JamesPa

The second video explaining it is now out and, as I am neither a father myself nor have a father who is still alive (its Fathers day!) I have the time to watch it. Its quite simply a small thermal store (filled with 'central heating' water but most likely at an elevated flow temperature as is normal for DHW) with a very large coil for the exchange of energy to the DHW, thus minimising the approach temperature. That's it. The only other 'clever' trick (if you consider it clever) is to arrange the settings on the heat pump to switch to DHW mode as soon as the store temperature drops by only (say) 3C, thus prolonging the 'life' of the store beyond that which you would calculate by assuming no heating whilst demand is present. On the video it was demonstrated with a 7kW Vaillant at OAT 7C. Nothing revolutionary so far as I can see except that it deploys pragmatism (ie it doesn't provide for all possible extremes of demands, just a reasonable demand), a feature that seems to be largely absent from the thought process in much of this area. Will the industry 'buy' it. Personally I fear not, because (I fear) there may be a preference to avoid altogether jobs where the customer may have to make a compromise (like waiting 15-20 mins between showers) and because (I fear) customers are now so used to getting everything they want that nothing less will do. That said, there are now lots of 'heat geeks' out there who will presumably be more easily convinced. Personally I'm very tempted, if only to avoid G3, but then I don't need (or even want) a 20 min shower at 20l/s and nor do I have over-indulged teenage children who are terribly concerned about climate change but haven't yet realised (or been told) that mitigating it may involve some lifestyle changes.

Plenty of 6-9kW electric showers around, similar to a more typical 8kW heat pump. I don't think hg are aiming this at large, highly insulated new builds where space for a large cylinder isn't a problem. Also will the cylinder run out in the time taken for a shower, their video suggests not (based on 10l/s delivery rate). Certainly if the 'requirement' is a 20 mins shower at 20l/s then nothing short of a vast storage vessel will do, but in reality 2-5 mins at 10l/s or less is easily sufficient to do the job. If we are to fix climate change then we will need to adapt and, dare I say it, make sacrifices. Also we need a wide variety of solutions to fit the vast variety of circumstances not the one rule fits all that MCS seems to like.

Two two port valves instead of a three port would surely solve this and allow you to choose either or both at will. I do wonder if minimising the required temp difference between flow and DHW temp (with a big coil or PHE) opens up some interesting configurations that may well have applications in some circumstances. WC would seem to be the issue, but perhaps just viewing the 'dhw cylinder' as a large energy store which can be deployed flexibly between DHW and space heating, and playing with flow temperatures as necessary to achieve what is needed at any point in time, has applications.

Interestingly the pictures of the HG mini store at 4:20 in the video dont show any port for a (pressure relief) vent. That suggests that its either vented (perhaps like Harlequin as @JohnMo suggests, or they have designed in a way to meet the building regs without a pressure relief vent and are prepared to warranty it, or of course its an artists impression (is the cylinder really purple?) omitting some detail. I guess we will find out in a couple of days. I cant see how a vented solution, unless its a thermal store with the attendant limitations, would be a replacement for a combi though, since the downstream pipework and fittings will be designed for mains pressure hot water. Unless of course there is also a water pump inside! Since combis seem to make quite a racket when heating DHW, the noise from a water pump would probably be considered acceptable.

I think that is essentially how Heat Geek achieve the high SCOP claimed for their 'super cylinder. By having a very large coil the temp difference between the flow temp and the DHW can be smaller, meaning greater Heat Pump efficiency.

From the table 3mins into the video linked to, it seems to be an 80l cylinder with a very large coil (or a PHE?) with all of the PRV, expansion vessel etc inside the casing, designed to fit in an under-worktop kitchen cabinet. I cant see anything to suggest that it does any 'real time' heating but of course it may; the gubbins for that (basically a PHE) may also be inside the casing. Its unclear from the video whether it is un-vented or vented. The table claims 14-34 mins DHW at 40C/10l/min, which in any sane world is enough, but of course wont satisfy some of the more extravagant demands that the MCS bods typically assume (which IMHO should be classed as a wholly unnecessary indulgence in a world which is heading for being turned upside down by climate change. It will be good when we have the full specs to understand what combination of compromises they have chosen/technology they have deployed, but it feels to me like it fills a gap in the market. Its notable that they are, in the video, positively encouraging other manufacturers to copying. Presumably they couldnt find anything that could be patented and/or decided it wasnt worth the bother and/or decided that sales would be maximised by gaining market acceptance, easier if there are multiple sources..

