Let's chat about our Air-to-Air heat pump heating system - we share our opinions

[@Extragonk]

Really cool run down, it's massively appreciated that you've both taken the time to discuss it on camera, it's a good format for the discussion and has helped fill in a lot of blanks for us. Cheers gang :)

[@TimAndKatsGreenWalk]

Thanks, and you're welcome. We might do more videos like this if they prove popular. It was fun to do.

[@jezlawrence720]

Really helpful, I'm looking at air to air now but it's so new as an idea for domestic heating rather than just for cooling that it's hard to get "living with it" information. Very useful video.

[@jeanh9641]

Thanks to both of you for sharing your experience on your A 2 A heat pump system.

[@willemhorak1]

Thank you for sharing all of this. We’re in the middle of installing a similar Daikin system. 3x outdoor units and 8x indoor heads for a large detached house in the south of the UK. Previous air to water heatpump system has been woeful (bad implementation from previous owners), and with the costs to redo pipes/ripping up floors, etc I decided to also go air to air route. We were using 120kwh per day with the air to water system, and it didn’t even manage to heat the house above 16c in the cold snap in December.

[@TimAndKatsGreenWalk]

Wow, I hope your A2A works better for you. 120 kWh is ridiculous.

[@Joe-lb8qn]

I had a house once which had ducted warm air heating and the air came out at ground level from vents. It was excellent, very fast response, worked off a gas boiler but presumably could also work off a A2A HP, but the house was designed like that. Tons of wall space as well. This type of ducting for heating and cooling is also normal for many N American homes. Retrofitting UK houses which are starting off from radiators and solid walls we are effectively stuck with wall units as the option I suppose but if i was building a new home Id look at ducts. Though TBF theres probably less control over heat in each room in that case

[@gerrykeane3165]

Excellent Video. Excellent presentation

[@markgilder9990]

I installed an air2air unit for our lounge 2 years ago and will be installing one on the landing to heat the upper floors. Very economical to run, cheaper than gas. Mine works out less than 11p per hour over an 8 hour period. Must admit I have to turn it off because it’s too warm. Also bypassed the internal thermistor and connected it to a wireless room state, which tends to even out the temperature.

[@rodden1953]

Have you got a battery and solar ?

[@ChrisJakins]

If we made a video about our a2a system it would be almost identical. Similar size house. We chose a Daikin 5 to 1 system. Our power usage averaged under 20kwh per day for December but that was unusually cold. Normally much lower. Cop of 3 is about the worst case. Our setup only has one unit for the whole downstairs which is fine but takes longer to get the room to temperature than upstairs rooms but not really a problem if leave it on long enough. I usually shut ours off at night except when it gets below zero outside. I also shut down when it is very sunny as that warms our south facing windows really well. The key to reducing power further is to look at where the heat losses are. Our next move is a new front door as our old one is very poor for keeping heat in. Then we too need to get some bathroom rads electrified.

[@TimAndKatsGreenWalk]

Yup, I think curtains for our bifold doors will help a bit with energy consumption.

[@chrismgeary]

Also interesting to hear about power consumption. On those really cold days last month, Dec 14-15, we used ~42kWh each day just for heating across the 5 AC units. I'd hope that we'd be nearer your figure once we've upgraded the terrible 90s aluminium windows. Thanks for sharing all your data and findings :)

[@TimAndKatsGreenWalk]

I suspect we could reduce that a bit but equally we could have used more if we wanted to be decadent. I think sharing this sort of information is definitely helpful though.

[@USA-GreedyMenOfNoIntegrity]

My Fujitsu floor mounted model blows heat or cool air out into the room from the top and bottom. I think Kat should cross stitch some covers for your indoor units❤. I always recommend two units vs one for redundancy. WiFi yes.

[@TimAndKatsGreenWalk]

Maybe Kat will do just that one day. We shall see.

[@YamR1rider-wn9rf]

Great videos, thanks for putting them up! Decided to look up other people's experiences after having a two room 9000btu each multi split installed in the bedrooms of my two bedroom (plus boxroom/office late 1960s bungalow. Not high end units like yours (mine are electriq brand), and mainly wanted them for summer but I've been absolutely bowled over by just how well they heat (it was 2 degrees here last night). So much so, they heat at least half the house including the office and kitchen - I am now kicking myself a bit in I didn't get a 3 way split with the additional unit to cover the lounge - if I had done that, I think I would have made my radiators completely redundant. Might add a single minisplit in future to cover that, but would have preferred the 3 into one single outdoor unit. I am very lucky however in that best friend is an FGas qualified electrician and thus I was able to get the system at cost and "mates rates' install. One additional thing to mention about the electriq system is that the app seems to be very solid, no issues at all! Thanks again for sharing your experiences!

[@TimAndKatsGreenWalk]

No problem. One benefit of the AC route is that adding extra units is possible at least so it's good to have that option available, as you say. I'm always surprised how few people realise AC systems can heat as well as cool, so hopefully these sort of videos might help with that a bit.

[@davidmack610]

Thanks very much for this series of videos, we had solar and batteries put in last year and we're looking at A2A heat pumps maybe later this year, so this info is really helpful 👍.

[@TimAndKatsGreenWalk]

Glad to hear it.

[@paulwebb3569]

Been installing these for over 40yrs. It's just a air conditioning unit with reverse cycle heating. Biggest problem now is the compressors are 230v but converted from a.c. to dc. thru a inverter pcb and most are not that reliable. Also repair costs can be very complicated and very expensive. Parts are difficult to get after a year or two. . So much to go wrong and believe me it WILL. I have two in my house but I can fix it. 😎

[@TimAndKatsGreenWalk]

Ok

[@rajanpatel65]

Great video, keep them coming, lots to learn before I make the plunge! 😊

[@engineerabetterlife8301]

Thanks for the informative video. It would be good to see the sizing calculations that you went through with your installer including the heat loss calculations and the heating energy demand.

