JohnMo

Woodcrete ICF, used exterior quality tile cement and real stone slips direct to the ICF. Photos were taken a couple of years apart.

Those wins only come if your boiler is short cycling badly in the first place. If it's running reasonable run times currently the saving are not really there.

I did my first heat loss calculation on degree days. But it was miles out. The degree days are closer based on 10 instead of 15.5 or 16.5 OAT. That is key step missed by people generally, made way worse by zoning. Winter average temp is somewhere near 7 degs, so around half the heat demand compared to design temp. So short cycling becomes ever present

May be written but not true, but it does make export and getting paid reality, instead of hopefully.

I found my best efficiency and by the way the lowest running was via charging the floor like a storage heater as a single zone. I could comfortably pour 6 to 8kW into floor via 180L buffer the gas boiler ran continuously for between 6 to 8 hrs. A thermostat was used to switch the heat off at below target, house temp then crept up to target and by an hour or two after bedtime was getting ready to switch on again. Now doing exactly the same with a 6kW heat pump (no buffer), the only wild card with that is defrost extends the run time. It doesn't achieve the best CoP (running mostly at night) but only paying 16p per kWh and flow temp is mostly in 30 to 34 degree range, so isn't really that bad in the grand scheme

Immersion thermostat. I found I had to lots of different configurations on the spreadsheet to get anything usable.

The calculation should be more like Units × 1.02264 × calorific value ÷ 3.6

Where the energy goes Just looking at the operation of my boiler. Boiler demand, a 1 min delay timer starts, I think it does a purge to clear unburned gas. So also doing more cooling and pumping energy to atmosphere. Combustion starts and there is a 30 second delay, to heat the heat exchanger. More energy going no where Then the circulation pump starts and the boiler ramps up. If it then trip after a further minute, most the energy has escaped with flue gas.

The condensing is occurring in the flue gas. There is lots of water vapour in the combustion air. You can see a similar example of this in a car exhaust, with water dripping out of the tailpiece when the car is cold.

You short cycle when you are adding more heat than can be taken away and absorbed in to the house or a big enough mass of water. My first attempt at running the boiler was direct to UFH with no mixer and 6 zones. The boiler could modulate down to 6kW, against a max house demand of 3.5kW. The cycling was on for about 2 mins, off for 10 mins. Open a boiler and just a metal combustion chamber with heat exchanger(s). Most boilers if the run cycle is too short, have a set period lock out from firing again for 10 mins. That is plenty of time for water and metal temp to drop. So it spends most of its time heating and cooling a slud of water and metal. Bad short cycling will not actually heat the house but use lots of energy. Big difference concerns is the energy price - 7p v 30p per kWh

I was regularly getting 110% efficiency against a heat meter with flow temps in 30s. Prior to that with flow temps in the 50s I was in the mid 90s with the same heat meter. What bit do you need explaining - condensing theory?

I would agree with that my first quarters gas boiler heating was more than twice the expected. Some mods (huge buffer) later it was as expected. Just short cycling away prior to the mods

Reapplied, this time I stuck in the MCS cert I have for the battery install (no MCS for solar install), DNO email for G98 acceptance. Will so what pops out the other end. But computer said yes.

Are you sure you have the heating fully switched off? Your making the thermostat call for heat, so its asking the system to switch on, depending how its wired in it may just over-ride. If you don't want it to come on, why make it call for heat, just wind to down to 16 so it doesn't call for heat

If you are going for a grant, then the installer is mandated into doing the heat loss calculations. But you can use your measured consumption as a sense check.

That's life I am afraid. Just have to factor the cost into the overall costs

If that's the case you really should be concentrating on insulation and airtightness. To 'require' that much PV would indicate you barely scrape through min building regs standards.

There are two ways to heat water with electricity, heat pump or direct to immersion. Neither are as straightforward forward as they first seem. But breaking down practicality Heat pumps when you need them most they have the biggest power need (lowest CoP) and you are likely to have least PV available. So likely no heat pump running most of Dec-Jan. Looking at my PV today, which was quite overcast I did 17kWh, but the useful window for driving a heat pump off-grid was about 3 to 4 hrs. The other alternative would be direct DC to immersion heaters. You need to match the output of the panels very closely to the the power rating of the immersion to get them to perform as they should. You get a CoP of one, but you get useful energy whenever the sun's out. Panels from city plumbing are cheaper than ebay. Watch this and the spreadsheet mentioned is attached https://www.google.co.uk/url?sa=t&source=web&rct=j&opi=89978449&url=https://m.youtube.com/watch%3Fv%3DkVaxAfXQPDU&ved=2ahUKEwjZ2vnXhcqEAxXkZEEAHfX8DHkQo7QBegQIDhAG&usg=AOvVaw2ys-gKyKBdBX1Ku7fZDZ-M Solar PV Calculator.xlsx

Ideal just rebadge cylinders so not likely to make one off. Try these https://www.cylinders2go.co.uk/

I tried twice and they said no. Have DNO sign off, structural engineer certification etc, even have an MCS cert for the battery, but not for the PV.

I thought he meant take all his roof off... Now I understand with the additional photo.

I was in a garden centre the other day they were selling calor gas internal gas heaters, like the old gas fires, but on wheels. That would be cheaper than electric heater to run.

Not sure why you need smart for UFH, but the Computherm RF range are good. I have Computherm Q20RF in my hall (£60 from Amazon). Nice solid feel, easy enough to setup, can select a hysteresis of 0.1, which is great for UFH.

New MCS Guide now explicitly states that an additional DC isolator is not required with inverters that already have integrated DC isolators - but to me the inverter is the only thing likely to fail, over time. The isolation switch on the inverter is fine, but does not allow to isolate the panels from the inverter, to then allow the inverter to be safely be replaced at some point in the future. So from a practical perspective I would always install one. Plus you can place it somewhere convenient, for yourself, electrician or fireman, rather than having to go into the loft etc. What fire risk is there in an isolation switch? That just sounds like he is making it up as he goes along.

Really zero need, UFH can do all the heating you need. If you have a thick screed, circa 100mm you can charge the floor like a storage heater on mostly cheap rate (E7 or similar). This takes a hit on CoP, but the electric is cheap. You can get cylinders in just about any shape you want, or get it made to the size that suits you. Get one with a 3m2 coil.