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Major news!!! Guess what? Sunamp have just emailed me to say that they are going to replace our unit as it is covered by the 10 year warranty on the core! They emailed me as I was typing the reply above.

First of all, my apologies for being silent for so long. TBH, having finally settled here in our new home I needed a break from self-build. Not for any particular reason at all, just that I'd been living and breathing it for so many years that I needed some time out, a bit of breathing space if you like. Old age seems to do this, creep up on us almost unnoticed (and I'm now in my 70's). Also I was spending way too much time here, to the exclusion of other things I should have been doing. Anyway, thought I'd post here to hopefully shed some light on how things have gone with our Sunamp adventure, and give a bit of a gentle warning. Those who've been here, and on Ebuild before this place, may remember that we bought a Sunamp PV right back in the early days, before this place existed. We ran that for well over a year, with a few minor teething problems, but it was enough to convince me to swap it for a larger Sunamp UniQ eHW 9, which I did in September 2018. That also had a few teething problems, but Sunamp sorted them out quickly and without fuss. Since then I've been more than happy with the Sunamp. It's provided reliable hot water, mostly heated by excess solar generation, in fact far more hot water than we have ever needed as it turned out to be a bit over-sized. The first time we went away on holiday I turned everything off and was amazed to find that when we got home a week later there was still piping hot water available. I cannot complain at all about its performance, it has been significantly more efficient than a hot water cylinder, which was the reason for me being so enthusiastic about it back in 2016. Sadly, our Sunamp died on Saturday morning, and ejected its phase change material all over the floor, down through the ceiling in the kitchen below: A check upstairs in the services room confirmed that it's death had been spectacular, with PCM all over the floor and a long icicle of sodium acetate crystals down the back of the unit, from the burst casing inside: To it's credit, despite this it had delivered two showers that morning before we spotted the problem. Sadly this was to be its dying endeavour. I contacted Sunamp, not because of any warranty claim (there was no warranty anyway) but to ask them to put me in contact with a local installer for a replacement. I spent the weekend looking at the specs of the newer Thermino models and, given that the 9kWh (11kWh) UniQ was overkill for just two showers a day I decided its replacement would be the smaller Thermino ePlus 150, with the PV02 key to better match it for PV heating via the Eddi (when summer comes back). I found a couple of online suppliers, price, including VAT looked to be around £1,800 or so, plus delivery, which sort of seemed OK. I'm not up to getting the old unit downstairs and the new one up stairs, so I contacted a few local plumbers. All said they wouldn't touch this job. No idea why, it's a pretty straightforward swap, as the PRV, TMV etc is all there, just a matter of re-jigging two 22mm pipes. Seems the technology just scared them off, or, perhaps, it might have something to do with dealing with Sunamp? After a lot of delay, Sunamp customer services came back to me, asked for photos, then went silent. I got on to them again and they gave me contact details for a couple of installers. I contacted them, first one got back to me saying it would be around £6k to swap out our failed unit for a new one. I questioned this. He said it was about a day's work. Now, I'm all in favour of paying a fair rate for a job, but I know how long this job is going to take and I know the cost of all the materials. I am not going to pay a bloke £800 plus per hour, no matter how damned good he is! So, looks like I have to fall back to hiring a stair climber and doing it myself. PITA, as I'd have happily paid someone a few hundred quid to do this (over and above the cost of the bits) but I point blank refuse to stuff over £4k in someone's pocket for a job that is so straightforward, especially when there are installers advertising prices of around £4k to replace an existing hot water system and cylinder for a Sunamp, a job that is a heck of a lot more work. Sorry for the rant, thought it was worth posting here as a warning to others thinking of going down the Sunamp route. I can't fault the performance, but if the cost of repair and maintenance by a Sunamp approved company is so crazy then it may give some pause for thought. I've half a mind to bin the Sunamp and just get a high efficiency 150 litre cylinder installed. No idea what that might cost, but I doubt it would be over £6k. PS: Seems I have hundreds of PMs that have accrued in my time away. Sorry, but I doubt that I have a hope in hell of answering them all!