[@TimAndKatsGreenWalk]

Yup, all details coming soon. Although as far as sizing calculations are concerned, the installer just measured the room sizes and suggested the units that would be appropriate. It was pretty finger in the air stuff to be honest. I did the heat loss calculation myself later on, which I will show, for sure.

[@The_GG_OG]

I had the same problem with the motor waking me up, now I leave the unit on all night but set the target temp to 10c which means the units stays off but the louvers stay open, then at 6 set the schedule to go up to 20c and the Louvre is already open and off it goes!

[@TimAndKatsGreenWalk]

Yes, I wondered about doing this. I might give it a try although the motor only wakes me up occasionally and I usually go back to sleep pretty quickly so not a huge deal.

[@paulcollins4683]

Hi Guys this is great and made me think again on what heat pump. Seems an air to air is ideal and with one of those new hot water tanks with built in heat pumps it’s ideal. Interesting you have one in the bedroom, we would only really want cooling in those, just need to see if an easier method.. just love the videos so far😊👍

[@TimAndKatsGreenWalk]

Thanks. Yeah, I'm looking forward to getting a heat pump hot water cylinder at some point too.

[@coolkiwi79]

I’m thinking just that - had a dude from SAHP come around to discuss a Solar-Assistente heat pump, which effectively is a hot water cylinder (looking at a 300 litre), with a small heat pump driver by a panel you mount outside. Works all day/night and is registered on SAP(?) so it improves your EPC rating for your house. Then, that would free us up to have an A2A heat pump(s) for our heating and rip out the radiators.

[@GaryDoesSolar]

Hi Tim, thanks for making this video. Wow, you've really got me thinking! There really is a way to drastically reduce gas consumption, and have the benefit of A/C in the summer (and even better - A/C using solar production). This technology looks to be huge going forward 🙂

[@TimAndKatsGreenWalk]

I think you're right, I suspect we'll start setting a lot more AC around and hopefully people will realise it's an effective heating system as well as being useful for summer cooling. Looking forward to your next video!

[@GaryDoesSolar]

Next video should be dropping at the weekend, Tim 👍

[@TimAndKatsGreenWalk]

@@GaryDoesSolar excellent.

[@colin6681]

Thanks for the video and effort in explaining every detail thoroughly. I'm convinced now to take the plunge with A2A. Couple of things I may do a bit of research on beforehand are I've seen outdoor units that can both supply ( up to 3 indoor units ) and supply energy to your hot water cylinder and also ( as I mentioned in a comment on another video) is the ducted system, whether this can be ' zoned ' or not. I'm looking to have the electric heated towel rails installed in the bathrooms too. Please feel free to find what you believe to be the best one and post a vid ! Thanks again.

[@TimAndKatsGreenWalk]

Yes, absolutely, I wish I'd looked more into both the option for hot water via an A2A system, and the possibility of ducting for upstairs. Still, that's the point of sharing this stuff, so that everyone can benefit from the learnings of others. I'll certainly do a video about the electric towel rails as and when we get that sorted.

[@TimAndKatsGreenWalk]

Ah, I just found this, which suggests you can zone the output from a ducted system: www.acrjournal.uk/whats-new/multi-room-option-from-one-indoor-unit/

[@colin6681]

Hello again. Well I finally got there and had the a2a ducted multi room fitted ( +1 high wall for inaccessible large living space ) fully complete only yesterday and I'm delighted with it. Was quite hot outside yesterday so shut all windows and put the system into cooling mode and in no time at all the whole house is at nice cool temperature. Will be interesting to see how it fares out in the colder months. Had it set up too from my phone/app so that's a big plus also. Was saying to my Wife yesterday I'm happy we didn't go with underfloor heating as obviously the cooling option wouldn't be available. Thanks for you tips T&K, I'll be keeping an eye on your posts. I believe you'll be doing one soon about electric heated towel rails ( unless I've missed it ) as this is another step on my own journey. All the best.

[@positivewellbeingshorts]

You two are amazing and thank you for the videos (I am new to your channel). Am looking at an A2A heat pump for AC (multi split too) and looks like a similiar size house. Love the parts where where you Tim talking about energy usage and detail and Kat just smirks (probably thinking here he goes again and will leave him to it), all good stuff and thank you for taking the time to produce these videos. Will probably watch them all again once I decide on my setup.

[@TimAndKatsGreenWalk]

Yup, she's very patient with me. We had fun making this video so might do more in this format if this one proves popular.

[@mentality-monster]

Thanks guys. Going to head in the same direction when our gas boiler packs up. Can't understand the faff of going for air-to-water when you lose the ability to cool rooms in summer. Having to keep all of that aging pipework full of water just seems such a backwards step to me.

[@TimAndKatsGreenWalk]

There are definitely pros and cons to both systems but having cooling is a huge bonus for us, especially given I work from home. Best of luck to you when you get your system installed.

[@asilver2889]

Or avoid the whole wet system altogether, if new build, such as my barn hayloft. No gas, A2W heat pump option has many downsides, rads, all that pipework, just off-putting and complicated. The option to install initially and then extend later is also attractive. Even 300m up in the Pennines, a/c would've been handy this summer for 3 weeks. Very useful to hear your detailed feedback, well done.

[@JulianIlett]

Two outdoor units also gives you redundancy. If one of those units fails, you can still heat parts of your house.

[@TimAndKatsGreenWalk]

Yup, I've had a few folks mention this. It's a good point.

[@chrismgeary]

For the app signal failures, it could be Android power management. Try setting the app to unrestricted battery usage. I had similar issues with Switchbot (which I ended up buying to stop the room overheating which seems to happen with my MHI kit on milder days, even on the lowest 18c temperature).

[@TimAndKatsGreenWalk]

Thanks for the tip, I'll take a look at that.

[@Extragonk]

I had I thought that from the symptoms it could be the app timing out it's connection so while it runs it isn't connected to anything and hasn't realise, this would also explain why a Tim fiddler sees it more as they are in and out the app more, but Kat uses it once and then closes it?

