J1mbo

Yes a very old thread but an interesting comment. I've had three of Pegler's bib tap burst in less than 12mo. They have check-valves fitted and I also have a combined isolator and double-check valve just behind them within the building. They all failed the same way - popping out the little drain screw on the underside. The interesting thing here is that only one failed in the frost. Surely it will need expansion space for the heat of the sun too?

https://solartogether.co.uk/landing

Surely a heat pump is ideal for a hot tub

Solar is now zero rated for VAT anyway

I would suggest sizing the batteries to deal with the solar and use them for rate-shifting "for free" as a benefit. 36kWh seems very large.

The short answer is: batteries tend not to cost-in for rate shifting. e.g. 36kW of battery capacity, cycled 80% daily for ten years. Total energy provided by them would be 36 * 0.8 * 3650 = 105MWh. Night rate saving about 8p as of 1st April typically, giving a benefit of about £8k allowing for charging losses. Obviously charging them from PV is a different equation.

well done, that is some going

Lead acid?

With the Vaillant, the curves can also be tuned by applying positive or negative offsets to the VRC700 temp sensor and the outside temp sensor (in 0.5 degree steps(. It’s a bit of a cludge but it does provide shifting of the curves up and down. Room temperature itself would typically be regulated to the readings from the wireless Ambisense controller (or the other one who’s name escapes me).

Well except that it should have been a G99 route 3 application.

See the post above. Car to grid also big area of interest in the strategy.

Or buy a PowerWall and join the Octopus Telsa tariff, and enjoy a symmetric 12p per kWh tariff. The downside if you hand full control of your batteries to Tesla in this scenario.

Wow so much negativity on here. It turns out that under RHI we’d all have been better off getting our EPCs immediately after having the ASHP installed because it increases the heat demand by 33% when primary heating source is ASHP, because the EPC assumes the property will be heated 24x7. This is generally found to be the best way to run heat pumps because the increase in COP more than offsets the increase in demand caused by longer run hours. Heat pump plus solar (electric) is probably the best combination to reduce carbon footprint. It might be worth checking that what you’re planning, because of the EPC, doesn’t leave the property unrentable because of the resultant EPC rating. Talk to your EPC provider and have them run it with the proposed changes to see what impact it has.

I guess they are trying to stop people benefiting from the old 40p FIT simply buying batteries to charge off e7 then dump it back for a nice 30ppkwh profit? Or arbitrage from other tariffs?

Perhaps they meant limit the export from the battery inverter to zero, which is a requirement for g99

20 panels of 235W each = 4.7kW. Panel output reduces over time, it doesn't say (from a glance) how old they are, let's say they are producing 85% - 4kW. 380W panels are as little as £100 (here) - 11 panels, £1100 probably plus VAT.

Certainly if using radiators, a straight line wc ‘curve’ isn’t really optimal because the radiator output doesn’t follow a linear relationship to flow temperature - check radiator data sheets to see. Some will provide a formula as well. It’s because the air flow will be increased with greater dT between the surface and the air, hence output rising at a faster rate than increase in flow. On the “others” camp - Vaillant ArothermPlus has configurable curves that seem to match radiator output nicely. The system does vary the flow temp with room temperature, both in terms of deviation from set point and the set point itself (when configured to do so). This has the handy impact that the system can be very responsive in morning heat up, if you work that way, by setting a higher target for a short period of time without impacting that much the overall COP achieved. It also has configurable floor and cap temperatures as well as maximum outside temperature for heating mode.

All you can do really is get another quote and compare. A system using micro-inverters will be more expensive, for example, than one using a single hybrid inverter (a box that connects the solar panels and the batteries). It's better to use the power than export, since export at 5.5p is below your cost. A challenge with a 24-panel array could be using it all in the summer. If you have/are looking to an EV then that might not be so difficult. Otherwise we are stuck with batteries (as specified) and then heating stored hot water. What is your daily demand, May to August? Do you have an ASHP? If you're heating with electric that might be a better investment (would reduce heating costs by 2/3rds). Solar and ASHP are great together but obviously a lot of money to find. If you want to use the system to provide backup power, bear in mind that it won't be able to support everything. Usually a separate consumer unit is provided for 'emergency' maintained circuits (e.g. lights). There could be quite a bit of extra electrical work required too, for example a ground spike and various relays if the inverter doesn't deal with the latter.

I don’t know that’s fair. Scaffold and access costs could easily be £1k. Running a company and providing a warranty costs money. For example the numerous regulatory schemes and bodies that will need paying, presales people, MCS administration, and of course all the usual overheads as well as those specific to solar contracts such as the 3rd party transaction insurance etc.

Cost of PV seems to be 6-10p per kWh over its life. Cost from the grid is now 30p and will likely reach 40p by the autumn. Obviously paying up front for 20 years of electricity carries risk but it looks like annual returns in the 15pc range currently. All based on UK numbers.

I would suggest getting yourself a copy of this publication: https://shop.theiet.org/code-of-practice-for-electrical-energy-storage-systems-2nd-edition

The RHI payments are based on the renewable heat generated, which in turn is based on the heat demand of the property as documented on the EPC, but also on the declared SCOP of the product. The latter is determined by the system design flow temperature (there is a table for each product) and hence the lower the design flow, the higher the SCOP, the more renewable energy, and the higher the payments.

See if changing a few radiators can lower the design flow temp, as that will increase the SCOP and hencd increase the RHI. But getting that all done in two weeks is going to be stressful imho

Do yourself a favour and get bigger rads.

Of your own use, yes, but a neighbour with the exact same house could have very different numbers.