to have constant power supply for her medical equipment Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 20, 2022 Share Posted October 20, 2022 32 minutes ago, Spud312r said: Thanks but possible to have 2 phase (2 x single phase )?? Yup, and Yup. 16 minutes ago, Spud312r said: Thanks for that . I will ask if dual (2 x single phase) could be provided , will that allow me 2 x 7kW EV inverters or a single 15kW EV inverter with and export limiter set for 14kW spread over L1/L2 I am not really bothered about exporting back to the grid, but it all helps, its the grid backup that's important with max PV/Storage size that I need, required to power house/heating/water and medical equipment and the ASHP (Stiebel Eltron WPL 25 AS - SCOP (EN 14825): 4.39) As my wife is disabled and the house just being electric, the idea is to have a EV/inverter setup and large battery storage in case we have power failure as she needs to have constant power supply for her medical equipment Your terminology seems a little jumbled.... PV have inverters, not EV. EV = Electric Vehicle? Please repeat your last, as we cannot advise until what you seek to achieve is understood properly Link to comment Share on other sites More sharing options...
Spud312r Posted October 20, 2022 Author Share Posted October 20, 2022 Just now, Nickfromwales said: Yup, and Yup. Your terminology seems a little jumbled.... PV have inverters, not EV. EV = Electric Vehicle? Please repeat your last, as we cannot advise until what you seek to achieve is understood properly lol sorry I meant PV .. EV point will be added for future usage Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 20, 2022 Share Posted October 20, 2022 (edited) FYI, you can have a 1000 solar panels and a lorry load of batteries if you go to a Hybrid inverter with all the panels and batteries on the D/C side vs all A/C coupled which requires grid ( DNO ) approval. You sound like you are looking of both EPS and UPS ( Emergency and Uninterruptible Power Supply ) which you CANNOT have with the majority of the of-the-shelf A/C coupled equipment, as these are required by law to 'island' during power cuts. I myself will be having UPS & EPS at my own house imminently, with all panels and batteries on the D/C side ( so no begging to the DNO ). Edited October 20, 2022 by Nickfromwales More info Link to comment Share on other sites More sharing options...
Nickfromwales Posted October 20, 2022 Share Posted October 20, 2022 1 hour ago, SteamyTea said: So all 3 were rubbish. Why stop at 2. Not after I boosted the cold mains with an accumulator, and increased the cold mains backbone to 28mm No rubbish on my shift mate Stopped at 2 as one bathroom was in the garage annex and was sporadic / guest use only, so it was agreed to leave as-was so no re-tiling / plumbing was needed in a recently finished bathroom. Link to comment Share on other sites More sharing options...
Spud312r Posted October 20, 2022 Author Share Posted October 20, 2022 39 minutes ago, Nickfromwales said: FYI, you can have a 1000 solar panels and a lorry load of batteries if you go to a Hybrid inverter with all the panels and batteries on the D/C side vs all A/C coupled which requires grid ( DNO ) approval. You sound like you are looking of both EPS and UPS ( Emergency and Uninterruptible Power Supply ) which you CANNOT have with the majority of the of-the-shelf A/C coupled equipment, as these are required by law to 'island' during power cuts. I myself will be having UPS & EPS at my own house imminently, with all panels and batteries on the D/C side ( so no begging to the DNO ). Exactly what I was looking at To satisfy the DNO a separate 5-7kW grid tied PV/inverter with export limited feed into the grid and providing normal AC loads and then 15kW PV/inverter (Victron) and 14kW Pylontech Force L2 14.21Kw Storage for the critical AC loads Well something like that - its depends on the DNO G89 application/certification/approval ? Current worse case house electric day usage during winter is around 26kWh , with new passive house with ASHP I expect this to be lower All from single phase 100A supply ?!?! Link to comment Share on other sites More sharing options...
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