[@TimAndKatsGreenWalk]

I think you've cracked it. I changed the setting you suggested and the app hasn't failed at all today. Many thanks!

[@chrismgeary]

@@TimAndKatsGreenWalk nice! Glad I could help :)

[@FoxInClogs]

My house has a gas heated, ducted air system, which I'm hoping to eventually replace with one large heat pump. (Like for like replacement.) I'm upgrading my PVs to a 9.5 kW (peak) system which will hopefully cover the running costs of my entire house, including EV and future heat pump. The up-front costs for this already runs into the thousands, so the heat pump will have to wait for now, unfortunately.

[@TimAndKatsGreenWalk]

Yup, all this stuff is not cheap, sadly, but doing things step by step can certainly help. Best of luck with your project.

[@Joe-lb8qn]

Hah just seen this, I just posted that i had such a house once. I loved that system.

[@David-bl1bt]

A very interesting and informative video, imparting your real-world experience, impartially. Regarding the defrost cycle, I don't believe that is is related solely to external temperature. We have these type of units in our property in Spain, we never have temperatures below zero yet our units still go into defrost mode, whether heating or cooling, so I think that you will discover that the defrost cycle will still be active when the weather gets warmer too. I think it is more dependent upon humidity rather than temperature....I could be wrong, but that is what it seems to me. Perhaps those with technical expertise could confirm? I always think it is strange that people object to these units and the pipe ducts in the basis of aesthetics. Everyone has a TV in their room with wires dangling from it, electrical cords draped from socket outlets to appliances, phones charging with dangling wires, speakers, walk lights etc. all these are deemed acceptable yet objections are raised when they want an efficient heating system but requires ducting or pipework! The advantages of are a2a system is that most, if not all the objectionable components are outside the property and fitted with very minimal disturbance to the inside of the property. I guess though that as such, the aesthetic objections are then passed on to the neighbours! I wait with bated breath for your deep dive video featuring all the interesting stats, bring it on!

[@TimAndKatsGreenWalk]

Yes, I expect we'll still get defrost cycles when the temperature is a little above zero but hopefully not as often. We've not had another since it got to about 5 deg outside at any rate. I'm also looking forward to recording the stats video. Should be fun!

[@protectiongeek]

@@TimAndKatsGreenWalk thanks for another great video with tons of info! I agree that you'll still get defrost cycles when the _ambient_ air temp is just above zero due to the relative humidity of the air (often 90+%) and the 'exhaust' air temp of the ASHP likely being below the dewpoint and cold enough to causing frosting.

[@TimAndKatsGreenWalk]

@@protectiongeek yup, agreed. I was being a bit too simple with my explanation in the video, to keep it brief.

[@dalemoore11]

Hi great video guys watched a far few of them now. I have a question if you don't mind? I've had 2 guys out for my house both want to fit 3 outdoor units for 3 bedroom 2.5kwh heaters ( I get the feeling they want to do this so they can just install a plug outdoor socket) am I rite to think one outdoor unit say 7kwh would need to have fuse box rcd power fitted to power one unit? Would it be more efficient running one compared to 3? I've got giv energy battery and solar Thanks for your time 👍

[@TimAndKatsGreenWalk]

Our outdoor units are 7 kW, although they only draw a maximum of 2.2 kW, so can be plugged into a socket with no problems. Both of ours are plugged into a pair of outdoor sockets that are a spur off of the ground floor circuit, which is a 32 A circuit so has plenty of capacity. You could definitely have a multi-split for your three indoor units, although it depends if they are all on the same side of your house or not as that might end up being the limiting factor. All our indoor units are on the same side of the house, so the pipe runs are convenient for multi-splits.

[@tievoli9816]

Hi, thanks for the video. I am in the process of a full refurb and extension. Thinking about taking out two combi boiler (one for upstairs and one ground level) and replacing the system with A2A. The house is 4000sqft and our largest rooms are 64sqm (living) and 64sqm (Kitchen). What do you think? sensible approach? cant really find enough information about A2A on the internet. We would be relying on A2A completely for heating.

[@TimAndKatsGreenWalk]

I'd suggest getting quotes for both A2A and A2W, and if you decide A2A also think about how you'll do your hot water and any wet room towel rails as those won't be covered by an A2A system. I've just electrified our towel rails and will be replacing our hot water cylinder with a heat pump one at some point, but that is extra complications you may not want. By the way I have a whole playlist about our A2A system, so take a look for more details.

[@danielhochohao]

Thank you for your video. Would u share some additional information regarding ur home? So it's easier to understand where u coming from to get those #s(u might have mentioned already on other videos) -size of house -age -insulation level -brand of mini split -seer and hspf # Do u turn ur heating all the way down to maybe 15c at night for the whole house and only keep ur bedroom warm? Would that be cheaper to run? If not, would running gas furnace as addtion to quickly bring up the temp for the whole house a good idea? Thank you so much

[@TimAndKatsGreenWalk]

Please check out the other videos in the series for more details, in particular the tour video a couple of weeks earlier than this one covers most of your questions. We don't use the gas at all, that would defeat the object of having this system. We're getting rid of the gas supply in fact. This system heats the house faster than the gas central heating in any case. We turn it off from 20:30 in the evening and it comes back on at 06:00. There are a few stats videos on the channel now covering the usage in much more detail so those might be of interest too. Basically take a look at this playlist: kzbin.info/aero/PLHcV5HZA45O92MJ9_VpdFJx278dyWpO4L

[@brianjohnstone3863]

Very informative. Do you use and PIR sensors in your house? and if so does the warm downdraft from the indoor units affect them? Thanks ~Brian

[@TimAndKatsGreenWalk]

I guess technically we do have them for our alarm system but we never use that so I'm afraid I don't know the answer to your question, sorry.

