Workerbee

I'm looking at the direct, electric heated sunamp model as I'm an all electric house. So does this mean I was right in thinking the sunamp can't be 'overcharged' to increase its storage like a direct uvc can be? I'd been looking at the 210 version because I thought it would be overkill for two people; it's sometimes quoted for 6 person houses. But if my back-of-fag-packet sums were right, then even a 210 wouldn't be enough. Only an 'overcharged' - or at least above 55 degrees - uvc would do it, with the additional benefit of a second immersion if a boost was needed. As @SteamyTeasays, though, I'd need to check for thermal cutouts.

Thank you everyone - it's been very useful hearing your experiences and knowledge. I've continued my research (ie put off making a decision); leaving aside the customer service question for now, I've got a list of pros and cons for the Sunamp vs uvc, which I can post if it might be of use to anyone in future. But one thought occurred which might swing it decisively in the uvc's favour, and it's that you can 'overcharge' a uvc - ie increase the capacity by keeping it at a higher temperature, which you can't with the Sunamp. I'm thinking of the Sunamp eplus (direct) 210 - ie Sunamp say it's equivalent to a 212l cylinder. Mixed down to 40 degrees with an assumed 10 degree cold feed, it produces 301l according to the tech specs. (footnote: is this right? It would imply a temperature directly out of the Sunamp of only around 53 degrees). The only thing I need dhw for (other than hand washing) is a shower. My showers are about 8 mins, my partner about 14 mins. 22 mins total. Assuming a 12lpm shower, that's 22 * 12 = 264l. If I get a great shower experience at 15lpm, that's 22 * 15 = 330. Either way, it doesn't leave me much wriggle room. I would then be relying on a rapid recharge time with on-peak prices, and if we had guests, we're stuck. In winter, even more so. But with a 210l uvc, I could heat it above 70 degrees and get more water volume. Am I missing something?

Brilliant, thanks @Nickfromwales - that's a much better idea than mine! Is compressive strength related to vibration in a floating floor ie the higher the compressive strength of the insulation, the less risk of stone tiles failing? If so, whether I could go for something like Ravatherm XPS X 300 SL and then a layer of insulated backer boards over the top. Or whether it's simply the act of bonding the insulation to the slab that eliminates the floating floor, regardless of compressive strength. In that case, I could perhaps go for max insulation value with something like tissue faced phenolic boards.

Thank you for that, @Russdl. Do you find the flow rate is as good as a uvc? Sunamp mentions main pressure hot water but nothing about flow rate, and I wondered if it might get restricted in order to maintain temperature, particularly when the incoming mains temperature drops in winter. I'm keen to have a decent shower experience!

Thank you @JohnMo - yes, £250 seems very cheap, which made me question it. Rough prices on text message rather than a formal quotation make me nervous! My fear would be deciding on a uvc over the sunamp then finding I can no longer get hold of him when the time came. The 210 was the sunamp size (uvc litre equivalent); the next one down is 150, and with potentially 4 showers a day from a powerful shower, I thought I should play it safe. If going with a uvc I was thinking of a 180l. I'd probably go with the multibloc solution. On paper, the sunamp is the much better solution for me both in size and price, so it's very sad that it's let down by reliability and customer service. I could forgive the former if the latter was excellent. That's why I wondered if anyone had had experience in the last year or so in the hope that things had improved, as much of the online discussion is from 2023 or earlier.

One was £2230, and the other was £3600. This is for a direct uvc (I think one was 170l gledhill, the other was unspecified) and pipework. Two others didn't turn up, another wanted to charge to quote, and the sixth offered to do it for £250 labour if I piped up to the cylinder (which is what I requested, to keep costs down). At that price, I wonder what he'd be like. Alternatively, I can get a 210 directly heated sunamp for £2k and fit it myself. Coupled with having a small property where space is an issue, the sunamp seemed a great solution in theory. Thank you for sharing your experience, @Nickfromwales - very useful. I'd read your comments on a previous thread when I was researching. It would be a great shame if quality and service hasn't improved.