I agree with pretty much all that @sharpener, @JohnMo have said. Unlike @Dave Jones I would turn thermostats and trvs up to 2c above target temperature ( instead of removing them - but with the same effect hopefully) and then use wc(water law in samsung terms) to run the heat pump as @Dave Jones and others suggest. This is the basic starting point from which to tweak if necessary, whereas a heat pump where the principal thermal control is external (eg an external thermostat) is starting from the wrong place. However adjusting central heating in summer is difficult/impossible, so practically speaking what I would do now is concentrate on acquiring the necessary information. I would pressurise the installer for the system diagram and the thermal calculations he did to size the system and emitters. If these arent supplied within say 2 weeks I would use the threat of reporting him to mcs etc to apply more pressure, giving him another week, then I would complain to mcs and any other body of which he is a member about failure to provide these things or an explanation of the system. Realistically its going to be September/October before you can tweak anything and expect to get useful feedback from the system in operation, so it's worth the time to see if you can get this info. If you want a third party to look at it instead of doing this all yourself I pmd a link to one I found (but can't vouch for). However they would be working with one hand behind their back without the above info, and also will find it difficult to prove any changes now, so personally I wouldn't actually engage anyone until later in the year (by all means make contact of course to explore what people offer). Once you have the system diagram and thermal calculations post them here so others can comment. In another forum there is an extensive discussion on a couple of the control settings for the water pump (settings 2091 and 2092) in relation to external thermostats. I don't think this discussion is particularly conclusive but if you are able it would be worth checking what values these parameters are currently set to as part of the information collection you are currently doing. I hope that helps, please post again when you have more info (or if you draw a blank!)

...which gets us back to the likelihood that the answer to the question posed (which was do I need a sparky to install a new circuit) is most likely yes in practice, even if technically it may be ok on an existing circuit. That said, people wire single ovens into a ring main with no problem, similar load (to a heat pump of 6-7kW), albeit generally for shorter period of time. I guess the 'diversity' argument doesn't really apply to a heat pump which can be on 24*7. But if the only other appliances likely to be on the same ring are low wattage, what's the actual problem?

Just had a look at some data sheets, even a 14kW ASHP will only require a max of 6.6kW or 29 Amps Sorry mis-type. I meant to say 16-32A!

Yes but wouldn't 16A normally be a dedicated circuit (which was the question)? Having said that, 2kW is presumably OK off an otherwise lightly loaded ring (which many are) or even a 13A spur or a lightly loaded 20A radial. I'm not sure if there are any rules requiring heat pumps to be on a dedicated circuit though and/or whether, even if there are not, some electricians/installers will nevertheless insist on one (obviously not relevant if you are self installing). Oh and in my most above 16-32kW should of course have read 16-32A! Sorry about that.

Yeah I know, I was just trying to simplify the description to the point where even people who aren't familiar with AC (but who may nevertheless read the thread) will understand it. The simplification is probably not necessary for this forum though even if emphasising, from time to time, the difference between kWh and kW is!

No refrigerant lines if you use a monobloc so no need for f-gas, but A2A does of course have refrigerant to connect up. Heat pumps typically take 16-32kW, so usually require a dedicated circuit, unless of course its a low capacity one.

OK so, if I understand you correctly, the way it works is that, in the 'on' periods of the burst mode there is import, in the 'off periods' there is export, and the meter averages the two out (or thereabouts) rather than recording both import and export separately. Furthermore is fortuitous that meters work this way because it makes it possible to design a diverter which doesn't generate as much interference (but still registers 'correctly' on the meter) whereas if they did separately record import and export the burst mode design would result in an unwanted billing. Interesting.

Interesting, I guess every day is a school day! Do inverters integrate the input power for as long as half a second. Its plausible that they do, but if not then burst firing surely wont actually match the load from the solar PV. Interesting that it fools meters though, is that legal, or does it only work because generation is approx the same as consumption so there is both import and export taking place but they both balance and aren't registered?

Get an electric car and use the excess to charge it? I have had both 'free' (or almost free) motoring since mid May and 'free' DHW since mid April.

The immersion heater is just a resistor, it will get hot whatever voltage is applied, just not as hot if the voltage is lower. Both actually work by cutting off the ac waveform at a point in each half cycle, the chosen point depending on the dimmer setting/amount of PV power available. This reduces the average/RMS voltage without needing anything other than an (electronic) on/off switch, and without having to divert power to a resistor (which would get hot in the dimmer case and wouldn't achieve the desired result in the PV diverter case). See explanation here. Your voltmeter registers this as a reduction in voltage because it is designed to return the RMS (root mean square - essentially average) value.