I've been trying to see if my theory about these issues being related to pressure might be born out, by comparing the specifications for the UniQ that we have and the newer Thermino (which seems to use essentially the same, or an extremely similar, core design). It's interesting that the pressure specs have changed. The UniQ has a minimum pressure of 1.5 bar and a max pressure of 10 bar, according to the last set of MIs I received, version 2.0, dated 17/06/2018: For the Thermino though these pressure specs have been very significantly reduced, to a minimum pressure of 1.5 bar but a maximum pressure of 5 bar, half that of the UniQ: Moot point for us, perhaps, as our well pump can only deliver 3.5 bar maximum and the pressure regulating valve has always been set to 3 bar, same as the pressure recommended for the Thermino, but it does suggest to me that there is a known pressure sensitivity issue. When combined with the emphasis in the new MIs that mandate the fitting of a pressure relief valve, set to 6 bar, together with the 0.5 litre pressure vessel I'm now more than ever convinced that the most likely cause of this failure is pressure, most probably some sort of repeated pressure shock from something like the shower turning off. Although we have a 100 litre pressure vessel only a metre or so away from the Sunamp, it seems possible, perhaps even probable, that this is too far away to mitigate some sort of fast pressure shock wave. This is all really just theory, but it does pretty closely fit with the known facts and details from Sunamp, and the experience of Jonathan Porterfield up in Orkney. Why else would Sunamp have reduced the maximum pressure permitted, and added these over-pressure mitigation devices, if it wasn't because over-pressure can cause issues like this?

It is indeed very good news, best I could have hoped for, as I really was not looking forward to trying to shift either the old one downstairs or the replacement back up stairs, TBH. I was even thinking of buying a second-hand stair climber, I'd found an ex-hire one for sale not too far away (Waterlooville) and was just about to agree to buy it and go down to pick it up, thinking that it would be worth it only if I used it twice, given the silly price I was quoted last night. On another positive note a local heating and plumbing company that I contacted yesterday called. They would have been happy to swap the unit over for me, and were very interested in the Sunamp, they'd not heard of it before. I spent five minutes on the phone explaining how it worked and the chap seemed keen to know more, so it may be that he might be interested in becoming an installer. He certainly seemed very down to earth and helpful on the phone.

Excellent news Jeremy and well done Sunamp if you’re reading this 👍🏻

Just to give an update on this, for anyone who’s interested: I got my estimate wrong in my first post & the builder, & his irate wife, have chased for payment several times on three outstanding invoices which total about £10,800. I haven’t paid any of this £10,800. I arranged for another builder to spend a couple of hours with me on site, looking at all the problems. He provided a report/quote detailing remedial works, etc. I paid this builder for his time, so I’m not going to feel bad if I decide to use another builder when we get going on site again. I’ve deducted his bill, the cost of the remedial works & around £2,500 for consequential loss (my time away from my business spent dealing with these problems) from the £10,800. I have yet to get a cost to get the drains sorted out; once I have this, I’ll end up with a figure I’m prepared to pay the cowboy builder if he sends me a credit note (probably around £9,000 – that’s the credit note – not the amount I’ll be paying). The mortar was assessed as being good & strong, so we’ll be OK to fix up then build off the wonky walls. Thanks @Roger440 for prompting me to get this assessed. I wrote the builder a very long email with pictures attached, explaining each of the main defects in detail, a breakdown of costs for remedial works & my intention to pay him once I’m in receipt of a satisfactory credit note + information he was supposed to give me which I have not yet received. Also, I included a detailed explanation of the saga of the c £7,000 he overcharged me earlier in the build, before reluctantly issuing a credit note, so in the unlikely event he makes a court claim, I have everything I need, all in one email. I sent the email just before Christmas & I haven’t received any more demands for payment, nor any other communication since.

