JamesPa

Mine is 50cm from a picture window in a room we use a lot. It's side on, and since no air comes out of or goes into the sides or top, I built a smart wooden structure with a smart ceramic top that hugs it on two sides and on top. It makes it look like a smart piece of furniture and the wood is styled to blend in with the wooden noise screen I also built. Twice a year it's simply lifted off for maintenance. You can also have ashps vinyl wrapped with a design of your choice. Obviously it depends on situation, but disguise doesn't always have to take up lots of space or be a long way from the unit, depending on it's orientation.

Absolutely to all of that, but a very different scenario (as I think you are suggesting) than a typical domestic one that the system described seems to be aiming at, ie an alternative way to do universal rather than very localised heating. Now if the ir panels were localised, directional, and followed people as they moved around so each person has their individual sunbeam, the scheme might just have legs. But then it wouldn't be cheap to install. Heated clothing is probably more viable.

Sorry but if that is the case then you are heating the fabric just like any other heating and your whole argument (basically that you heat only the person so don't need as much energy to have the same 'feel') falls apart. This really is a load of tosh, at least in the way you describe it. Fundamentally (as you have now positioned it) it's resistance electric, end of.

Indeed. Even less reason to throw away a perfectly good cylinder. For a long time the industry insistence on doing so has annoyed me, it now annoys me even more.

in response to Yes but you could combine both ideas given that at night the baseload is smaller. And simple switched automation would avoid the need to 'pay attention' Car chargers already come with load measuring/limiting features and ASHPs come with electricity company shut outs. A bit of logic controlling both would very likely deliver a solution invisible, or almost invisible, to the householder. The more we discuss this the less convinced I become about the need for mass infrastructure upgrades of the scale often discussed, provided we are sensible. Ahh - I just spotted the problem!

Good (that the DNOs are imposing limits). I really don't see why we should all be forced to pay for the fact that some people want an indulgent lifestyle where they expect to have everything they want exactly when they want it. There is almost no harm in occasionally turning down a heat pump or an EV charger for a short period of time to avoid unnecessary demand peaks forcing unnecessary mass infrastructure upgrade. Those who want the luxury should pay for it, the rest of us should have a sensibly moderated house system and shouldn't be forced to pay for infrastructure upgrade beyond that needed to deliver to a sensibly moderated house. I could easily find myself arguing for forced downgrades to 60A or even less, unless you make a very substantial capital or recurring contribution.

Depends on your reheat regime. If, like me, you reheat once a day it won't materially affect stratification. Thats also the case if you reheat when the tank is basically close to empty. If you do continuous reheat it will, but then stratification doesn't matter as much.

One installer I contacted during my exploratory phase uses this arrangement as standard. I think mainly for performance but also as you say it's cheaper.

Correct. The usual retrofit arrangement I believe is to tee off the cw inlet pipe (after the prv) and the dhw outlet pipe, so no extra bosses needed

Interesting comment this one and doubtless true in many cases. My Vaillant heat pump doesn't talk to the immersion at all so cant 'use the immersion instead'. The heat pump also does its legionella cycle natively. I wonder what it does if it doesn't like what the DHW loop throws at it. Probably it just turns the flow temp up to 75, which is where a boiler might be, and all (except COP) is good. Interestingly some of the Vaillant heat pump cylinders have coils with quite a lot less than 3sq m coil area. As you say:

Heat pump cycles, takes longer to heat the water and ultimately may not heat to quite as high a temperature and will do so less efficiently. Not a complete disaster despite what some would have you believe, but at the same time not the perfect outcome that many expect to be guaranteed. Hence (I suspect) the industry insistence on changing out cylinders.

Doubtless so, but electrification (heat pumps and EVs) change the medium term (think periods of many hours) base load significantly. Thus the existing peaks are layered onto a much higher base, and so the delivery capacity needs to be much higher. This can, so far as I can see, be mitigated if the existing peaks (which are generally short term) are smeared over adjacent time periods, which a relatively modest battery can do. Thus a house, instead of requiring 90A peak to cope with kettle (say 10A), cooker (say 20A) , heat pump (say 32A), Iron (say 10A) and BEV charging (say 20A), may only need to cope with heat pump plus BEV charging plus the 400W accounted for by everything else when averaged over over a day, about 60A. Thats means that the infrastructure as a whole needs 2/3 of the instantaneous capacity, quite a difference. Of course an alternative local solution to aa battery is to turn down either the electric car charger or the heat pump when the other items are drawing their peak. This would be less resource hungry and may actually be a better solution. However it would require coordination between industry sectors that, at least currently, seems unlikely. maybe that is why electricity supply company shut out is built into at least some heat pumps, so that the supplier can effect the shut down when they need to, presumably in return for a tarrif break. All very rough and ready but illustrative I think of the opportunity that micro-balancing offers. Some people are already railing against being 'controlled' or 'restricted' by the electricity companies and what everything simultaneously, but the same people will complain bitterly when they are asked to pay for the infrastructure upgrades which are necessary to give them that luxury. Something has to give, whether its through carrot, stick, or a combination of the two. You cant bake your cake and heat it.