[@RobFisherUK]

Will look forward to your scatter plot. I should do that myself. Also a programmer. I'm using Pandas and Jupyter Notebooks and Matplotlib at work and at home I'm working on a Python script that runs inside Home Assistant and can use different temperature sensors in the house to make decisions and control things. You might be able to automatically solve your power cycling problem with that sort of approach. Fwiw my Mitsubishi Electric system defrosts more frequently but spends only 1-2 minutes doing it. Your units do look nicer than mine, tbf. I have one "floor" mount unit. I don't find it affects the efficiency much: auto vane control seems to do the right thing with air direction. It blows air either up or out according to its mood. It doesn't feel like a radiator but it's fine. The unit in my kitchen even detects where people are and blows air towards or away from them according to preference. I quite like sitting under the blast of warm air. More than sitting by a warm radiator in fact. Btw I'm not totally sure if heat output increases just because you turn the fan up. I've been leaving my fans on auto, though and haven't tested it. Two outdoors units gives you some redundancy if one breaks down, too. Sorry I keep writing essays under your videos. I do find it all fascinating.

[@TimAndKatsGreenWalk]

Haha! No problem. Incidentally the stats video is out if you want to see the scatter plot and I've got another spreadsheet video planned coming soon too.

[@RobFisherUK]

@@TimAndKatsGreenWalk excellent, will take a look later!

[@geraldinehansford4143]

Thank you for these really informative videos. You mention in your 'tour' video that the wall unit is really quiet (approx 20db) when running on low 18C. What is the noise level like when the unit is turned up to higher heating eg 21C? Is it intrusive? Thank you Tim & Kat 🙂

[@TimAndKatsGreenWalk]

The noise is more to do with the fan level rather than temperature. You can set it to 21 but still on fan level 1 and it's the same volume. We only tend to put the fan level up if we want the heating to happen quicker, which is pretty rare. We wouldn't usually leave it on a higher fan setting for more than an hour, say, so doesn't intrude much.

[@denisbassom172]

Like the split between stats and update

[@TimAndKatsGreenWalk]

Ok

[@kin9225]

Excellent video. I have 2x Panasonic aircon(1xbedroom, 1xliving room)I’d like to make a few comments on some of the points you touched on. Defrosting, not sure about yours but mine still uses power during very cold nights, minus 3-4C, even if the heat pump was turned off, it still uses power to heat up the fluid inside the compressor, upto 1.1kw over night. You also mentioned that you only used 30kw on heat pump compared to 80kwh with gas boiler, but based on current electric rate of 30p, that’s £9 but 80kwh gas rate of 7p only comes to £5.60. There are more , but can’t remember now 😂 Am I correct? Or have I missed something? Ive ordered Octopus air to water heat pump, surveyor should be coming during the next few weeks, although my current gas usage is almost zero, I got the feeling it’ll actually cost me more to run the heat pump!

[@TimAndKatsGreenWalk]

They've never used power overnight, at least not so far. We can run our heating for 9 p/kWh now because we can charge up our battery overnight and use that to support the heating, so combined with a COP of 3+ that makes it extremely cheap to run. Combining heat pump heating with home storage batteries and solar (provides a small top up over winter) provides very high savings. 30 kWh was only on the extremely cold days, most days it's much less. Gas on the same day would have been closer to 100 kWh.

[@kin9225]

@@TimAndKatsGreenWalk my comment must have came across a little negative, but I can tell you I’m a 100% fan of heat pumps, your video came to me as recommended by the KZbin algorithm, so that was a first one I’ve watched, my comment was based on someone who has no battery storage. You should get a quote from octopus for ASHP , it includes everything from pipe works, radiators and tank, my total cost only £560 all in!! But personally I’d have preferred a hybrid system as my annual gas usage is only around 5000 kWh, keeping my gas boiler for that instant hot water/shower is far cheaper and useful than having a full tank of hot/warm? water on standby, and also that extra boost of heating should I needed it. But I won’t able to get the £7500 discount, just my 2p🤔 BTW I’ve subscribed.

[@TimAndKatsGreenWalk]

@@kin9225 well, we no longer need an A2W system as our A2A works just fine for our heating needs now. As it happens I've got a video coming out this weekend that covers the hot water side of things. You'll probably find that an A2W system will give you cheaper hot water than a gas boiler since you benefit from the excellent COP (probably 2.5+ for the HW) and in combination you could heat your hot water using cheap overnight power, like we're doing with charging our batteries, making it probably half the cost of gas for the same amount of hot water. Modern unvented hot water cylinders are very well insulated nowadays, ours only loses about 1 kWh per day, which when filled by a heat pump amounts to a loss of less than 0.4 kWh of electricity per day (which at cheap rate is about 3.6 p). And by ditching gas you save the standing charge too, which is way more than that. But definitely consider batteries and solar if you've not done so already. The combination with heat pump heating is really very beneficial.

[@kin9225]

@@TimAndKatsGreenWalk I very much look forward to your upcoming video! I do have a 4kw solar and a 5kw sunsyck battery.

[@TimAndKatsGreenWalk]

@@kin9225 ah, great. We have 14.7 kWh of battery which helps with the heating for a good chunk of the time but even so we'll still need some peak grid power when it gets colder (so far this autumn the battery has covered the heating completely). You will probably find you use up your battery pretty quick in the winter, so you might not achieve quite the same level of savings. But it all helps!

[@SpectrumGeeks]

Great video, I am nearish to Gloucester and looking at AC. Would you share the name of your installer?

[@TimAndKatsGreenWalk]

He's called Jamie and runs Just Chillin' in Stroud. Should be able to find him with a Google search. Worth getting a couple of quotes, mind, just in case.

[@SpectrumGeeks]

@@TimAndKatsGreenWalk Many thanks. I have got a few quotes already, but be good to get another from someone where you have seen the work (if that makes sense).

[@TimAndKatsGreenWalk]

@@SpectrumGeeks ah, great, that does make sense, yes. I hope your install goes well whoever you decide to go with!

