J1mbo

Vaillant should have provided a schematic for your specific install and that will state the type code. Note that there is also a heat exchanger present Boolean in the heat pump interface setup (default setup passcode 17 btw). The VRC flow temp target would be the VF1, since that is essentially the radiator circuit flow temp. The heat pump flow temp target will vary and be higher due to the thermal step across the buffer which will vary with load and flow rates. The heat pump side will usually run at full pump speed. The radiator side pump speed should be sufficient to achieve about 5K delta across the flow and return when everything is stable.

@MikethePump do you have a heat exchanger?

Yes that’s definitely the way to go. As it’s over the battens it doesn’t seem like such a big deal to me. Though I might need to re-felt which will make it a bigger job obviously.

Vaillant tech will take the easy way to get out the door within their allotted time. They also disconnected the VF1 on mine at one point. It's now installed in the buffer pocket and everything working as it should. Probably yours was a combination of curve, VRC700 citing, and radiator circuit flow rate, and possibly circulating system volume.

Thanks, yes they are flat concrete tiles. There will be so few left, they could easily be laid new and certainly around the flashing areas. Re edge protectors. I've seen these on several installations recently. They look to be solid so would eliminate the underside cooling and hence reduce output? Although they do improve the look of the installation somewhat.

Thanks. My understanding is that LPG is basically a by-product and that most industrial process machinery is not allowed to use it, which leaves demand for it pretty flat with bottled supplies, home heating, and refineries themselves basically which I suppose is holding down the price. That said, the spot rates seem to be following the price (per kWh) of oil so it seems the LPG suppliers must be well hedged for now and that the current party is unlikely to last.

I would be very interested to find a verifiable source of anything remotely close to this figure that is available now.

Or even worse, the bbc

Sorry this is for retrofit. 1970s house with a standard trussed roof.

Any thoughts about in-roof panels? IMO the end result looks much better and I am aware that most systems will produce slightly less output. OTOH there is presumably much less stress on the roof.

lol quite possibly

There is news today that Offgem are opening up 30 minute metering for time of use tariffs more generally very soon. And Octopus are meanwhile offering to "give you free power at certain times if you can reduce your energy use when the UK’s energy mix is dirtiest."

Sorry deleted incorrect info

any idea when these 540W panels are likely to be available @Nickfromwales?

CCTV, a few WiFi APs, router, PoE switch and a small NAS - could be 100W. Newish fridge and freezer probably 30-50W each on average (and 250W when defrosting btw). Probably another 20W in standby appliances. Then we have things on charge, smart bulbs, aerial amplifiers, the light in the loft that's been left on for six months, garage door opener, PIR controller lights..., it's surprising what is on and how all those few Watts add up.

Including batteries.

Nothing flash @Marvin. Just a PV system say 6kWp with maybe 8kWh of battery storage. The main issue as we all know is that we buy from the grid at (soon to be) 28p, but sell it back at 5p or so. So maximising the solar used is key to getting best return on it. The other problem is that PV generates most when basically we tend to not need it. In the day the systems can charge batteries and heat water, then you cook your dinner and run the dishwasher for free later. And since those appliances all use electricity in bursts, the batteries smooth it out to use as much PV as possible. Had a few quotes with similar metrics. £10-13k cost and £1200-1600 pa grid saving. Assuming system life actually is 25 years and 28p persists (both key assumptions obviously) then it’s providing 12% on a straight line depreciation basis. Ok so panel output will decline a bit, but energy will probably increase by more, but there’s lots of uncertainty so I’m just looking at in in a simplistic way.

Because of the very limited feed In rates, the batteries are really an essential component. But with 12%+ return (at 28p) systems with batteries are pretty attractive imo

from personal experience. 2019 - 12p 2020 - 15p 2021 - 21p (cap) 2022 - 28p as of April on cap and possibly another double digit percentage rise in September. very obviously, this is not a 28% rise.

The return based on the new cap of 28p is ~12% including system depreciation based on quotes I'm seeing. The question is how long those rates will last. I'm leaning towards getting a system at this point.

It's amazing how much things have changed in six months!

By monitoring the fuel consumption of the existing system daily and charting that against degree-days a good estimate of the daily heat demand can be found. Now is a good time of year to do so as there should be a few cold days yet to come.

Problem is that precisely when the extra output is needed, -10°C in this case it seems, the ASHP will have a lower than nominal output.

I find hot water demand is about 4.5kW per person per day, although it will vary widely between individuals. On that basis a unit able to provide about 150kW per day for heating and 10kW per day for water should be ok.

There is unlikely to be much appetite to add further to the cost of gas any time soon. We might get some relief from the CCL from electricity though.