You are mixing a couple of things. You talk of an 'ashp cylinder' by which I assume you mean dhw cylinder. Yes an ashp can heat a dhw cylinder and that is the normal arrangement. But whatever alternative you were planning to use (what?) for dhw with electric ufh will also work with an ashp as a separate system, just as it would be with ufh. So in your mind think about the two separately. If you are going to batch heat to store energy, the only real control you have of your house temperature is how much energy you store. Whatever you store will leak out into the house, just like a storage heaters. So Hives etc may be pointless, multiple ones definitely so, and there won't be much instant control the aim is to get it right with little real time feedback. What you ideally need is something that looks ahead at the forecast and tops up accordingly. Others will know if this is available. Failing that a weather compensated control system with a long time constant. Several on the ashp forum do batch heating so it might be worth posting a batch heating question there as well as on the ufh forum. Electric ufh will be three times as expensive to run as an ashp. If your house is passive or nearly so that's fine, otherwise be prepared for big bills. Just a few pointers, obviously you are early on in the process so time to think.

Yes and yes Agreed

You need to bear in mind that in winter you arent going to generate enough from Solar PV to cover your energy use in summer you will, unless you have an electric car or aircon, generate more solar PV than you can use in a day. As its pretty impossible to do long term storage cost effectively, the excess will be exported. You also need to think a bit carefully about what you want to do. There are two possible uses for batteries namely (a) to store excess generation from solar PV and (b) with a ToU tarrif, to import when energy is cheap in order to reduce your average energy cost. You need to decide which of these you are doing because it affects the choice of equipment and the battery size. If you want to take advantage of ToU tarrifs then the maximum useful battery size is set by your energy consumption outside the cheap rate period. Make an estimate of that and you have an upper limit for the useful battery size. If you have ASHP heating at say 6kW, a typical 4MWh/year electricity consumption excluding heating, and the cheap rate lasts for 6 hours out of 24, then that's about 6/24*(4000/365 + 6*24/3) (3 being the ASHP COP) = 45kWh. On most heating days however your heating will be operating at half max capacity or less so a more realistic figure is 6/24*(4000/365+3*24/3) = 34kWh = 26kWh. Both are probably larger than you can realistically do. There are also cheaper ways to do part of the energy storage namely in your DHW (about 10kWh can be stored in a 200l cylinder) via a diverter/timed heating or in the slab if your house is on a nice insulated concrete base. The numbers are only examples, you need to substitute your own figures and your own situation. If the sole objective is to store excess PV then you need to think about how much you can use 'real time' and how much you have to time shift. This is dependent again on your actual circumstances and there are two many variables to provide a meaningful example without more info. I did do one quick calculation for one particular scenario. 5kWh is in the right ballpark however, depending on your DHW usage, using a solar diverter to store the usable excess may be much more cost effective! If you have (or plan to get) an electric car and do miles on a regular basis, as opposed to irregularly, thats a very large battery sitting outside which you can also use. I realise none of this gives 'an answer' and thats because its very dependent on your situation. The basic message though is that, if you just put in 5kWh you probably wont go too far wrong, however there may be more cost effective measures you can take. Please bear in mind that the environmental credentials of battery storage (as opposed to simply exporting to the grid) are at best questionable, so whilst PV and ASHPs can be justified on environmental grounds in addition to any cost justification, battery storage cant easily be justified on environmental grounds so needs to 'pay its way', at least in my book. For me I can't make the numbers stack up, I have an electric car and solar diverter so already can store energy. It's possible that, once I get planning consent for an ashp (which is proving challenging), time shifting import to take advantage of ToU tariffs will tip the balance.

Irrespective of the heat source you have three different heating elements which, unless sized appropriately, potentially require different flow temperatures to operate at their optimum. That's a challenge whether you have an ashp, a gas boiler or an oil boiler. That's why I am a bit concerned that the architect may have specified it to look right, leaving it to 'others' to make it actually work, which the 'others' may or may not have considered 'in scope'. The obvious route in the ASHP case would be to design all three to work at the same flow temp by using sufficiently large rads, very large towel rails and maybe spacing the UFH out a bit more so it could run a bit higher than 35 (but not too much higher otherwise you burn your feet!). Alternatively match the flow temps for rads and UFH (by using large rads) and treat the towel rails as a separate zone like DHW, to be turned on only when needed and diverting heat from the rest of the house. OP reports something that the architect said which suggests that this might be the intent. You could potentially mix flow with the return from rads to create the flow temp required for UFH. But it wouldn't be reliable if the rads were on a different 'schedule' to the UFH. Not sure how you could mix down from towel rad flow temp if the design means that they do require a high FT. I get the impression the house is low loss, possibly even close to passive. If so maybe that the idea is that the rads upstairs are secondary, and most of the (small amount of) heating is from the UFH downstairs. This would work if its reasonably open plan, several on here have reported houses where the principal (or only) source of heat is downstairs. In this scenario the towel rails are only for heating towels and potenitally everything could be run at 35C. But that's not consistent with what the architect appears to have told the plumber. A poor option is to run it all at HT and put thermostats on the UFH and rads. The Heat Geek guy seems to have ruled that out/advised against it, but it would be consistent with what the architect appears to have said. Running it all at say 55 wouldn't be too bad from an efficiency point of view (although a bit of a shame given UFH, but if its a low loss house not so important in absolute terms). I'm not sure whether this would be too hot for the UFH. Modulated and sufficiently deep in the slab it could well be OK. What is clear is that it needs thoughtful design to work at all, and very thoughtful design to work efficiently. Whats not clear is whether that thoughtful design has actually taken place. Schematics and heat loss calcs needed!