[@SpectrumGeeks]

@@TimAndKatsGreenWalk Thanks again Tim, had Jamie around for a quote and seems like a good guy, and quote is similar to others, so always prefer to use someone "known". I checked other videos but perhaps missed it, but why did you decide to go the Toshiba, and not Fujitsu, Pansonic, Daikin, etc?

[@TimAndKatsGreenWalk]

@@SpectrumGeeks cool, he did mention he'd been asked for a quote from one of my viewers, so I'm glad that worked out for both of you. The main decision came down to the look of the indoor units. I showed Kat a load from different manufacturers that I'd been considering (including most of the ones you mentioned) and she immediately picked the Haori units. Simple as that really.

[@joedanielbradley]

Hi Tim and Kat. Thanks for the videos i've foinf them incredibly useful when lookong in to upgrading my own home. We have just had the Haori system installed in our home as our main source of heating, with the added bonus of cooling. We're really pleased with the look and performance so far. I have been trying to get the units connected to the Wifi so that I can program them via the app however i'm really struggling as it fails on checking adapter prvisionong status every time. I was wondering if you had similar issues and if so how did you resolve them. Thanks Joe

[@TimAndKatsGreenWalk]

I managed to get mine to pair with the app without too much trouble. I don't think I had the problem you're experiencing so I'm afraid I don't know what to suggest. If you can't get it working it probably requires a call to Toshiba support. Good luck!

[@joedanielbradley]

@@TimAndKatsGreenWalk thanks for the reply. Managed to get it working in the end but had to create discreet 2.4ghz WIFI network for them as my mesh routers automatically combine both 5ghx and 2.4ghz signals. Then I had to disconnect my phone from the WIFI and reconnect each time before adding one of the units. A complete faff but got there in the end.

[@TimAndKatsGreenWalk]

@@joedanielbradley oh boy, that's annoying. Still, I'm glad you got it to work in the end.

[@FoxInClogs]

Thanks for your informative videos. It's nice to hear from people (EVM too!) who don't have something to sell or an axe to grind. Wouldn't an air-to-water heat pump be a better option for radiant heat lovers, instead of infra red panels?

[@TimAndKatsGreenWalk]

Yes, absolutely, if you prefer radiators then A2W would be the way to go imo.

[@FoxInClogs]

@@TimAndKatsGreenWalk I've had an air-to-air system installed in the attic (my home office) which wasn't previously heated. As you pointed out in a previous video, this has the (even more important) AC function for the summer, when it could otherwise reach 30C (plus!) I'm more than please with this in both respects & it's a lot more efficient than the fan heater I used to use.

[@TimAndKatsGreenWalk]

@@FoxInClogs I'm glad to hear it. I'm certainly looking forward to next summer now that I won't roast in our home office.

[@FoxInClogs]

@@TimAndKatsGreenWalk My experience is that 25C makes a pleasant enough working environment in the summer, without using too much energy.

[@johnh9449]

I have a 1.8m x 0.67m vertical double anthracite designer radiator in the kitchen which is so nice to stand against if you've just been outside on a cold day! Even at 37°C body temperature water flow you can feel the warmth on your face as you walk past. The dark anthracite helps radiate. A 300% to 400% efficient heat pump is certainly more efficient for this and a better option than a 100% efficient infra red panel. I think Tim said he had micro bore pipe which limited his options. Normally central heating has 15mm radiator pipes which can deliver around 2.75kW @ DT5 for a heat pump but drops to 1.15kW at 10mm. It depends how big your radiator needs to be.

[@rigel1632]

Appreciate its long past your original posting but IR panels in the little used rooms could be a good option.

[@TimAndKatsGreenWalk]

It's something I've looked into, yes.

[@johnh9449]

Interesting to hear your comments and comparing it to my system only yours is air to air whereas mine is air to water. You also have yours set to 18°C in some areas and turn it off at night whereas I've set mine to a constant 23°C with one central thermostat and heating the whole house with all rooms open and run it continuously 24/7 to maximise COP. I ran the gas boiler the same previously so it's a good comparison now it's replaced with an ASHP. It's definitely cheaper, just as warm, more stable temperature and cheaper still with solar PV plus battery to drive it. I did consider air to air but you don't get the BUS scheme grant for that and can avoid planning permission issues with a heating only ASHP. I presume you are using weather compensation? It's interesting with your comment about the walls being warmer. I did notice when the weather snapped from about -4°C to +12°C in a few hours which reduced the flow temperature to 32 °C, the house temperature dipped and struggled to recover immediately. I had been optimising the weather compensation and reducing flow temperatures to minimise short cycling and raise COP and so tweaked the high ambient limit slightly which raised the flow and restored the house temperature quicker. That episode demonstrated that cold within the walls still sucks heat out for some time even when the outside ambient temperature rises considerably. The walls are not unlike storage heater bricks after all. I notice you have bonded bead cavity wall insulation like me. Do you have 300/350mm loft insulation? It will be interesting to have an eventual year's worth of comparison.

[@TimAndKatsGreenWalk]

Yes, we have very thick roof insulation. I believe our system has built in weather compensation but there is no way to control it as a user, so far as I know. Perhaps there are some installer settings somewhere but I've seen no way to change them.

[@asilver2889]

Air to water heat pump systems are low temp, slow response, so really work best if on all (most) of time. Can't compare with A2A really.

[@johnh9449]

@@asilver2889 They are different but comparing is still interesting. With A2W the thermal mass of the water certainly acts as an integrator slowing the response but providing thermal storage and the emitters are different to A2A of course but commonality exists regarding the heat pump itself and the thermal characteristics of the house. Short cycling is to be avoided in A2W and A2A ASHP. Zoning can also be a common problem. Ultimately a comparison can be made between the energy loss from the house at a given temperature and the energy input. Looking at Tim's figures he's using nearly half the energy compared to my system but he has his temperature set several degrees lower and isn't heating all areas at all times - so that's an obvious difference in requirements that makes comparison difficult but still interesting. I'm running an easier comparison between my old gas boiler and my new system with the house and temperature unchanged. I did consider A2A but there's no BUS grant and you need planning permission as well as DNO approval and it doesn't do hot water. I have an MCS inspector coming round for a coupe of hours to check the installation. No doubt we'll have an interesting chat.

