JamesPa

Thanks everyone. No batteries and yes the ev is (sometimes) on the drive when sun is shining. I'm certainly not doing anything involving the cloud, too complex and low able to fail, but folding back wires gives me some possible ideas. The immersion is on a separate circuit so perhaps I can fold that into the ct clamp outside the cu to do the sum. I also need to do the calculation on daytime export tariff vs nighttime import tariff, it maybe it's not worthwhile trying to play this game, and instead just export during the day and import for ev charging during the night (which is a lot simpler!). The diverter has a second load port which switches on when the primary load is satisfied. If EV chargers had an 'enable' input then this could, in principle, be used instead. However so far as I know they don't, and I'm not comfortable switching a 45A load on a relay.

I have solar PV with an immersion diverter. I am about to buy an electric car. In my ideal world, when it sunny, the PV would first heat the DHW then charge the car. I know this can be done if you buy the immersion diverter and ev charger box from the same company. I also know that many EV charger boxes can accept a CT input to allow them to 'soak up' extra power. However the immersion diverter is already doing that, and the two will (presumably) simply fight each other. Does anyone know a way to get them to play nicely other than by both coming from the same manufacturer?

Under the flight path for landing some of the time actually.

I guess that depends on whether the zone valves can resist the pressure differential and whether there is a 'way in' for air toreplace water.

I have seen this recommended. Basically a couple of motorized valves (ie zone valves) kept open by electricity, which therefore close if the power fails. As @sharpener says they can (depending on physical layout) replace the diverter valve (applying Occams razor).

My understanding too, presumably to let air in one and water out of the other. One alone would release the pressure from the pipes which may suffice, particularly if the cold ones are plastic (this is imho a good argument for plastic pipes on the outside, but I guess that the pipes inside the pump aren't plastic!).

They are made of conductive metal so, if it's cold and the water isn't running, will trigger in good time. If the water is running enough heat will reach the sensor to keep them closed. The logic of not insulating the valves is that, if you do, they might take too long to trigger also the water has to go somewhere not into the insulation

They have already (sort of) in the way that they have written 'The MCS Planning Standards'.

Well done! If at any time another voice would help please PM me. I'm well fed up with this industry and the way Government seems to rely on people who clearly have vested interests to inform them. I have tried several avenues to get a seat on a table somewhere which might make a difference, but with no success (yet). As if the industry itself weren't enough, I'm also doing battle with my LPA which wants me to achieve 25dB(A) at the most affected assessment point, which is a ludicrous requirement.

In fairness I should add that there clearly are 'good guys' out there who know what they are doing and do it well. I certainly don't have the information to speculate whether the good guys are the majority or the minority (they were definitely on the minority when I was getting quotes, but that might have changed with time or may be a local phenomenon). There is likely also a bias in the 'reporting', people who are unhappy may be more likely to speak about it, those who are happy just get on with something more interesting than their heating system.

Oversizing seems, sadly, to be endemic from what we hear on this and other forums. It's a backside covering exercise by people who don't know how to design a system properly. The whole industry is just to accustomed to shoving a 28kW gas boiler into an 8kW house, leaving the flow temperature turned up beyond the point at which the condensing feature actually works, shoving in trvs and letting them sort it out. Nobody complains because the house isn't cold and, until recently, nobody cares a fig about the efficiency of gas boiler systems. So with no skill in system sizing or design, the safe route is to oversize heat pumps too, because people don't complain if the house is warm. Except that those currently getting heat pumps do care about efficiency, hence the damage being done to the reputation of the technology. Worse still oversizing frequently drives unnecessary components and costs, eg buffer tanks, unnecessary pipework upgrades and the like. It's a dreadful state of affairs. As regards the phe solution at least one other hp manufacturer also sells a similar product (Ideal I think), and the installer I hope to use if I ever get planning consent for a heat pump fits them as standard. They are unfamiliar to your average plumber and there is a pump to worry about, furthermore they provide a way to reuse an existing cylinder which the industry certainly doesn't want to countenance. Hence why they are not popular afaik.

Or for a sort of ready made solution buy the mixergy heat pump add on kit and throw away the interface module (or use it if you can work out what it does). I'm not sure what the best control strategy for the pump is, probably just on/off based on a temperature sensor on the flow from the heat pump as it enters the phe. Set a pipe stat to say 50C, job done. Might need a relay to reverse the sense if you can't find a pipe stat with changeover contacts.

not sure why not having the prerequisites should be a barrier. Based on what we hear on this forum and others, a fair few heat pump installers/system designers don't have the pre-requisites for doing heat pump system design/installation, and they are charging for the service.

