sharpener

If you can let me have details of your contacts there @JamesPa I will send them the following: <Government's Air source heat pump (ASHP) grant system only benefits the closed shop industry. It costs more to the end client and taxpayer, and is a hindrance to the UK reducing emissions. I have been trying to install a heat pump in our barn conversion in place of the existing oil boiler. I have contacted numerous installation companies as well as two utilities that offer heat pumps, Good Energy (who have quoted) and Octopus (who say our installation is too complicated for them). 1st problem: the house is large and has solid stone walls and so needs a large (12kW) heat pump. These are bigger than the 0.6 cu m limit under Permitted Develpment (PD) so it needs formal Planning Permission. This costs £270 and will put a minimum delay of 10 weeks into the project. Some planning authorities also use this to impose impractical noise limitations far more stringent than required under PD. 2nd problem: the existing hot water tank has a heating coil that is "too small". All the installers insist I will need to replace the current tank which will mean dismantling the airing cupboard to get it out and ripping up the landing floor to fit new pipework, at an extra cost of £2k or more. I am a Chartered Engineer and have proposed three different technical workarounds: an extra pump, a separate heat exchanger or an extra plain tank. None of the installers will listen. 3rd problem: the government's Boiler Upgrade Scheme offers a grant of £5000 to fit a heat pump, but this is only available if you use an installer registered with the Microgeneration Certification Scheme (MCS). In addition, the fitting of heat pumps is only ever exempt from Planning Permission under the Permitted Development rules if you use an MCS installer. This requirement has nothing to do with Planning or the environment but was written in by MCS themselves. So the MCS installers are a cartel which has little incentive to compete on price and will not entertain ideas that would reduce the installation cost (see 2. above). In practice the £5000 grant is spent on the additional paperwork and the over-specified systems that risk averse MCS installers like to fit, and does not benefit the consumer. 4th problem: ordinary plumbers that are used to fitting gas boilers are kept out of the marketplace. The additional costs of registering with the MCS scheme and completing the resulting paperwork (anecdotally over £1000 per job) dissuades them from entering the heat pump business, so perpetuating it as a closed shop. 5th problem: householders cannot easily do the work themselves. If they fit even the smallest heat pumps it requires Planning Permission. The major heat pump manufacturers only offer extended warranty terms if they are fitted by an approved installer (in practice, an MCS registered firm). So by keeping out the ordinary plumbers, and houselholders who are competent to fit their own systems, it is a nice business for MCS companies. But there are far too few of them to meet the target of xxx installations per year so the requirement to use them needs to be abolished if we are to get anywhere close to meeting those targets.>

Output. You could connect the 3.4 to the output and that would keep going and the 3.1 to the input and it wouldn't. If you had the 8kVA unit then both could be kept going. Or sell the 3.1 and use an MPPT like my setup. Depends rather on the value you place on riding through blackouts, and whether you need more than 5kVA (4 kW continuous) to power your loads. If you want to integrate yr generator then the Quattro range have a Grid input plus a Generator input, they can be configured in all sorts of ways e.g. autostart the generator according to state of charge etc. But more expensive. 5-9kWh of battery strikes me as small, I put in 7.1 to begin with but upped it to 10.65 as it wasn't enough to keep everything going until the E7 cheap period. Also I needed more capacity to use all the current available from the second PV array. 2 hrs endurance in a blackout is a good rule of thumb for min size. Various solutions to this on the Victron forum.

Victron is the go-to brand, it will do all the above using its ESS software with fully automatic changeover, no external switches or relays required. Can connect an equal amount of PV to the o/p and they will keep going in a blackout. What size are the two you have got? I have had the MultiPlus II GX 5kVA for 18 months now, DIY install, is large enough to supply the whole house, works a treat with 10kWh of Pylontechs. I have 3.68kW of AC PV and another 3.24 of DC connected via an MPPT converter. Good support and excellent user forum here.

Yes, it struck me that way, there was some earlier discussion (and a link to the Solarcoil website) in this thread but I don't think we found an answer.