[@andrewstephens8859]

@@TimAndKatsGreenWalk Tim, is your system linked to an external thermometer/weather forecast web connected? I had briefly imagined it might be something akin to PID load compensation modulation of a gas combi.

[@TimAndKatsGreenWalk]

@@andrewstephens8859 the outdoor units have thermometers built in, but there is no weather forecasting. The power draw does vary based on the outside temperature.

[@martinweston8147]

May have been nice to state the main discussion points at the start and then you could say skip to 7min for X or min 21 for Y.

[@TimAndKatsGreenWalk]

Yeah, I'll do that if we do another one like this. The chapter markers are in the description already though, so that's more or less what you're after.

[@samwoollard4491]

Not sure if I have missed it in a previous video, but how much was the whole installation?

[@TimAndKatsGreenWalk]

This video has the full cost breakdown: kzbin.info/www/bejne/hnrKo4Fvqq-Zfrs

[@waqasahmed939]

Have you perhaps considered getting an air to water heat pump for: The radiators in your bathroom A water tank ? I'm thinking of doing mostly air to air, and a tiny bit of air to water. My rationale is that air to air is mostly better because my piping is microbe, and my radiators are ageing. However there's still the issue of radiators in the bathrooms / heating hot water. I figure that a small ASHP for just that would be better than a fully electric radiator in the bathrooms

[@TimAndKatsGreenWalk]

The bathroom radiators would require so little energy to run that it really wouldn't be worth getting a whole separate heat pump system for that. I am considering a heat pump hot water cylinder, however (e.g. Vaillant aroSTOR).

[@dorsetengineering]

@@TimAndKatsGreenWalk there might also be the option to add an f-gas heated hot water cylinder to one of the outputs on your least-used outdoor unit. These are very common in Australia and in commercial installs here in the UK. Just another pair of f-gas pipes to the hot water cylinder. Might be worth talking to your f-gas installer about this option.

[@TimAndKatsGreenWalk]

@@dorsetengineering I think the pipe runs would be tricky in our current setup but that is an appealing option, for sure.

[@viktors13118]

Hi! Any issues with dust level in the air when units are working?

[@TimAndKatsGreenWalk]

Not that I've noticed.

[@James-zu1ij]

Do you have any thoughts about what would be the most efficient for a one-person (3 bed) household? At the moment I'm very happy at 15C and tend to only heat one room or 2 if I have a guest staying. Essentially, It's a question of how many KW does my living room lose in regard to sizing the system. But at the same time, I'm thinking to put 3 units in, i.e. the living room, guest bedroom downstairs, and the hallway (hot air will rise into the bedrooms from the hallway) Being single means I can be frugal so I don't want a massive system.

[@TimAndKatsGreenWalk]

A 3-way multi-split sounds like a good fit for you, for sure. The one in the hall is definitely a good idea, our hall one does a lot of the heavy lifting keeping the core of the house warm, so I expect you'd have a similar situation. The indoor units tend to have a lowest power rating of 2.5 kW, give or take (in cooling mode, slightly higher in heating mode), so the outdoor unit would probably need to be in the ball-park of 7.5 kW but it's not crucial. You could get away with a lower rated outdoor unit if you don't expect to have all three indoor units on at the same time. It depends if you go for a more powerful hall unit or keep it the same rating as the smaller rooms. Our hall unit is 3.5 kW while the smaller rooms are 2.5 kW, for reference.

[@sjcsystems]

The point I was going to ask is...have you zoned the indoor units? They can either all heat, or all cool. In the spring and autumn, is this going to be a problem?

[@TimAndKatsGreenWalk]

The arrangement of the indoor units more or less dictated what external unit they're connected to (in terms of pipe runs), rather than any thought of zooning them. We don't anticipate needing to have them operate in different modes at the same time though, so it shouldn't be a problem, hopefully. At least I hope not!

[@lawsonspedding6136]

The remotes would seem to be a better option !

[@TimAndKatsGreenWalk]

We actually got the app fixed so it's all good. The app allows you to control all of the units from the comfort of your sofa and it's much easier to use for scheduling.

[@Owen_ie]

A2W systems are most efficient when running at low flow temperatures in weather compensation mode, I can't find any information on the most efficient way to run an A2A system. If you have any information it would be worth making a video on. Also I have been pricing up an A2A system and two 2x1 systems is slightly cheaper than a single 4x1 system. Two external units would take up more wall space, but if one broke it would be cheaper to replace and you would have a redundancy.

[@TimAndKatsGreenWalk]

The only thing I've heard is that running with low fan speeds is more efficient but presumably that's just because the external units have to work less hard to provide them with the necessary heat. Good point about having the second external unit.

[@0Tweaky0]

12KW a day at 0.26 per kw =£100 a month or just over is that good? Also add £15 for standing charge

[@TimAndKatsGreenWalk]

Works out about the same running cost as gas, since you need over three times the kWh of gas for the same heat output. If you can get rid of gas entirely then you also save the gas standing charge.

[@usramx]

My 3 unit Mitsubishi manual states that the optimal heating temperature is between 22 and 24 celsius. Are you sure you are not setting yours at a too low temperature?

[@TimAndKatsGreenWalk]

Are you sure that's not in reference to cooling mode, rather than heating mode? I can believe the optimal for cooling mode is 22-24. That's pretty high for heating mode though. If you thought I was talking about cooling mode you're mistaken, we use these mostly for heating so the settings I mention are for heating, not cooling.

[@usramx]

@@TimAndKatsGreenWalk it is heating mode that we both are reffering to hence my comment. Model SCM50 ZS. I am curious what your manual is stating?