If you already have a 250l UVC and are considering buying one with a phe, why not add a phe and pump to your existing cylinder to 'upgrade' for heat pump compatibility. £400 vs £1200. Thats what all heat pump installers should be offering where there is an existing DHW cylinder IMHO.

I was thinking the same. My neighbour has a very noisy heat pump for their swimming pool. There is no fence to speak of and I can hear it from 10m but no way from 20m. Maybe the neighbour has super powers when it comes to hearing. More seriously, if 20m isn't far enough there is no hope for the UK rollout. To my mind we have to get over the fact that heat pumps make a different noise to all the other noises that disturb our silence and which we all tolerate, accept it unless it's truly extreme or tonal, and move on.

Principally that more of the tank is heated so you can have a smaller tank. Also arguably greater efficiency (see the mixergy blog on this). You can probably get a smaller approach temperature (different between flow temp and dhw temp) also. Furthermore the coil isn't taking up space in the cylinder. The other potential advantages are situation dependent and mostly applicable to retrofits. It can be done as a retrofit to an existing tank which otherwise has an insufficiently large coil, and/or the phe doesn't have to be colocated with the cylinder (I can't actually think of a specific circumstance where this is useful but there is bound to be one!). On the negative side it's more complex and less familiar to plumbers. A couple of heat pump manufacturers cylinders use a phe and pump instead of a coil (Mitsubishi, plus I think Ideal)

True ... unless (it seems from a quick read of the relevant legislation) you have made deliberate efforts to conceal it, in which case a magistrate can override the time limits. I wonder how this plays out if you have erected a screen to reduce the noise impact to your neighbours? Hopefully a case that is unlikely ever to get to court!

I'm interested in this comment. One ashp installer I am talking to suggests a pump plus phe instead of a large coil in the cylinder. The cost is no different because it allows you to use a cylinder that doesn't have a coil (£400) as opposed to a heat pump specific cylinder (800+). The arguments for the arrangement seem potentially convincing to me, although there is the noise of the pump to consider. It also introduces the possibility to put the pump plus phe remote from the cylinder, or retrofit an existing cylinder which has an insufficiently large coil, both of which have applications.

Possibly. But LPAs can (and in the case of my lpa do) impose (much) more stringent requirements on requests for express permission than those which apply to PD. So there is no guarantee that permission will be granted, even if the pd requirement iset, because the criteria are not linked.

Quite so. Your only avenue here so far as I can see would be to argue that this is immaterial in the situation. I have no idea whether that would succeed in court but I wouldn't want to rely on it if my heating depended on it.

Planning and building regs are completely separate branches of law so best not to conflate the two!

Possibly (I'm saying possibly because it's a legal question not a question of fact, so the answer may not be what you would think/want), but the LPA, if they choose to enforce, will ask for the MCS certificate and if you can't produce one will decide it doesn't comply. At this point your only option is to take the LPA to court to challenge their view. You would then have to prove that the standards are equivalent to the satisfaction of a judge. The judge won't have scooby, so he/she will rely to a large extent on expert witnesses. They will come from the LPA or MCS unless you employ your own. Even if you do employ your own the judge could seem that 'standards' means recognised standards and dismiss your defence at which point your only course of action is to appeal this interpretation in a higher court. So you might be successful in demonstrating what you claim, but it's going to cost you time, money and a lot of anxiety. The only other argument you might make is that any non compliance is immaterial to the situation. Again your LPA will dismiss this argument so you will end up on court. I don't know what the case history says about whether requirements that are immaterial in a particular case matter when deciding if the PD rules are met or not, you would need a planning lawyer to answer this!

That interpretation makes no sense as it excludes any noise requirement for the installation, and it's also inconsistent with the wording of the legislation which specifically refers to 'the MCS planning standards'. So to be clear PD is dependent on MCS

No, but it's referred to/called up very specifically in the legislation. Without this interpretation there is no noise standard called up at all, further confirmation that this is the interpretation.

That seems to be the odd thing. If you are doing a larger development which happens to include an ashp in, the LPA it seems frequently doesn't inspect the ashp aspect in much detail, and thus passes it in circumstances where it may well not pass the ashp as a standalone development. Together with the restrictive PD rules it's madness.