We should be banning new builds from having gas heating. If you are a new build then accommodating a HP is no problem. The building industry always carps on about how expensive it will be. Bollocks. They say that about every single thing and then cut every possible corner anyway. If they had their way we'd have single glazed solid block walls with no insulation at all.

Thanks for the kind words (and to everyone else that's said similar). I'm reasonably confident that Sunamp are on top of this, if I wasn't, then I'd not have still been of a mind to buy another (before Sunamp agreed with the warranty thing). My view is that they have been going up a learning curve with these things, and, from what I've seen since 2016, when I first got involved with them, their technical approach has always been very good. The original Sunamp PV, for example, was technically a bit over-engineered. It was a complex solution to the challenge of evenly heating the PCM, using the same heat exchanger used to get the heat out to put the heat in, via multiple non-return valves, a variable speed pump and an inline electric heater. The thing was, if anything, too clever for its own good (although I still have the view that it was the best way to produce a more or less infinitely repairable unit!). It must have cost a fortune to manufacture though, given all the parts it had. If I had to guess, I'd say the primary cause of the early UniQ issues related to the switch to embedded electric heating elements and controls that were not really well-optimised for efficient charging from PV. This had been the unique selling point for the Sunamp PV, and the reason I was so enthusiastic about it, it was, as its name suggests, optimised for utilising excess PV generation (and it was very good at it indeed). What I'd not realised was that they had looked at the market and realised that it was a LOT broader than just people looking to make best use of their solar panels. They may even have been a bit prescient, and guessed that export payments might increase (now up to around 15p per kWh payment on some tariffs) and realised that this might kill off those looking to utilise spare PV generation for water heating. TBH, if we were able to have a smart meter (we can't - not enough signal here) then I'd not bother with using PV to heat the water, it'd be better value to sell any excess at 15p/kWh and then buy in off-peak at around half that price to heat the water. We have a heat pump, used solely for running the UFH and pre-heating the supply to the Sunamp (via a plate heat exchanger inline with the inlet) and it simply doesn't make sense to run that at the 65°C required to charge a Sunamp via hot water, as the COP is absolutely appalling at that flow temperature, especially in very cold weather. This is pretty much what convinced me to go down the path of an electrically heated hot water system, that could be heated in winter using cheap off-peak electricity (currently 6.308p/kWh on an SVR E7 tariff), and also use excess PV when that was available. Not a one-size-fits-all solution at all, but one that seems to fit well with our needs. Overall, I've always been impressed with the performance of the Sunamp. Having oodles of hot water on tap and just never having to even think about whether there is any need to be a bit careful with it is a lot less hassle. For years it has just sat there doing its thing with zero attention from me. About the only thing I do is glance at the Home Assistant screen each day to see how much energy we've used heating the water, and that's really only a casual interest thing (like noticing we've used an extra kWh of hot water because my wife's washed her hair . . . ).

Welcome back @Jeremy Harris . Not to worry about the back-story : we'll kill the fatted calf anyway. image stolen fair and square from Wikipedia

I’d say that would be good practice. Don’t think it would wick moisture much or any significant consequences, but you never know. Id guess not a big benefit in going much below level of floor insulation for cold bridging, marginal anyway. I often suggest 1st course of inner leaf from sub-floor/insulation level, should be in thermal block for the cost/benefit

What worktop? Anything other than a simple straight run, I would get a trusted joiner in to cut and do any joints. That is just what I did with our island, a joiner I know and trust did a very good job of all the cutting and finishing of the oak worktop, far neater than if I had tackled it myself. Likewise the main worktop was stone on on supply and fit contract.

My only thought is you will discharge the battery you are connected to, so they will end up imballanced. So connect it with large croc clips and periodically move it to the next battery so they all get discharged just a bit until you get the main inverter / charger sorted.