[@TimAndKatsGreenWalk]

@usramx 24 is way too hot. Most people are comfortable between 19 and 22 deg. You should set your temperatures to what you feel comfortable with, not hotter than needed. If you have it set higher than needed you'll use more energy. 22-24 would be uncomfortably hot for us and use significantly more energy than setting to 20 or 21. What the manual says is irrelevant, your personal comfort is what matters. If you're comfortable with your heating set to 24 then fill your boots, but your energy bills will be a lot higher.

[@usramx]

@@TimAndKatsGreenWalk Of course it is the user who decides in the end. I am thinking about the efficiency which probably goes down when not following manufacturer indication. For me 22 degrees is perfect both in terms of comfort and cost.

[@TimAndKatsGreenWalk]

@@usramxas I said, if you set the temperature higher you'll use more energy for a couple of reasons. With heat pumps the smaller the difference between the outside temperature and the set point temperature the more efficiently a heat pump will run. It'll be *less* efficient set to 22 than when set to 20 (and even more efficient when set to 18 or lower). Heat loss from your house is also proportional to the temperature difference between inside and outside, so if your house it at 22 deg then it will lose more heat than if the indoor temperature is 20 deg, and so you'll need to replace that with more energy. When your manual says "optimum" it's not referring to energy efficiency. If you're happy with 22 deg then that's the right setting for you. But it's not more efficient than setting to 20, I can guarantee you that.

[@jimgannon7539]

Whats you power bill like on frosty days. I hear mad amount of power used to defrost unit on cold days.

[@TimAndKatsGreenWalk]

The defrost cycle takes only a few minutes and at its coldest in Dec that happened a few times per day, so not much is used for that vs. actually heating. Take a look at the next video about our demand vs. temperature stats to get an idea of what our energy usage per day is. Multiply by your tariff and you'll see roughly what it would cost. Very similar cost to running a gas boiler, essentially.

[@tom.jacobs]

Thanks for this. Here a (5kW) floor-model installed about 2 months ago in a almost not isolated living space (coming from cop 1 electric, the radiators needed replacement). Not yet experiance with wall-mounted (will be later, after new roof) so I can not compare. Finding the speed also crazy fast (much quicker than the radiators) and the noise pretty low. I can relate to people missing the radiating heat (for instant heating), but staying near the unit takes that away. Pro's are the somehow better flow (although: don't expect the floors at a distance getting warm) and here had easier/better looking install (because the ducting don't need to go up). Also looking for a solution for water (heatpump boiler/e-boiler) and bathroom. Looking forward for the nitty gritty of energy usage [and ways to better log/follow them: unit is directy mounted - so can not place a measurer- and app is not logging a lot], here averaging [december] also about 10kWh/day [1 not isolated livingspace 60m2].

[@healthbytes7360]

Always wanted to ask. Wouldnt it be better to have storage heaters to get heated at low price as low as 7p. and then use this instead of A2A and A2Heat airpumps? Please can you share your thoughts?

[@TimAndKatsGreenWalk]

Storage heaters are only 100% efficient at turning electricity into heat. Heat pumps are more like 300-400% efficient, so you need far less electricity to get the same amount of heat. If you also have a battery you can charge that up at 7p and that can then help to run your heat pump, making them significantly cheaper to run than storage heaters.

[@healthbytes7360]

T@@TimAndKatsGreenWalk Thanks so much. keep up the great work. Really confused at the moment to go ahead with A2A or a2 w. I have an oil boiler and all the pipe works in place, so considering A2W but i really like the option to have cool temperature at hot weather. In your opinion which fits best?

[@TimAndKatsGreenWalk]

@@healthbytes7360 well, that depends on a lot of factors. If you've not done so already take a look at this video I did on the pros and cons of each system: kzbin.info/www/bejne/qoTXnZ6iq5admacsi=UPcQEVJaECFenUgM I think that a well planned and installed A2W system is probably going to be more efficient (lower electricity consumption for the same amount of heat) and you get hot water with it, but the benefit of cooling in the Summer does give A2A a big plus point. Now that the boiler upgrade scheme is £7.5k for A2W you could pretty much get an A2W system essentially for free, so I'd be tempted to do that and then get a mini-split AC system in a couple of rooms where you'd most benefit from cooling in the Summer. That will probably be the cheapest and most flexible system, assuming you have enough space for the extra outside units. It's always a compromise!

[@healthbytes7360]

@@TimAndKatsGreenWalk thank you for your valuable input, hugely appreciated.

[@TimAndKatsGreenWalk]

@@healthbytes7360 no problem. Best of luck with making your decision!

[@rodden1953]

i live alone in a 3 bed house i dont really use upstairs only the bathroom so i wont be having any hot water . im thinking of keeping the gas boiler for a year to see how i get on with A2A before having the gas removed . also i saw a guy who said they work better low down near the floor , what do you think ?

[@TimAndKatsGreenWalk]

It's a good plan. We did something similar, keeping the boiler for the first Winter before getting rid of it in the Spring once we knew we no longer needed it. We specifically wanted to free up the wall space where the radiators were so preferred the wall mounted units rather than the floor ones, but they both work well. We direct the warm air straight down so that it spreads out nicely along the floor before gently warming the whole room, but with the floor mounted units they work more like radiators so the air rises up in a more traditional way. It comes down to preference.

[@rodden1953]

@@TimAndKatsGreenWalk Oh thanks i didnt know there were floor and wall ones , im learning about it , im talking to someone who will do the job he said id probably need an 8kw heat pump . i see you said you didnt really need 2 . i have solar and a powerwall so far ive almost ben off grid for 4 yrs . i shall have to watch more of your videos they are very helpful thanks

[@TimAndKatsGreenWalk]

@@rodden1953 no problem, I'm glad you've found them helpful. 8kW sounds plenty for you, I agree.

[@brackcycle9056]

Could you just set the louvre position & disconnect the motor , to stop its noise? ( radiators aren't silent either with pipes creaking) . How many KG of refrigerant do you have?

