JohnMo

You can pick up solar thermal for a good price if you look around, as it's gone out of favour with PV getting cheaper in recent years. Another option is PV, two ways to do that, normal grid connected with a diverter to immersion not that good for hot water except in summer. The other is to use PV for direct water heating. You can use DC from the panel to an MPPT tracker then to the immersion. Or direct to immersion, but have to careful matching everything up.

Every day's a learning day

Alway thought it was the doors never shut properly (or other customers couldn't be bothered closing doors behind them) and the owners refused to heat place.

Why would you need 6 to 8 air changes per hour. With an airtight house you are looking at 0.3 or 0.5 to comply with building regs (depending on which part of the UK you live). Normal housing stock my leak at the rate you quote at 50 Pa, but that is equivalent to the leakage rate in a howling gale in normal terms.

By direct charge I was referring to heating the contents of the store directly, instead of by heat exchanger (coil or plate heat exchanger).

But does what you are proposing comply with the interlinked requirements. Are making it more complicated than it needs to be, with more points of failure? Shouldn't you really have a sounder at each detection point? Do you need a UPS (backup battery) to manage the system you are proposing? What happens if there is a fire and mains breaker trips? A normal install, each unit has its own battery, so it doesn't care if the power trips. It makes a loud noise at source of the fire and every other detection point. Simple.

There is no reason a TS cannot be used, but you will need to watch a couple of things. Overall heat capacity is reduced due to lower temperature within the store. With ASHP, you will need to either direct charge from ASHP or go via a plate exchanger, as the normal TS coil is designed for 70/75 degC + input temperature. At ASHP temperature, you will not get the heat transfer rate required to manage the supply and return deltaT to the ASHP. Also same is true for DHW supply, you will need to oversized the heat exchanger to get a decent flow temperature. So PHE is the easiest option or a a huge coil.

Isn't this a repeat of a thread a few weeks ago? That went round in circles.

To do it properly, the steel and any other structural aspects would need to be specified and signed off by a structural engineer. Not sure they would be able to do that, without a drawing, so they could determine the imposed loads etc.

That's interesting, no mention of hot water storage (or did I miss it). Somewhat shows the pasteurisation cycle of 60 degC is not a thing of concern in the UK. Otherwise it would get a mention. But the main issue for most households is with infrequently used outlets, we have a couple, and so will plenty of other people.

Very nice

I have a Heta Scanline 8, with soapstone top and sides, to slow heat output. Couple of small logs and min air, puts out a gentle (ish) heat. Have a managed a hour with it on, with all the internal doors open, before melting and having to open the windows. Not sure a boiler stove would be on enough or for long enough, to be worth the added expense.

If you read MCS manual it states "Heat pumps should be selected as closely as possible to the design heat demands. MCS Standard MIS 3005, requires the unit to achieve 100% of the duty at an external temperature condition exceeded for 99.6% of the year, if reasonably practicable. " So the delta T of 25 should really be used - 2.8kW. not 30 degC which possibly only occurs for a day or so per year. So you need to look at the data sheets and make sure at the output can match that. You need to make sure you can turn down enough at warmer temperatures (much more normal than the lowest extreme) so that you don't short cycle

Mine is still going through. They also asked for the original documentation, when I asked what they were looking for, I just got a reply, please send through all the original documents. So I printed a type approval cert from the internet for the inverter and sent that, attached an email. They were quite determined I had to give a schematic. Still not sure if they have accepted the schematic I sent them. Got the electrician to sign the g98 form as the qualified person.

I used thermolite blocks, topped with engineered concrete blocks 65mm thick. This gave a good fixing point for the walls above. Floor build up from top is 100mm concrete screed, 200mm PIR insulation. So the thermolite block starts above the insulation. Gives an effective downward u value of around 0.7 at the stub wall.

If you search grunfos for the model, they may an expect start stop life on their datasheet

Your total heat loss has to be weighed against. Average heat loss from pipe, (somewhere between the lower pipe temp and supply temp). Plus the energy to reheat the system (pipes, pump, valves, insulation etc) after cool down. Plus the huge number of start starts per year and wear and tear on pump and motor from frequently stopping and starting, so premature pump replacement is also possible. Frequently injecting cool water into your cylinder that will mess with cylinder stratification, decreasing cylinder effective capacity. My pump/stops 720 times per year. Your between 7 and 14000 at a guess.

My pump has a rotary timer already built in, I just run for a couple of hours in the morning and evening, but my secondary circulation only goes to our ensuite. Not sure of the logic running for 4 mins every 12. Not sure what you gain, your water will hot, warm, hot... You may as well run all the times you are home and awake.

Although mains water is dosed with chlorine, so unless you have opened the line for repair or maintenance, there should be no bugs to grow.

+1 on doing it yourself with LoopCad.

I got all my UFH equipment from Outsourced Energy. Good prices and service. https://www.outsourcedenergy.co.uk/shop/ They do design and installation also.

What someone has set the curve to look like my not suit you, I may like a 19 degC temperature you may like it 21. This and the thermal properties of the different houses, will give different requirements for the curve. But your curve should be a straight line. All the ones I have seen start at 20 degC outside temp, and 20 degC flow temp. Then it's a matter of finding a cool day, move the thermostats out the way (set at max), let the heating run for 24 hrs, if house is cold increase curve angle upwards, if to hot vise versa. Once your house gets to the temp you want, bring the thermostats back to just above the normal house temp as limit stops.

Does your unit have an outside air sensor? If it has, has it been setup to run in weather compensation mode, hence the installer saying to run 24/7/365. If it hasn't could one be installed? If you are in weather compensation mode the thermostats should only come into play to limit the room temp, so should be set slightly higher than you would like the room temp. If the rooms are routinely getting to hot, and removing the call for heat, the weather compensation curve needs lowering, so you are putting less heat in to the floor. You can fine tune individual room temps by tweeking the flow rates of individual circuits, lower flow rate equals cooler floor/room. But don't do this until you have the weather compensation curve set correctly. Night setback should be 1 or 2 degrees only. Other wise you use too much energy trying to recover the next morning.

I had a couple of high spot on my finished floor. Make sure you use a grinder with extract to connect to hoover. Grinding makes lots of it. Get plenty of bags as they get through them quite quickly. Don't use a Dyson as they fail with building dust. Get a decent mask and goggles.

Passivhaus state not to start the MVHR until the house is fully sealed, due to dust getting in and you can't get it out afterwards.