I think you are right But the potential to mitigate the cost of infrastructure upgrades if done right is enormous. A home battery can smooth out individual demand more or less completely, and its pretty much guaranteed that you are at home (and hence the car is available) when your personal demand peaks. If we can succeed in smoothing out the demand of a significant proportion of customers, we don't have to spend anything like as much on infrastructure upgrades. This needs (and is presumably getting) a lot of thought, although the recent (understandable - at least politically) decision not to adopt zonal pricing probably makes it more difficult. Incentivisation could be 'carrot' (eg by limiting the incoming power available to something way below the typical 23kVA (100A) or 'stick' eg some severe incentives, or a combination. I strongly suspect, however, that its easier just to do the infrastructure upgrades, whack our bills up and 'blame' net zero rather than have a well thought through but politically even more contentious plan. Furthermore the infrastructure industry is incentivised to push for infrastructure upgrades. Maybe there is a sweet spot to cover kettles and ovens which presumably account for the 'spikes', and switching of heating for half an hour or so when the spikes occur (some heat pumps at least specifically provide for an electricity operator shut out). Personally Im far from convinced that the massive infrastructure upgrade needed to cover our every whim is justified or justifiable.

Which may not be when it suits the local grid so far as I understand it.

Interesting. I know leafs use chademo for fast charging, but I thought that the home charger interface was universal. Maybe it is but that doesn't preclude the v2x from not being universal. I confess to not knowing much about vehicle electric interfaces.

Fair enough but ... not having a battery because it's too much hassle also removes the option to balance the grid! Meanwhile having one with zero export allows self consumption to be zeroed out. So I don't really see the rational objection. If you want to export then fine, a bit more hassle justified and you will get paid for it so that's a fair exchange. DNOs should be enablers not barriers - oh, I forgot, they are privatised monopolies.

It could be set to zero export, then it should just be a matter of certification rather than permission. Not sure what the intent is here and of course if you already have solar that potentially complicates regulating the export. On the other hand if octopus can offer it there are clearly ways through.

Its nice to hear that I'm not the only person who has come to that conclusion! Standalone Zaptec Go2 available here for ~EUR1000. Annoyingly they will ship to plenty of countries outside the EU, but not the UK. I wonder when the technology will finally come here other than through some sort of complex deal, my dream is to swap my petrol Fiesta for an aging Nissan leaf, thus getting a 24-30kWh battery for about £5k, which will also serve as a second car for the few times we need one.

Is there a reason to dismiss installing a PHE plus circulation pump as an add on the the cylinder, thats the best technical solution AFAIK to effectively to increase the coil size, which is the only material difference between a heat pump cylinder and any other UVC. Even without you may well be able to get the cylinder to 55/60 with an R290 heat pump operating at say 70C flow temp. That will still be more efficient than the immersion and if you do the DHW run at night cheaper. Throwing away a perfectly good cylinder is, in many cases, a madness foisted on us for no reason that has been properly explained IMHO. If your chosen installer wont allow you to keep it, find one who will.

@mikeysoft I can only echo the good advice above. We have been brainwashed by the manufacturers of central heating controls into thinking that (a) we can control rooms individually to our hearts content and (b) we save money by doing so. In a very lossy house where the insulation between rooms is better, or at least as good, as the insulation between the house and the outside world, both of these are true. However in a reasonably well insulated house, and certainly any modern house where insulation between rooms is far poorer than the insulation between the house and the outside world, neither is true. This is simple thermodynamics, heat will travel from hot to cold and thus will tend to equalise temperatures, and there is nothing you or the heating control manufactures can do about it. Nevertheless they have to maintain the fiction in order to remain in business. In most cases micro management neither works nor is it possible, if you try hard enough you can maintain modest temperature differences between rooms where doors are kept shut and which are physically separate, but in most cases nothing more. You can also maintain some difference (usually the wrong way round unless you are careful or sleep downstairs) between two floors. Neither I nor anybody above is saying you should ignore this, but if you start with the assumption that the whole house is a single zone and depart only when its (a) actually going to work and (b) absolutely necessary, you are very likely to get a better outcome. Of course this is magnified if you have a heat pump, but still applicable if you have a boiler. Similarly with carpet over UFH. The heat for which you have paid will escape by the easiest possible route. If that's downwards, out of the house, the physics doesn't care one iota, and no amount of hoping its otherwise is going to change things. Given how much people like carpet, I'm surprised that there isn't one with embedded conductive (eg carbon) fibre - maybe there is!

Ok so (a) what @Nickfromwales and @JohnMo said about the thermostat and (b) how do you know there is a call for heat (you say there is but how do you know?). What's the current oat and what is the target room temp on the VRC720?

Surely that is the key. The Vaillant manual that O looked at says 'Room thermostat is blocking heating mode'. Have you got a room thermostat and if so is it working. If you haven't got a room thermostat (there is no need with the VRC720 since it has an internal temperature sensor) have you/your installer told the boiler to ignore the demand for heat signal and/or that there is no room thermostat. As an aside the outdoor sensor is presumably so it can do weather compensation, has the compensation curve been set?

Fair enough, you aren't really using it as a thermostat though, just a time clock! Very sensible repurposing of an otherwise redundant piece of kit.

If your house has a thermal time constant such that batch charging is practical, then using a room thermostat as a controller isnt going to be much use anyway, because its a 'rear view mirror' - ie it tells the heating what to do when its too late (because of the response time of the house). That's one of the basic features of weather compensation, it tells the heating what to do before its too late. The more you think about and actually use weather compensation, the more baffling it becomes that we shunned it for boilers in the UK (unlike some more enlightened countries).

Why bother with a thermostat. Just use weather compensation. Seriously! Obviously this is a bit house and person dependent, but for many, pure weather compensation with any 'thermostats'/trvs etc used solely as limiters (ie set a couple of degrees above target) not controllers is the way to go. It's certainly the most comfortable for my house, way more so than any complex control I have from time to time played with either with my former gas system or my ASHP. Oh, and it's also very likely to be cheaper doing it this way. The controls industry has taken us for a ride in recent years. Boilers do weather compensation too, are more efficient if you use it and likely to be more comfortable, yet we instead are encouraged to spend lots of money on overly complex add on controls. It's time for them to get their comeuppance