[@TimAndKatsGreenWalk]

I'm not messing with the units, they're pretty expensive! But yes, overall they're quieter than some central heating systems we've experienced. Not sure how much refrigerant is in each system, not much.

[@TimAndKatsGreenWalk]

The data sheet says 1.92 kg refrigerant charge for each outdoor unit.

[@johnfreshwater3790]

Hi. What made you choose a2a rather than a2w?

[@TimAndKatsGreenWalk]

I cover that in the previous video in this series, so I suggest checking that out. It's the pros and cons one.

[@The_GG_OG]

Something you have n’t touched on is that I suspect that this system costs the same to run as gas given electric is 4 times the cost but a2a is 4 times more efficient therefore cost are similar to gas? have you also installed solar to reduce the cost?

[@TimAndKatsGreenWalk]

Solar and battery are due imminently, but yes, I'm planning on covering the running costs more thoroughly in the stats video.

[@markgilder9990]

I run mine of solar. Would like batteries but too expensive at the moment.

[@sammysnake2309]

Hi Tim & Kat great information and info about your A2A system👍 I’m looking at having a very similar system, yours has been installed really nicely and is very neat with the trunking etc. Could I ask who your installer was as I’d be interested in asking them to quote for my system. Thank you.

[@TimAndKatsGreenWalk]

They're a small local one-man company called Just Chillin', in Stroud. I'm not sure what their catchment area is though but you can try!

[@davidbou7141]

Is this guy working as an actor on star trek?

[@TimAndKatsGreenWalk]

You what?

[@gavintillman1884]

Confused that air to air would have a defrost cycle? I’d expect to see it for air to water.

[@TimAndKatsGreenWalk]

It's still a heat pump at the end of the day, so the outside heat exchanger will get colder than the outside air, and therefore will get below freezing sometimes.

[@gavintillman1884]

@@TimAndKatsGreenWalk understood but the coolant will typically be something like R32 rather than water. Something that will be liquid or gas (depending on where in the circuit it is) rather than solid.

[@gavintillman1884]

With air to water, it’s the water that freezes. Not the coolant.

[@TimAndKatsGreenWalk]

@@gavintillman1884 air to water heat pumps still use a refrigerant gas to transfer the heat and it's that gas that flows through the heat exchanger in the outside air at a temperature below that air so that it can absorb the heat. The water flows through a separate heat exchanger where the refrigerant gas has been compressed to raise its temperature to higher than the water so that water gets hotter. The water never flows through the cold part of the outside heat exchanger and so never freezes. It's the water condensing on the outside heat exchanger that freezes and needs defrosting, not the water that flows into the house from the outside unit.

[@TimAndKatsGreenWalk]

There's a good video on the Heat Geek channel that shows how air to water heat pumps work.

[@MT-xy7fw]

The problem is the gas is 10p per kwh vs 30p per kwh for electric so even with the cop of 3 it about the same cost. how will you ever recover the £8k+?

[@TimAndKatsGreenWalk]

Indeed, and totally not the point of doing this.

[@jeanh9641]

Thanks for sharing the detail about the cost and the 'no VAT' information. Did you claim £5000 off Air Source Heat Pump Government grant?

[@TimAndKatsGreenWalk]

No, annoyingly air-to-air doesn't qualify for the BUS grant for various reasons. The install was cheaper than an A2W system though, so accounting for the BUS for A2W they work out quite similar.

[@robfee2065]

Stats etc ASAP please

[@TimAndKatsGreenWalk]

Jeez, have some patience, please, I can only make these videos so fast.

[@USA-GreedyMenOfNoIntegrity]

@@TimAndKatsGreenWalk more coffee then😊

[@JohnR31415]

Get home assistant running… ditch the app.

[@TimAndKatsGreenWalk]

More equipment and setup needed though, which I'd rather avoid. The app works fine for our purposes.

[@asilver2889]

Great video series - one of best for UK. But really you guys - 18° in bedrooms?? That is warm - my evening living room temperature with wood burner just about. It must be an upbringing thing. Bedroom right now is 13° and perfectly OK. Yorkshire grit.

[@TimAndKatsGreenWalk]

If you like it that way knock yourself out. I'm not telling you how to live.

[@crit71]

Great video, but.......why are all these videos popping up calling it air to air Heatpump heating. It's Air-conditioning. Nothing more.....nothing less. These videos will almost certainly confuse the hell out of the average user. This isn't new technology. They've been around for decades.

[@TimAndKatsGreenWalk]

It is both of those things. Calling it an air-to-air heat pump ensures people don't assume it's just for cooling, especially given that we're using it primarily for heating, which most people don't realise is something AC can do too. A2A is just a bit more of a general description, that's all.

[@RobFisherUK]

It's because air conditioning is a decadent, gauche, polluting thing that Americans use (spit) but heat pumps are for bien pensant, civilised Europeans. 😜

[@jimgannon7539]

Much trouble, convincing kat to spent all that money. on heat,solar ect..

[@TimAndKatsGreenWalk]

None at all. We're pretty much on the same page about most stuff, luckily.

[@TommysDaddy]

What thermometers / monitoring equipment do you use (for your 'research') ? Is data collection automated ? Do you use an app like 'Home Assistant' ?

[@TimAndKatsGreenWalk]

I found a source of historical data for all the modeling of external temperature vs heating demand (check the description of the stats video for a link). That gives me the ability to get decades of data providing a much better statistical measure (the stats video explains it all in exhaustive detail too). I don't use Home Assistant, we just have a few internal "dumb" thermometers that we can glance at as and when we want to know what the temperature is in a given room.

[@TommysDaddy]

@@TimAndKatsGreenWalk Thanks Tim. I've started the 'dumb thermometer method too ! I saw another KZbinr talking about his 'Home Assistant' set-up so I was interested . . . well it killed a few hours while I installed Hyper-V & virtual Ubuntu just for the sake of it . . . very interesting . . I am sure I'll find a use for it one day !

[@TimAndKatsGreenWalk]

@@TommysDaddy yeah, not sure I can be bothered with all that.