Boxy Posted December 3 Share Posted December 3 Hi I’m doing a self build and I’m looking at installing a2a as the main heating source along with a Mixergy cylinder there’s no gas to the site and no solar 3 bedroom detached full house at front with a large sloping roof down o single storey at the back with a large dormer 10 x 6.5 footprint I’m looking at a 2-2.5 kw wall mount in each bedroom 3.5m x 3. M each and a 5 kw wall mount in the l gaped open lounge-kitchen diner 6m x 6m 3.5 m wide being built with 90 mm kingspan coolltherm in the walls -150mm kingspan in the floor 300mm in roof -triple glazed 2 things do these units sound about right and roughly how costly would it be to run anybody got a similar setup Link to comment Share on other sites More sharing options...
ProDave Posted December 3 Share Posted December 3 Hi and welcome. Don't get too fixed on the build at this stage unless it's already on order? My gut feeling is you want more insulation than that in the walls. Before sizing the heating you need to do a proper heat loss calculation rather than guess. Then you can size the heating accordingly and get a good idea of running costs. Any reason for prefering A2A rather than A2W and UFH? And in any event with a big roof like that why not solar PV? Link to comment Share on other sites More sharing options...
JohnMo Posted December 3 Share Posted December 3 32 minutes ago, Boxy said: looking at a 2-2.5 kw wall mount in each bedroom 3.5m x 3. M each and a 5 kw That's a lot of heat your adding via a2a. Think (know) you need to do a heat loss calculation. Your biggest issue will be a sensible amount of modulation. Are you planning a multi outlet with one outdoor unit? Why not just UFH and an a2w hp? Link to comment Share on other sites More sharing options...
Boxy Posted December 3 Author Share Posted December 3 The brickwork is up to roof level the insulation is fine with building regs it’s equivalent to 150mm rock wool the concrete floors are already in and the roof is mostly taken up by the dormer with the smaller front part facing in the wrong direction-a2a because I. Don’t particularly want a wet system and the added benefit of cooling in the summer Link to comment Share on other sites More sharing options...
Boxy Posted December 3 Author Share Posted December 3 Yes we’re looking at a outdoor unit with 4 indoor cassettes which won’t all be running 2 bedrooms will be used initially going down to 1 in a couple of years and through lounge dining kitchen used - I’m also considering mvhr Link to comment Share on other sites More sharing options...
Boxy Posted December 3 Author Share Posted December 3 We are currently having our saps and overheat calculations done ( bit late I know ) so this should give us a better idea Link to comment Share on other sites More sharing options...
JohnMo Posted December 3 Share Posted December 3 2 hours ago, Boxy said: I’m also considering mvhr Are you planning on being very airtight? Link to comment Share on other sites More sharing options...
joth Posted December 3 Share Posted December 3 4 hours ago, Boxy said: Mixergy cylinder Any particular reason for that extra complexity? For less cash you can get a super insulated UVC like OSO SX Electric, with lower heat losses it will perform as well as the mixergy but not need a cloud internet connection or risk going obsolete if the manufacturer turns off their servers. a2a will work fine if you size it correctly - main thing is being comfortable with blown warm air heating rather than something that warms up the fabric of the building. 1 hour ago, JohnMo said: Are you planning on being very airtight? This is a doubly important question if using a2a, as a draughty building will be more susceptible to losing the warm-air heating before it does useful work (vs fabric radiated heat from UFH). And MVHR is best thought of as a solution to solve poor air quality in a highly airtight building. 1 Link to comment Share on other sites More sharing options...
Boxy Posted December 3 Author Share Posted December 3 With the latest building regs and saps you have to have a air test done and apparently it has to be really airtight in order to pass the test if it fails building control won’t sign off regards the cylinder because I’m heating it purerly on electric I wanted something that would use the cheapest nighttime tariff and then just top up during the day after the morning showers ,but only enough for what we use until the tariff drops lower at night again Link to comment Share on other sites More sharing options...
JohnMo Posted December 3 Share Posted December 3 39 minutes ago, Boxy said: latest building regs and saps you have to have a air test done and apparently it has to be really airtight But tight enough to warrant MVHR is another question. Think BR is pushing you to have an airtightness of 8m3/m2 to scape a BR pass. You really need to be a third of value to warrant MVHR. Which unless you build with that in mind will be difficult. You would be better planning for MEV or dMEV, but with humidity activated trickle vents and humidity demand fan speed. 6 hours ago, Boxy said: Mixergy cylinder Are you talking about a heat pump cylinder or just an immersion cylinder? Link to comment Share on other sites More sharing options...