If there have been changes to the installation requirements since early units were sent out - and if this is due to safety-related changes - shouldn't Sun Amp be contacting all of their customers to have their system checked? Especially if they sent out early models without full installation instructions or adequate testing! There should also be a prominent notice on their website. They have a duty of care 'in-principle' and probably a legal obligation too - I'm sure the OPSS would take a view on this. I remember 25+ years ago installing some of the first Sunny Boy inverters in the UK. They were IP65 rated for use externally, but, crucially, not if they were laid on their backs. A lot were fitted beneath solar panel A-frames on flat roofs. The first we knew were multiple reports of failure and we realised the problem when one of our lads took the lid off to see inside. The resulting explosion of flame singed his eyebrows off - but we could then see 2 inches of water sloshing in the case. We replaced affected inverters on all sites and proactively contacted customers to switch off their systems until we could get to them. This was before the manufacturer confirmed the issue and agreed to replace every damaged unit. They reprinted their manuals and issued extra ones to wholesalers with old stocks, so I can't fault them. I wasn't happy about carrying multiple Iron-core inverters up and down stairs for the next few weeks though - those old SB2500 models needed two people to carry! The point is there shouldn't be stories like yours on here - Sun Amp should issue a recall notice as other responsible companies do.

Get a laser level.

Great news - do you think they are lurking on the side somewhere .

Very possible, my unit has the serial number 221, so was early in production, for sure, so early that they hadn't really finished writing the installation instructions, as I remember getting at least two, possibly three, different versions from them. There are mandatory requirements on the new Thermino instructions that weren't on mine. The most obvious is that they now require a pressure relief valve on the cold water supply, rated at no more than 10 bar. This is in addition to them now stipulating that the 0.5 litre pressure vessel needs to be close to the inlet. Putting two and two together I suspect the cause of the failures may possibly be related to over-pressure events in the heat exchanger. I have a 100 litre pressure vessel in the supply to ours, plus the required 2.5 bar pressure regulating valve and in theory it shouldn't be possible for the Sunamp heat exchanger to ever see more than 2.5 bar. It's supposedly rated at 10bar anyway. What I don't know is how the heat exchanger is constructed. I'd assumed it was just a zig zag of copper pipe with perhaps some copper fins. Perhaps there is some weakness that can develop that's related to pressure cycling, or short pulses of over-pressure from when a tap is closed suddenly. All just guess work though, based solely on the way Sunamp have imposed new mandatory installation requirements.

@Jeremy Harris It should have a 10 year warranty on the PCM. Sunamp Warranty (pre June 2024)

Welcome back @Jeremy Harris, nothing useful to add to this thread but I wanted to say I have learned a heck of a lot from your posts on the forum (and still getting my head round some of the more technically inclined ones). Thanks for all your input over the years.

Hi all! Long time listener, first time caller. My partner and I are wrapping up a renovation project, turning a 1970s semi-detached into our home for the next ten years or so. We “moved in” yesterday after about a year and a half of work, but we still have a lot to do, including finishing the flooring, tiling, kitchen, and a lot of the electrical works. So very much still a building site!

Excellent news Jeremy. The 0.5L expansion vessel you mention seems tiny? What is that for? That won't take up much expansion of hot water. Compare that to something like a 25L expansion vessel on a typical UVC and even the closed UFH circuit in our house has something like a 10L expansion vessel.

Chances are, a lot of the "damp" is condensation due to moisture in the house hitting cold walls and possibly not enough heating in the house or ventilation of the house. If you dared to ask a "damp specialist" then of course they will say it is damp and give us lots of £££ to fix it.

Firstly, I've read and learned lots from your posts, especially the spreadsheet for heat loss so thank you👍. Insurance claim and let them deal with the clean up and disposal

It’s like a scene from Alien. Good news and well done Sun Amp. However, such a catastrophic failure is either a design flaw or a manufacturing flaw.

correct. Currently elec/gas in the uk is about 4:1 With one or two exceptions this is the highest ratio in europe The majority of Europe has a ratio at or below 3 which makes HP's a no brainer.

