Dan F

In respect to use of PV across phases yes, with a 3-phase supply and vector-sum meter it doesn't matter which phases are producing and consuming. If you have constant production of 5kW on phase-1 and constant consumption of 5kW on phase-2 for an hour then the meter will record zero import and zero export. If the meter wasn't vector sum, then it would record 5kWh import and 5kWh export and (given import tarrif is more export tarrif you'd be paying something instead of nothing) Once you introduce a battery though, there is a bit more thought to it to ensure higher levels of self-consumption, as you really want 5kW load on phase-1 to all come from the battery (even if inverter is limited to 3kW/phase. The video also explains how this works (with batteries that do this) Import is not offset against export over time. Vector-sum metering is the way the instantaous power usage is recorded only. If you export when the sun is shining and import in the metering the evening then this counts as seperate import and export with different pricing. The alternative to this is a specific "net metering tarriff" where import cost and export cost price/kWh is the same. With this type of tarriff a battery makes no sense, you are right, but the only such tarrif in the U.K is the Octopus Tesla Tarrif which required batteries to join.

You didn't read @markharro requirement which I responded to, he said "export without constraint"!

Yes, in theory, but to simplify things you ideal want the same company to install your PV and batteries as a single package with a single VAT invoice. To make thing even simpler, find a supplier who will zero-rate it then you don't need to reclaim anything

You can't avoid this I don't think. If you only export max 3.68kW per phase though, it is simpler. Most flexible/extensible system IMO is Victron. Given its seperate composable compoments (inverter-charger, MPPT, brains) it does cost more than a chinese all-in-one hybrid invert though.

I couldn't have put it more eloquently 😀

It's in real-time.

Apoligies if off-topic, but interested to know how you achieved the ebusd connection and how you "found" the registers relevant to heat pump etc.

This video will explain phase compensation and how it works with/without batteries: https://www.youtube.com/watch?v=pTfOYlboarw. The decision you have to make is: 1) Will loads be connected to one phase only or all phases? 2) Do you want i) single-phase AC-coupled PV inverter ii) i) three-phase AC-coupled PV inverter iii) DC MPPT's. 3) In the future will you use a packaged battery/inverter solution (e.g. powerall) or a hybrid inverter + batteries. 4) Aside from storage size of batteries, you need to think about power in kW that you require from a battery storage system. Which type of PV system you use depends on required power output and what battery you plan to use. A couple of examples: - If you plan to use Tesla Powerall(s) which provides 13.5kWh and 5kW per battery (and supports phase compensation) then you best option would be AC-coupled PV inverter. - If you planned a Victron system then both DC MPPTs and AC coupled PV inverter would work, but it's likely cheaper and simpler to use MPPT. Victron system can be system to any storage size or power output and also support phase compensation. - If you planned to use a all-on-one hybrid inverter then this would work wthout an AC coupled PV inverter and you could buy this now without batterie and then add batteries later. If would be important though to ensure it supported i) sufficient kW output ii) phase compensation if you have loads on all phases. The SunSync hybrid inverter you have been quoted for is single-phase. You could defintly use this if you wanted to, the only issue with this approach is that you're future battery storage would be on a single phase and you house load may (?) be split across three loads. Unless you have very high loads or any three-phase equipment you could keep everything on a single phase which would simplify things. SunSync do do a three phase version too https://www.sunsynk.org/3-phase-hybrid-inverter

It works like this if the inverter supports it, yes. Not all inverters support this though. Also the correct term is "vector sum metering" I think. Net metering typically refers to a tarrif which has the same price for import and export. This approach doesn't need a hybrid inverter specifically, it can also work with AC-coupled batteries and with component-based systems. I know it works with the following: - Tesla Powerwall (using Gateway) - Sonnen - Victron (with an inverter per phase). I think it might work with Solis hybrid inverter, but couldn't get a clear answer from them. Also couldn't get a clear answer from LuxPower. Importantly the electiricty meter that use used (connected up to powerall, sonnen or victron) also needs to measure using vector-sun.

I thought we determined that all UK 3-phase smart meters do (or at least should) use vector-sum metering. I haven't actually looked at mine and tried to determine if it is using vector-sum metering or not though. I guess you'd ask your electriciy supplier, but beware that you might get some strange looks when you ask about "vector sum" from a lot of people. I found that varous PV/battery suppliers I talked to didn't understand this either. Our meter is a Octopus installed "Sprint 211".

yes. You'll likely want mutiple wifi access points around the house as in general the this is the best approach to achieve good coverage with slightly lower power, rather than a single "wifi router" someone central which tries to reach the whole house. In this sense the wifi built into UDR may or may not be valuable, depending on where this will be located relative to ceiling/wall mount AP's. But if you won't have a rack, don't need an internal HDD for video storage, and the price point on UDR is lower, then may still makes sense.