Boxy Posted December 3 Author Share Posted December 3 Just the Mixergy cylinder with immersion heaters Link to comment Share on other sites More sharing options...
JohnMo Posted December 3 Share Posted December 3 29 minutes ago, Boxy said: Just the Mixergy cylinder with immersion heaters You can (you need to do some searching) get heat exchanger modules for A2A that allows you heat a water cylinder. Have a read on this thread https://forums.moneysavingexpert.com/discussion/6414827/moving-from-nsh-to-a2a-heat-pumps Link to comment Share on other sites More sharing options...
JohnMo Posted December 3 Share Posted December 3 Info on cylinder heating from A2A https://youtu.be/9domQlKtbBQ?si=qnuT_Y9UgAR-zfUs Link to comment Share on other sites More sharing options...
Iceverge Posted December 3 Share Posted December 3 8 hours ago, Boxy said: with 90 mm kingspan coolltherm i Don't do this. Use EPS beads or mineral wool instead.. Our a2a is in and working well with 3 weeks. COP of about 3-4 at a guess. Link to comment Share on other sites More sharing options...
Boxy Posted December 3 Author Share Posted December 3 The insulation is already in which air to air system do you have and how many units -is it a new build Link to comment Share on other sites More sharing options...
Redbeard Posted December 3 Share Posted December 3 You need a heat-loss calculation. Your SAP assessment should help when it has been done. Link to comment Share on other sites More sharing options...
Redbeard Posted December 3 Share Posted December 3 (edited) Double post Edited December 3 by Redbeard Link to comment Share on other sites More sharing options...
SBMS Posted December 3 Share Posted December 3 3 hours ago, Iceverge said: Don't do this. Use EPS beads or mineral wool instead.. Our a2a is in and working well with 3 weeks. COP of about 3-4 at a guess. Does your a2a supplement an ASHP or is it your sole heat source? Link to comment Share on other sites More sharing options...
Iceverge Posted December 3 Share Posted December 3 We have a single Daikin FTXM25R in the hallway a couple of these in the bathrooms for showers. Heat demand of the house is low though. Link to comment Share on other sites More sharing options...
SBMS Posted December 3 Share Posted December 3 27 minutes ago, Iceverge said: We have a single Daikin FTXM25R in the hallway a couple of these in the bathrooms for showers. Heat demand of the house is low though. Why did you get the a2a? For cooling? Link to comment Share on other sites More sharing options...
Iceverge Posted December 4 Share Posted December 4 13 hours ago, SBMS said: Why did you get the a2a? For cooling? No for heating. We were tipping along only with a plug in radiator but at 3.2MWh annual heat demand and €0.25 average electricity price the heating bill has risen to €800. Hopefully the A2A will reduce the bill to about €200. 2-3 year payback. Link to comment Share on other sites More sharing options...
Boxy Posted December 4 Author Share Posted December 4 Air to air solely for heating the a2a heat pumps at the moment only do a 120ltr cylinder (not big enough ) I know bigger ones should be coming soon I’m now looking at adding possibly 4 solar panels (self install ) while the scaffolding is already in place and integrating them into the roof this should assist will the Mixergy cylinder 210 ltr solar x any thoughts the 4 panels are about £1600 the electrician can wire up while wiring the whole house Link to comment Share on other sites More sharing options...
SteamyTea Posted December 4 Share Posted December 4 6 minutes ago, Boxy said: I’m now looking at adding possibly 4 solar panels Are they going to be grid tied? Link to comment Share on other sites More sharing options...
JohnMo Posted December 4 Share Posted December 4 1 hour ago, Boxy said: any thoughts the 4 panels are about £1600 That is really expensive. Just been on city plumbing and priced 4 panels (425W) and everything else you need for a full install, mounts, isolation switches, stickers, cable etc and it was £655 plus Vat. So someone is ripping you off. Link to comment Share on other sites More sharing options...
Boxy Posted December 4 Author Share Posted December 4 4 hours ago, JohnMo said: That is really expensive. Just been on city plumbing and priced 4 panels (425W) and everything else you need for a full install, mounts, isolation switches, stickers, cable etc and it was £655 plus Vat. So someone is ripping you off. Air to air solely for heating the a2a heat pumps at the moment only do a 120ltr cylinder (not big enough ) I know bigger ones should be coming soon I’m now looking at adding possibly 4 solar panels (self install ) while the scaffolding is already in place and integrating them into the roof this should assist will the Mixergy cylinder 210 ltr solar x any thoughts the 4 panels are about £1600 the electrician can wire up while wiring the whole house Link to comment Share on other sites More sharing options...
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