Nice to hear from you again @Jeremy Harris old fruit. I think you will outlast my 10 year old Makita battery

Baxi delivered the boiler to me personally on a pallet Friday. I was also shocked by this! A manufacturer supplying an end customer with a product that they have refused to fund to fit, it's a little unseemly to say the least but I have no intention of fitting it myself. It's not second hand, has all paperwork with it and my (or indeed any plumber) can activate the 10 year guarantee once installed. My own plumber does a lot of work for builders and reckons he can sell it on my behalf. Of course it will be less than book price but be mutually beneficial.

Welcome. I like your 'kitchen units'. Look like they'd also bee good for storing power tools in.

You are being a sensible, pragmatic researcher. Membranes, insulation, and service voids are great but must be used properly. I'd venture that the "back to nature" methods are the ones to be cautious about. Nature has no idea of house building.

this is my project - sorry have been offline for a while. Just as an update, over Christmas I had a builder friend call and run through the plan of attack. In short, new floor slab with UFH - for the walls we're going to dry line internally with a metal stud set off the wall by 10mm or so. The insulation between the stud will be either a hemp combi jute, or gutex thermoflex. wall will be slabbed with a gutex thermoroom board on a finsa vapourstop. skimmed with a breathable lime render. when we reviewed the floor joists, they weren't too bad. any bad sections were tight to the external wall. so the metal stud approach will also act as a support for the existing floor joists.

I know you were very early Jeremy (possibly even before full production had ramped up?) Is it possible your purchase pre-dated the 10 year warranty?

The problem is that many people do not know about it.

Welcome back. I will come over hand help (make the tea) while the strong boys do the lifting. There are still discussions about 'thermal mass'.

Any specific one? It's guava season, maybe that's it?

I seem to recall that WEEE doesn't cover transporting the item, unless you're having a similar product delivered?

@Dunc (& @Tuppers) funny you say that - that was the first proposed design (initial render attached - before the pantry was included also). Here was our thinking: The panoramic window is a centrepiece of the house's design and we want to enjoy it. Once we realised we didn't need a TV in this room, it allowed us to move the sofas away from the wall and swap with the dining table. Putting the dining table in the window centre might look 'show home picture perfect' (as we thought with earlier layout discussion), but feels like a waste of the best place to relax and enjoy the view (the additional 2 images I have edited using Procreate to overlay a photo of the view we'll have). In the evening, when the dining table would be most used, the curtains/blind will be closed, so the view wouldn't be seen anyway. Our current table has bench seating both sides and so it won't be much of a change for us. The benches will allow us some much needed hidden storage also.

Does breathable matter if the wall is (presumably) solid?

I've only used hemp batts against brick and stone walls, but provided the concrete is dry and resistant to rain penetration from outside and the thickness isn't great (rule-of thumb - no more than ½ of the EWI thickness), then I wouldn't expect a problem. However if you can install enough EWI, that would normally be the preferred option, rather than insulating both sides. The wall is then more closely coupled to the inside temperature, the possible build-up of humidity in the IWI isn't a concern, and it's easy to hang things on the wall. Consider also how you'll link the wall insulation to the ceiling / roof insulation. And how you'll tackle airtightness.

It was easier getting a quote from build zone. Easier organising warranty inspections with building control. Could pick up the phone and speak to someone at self build zone. But if it’s just a box ticking for a mortgage you’re probably fine to go the cheaper route? I think protek does cover you if builder doesn’t in first two years so they are probably like for like in many respects:

You’re back ! Knew you would ! I’ve tried to match your level of expertise and knowledge in your absence. Think I did ok 👍

Get the ratio of gas to electric to less than 1:3 and making a HP cheaper to run than a boiler becomes much easier. At that point people will start to adopt much faster.