Made worse by the only real measure of success being the number of grants doled out not the reduction in carbon emissions. Govt departments really really want to spend the cash once it has been allocated by the Treasury, because having them claw back unclaimed money is an admission of failure. Quality of outcomes ranks a very distant second. But given the current handwringing about the poor uptake under the BUS I do have faint hopes they might make it easier to get at the money before the next election.

Some interesting projects under this Government scheme. Also a subsided training scheme has been announced, some details here. Apols if you knew this already, I didn't.

Happy to report that the pdf bought from UK Planning Maps passed validation by ####### District Council yesterday. The online markup for the site boundary worked OK for me after a bit of practice despite what one of the reviews says. The hard copies turned up from Kirkwall 48 hours later, not really necessary but bought as an insurance, printed on good stiff paper and not creased in transit. I edited the file to add the proposed heat pump (a tiny rectangle 3 x 9 pixels!) using IrfanView, which is a free download, to convert to .bmp and using MS Paint to edit, then the reverse. Some advice on the website on how to do this would be helpful. Conclusion: does what it says on the tin!

There's a proprietary device for doing exactly this, mentioned in the Mixergy-lite thread IIRC.

Only if it runs parallel to the first floor floor joists. My experience with plumbers is they do not know, do not understand and do not comply with the quite strict rules about holes and notching. I kept back a £500 retention until they produced a structural engineer's letter confirming that what they had done in contravention to the rules was acceptable, which never happened (they sent a span table for non-load-bearing ceiling joists which I rejected as irrelevant). Some of the £500 went on doubling the affected joists which I did myself. The prime contractor was a loft conversion firm, and when a neighbour saw their site board outside he told me he had won a court case against them for £50k damages so I had got off lightly. Later they went bust - for a second time. I did not feel very guilty.

So "primary circulation" (rule b) seems to trump the "1 metre" bit (rule c). All qualified by "In a new system". Does an old hw system incorporated into a new HP system become "new" or not @JamesPa ? Personally I don't care about pipes that are within the thermal envelope, especially where they pass through the airing cupboard.

From data sheets it seems for a given frame size they differ only in refrigerant charge, software and possibly max compressor, fan and pump revs. Hence it would seem entirely possible to downrate a unit once installed if it proves to be too big, does anyone offer that as a feature?

Fitting their fancy tracker will not help much, the toerags will quickly learn to recognise them, remove them and leave them on site behind a bush. A spair pair in one of the interconnection cables could however easily be linked to a wired or wireless burglar alarm and it will then alert the entire neighbourhood at the time if the wires are disconnected or cut. Better still one core in each of two cables. And/or linked to microswitches on the covers and inside the mains isolator.

MCS guidance here, you will see they suggest a bigger HP can get away with a smaller cyl because of greater reheat capacity, not seen this on cyl mfrs web sites (try googling hot water tank sizing, you can choose any answer you like over a wide range!). Conversely if you are trying to minimise the HP size then a bigger tank will help avoid the need to reheat it when space heating is required. With the solar thermal as well you might be able to heat only at off-peak times. 3 sq m surface area will be fine with a 5-7 kW HP. Makes a lot of sense.

Surely they would not add the mechanical complication unless it was necessary for some performance reason like achieving a reasonable turndown ratio - which may still be uncompetitive so they don't publish it. Hopefully @markocosic will be along to tell us, if he is not on holiday.

"they" is Samsung re the OP, Good Energy quotes are based on Midea FWIW so I imagine they are not rubbish.

PV since that is what I have but could of course be either like @embra in the other thread

Sounds a retrograde step! Will he not just add a plate heat exchanger to the exisiting setup? Or at least keep the solar tank as a preheater if you have the space. Our installer wants to put in a new 300 l tank for 4 bedrooms, saying this is required for an occupancy of 5 people which he gets from some table calling for [#bedrooms +1] so if this is correct you would need 300 also as @ProDave suggests - but I have not given up on the heat exchanger approach. Assuming reasonable insulation the HP will only be called upon to replace the HW actually drawn off, so if your usage pattern does not change then an increase in tank capacity does not matter to the HP as it will not necessarily being heating from cold.

