JohnMo

When I compared my boiler and ASHP install. If I had just installed the ASHP and not the boiler, my overall cost delta, would have been an additional £500 for the heat pump. No grants taken. New build, heating system and plumbing is the same cost, cylinder the same cost. So the only change for me was the cost of the ASHP over the boiler I purchased and some additional outside pipework. Shop around. You really don't need to pay Vaillant prices.

Do all your hot and cold in no bigger than 15mm, otherwise you will waiting for ever and a day for hot water. You don't need separate feeds, unlikely to use all three colds in the ensuite at the same time.

Because there is only 24 hours in a day. If you are heating DHW for say 3 hrs that leaves 21 hours. So instead of dividing by 24 you really need to divide by 21. Undersized is really as bad as oversized, especially if it starts trying to activate immersion heaters to help it cope. Quite like a Hybrid heat pump, smallest heat pump topped up by gas when you get the frequent defrost temp and below (about 3 degs and below).

If your fans not doing to the job and you need to dehumidifier. Your fan is rubbish and needs to be replaced. Cheap ones are cheap for a reason...our last house the builder installed cheap no brand intermittent extract fan and after the first year it would not hold a piece toilet roll in place running at full speed. My first port of call would be the extract fan. Greenwood CV2GIP are ace through wall or ducted.

For the renovation yes, or extension. Doing UFH correctly on a renovation so you get really low temps isn't easy and if you do the rest of the system flows at a different temp, so it a fudge, your heat source efficiency doesn't gain. Fan coils, set your flow temp at 35, your heating is sorted, set a heat pump at 12 to 15 and the cooling is sorted also. UFH will always include an additional chunk of downwards heat loss, that you don't get with radiators or fan coils. Example I have a floor U value of 0.09, so pretty good and the floor sits at around 23 to 24 during the heating season, with a room temp of 20, my downward heat loss automatically increases by 15 to 20% because of it.

You need to add the allowance for DHW heating also to the 3.08kW. Plus the 3.08kW is an average figure it doesn't account for the worst heat day or the design case, of around -3. So DHW will add 0.5kW and doubling up the consumption to allow for the coldest days gets you to, 6.7kW ball park. Now the bit missed by a lot of people, is every manufacture uses a different scale to size the marketing size of the heat pump. So you need to look at the technical datasheet for each specific heat pump and look at the max output at the coldest design day temp. Based on the above an 8kW at -3 het pump is close to what you need, but that's only a ball park, you real heat loss calculation to size correctly

Done plenty of experimentation with my house, tried Weather compensation etc.Find the cheapest to run by far is E7 tariff, run heat pump at 35 degs starting at around midnight then run until the thermostat says stop. The heating then stay off until the next start time of around midnight. Why that big on a new build? Are you sure you need that big, my 6kW is huge, and it only puts out 6kW max, the Vaillant puts out way more than 12kW when you read the specs.

Good for Australia, not so good here

Everyone has different ideas, I just refuse to go under walls (for any reason), where a mad joiner can drill holes straight into a pipe by not being careful. Also hate small loops as this ends up driving a buffer, bigger manifold for a needless loop, manifold actuators etc.. Trial copy of loopcad will tell you if you are likely to overheat any areas, so any remedial actions can be completed before you install.

Are you reading from vertical or horizontal, from horizontal makes zero sense. 0 tilt i.e. horizontal/flat will give best part of nothing in winter.

I have a cool energy diverter, this can provide electric to two immersions sequentially, heat top first then bottom.

I really wouldn't install loops in these rooms, your manifold will be in this room and all the pipes having to go through the doorway. Big curve through that room with the pipes will provide more than enough heat. Then just do it all a single zone

With all piping systems you need to keep a watchful eye on head loss, with plastic being smaller than copper. Fitting have a quite big head loss and several in a line can have a dramatic effect once you start adding them up.

Me neither and I am over 60, soon as saw BTU I moved to the next thread. Leave BTU to USA.

A sanity check is your gas usage. Not sure of your DHW usage, but say it take 7kWh for that, each day. So you need your kWh usage for the heating season (your bills is a good place to find that) so, divide by number of days since you switched on the heating, to get an average per day, take away 7 for DHW. That will be the average kWh per day, double that figure will be somewhere near your worst day. Then divide that by 24 to give a kW heat input. Total kWh / days heating = average kWh per day Average - 7 = average heating day Average day x 2 = worst day Worst day / 24 = heat input kW On the worst day - most days not that

No it's based on the return temperature not the flow temperature

I just used white solid plastic pipe

I checked and ours wanted photos only, but had to show a tape measure to prove size. But check with your planning officer they are all different with different expectations.

The heating system and cylinder are run independently via a diverter valve so the cylinder doesn't care about the heating system. Only way to be sure is to do a head loss calculation. Our head loss to the cylinder was too big, so installed an additional pump in the return line at a fixed speed, pump starts at the same time as the diverter valve moves to cylinder heating and shuts off as the valve moves to UFH.

Why not cut out the middle man get the heat pump you want and a local plumber to install? Could be cheaper than the grant from the sounds of it.

Get accoustic ones https://www.titon.com/uk/products/window-door-hardware/window-vents-window-door-hardware/sf-xtra-sound-attenuator-vent/ But ideally also humidity activated ones. They are available https://brookvent.co.uk/acoustic-vents/ Also Duco and Aereco.

For me V2G is just a red herring, the suppliers will do just that - supply to grid. Tech been about for years. I would question if you actually need a 9kW heat pump hydrid. It would suggest your heat load is massive, the ASHP should run on its own down to about 7 degs and that is how you would size it, the boiler starts to kick from there and takes over the additional capacity required. It is more normal to see a 4 or 6kW heat pump a hybrid system. Battery for starting the ASHP. Battery size is really the important bit it's the inverter capacity - how many amps it will kick out on demand. I know my all in one starts a 6kW ASHP without issue. Size will determine how long you can draw from it before it goes flat. Question is do you need 100% capacity for all situations, answer is no. Last two days have been rubbish for solar and close to zero overnight battery ran out at 7 pm. No big deal. Really cold day, your hybrid will be mostly gas boiler run, so way less of an issue for battery capacity.

Mine started with a combi boiler, same as the original poster. If starting from scratch with an unvented cylinder you really should take the cold water from the UVC inlet group as a balance supply. If retrofitting as I did, I have a house inlet pressure control valve, as well as inlet control group on the UVC with the cold balance feed closed off. You also need a check valve on the UVC hot outlet to stop any reverse flow. Ideally you would feed cold to the cylinder inlet group, and balanced cold water from inlet control group to the cold water manifold. Hot water direct from cylinder to manifold.

We have the same, two of in the house, never ran out of water.

I don't disagree. But they all do apprenticeships, if joining those trades as a 16 or 17 year old, those apprenticeship would have taken 3 to 4 years. Why aren't they learning these basic skills or are they, and they choose not use them, as a rule of thumb is simple, even if its wrong or inappropriate. I did most of my plumbing because I could and what I didn't know, enjoyed the learning curve. Not because I didn't want to pay a fair wage. Electrics not interested in the subject, so paid the professionals for everything start to finish. They charged me their normal rate - used same company for the last 10 years, on 4 house renovations and a new build.