I had another thought about this system. It combines towel rails which usually needs high ft to emit much heat, radiators which usually need a medium ft, and ufh which generally relies on low ft. Of course it is possible to design such a system to work well and efficiently, but it does need design. I hope it wasn't specified by an architect to 'look right' without any consideration of the thermodynamics, and then installed (possibly quite reasonably from a contractural standpoint) by a plumber according to the drawings but without further design! @carou we need more info from you. System diagram and thermal design if you have them.

I think its reasonable to assume that the policy intent was to avoid giving PD rights for air conditioners. Unlike heat pumps used for heating, these operate for extended hours in the summer when people are likely to be outside and thus more disturbed by the noise. Furthermore they don't contribute at all to the mitigation of climate change (and therefore there is no reason to give them special treatment), whereas heat pumps used for heating do contribute to the mitigation of climate change. Without the restriction the anti-heat pump lobby would be able to claim that the rules were making it easy for people to disturb their neighbours enjoyment of the outside in summer, without achieving anything for climate change. The fact that it isn't actively policed doesn't really matter. If your neighbour is annoying you in the summer because they are operating their heat pump in cooling mode, then you can complain to your LPA. If they have installed under PD then its their look out, and they will likely be told to desist from using it in cooling mode - no need for your LPA or you to prove its a nuisance, your neighbours haven't got pp which is absolute. If your neighbour isn't annoying you, then they aren't doing any material harm. All in all I would say that this is a sensible policy intent, and the way it has been implemented also sensible, It allows the violations that matter to be dealt with easily, whilst allowing those that don't matter to be ignored if the LPA choose to do so. Nothing dumb about it at all IMHO, unlike the rule which gives MCS an effective monopoly over heat pump installations under permitted development, which is dumb, anti-competitive and steps well outside the boundaries of what the planning system is supposed to be about.

Basically agreed (longer answer sent in PM) I'm guessing the architect didn't know much about heating (many don't so far as I can tell) and the installer might have been a general plumber and/or took the view that his/her role was to do as he was told from by drawings. It occurs to me that, for a new build particularly, its quite possible to arrange things so that nobody involved has a clue or can reasonably be expected to have a clue, and thus nobody is really accountable. In this case the plumber could possibly argue zero responsibility for heating design on the grounds that the architect has specified it. Obviously not if you are claiming the grant the installer must have MCS, but if you aren't claiming the grant then they don't. By way of a concrete example of this I was recently involved in a community centre build where the architect employed an M&E consultant to spec the (ASHP) heating, which he did in considerable detail. The plumber could quite legitimately have followed the design to the letter, and the architect have been covered (at least to first order) on the grounds that he had taken advice from a professional. As a customer I had no contact or contract with the M&E designer. Fortunately I spotted that the design was obviously a piece of hopelessly overengineered sh1t, and intercepted it early on. Had I not done so it would likely have been installed as 'designed' (which would have involved much unnecessary work) and we would have had the devil of a job holding anyone responsible. Caveat emptor!

If I understand this correctly the 'problem' is that the system is switching (a bit noisily) on and off at the present time. Any heating system is going to do that when the ambient temperature is close to the demand temperature. Best at this point just to switch it off altogether or turn the controlling thermostat down (or the temperature limiting stat up) so it doesn't trigger. Having said that you should ideally not be using external controls to control the heat pump, that is best left to its native control. Do you know what the Honeywell thermostats are for. If correctly installed they should be used as temperature limiters only, ie the native control of the heat pump does most of the work (using weather compensation) and they are set above the design temperature to kick in only when there is excess heat eg due to solar gain. You dont need a smart stat for that, a dumb stat does the job. Were you left any documentation/instruction on how the system operates/a system diagram - you should have, and if you weren't I would first complain about this as its easy to fix and indisputable. They do this, but if the honeywell is doing the actual controlling it wont help much. I would understand/get the control system sorted first! https://midsummerwholesale.co.uk/buy/samsung-heat-pumps/samsung-ehs-wifi-controller-kit-mim-h04en Is this space heating or dhw heating? In what circumstances? How do you know its 'louder than normal'

Since I installed pv in 2011 I have turned off my gas boiler completely from May to September. So far the circulation pump hasn't seized!