There is full performance data here, it seems not to be available on English-language web sites but is easy enough to work out. Your experience is similar to mine, installers play safe and make conservative assumptions as do Vaillant tech support. Watch out for lower than necessary OAT (Outside Air Temperature) assumptions, they should vary by region, the table is on p10 here. Also if you have additional heat sources e.g. WBS (Wood Burning Stove), AGA, MVHR (Mechanical Ventilation and Heat Recovery) make sure they know these are available to help out below the design OAT. Equally supplementary water heating by solar PV. These considerations are not officially allowed by MCS but might tip the balance of thinking. Arotherm + specs seem to be quite generous so you may well be right and could get away with a smaller unit. I was orginally told their 12kW was too small but after arguing that the proposed 15kW Stiebel Eltron was physically too large they reworked the figures based on 18C everywhere (?) and conceded the Vaillant would do the job. They also proposed to put lever valves in so an inline heater could if necessary be installed in the light of experience over the first winter.

IIRC @markocosic says they achieve their turn-down ratio by using hot gas bypass which knackers the CoP.

Grant and CoolEnergy can be interfaced quite easily to an existing S-Plan system as they accept external contact closures as inputs. But they are both R32 and I would prefer R290, Grant are bringing one out next year (also made by Chofu).

Various, e.g. lack of North arrow, no scale bar, no copyright licence, cba to put all that in when I could download one said to be compliant as per link above for under £20. Remains to be seen if it will pass muster, I will post back here either way.

But you also want a low unit price. Adding say a further 50mm acoustic insulation inside the casing all round would cost more and the unit would also be 100mm deeper front-to-back. I for one would rather take remedial measures elsewhere on the site. In time the best acoustic design ideas will percolate down to the cheaper models but I don't think you will ever get >10 kW HPs to be completely quiet, they have been trying this with aircon and cooling towers for decades but the physics are against you.

There is a Quiet Mark scheme already, here. But I don't think you can simplify the issue to any go/no go certification scheme as an underlying problem is the wide range of sizes of HP available, another is the different shapes of the unit. This results in a "horses for courses" situation. So for example the Stiebel Eltron 15kW has a single very large fan and a lot of soundproofing inside the case, it is does not have the Quiet Mark but is in fact 5dB quieter than the 12kW Vaillant which has two smaller faster fans and a tall slimline form factor. Either will require a screen between it and my neighbour's window to meet the MCS limit, but for the Vaillant it needs to be a bit bigger as full screening wins back the 5dB difference. However the tall thin unit is preferable for me as I have only a narrow yard to put it in. Whether a fence panel will in actuality give a 10dB reduction in sound power seems unlikely to me, but the MCS process is (thankfully) based on visual lines of sight alone.

ATM I have an oil boiler. As mentioned elsethread I am still trying to agree a spec with >0 HP installers, and in any case am waiting for my planning application to be validated. So posts about the control of an HP based system are purely conjectural at this stage. I agree with the received wisdom to run on WC using the TRVs only as high temp backstop limit and as zone valves for rooms that are out of use (don't start!) But I also hope to have a thermal store which I plan to heat to 55C at the same times as the HW cyl is heating, this should act as a big heat sink and avoid the HP short cycling with the (small) coil, so avoiding the need to change the cylinder. I calculate that heating the TS to 55 off-peak will still be cheaper than running the HP on weather comp at peak rate. And if there is surplus PV it will be entirely free and a good way to store the energy which would otherwise be exported to the grid without any recompense.

The electronic TRVs that are part of the Honeywell Evohome system do that also. As the room temperature approaches the setpoint you can hear the motorised valves making small adjustments to turn the flow down so there is no overshoot. The main problem with it as a system is that they use a proprietary ?460MHz? signalling protocol so it will not interface with Zigbee or any of the other open standards. And they designed it with no ability to add repeaters so it is very stretched to cover a biggish house with thick stone walls.