S2D2

Some thoughts on the DIY unit here: I've been happy with mine and offset whole house gas heating with the single unit. It's been working very well in combination with the PV since installation in March, but hasn't had a full winter to test it to its limits yet, though we did have negative temperatures in March. There are downsides (see thread) but overall no huge catches, it will pay for itself.

No specific rattle, just if a hand is placed on the front panel the noise is notably reduced so I was going to stick some rubber on inside or something. I did find a loose screw in the box but none visibly missing, I will check when I open up the front panel but assume it was dropped and replaced. Like yours it's just about audible inside the house in the adjoining room to that wall but far quieter than even the wet central heating so no issues at all from that. I did wonder whether a ground slab and rubber feet would have been better but it's not close to audible enough to make me change anything. Spacing the rubber feet that make contact with the wall out a little so the rubber doesn't contact the bracket and overall levelling the outdoor unit also notably reduced noise.

Looks good, it was beyond me why the supplied insulation left a load of exposed pipe, I also slapped some offcuts on to at least cover it but it was performing so well I've never got around to doing anything more significant. Does your front panel of the outdoor unit have any resonance? I'm still meaning to stick a damping panel on mine as it has a tiny bit but again never got back to it, it's tucked round the side of the house so never an issue.

https://www.visualcrossing.com/ is quite good, also has hourly data. There's a daily limit to the amount of data downloadable for free accounts.

Given these are designed for hot drinks I'd be surprised if they compost quickly, I'd definitely remove them before planting.

Coil whine? Not everyone can hear it. Up to manufacturer/installer if they consider it a fault depending how you bought it.

Thinking about this also and I've come across a few paver sets that are designed to be laid 3.6m deep, so I think that will be a good size. How tall will the planter walls be?

Carry on and remove them when you're ready to connect up the pipes. I just attached the extension and coiled the excess behind the unit, the adaptor would be a neater solution though. I presume you would have to release some amount of charge though as it's designed for the length of pipe. Manual tells you how much to add per metre extended, but that sounds too tricky for the opposite (kit required). No idea what the impact of an overcharged system is.

I could be wrong, but I think you're looking for EN 14825. There's a decent explanation here: https://www.varmepumpsforum.com/vpforum/index.php?action=dlattach;ts=1505933467;topic=65119.0;attach=49952 An average year is binned into temperatures which gives a good agreement with lab test data, I was pleasantly surprised with how accurate it should be. There are quite sweeping climate classifications (average, cold, warm) but it seems to do the job. It's calculated from lab testing points, so I believe it would be performing weather compensation in those conditions yes. Caveat this entire post with I've never actually read EN 14825, I just thought it was interesting when looking at A2A manufacturer claims.

Just in case anyone is doing these sums, I'm not sure I agree with the logic here. You have to have a battery to be on Flux, so your next best bet without a battery would be Octopus Outgoing at 15p/kWh. That means every bit of export is worth 8p more, regardless of inefficiencies. This is the "worst case" benefit - as if you bought the battery but aren't actually using it other than for the higher daytime export rate. Based on your 23p export you look to be in Eastern England so are paying 34p for import. You would actually charge your battery in the cheap period 2-5am, so for 20.4p, or 22.7p after 10% losses. Everything you import to battery to offset usage (outside of PV generation) therefore saves you 11.3p. This is better, but not a likely use case for summertime Flux, as there is plenty PV to charge the battery without taking from the grid. Therefore in summer, your usage for the battery is shifting from daytime export (which without the battery is 15p/kWh) to the peak Flux export window, 36.6p for Eastern England. For each kWh you shift you gain (36.6 - 15) = 21.6p - by far the best return on battery usage. As an added benefit, you also get +21.6p for any generation in this window, but again you have to have the battery to be on Flux. This is what I believe to be the intended use case for Flux, Octopus are running an experiment where you are paid to load shift the National Grid a tiny bit with your battery, and so pay you a higher export rate for that service. I'm not arguing that batteries are green, or worth investing in for Flux alone which can disappear at any time (it's a flexible rate tariff and Agile Outgoing is already averaging about 9p/kWh) - I just wanted to highlight the sums are a little more complex, 8p/kWh is a long way from 21.6p/kWh, the actual value will depend on your individual usage and lie somewhere between the two (in Eastern England, other regions have slightly different rates). Winter is also a very different story due to the peak import window, I haven't done the sums on this but I don't think Flux will stack up well for winter when options like Cosy exist. I'm also a firm believer that installers are oversizing batteries from a ROI perspective and consumers shouldn't be dragged in to this when a small battery will gain 90% of the ROI benefit. Mine is 2.8kWh usable capacity.

