RichardL

To echo the above, A2A is good and you can dip your toe in to phase it before removing radiators if you need to. Its in its element when outisde is >0ºC, still works when its below freezing but needs to work harder. Generally you can get away without having an inside unit in every room - depending on house layout - the warm air moves around so pick some key places - perhaps a landing upstairs or the master befroom than all bedrooms for example. In my example upstairs we will put a unit in the master bedroom and infrared panels in the 2x less used rooms just to take the chill off rather than permanent heat. You can't really put a2a in a bathroom either unless you go ducted. In my case I'm putting infrared panels in the shower room & bathroom. A challenge, with the system I have anyway, is control. The default mechanism is a remote for each inside unit, each remote with a clock/timer, rather than a central timeclock. There are solutions including cloud based and cable based (I don't use cloud for my house utilities) - just need to be aware its different. The system moves air - its very quiet inside and out but not silent - every now and again it may reverse the flow to stop the outside unit freezing and you may hear a swooosh when it does so. If you don't like the idea of warm air circulating, rather than oldschool radiator convection it may not be right for you. Bonus right now is the solar kicked in last month with the sun higher in the sky so the a2a is run more and more from sunshine than off peak power stored in batteries. I'm not an expert - just now in phase II of expanding A2A to my whole house (first install last september as an over winter test) to slowly replace oil heating.

Potentially go A2A instead - sweet spot with electric giving more out than in, but only needs to get the air temp into the 20s rather than water to 50s. If you don't mind the warm breeze of course & doesn't help with hot water.

Hi, Connectivity between the meter/current detector at your smart meter and the inverter so it knows grid import/export. Depends on your setup I guess and if the above are close to each other? I guess not the panels themselves - more the supporting infrastructure.

I'd Route - Power lines + a couple of runs of CAT6, one CAT6 for a meter one for - who knows signaling/anything - but its cheap and easy to route when things are open .

I would avoid a media wall - things change size/shape requirements over time (even if you persuade yourself they wont) Best option looks like putting the TV on the unit in the foreground - the wires will naturally be hidden by it.

Phasing - if on a retrofit - removing the main boiler which does space heating and hot water. Not having to replace it all in one go - Phase 1 might be for space heating, Phase II the hot water including removing the old boiler? Siting/location - not be constrained where the hot water feed from the boiler is because the combined system just needs electric. If the hot water tank only needs power and a cold feed it has more options - closer to the bathroom than the boiler for example - a loft space - a cupboard in the end of the bathroom.

Re Possible advantages to split space heating from hot water: I have'nt done the in depth maths on this - just thinking out loud. 1. Install phasing - no need to rip out (or upgrade later due to failure) an entire system - just smaller focused components. 2. Hot water siting - no longer constrained for the boiler hot feed to heat the tank since the pump is built in. (or Air source trunking lines) 3. Reliability? - questionable since its more components but are they simpler and focused on their core use? Perhaps more robustness of system overall since hopefully nothing fails at the same time? 4. Cooling output - if you can get at it - I'd love to route this to my conservatory in the summer for a 'free' byproduct cool air stream, or even the other way might be more efficient - to draw the air from the conservatory - Current MO is the conservatory to house door left open in the spring/autumn for free heat during the day - low tech - manual - but works. Hopefully too there is some saving by not forcing the space heating heat-pump to produce 50? ish degree water for the hot water tank every day & it can focus on cooler water for heating -or- if A2A there is no warm/hot water anyway. Plainly makes a difference re retro fit vs. new build in terms of flexibility to plan component location.

@Garald Did you come to a conclusion re the integrated cylinder heat pump efficiency vs the space heating A2W heat pump? Given the same air input (outside air) If the efficiency is equivalent - separating the processes has some merit.

Yup - +It would be nice if the smart meter did the same! - but for import/export etc. Needs a bit of design socialism / interoperability LoL Thinking on - battery SOC is available in a register - you can get at it and drive a relay - technically possible

I have a solic diverter which starts diverting if it sees anything go the grid, and once it starts tries its arm at increasing the diverted power provided nothing is imported from the grid - i.e. will drain batteries if given the chance. Anything can start the solic diverting - like a pulse of energy to the grid as something big turns off in the house. The easiest option I could see is a timeclock between the solic and the immersion - choose one with a battery backup so it remembers the time. Then the timeclock only allows diversion to the immersion in the afternoon when I'm likely to have solar and stop when the boiler timer is due to top up the water anyway. Crude yes - cheap and simple - yes.

To be honest I was going to keep the DHW completely separate from the space heating. Especially with the self contained heatpump/tank kit - there didn't seem any reason to change DHW at the same time as heating generally. I'm Mitsubishi Electric for A2A space heating. Valliant Arostor was on the shortlist for hot water - but need to do the space heating first.

I've an idea you're outside permitted development if its on a roof and/or visible from the main road of the property. Worth checking planning rules before committing.

With care if you release the cable clips from the rafters + the remaining rafter height you could probably tuck insulation underneath without disturbing the wires -or- potentially tuck it under without even removing clips. Either with thinner insulation types, or i'd be inclined to compress the insulation a little along that edge vs. anything near a re-wire?