This is correct. When you bring battery storage into the mix it gets a bit more interesting though, as ideally, if you are using 8kW on phase 1 but the inverter can only cover 3kW you want to export 5kW on the other phases to compensate for the 5kW import on phase 1. This is why I asked the OP about how they will load the phases, because if loads are spread across phases and battery storage is planned, then IMO it's important to install a solution that supports this phase compensation.

Do you hqve a modem which is seperate to the Hub2 box? Do you have your PPoE username and password? If the answer to both of these questions is "yes", then correct, no need to use HUB2, just conifgure unifi kit to talk to the modem.

It's not just about your 3-phase supply. It's also important to consider: - Do you need to be able to export from PV on all three phase in order go beyong 3.68kW/phase limitation or is DNO happy for you to export 8kW on a single phase? - Will you house loads be all on a single phase, or will they use all three phase?

We installed WWHRS but there is a gotcha to be aware of: The simplest way to install WWHRS (System B) is where the cold feed feed for the shower goes via the WWHRS We knew this wasn't the most efficient approach, but the plumbing for the other approaches (System A or C) wasn't nearly as practical given the showers aren't particularly close to the hot water tank. Also, looking at the data the efficiency data there didn't appear to be a big difference either. The reality though is that with System B, the efficiency of the WWHRS is directly related to your UVC temperature. So, if your UVC temperature is 48C and it reaches the shower head at 45C, the WWHRS is hardly recorving anything at all. (The efficency data I looked at was, I beleive, assuming 60C hot water) So, we now have an interesting question, which I haven't tried to answer: - Should we heat tank to 48C, get better COP and not get hardly any savings from WWHRS - Should we heat tank to 55C, get poorer COP, but recover save energy by recovering heat vis WWHRS. The way to avoid this is to use "System A", but it's too late for us to switch to this now and it's a lot of plumbing to do this for 3 showers in different parts of the house

The minumum output of both these heat pumps is the same, so no advantage (apart from maybe price) to go with the 3.5kW model. They are alsmost certainly the same unit with compressor rpm capped on the 3.5kW model. The 3.5kW also won't be able to heat your hot water tank as quickly. There minumum output of these is around 2kW, so you'll need to ensure system has a enough volume and/or use a buffer to minimize on/off when it's heating load is lower due to higher exterior temperatures. What emitters are you using? UFH?

From what I remember it's Heating demand < 15 kWh/(m²a) or Heating load <=10W/m². That said, I'd i) try to understand why you heating demand is not lower ii) ensure there is a bit of a buffer in the numbers ideally

Depends if you consider income due to PV export, or if using telsa tarriff for example.

Thanks! What part of the country? What batteries and inverters are you planning to use?

Definitely. I'm in the progress of sourcing the kit from someone that is doing a bulk buy of batteries and victron inverters. I plan to do the Victron configuration myself, but I'll need an electrian with some battery storage (and ideally victron) familiarity who isn't going to run a mile and not want to touch it. I would ask our electrican, but he hasn't been back in 9mths and still hasn't installed any LED strips or labelled consumer unit and grids 😞 But that's another story.

Yeah, sorry. Maybe I got mixed up with the Mulitplus II 8000 and 10000. How is your system build coming along and what has your experience been source bits and building this yourself?

Got it. When I last looked earlier last year only Multplus 3kva and 5kva had approval, nothing else (even before the new requirement), but looks like they been working on approvals since. I'm 3-phase, so going to use 3 x Multiplus II 5KVA's anyway which I see are compliant, so should be good. Just need to work out what batteries I use and who to uuse to install (or if I do some of itself myself).

Good to know. I thought it had to be listed as "compliant" on https://www.ena-eng.org/ list in order to get G99. It strange though as. while it doesn't show compliant, it does have a cetificate avaialble!

Did you not consider fancoils using ASHP, instead of A2A? Fancoils you mean? No UFH cooling?

Given 217m3/h, the best (theoretical) outputs you can expect are going to be: - Heating 2.3kW (assuming 50% RH, 21 inside temperature, -2C outside temperature, 90% efficient MVHR and 55C ASHP flow rate) - Heating 1.6kW (assuming 50% RH, 21 inside temperature, 7C outside temperature, 90% efficient MVHR and 45C ASHP flow rate) - Cooling 1kW sensible (assuming 50% RH, 21 inside temperature, 35C outside temperature and 90% efficient MVHR, and 7C ASHP flow rate). You'll also get dehumification on top of this. So heating may be somewhat significant, depending on your heat loss, but it's an inefficient way of heating that won't get you same COP vs UFH; with my ASHP it means 2.4 COP (@-2C) vs. 3.6). The (sensible) cooling output is low though. It's impotant to look at these numbers within the context of you heating/cooling load and other emitters you have planned though. It would worth getting CW8 for these flow rates, and not the CW6, so you are at the low end of the recommended flow rates. But, there is no reason to get CW10/CW12 unless you increase these flow rates a fair amount, which would probably mean a larger MVHR unit too. (CW10/CW12 do have slightly reduced pressure loss, but this is minimal)