Thanks @nod - what was the issue the installers had with them?

Thanks @JohnMo - no, I couldn't seem to find much beyond about 2023. I got the impression from the threads I'd read that most of the issues (leakages, charging only after dropping below 50%, etc) were mainly from early models. I'm an all-electric house, so I'm looking at the direct version (Thermino ePlus). The size and shape is the main attraction for me, as I could stick it in a cupboard. In terms of a direct unvented cylinder, I could find a way to fit one in if I had to, but it's not ideal. Finding an installer isn't straightforward, either; of the 5 or so I've had around, two didn't bother quoting, two were expensive to the point the Sunamp is the cheaper option, and one was suspiciously cheap.

I'm thinking I might starting insulating the room and then I'll have more of a feel for the space that's left. What are people's feelings for dealing with a floating floor? It's a concrete slab and I'll add insulation, then electric ufh, and stone tiles. The kitchen will have the same build-up. I'm thinking the safest way to avoid issues is to use XPS tile backer boards: as well as their very high compressive strength, I could stick them directly to the slab, which effectively eliminates the floating floor. The downside is cost - putting down 70mm tile backers on the bathroom and kitchen (c. 16sqm) might not leave much change from a grand. Kingspan reckons 50mm PIR topped with 22mm chipboard or marine ply would be fine, but I'm not so sure...

Hello! What are people's feelings about the Sunamp Thermino in 2025? I've read every discussion thread I can find, including a few excellent detailed ones on this forum; however, many of them seem to be from a few years ago and I couldn't find much recent discussion; and given this is a rapidly emerging technology I thought it might be worth revisiting. The main benefit is size; there are others, but that's the key one. On the other hand, many of the threads mentioned issues with customer service, and reliability. Towards the end of several threads I got the impression some of the reliability issues were to do with early models, and firmware updates and newer versions had solved them. Is this the case, and has the customer service improved, too? Any thoughts greatly appreciated!

Hello again! Here's a basic diagram of the tiny bathroom. It's actually slightly larger but I've taken into account the insulation I'm intending to add. I'm thinking I'll keep the shower in the same location as the old one, but remove the raised slab as previously mentioned. Preferably I'll build curved stud walls so it's a walk in shower, but might have to resort to a glass door if space is too tight. I'll put the toilet and basin on the far side against the 1610mm wall.

Yes, I can put something together. Given that the shower was going in the same location as the old one, I'd just been intending to find a former that could accommodate where the waste currently was, but I guess it could be moved and I could cut into the slab to fit it.

Brilliant, thank you! Just one other thing - the slab finishes short of the wall and the waste is currently bedded on sand (I think there's a dpm under the sand). Am I okay to leave this as it is and just lay the wedi boards across, notching the underside to accommodate the waste pipe as it rises through the floor? Or should I provide more support for the boards? I will remove the u-shaped concrete that's sitting on the slab and which supported the old shower tray, and replace it with wedi as you suggested. And should I replace the waste to use new plastic, or is the old okay? Thanks again - I feel I know where I'm going with this now!

Thank you very much for this, @Nickfromwales - that's very useful. So it sounds like xps tile board is best for stability for the whole room, (ie under the shower former and everywhere else, for tiling on to). I can stick the xps to the concrete slab and it will help eliminate the floating floor issue. Can I increase the thickness without losing stability? The room previously had 50mm polystyrene and 22mm chipboard, so I've potentially got around 75mm to play with and I'm concerned 20mm wedi board wouldn't be a lot of insulation. Or could I potentially use phenolic/PIR underneath then a thick layer of wedi board on top? Thanks again!

I'm now wondering if I can do a hybrid option for supporting the tiled floor and shower former. Could I get the best of both insulation and support by having eg 40mm phenolic then a thick XPS board eg 30mm on top that I could tile on to? And for the shower former just have XPS underneath (50mm?) and miss out the screed, to maximise the insulation?