FWIW - I'm retrofit and moving off oil fired heating and hot water. Wasn't keen on A2W for various reasons so the plan is A2A for heating and probably a self contained integrated cylinder heat pump unit for hot water - i.e. separate the systems - run them both from electric but lose the concept of a hot water circuit from a boiler for heating and hot water. Re cylinder heat pump for DHW Less integration provides options - suddenly it's an electric cable as the requirement to transfer energy around the house rather than a 22mm pipe full of hot water and a boiler burning oil to provide it. The idea of a single hot water unit with cold in/hot stored/out electric feed and COP 2-3 etc seems good to me - simple install (if I can work out its vent requirements). Ideally it would take warm air from the bathroom/kitchen - but retro fit again that may not be practicable. Solar PV heats the water march-sept with a bit of luck. Re the point on retro vs new build - phasing A2A provides a phasing option - i.e. the experiment with lounge/office last year on heating, expand this year then at some point that final component for hot water meaning the oil can completely go. Hopefully I avoid mis-sizing the heating or any part of the oil phase out since the oil is still there in the interim. There's no particular rush though - the oil boiler can pickup the gaps as I upgrade. Each room will lose its radiator and can phase that too including the redecoration etc.

Absolutely aligned with this comment & based on experience with a home multi-split - if a little white-noise - fan noise annoys, or you have heating on in bedrooms at night then think twice. It's a quieter version of that constant hum in any large office space, not constant since it runs on a thermostat - unless its cold outside You can turn down the fan to non-audible - but if its sub zero outside the fan will be 30-50%. Front room with the telly on or normal talking I doubt you'd notice. Bedrooms to heat up in the morning to get up and evening before turning in - but off overnight - again perfect. Side thought- if you enjoy finding that hot draft spot in a shop under the aircon outlet or by the door air curtain then certainly consider A2A

I agree with your point - but I guess its a double edge sword that monobloc's just need a plumber whereas aircon is more specialised. There are cowboys everywhere who will falsify experience - but anything that stops the 'double-glazing salesman' opportunist jumping into the market without training is a good thing IMHO - (hopefully they are all occupied with conservatory roof insulation)

If you have good loft access a ducted A2A may be a good option... only one unit in the roof then large diameter pipes to each room with dampers to control which gets heat. Then only one connection from outside to inside - and one condensate run, probably from the roofspace towards the eaves and into gutters? Re your question - my existing units are positioned so they have a downhill run to an outside wall, in a loft space. It will be a challenge for the rest of the house and I think at least one bedroom unit will need a pumped/uphill condensate run.

Only tip from installing A2A multisplit is check how its controlled. These systems seem to default to battery remotes each with their own time-clock - so while the flexibility of per-room temps is good - keeping all those timers at the right time is less than ideal. There are more central control systems available however the price seems massively high and easier to install DIY. Similar with ducted - I think you have central control then active dampers if individual room temp control is required. In any event you would need some sort of duct dampers, even if fixed, to manage relative temps and avoid that workplace issue of the 'hot meeting room'

Part way through going to A2A, I installed one multisplit for the lounge/home office last year under permitted development. That was a test - especially for sub zero temps over the winter. It certainly pulls the juice when its very cold - but the plan is as electric use goes up my oil use goes down and I'll probably end up in a similar cost space but without the home burned hydrocarbons. The experience was good enough to progress with more this year - its a different heat from radiators of course - but seems like a good option vs A2W and the limited / constant heat output. A2A has the potential for no radiators rather than larger ones - admitted there are still boxes on the wall for heat though. Currently dependent on planning for more boxes outside - I'll end up with one at either end of the house - broadly living area/bedrooms split. Re installers - they do like to put the internal units on external walls so you need a bit of thought over where they go and especially if you want to hide trunking etc - but its all possible.

Watching - and intending to go A2A for DHW once the heating is off the oil boiler. A2W doesn't seem a great idea on a house (my house) that is insulated but has built in ventilation and needs more of a punch than 50ºC rads to keep warm. Dependent on the planning process for more outside units for a couple of months.

Don't see why not - I used a spark to wire in fused spurs since its bathroom and you can't legally DIY it. Also added a pressure valve to the radiator since its now a sealed system - i.e. bomb if you just keep feeding in heat with not expansion possibility for the water/inhibitor inside it.

Thanks - getting the heat from the kitchen/bathrooms isn't an option - good pointer on the Ecocent though - thank you. The strategy is more like independent space heating and HW hence looking at these units.

I'm researching air source water heating - Vaillant Arostor or similar. They all have options of intake and exhaust variously drawing and feedback into the house/roof/external etc. Exhaust cold air I'm UK - so the exhaust is definitely going outside - perhaps through my conservatory if I can route it - but mostly I dont need the cool air output. Input air question The input side I'm unsure on - if it takes air from the house it feels like I'm robbing peter to pay paul - i.e. in winter at least - heating the house then the Air source water heater nicking some of that heat back into water. Seems like in winter I should definitely be drawing the inbound side from outside the house, Whereas in summer/when the heating is off - draw air from inside the building. Is my thinking correct?

Excellent user interface - passes the family test, i.e. not being funny just doesn't need a manual to work it out, and reduces any complexity on the backend systems to a simple timeclock and function on/off switches. I guess no wifi/internet/cloud dependency - I love tech but making my heating system dependent on an external plethora of servers etc seems a bad direction to go in.

I can't help with your specific issue - but a parallel which might help shed some light. I use wifi calling on my work phone, when a new phone was issued - same number but new sim the option went away.I had to call the network provider to get it re-enabled on the specific SIM serial # (rather than phone #) and a cold re-start on the phone. Wifi calling was enabled on my account but not on the new SIM. It may be a case of getting through to the network helpcentre? Update/thought - I also had to take the phone to an area with a signal to get it to turn on the wifi - which is daft right - but it seems like it had to 'phone home' on the phone network to see the permission to turn on WIFI calling.