PVGIS: https://re.jrc.ec.europa.eu/pvg_tools/en/#MR Nothing wrong with that pitch, PVGIS will show you the generation which you can compare to South, probably less of an impact than you were expecting. West has the unexpected benefit of pushing more generation into the peak flux export window, if you're installing batteries too.

You can, but only by storing the heat in the house (i.e. overheating it). It wouldn't be worth trying to store it in the porch as there is so little capacity and the losses are huge when the sun goes down. I use a conservatory in this way if heat demand and sun intensity are both high. Open the doors and let the house heat up to 24 then close them. It's up to you and the thermal behaviour of the house as to what you consider a comfortable maximum.

It's by far the least significant of the three but had enough of an impact for me to leave it in. If I get around to the known airtightness issue jobs I imagine it would become even less significant. Good airtightness and insulation would see it removed entirely as an input variable I imagine.

+ @SteamyTea It doesn't really matter for calculating peak load but for interest I was able to get a much better regression fit by adding the following variables to a multivariate regression: Solar energy Temperature delta HDD*Windspeed R2 = 0.93

Yes, 3.68kW if you go the G98 route. Back on topic, the one thing I'd change is to go G99, there are a few more fast track options now which let you get to 7.36kW which would save some complicated battery management I've set up to ensure capacity remains for excess PV when the inverter is running full whack. Ask the DNO early, no point putting 16kWp panels up if they say no to anything but G98.

Had something similar in a previous house, double the thickness and add the front edging strip set back slightly, rock solid. It was, by chance, replaced with 18mm ply as a snagging issue which was horrendously saggy. That went in the bin and it was replaced again.

Best day of generation so far here too, 32kWh and counting. May's utilities bill (gas + elec inc. standing orders) is currently sat at -£2.85 👍

Yes, we're talking about the inverter limitation, not the panels. I don't know anything about the DC max other than it's listed on the data sheet for the inverter. Wrt the panels question, the biggest power output I see (119% of kWp rating) is not on a cloudless day but rather when there is a break in the cloud so the panels are cool then suddenly receive both direct sunlight and indirect sunlight from clouds. This transient nature makes it very difficult to determine whether the inverter reacts and pulls it back to DC max or whether it's just a change in indirect sunlight levels that reduces the output. Someone who knows more about inverters may be able to enlighten us.

To clarify, I'm referring to the inverter's stated DC max of 5.5kW, the panels are 5.2kWp which as you say is regularly exceeded due to the artificial conditions in which it's calculated.

Yes I've seen 6.2kW today on a 5.5kW "max" - never for long, I assume it's a nominal max which it can go over for short bursts.

Yes it depends how long you spend generating more than 5.7kW PV. The answer is probably no but depends on the install. PVGIS hourly data gives an inaccurate estimate of this or you can review the data in your online account for the inverter to see if you've had much clipping.

If the SE is pulling 5kW you will only have 0.7kW left to go to AC due to the DC limit. It was probably a fast track G99 or something, which was limited to 2x3.68kW devices.

Max DC 5.7kW also, so if the inverter is pulling around 3.9kW DC side before losses for AC that leaves only 1.8kW headroom for charging the SE.

Yes, it should be stated on the data sheet for the inverter.

An extra caveat to the above is the inverter will have a max DC rating which will limit the DC side (inverter + battery). For my G98 inverter this is 5.5kW so no point sticking a 10kWp array on it.