You are carrying out a "material change of use" as per Regulation 5 of the Building Regulations, you appear to come within circumstance a) , i.e the building is used as a dwelling where previousy it was not. Regulation 6 sets out the various technical requirements of the Building Regulations that apply to the various types of change of use. Those technical requirements for circumstance a) do not include Part K - Protection from falling. Thus in your situation the minimum guarding heights etc do not apply, the building is as existing. That is not to say that if you feel some of these cill heights are too low that you should not deal with them but just that you will not be obliged to deal with them.

THAT is the bit that is so wrong and would be so easy to correct. No wonder the cheaper generators are making big profits, because the system over pays them, making people talk about windfall taxes to punish them. All that is needed is change the way the market works so they all get paid a fair price for what they generate but not excessive, and no excessive profits to upset anybody. I would love whoever devised this market system to explain why they think it is right the customer should pay inflated prices and thus pay excessive profits to the cheaper suppliers. We keep being told the more renewable generation we have, the cheaper our bills will get. Under the present system that is a LIE. Prices won't get cheaper until there is enough renewable to power the lot and we don't need the gas generators to bid for any.

Maybe I’ve got the wrong end of this one, but I’m thinking… Any property could work out with an ASHP with the right heat emitters, be that large rads or UFH. The most common heating system is gas with rads designed first high flow temperatures. Replace a gas boiler with an electric heat source providing a high flow temp will increase bills (be it resistive or heat pump based). Expecting peeps to replace working rads just to enable them to spend yet more capital to save the planet a little bit is rather hopeful. So…. hoping for wholesale voluntary transfer to electrical based heating is not going to work. How about we think about banning new houses having gas boilers and we accept slow change…. Oh, they tried that one then worried about re-election. Sigh.

This is a root cause of reluctance. Gas is cheap vs electricity. If the ratio was 1:1 people would be ripping out gas boilers so fast the scrap yards be overwhelmed. If the ratio was 2:1 or even 2.5:1 it wouod be simple to break even vs gas. At the current 3-4:1 range it's hard. Shifting a load of the green and social taxes onto has would help. Reforming the energy market to get rid of the "last unit sets price" method would be a huge win for electricity.

100% the Internet should never be a requirement for any of your house functions.

Sorry going to be a bit blunt - BUS scheme is really targeted at people with disposable income or more money than sense. No sane person would pay, the stupid prices you see on here often quoted. Exceptions are those that end up paying next to nothing, quite rare from what you read, and they have to do quite a bit of work themselves or be through an umbrella scheme, which is milking a flawed system h and why not.

Not sure if this is fixed already but try posting on the open energy monitor forum - there's a lot of discussion about Daikin's on there. More about getting them set up properly but there's a lot of experience.

This is constantly done - review the select committees and various research committees investigations on the .gov.uk site. The issue is the annoying tendency of people ("stakeholders" i.e. including non humanoids like corporations etc) with different incentives and different goals also chipping in with quite different recommendations. Government, quite reasonably, cite the impact on economy and jobs as being as important, for example. Then, between a crusty self builder and a smart, well spoken, polished type flashing some credentials, who do you think gets called to give evidence and shape policy? For example, in a call-for-evidence on housing performance, we can all chip in with how we think all new homes should target Passivhaus levels of performance and give some good engineering and scientific evidence for our opinion, but all the Persimmon guy who employs thousands and donates to The Party needs to do is rub his fingers together. 🤌 It's the age-old story of lobbying.

This is just one but there are others floating around. https://www.diynot.com/diy/threads/noise-from-unvented-hot-water-system.590373/

I don’t know the answers to those questions. So I’m going to try to allow for all eventualities where I can without wasting tons of money. I’m putting a Fancoil into our bedroom, with a drain and also insulated pipes to the manifold and room to allow isolation valves and a volumiser (that really is a word that should be confined to hair product adverts!) so that if the ‘above dew point’ approach isn’t enough we can reconfigure without ripping out walls. So, no immediate need but a bit of bet hedging.