sharpener

Can you check if the diverter valve is moving to the DHW position when it is supposed to be heating the HW? If so it is perhaps a performance issue, if not then a control problem. Personally as @JohnMo says I would not worry about the legionella cycle in normal everyday use unless you are immunocompromised or something. But a useful stick to beat Octopus with and get them to deliver on their contract. What is the refrigerant in this HP? What max temp is it supposed to be capable of, and so will it need assistance from the immersion to achieve anti-legionella temp? Is there a Daikin user group on FB like there is for Vaillant?

No. They actively suggested putting my installation date back until after Easter. Yet they say they do not have much HP installation work scheduled at present (they do solar PV and other things as well) so have the capacity to do it earlier if I wish. We discussed the perverse incentive effect on their project flow but they didn't seem concerned. MCS are asking for increases from 2025. Other thing from them is this but not very relevant.

Thanks for taking the trouble to do this @JamesPa. It covers a lot of ground and I can't fault any of it. Except perhaps that the ENA already holds a database of HP (and other eqpt) approvals for the DNOs to use so that to my mind adding the noise levels would be a natural extension of it. The "assessment location in free space" issue is a good one. I am assuming by "any part of the..." they intended to mean the window in question, but as with much else it was badly drafted. The definition of habitable room is another. I listed a few in an earlier posting. Hallways and landings are arguably not rooms at all, but many so-called "rooms" are not noise-sensitive e.g. boot room, utility room, plant room, and some non-rooms are e.g. lounge, study, office, snug. BTW the "1m from property boundary" rule belongs in a different discussion, but our prospective installers came again yesterday and I was alarmed that their TD firmly believed the minimum was 5m. Though he was quickly disabused by his colleague. KUTGW

That's the ideal from the customer PoV but why would the installer bother? It's more hassle and if he leaves it installed I imagine he will get an ongoing commission from the renewal subscription fees to Homely, that's how these things often work.

The prospective installers came for a further(!) site visit yesterday and remarked there was a possible increase to £10k w.e.f. ?new tax year? Has anyone heard anything to this effect? I thought I was keeping an eye out but have seen nothing myself.

I imagine since this is easy to do you will have tried it by now. Did it work?

Tagging on I have done the same with the bearings in a lawn scarifier that was under 8 ins of floodwater and an oil boiler with a very noisy motor, from simplybearings.co.uk in both cases but I am sure there are plenty of others.

Isn't that just for boilers to ensure condensing? I thought the requirement for HPs (whether for Part L or MCS) was lower than that. Doesn't 55 flow and 20 delta T give you 35 return and an avg of 45? But I have always doubted the 20 d T, with boilers vastly oversized I don't think in many cases the modulation will turn down low enough once the system is up to temp to maintain such a high differential. Then the return temp will creep up, the rads increase their o/p, the TRVs reduce the flow even more, vicious cycle. I conflated three thoughts here, let me have another go... 1. Octopus may make a big thing of high temps from the latest HPs, but they are still limited by the rules as to how high the flow temps can be. 2. Even so they can steal a march on the independents by a willingness to sail closer to the wind than the competition. 3. However this will not be enough to avoid upgrading rads unless they were designed for the lower flow temps mandated (recently) for boilers, which in most retrofit cases they won't have been. Meanwhile I have looked again at the emitter table and I think doing the full upgrades now is probably the best thing for the following reasons: 1. Several of the rads are significantly undersized already so in particular the landing and my study are always cold. 2. Fitting the HP will involve a clean and flush and it would be a pity to have old dirty rads still on the system afterwards. 3. There is only one rad which can plausibly be cascaded to be adequate if moved to a smaller room. 4. I could do it all myself, either piecemeal or in one hit, but either way OH is not keen on my spending the time it would take.

To qualify for the BUS grant even Octopus will have to appear to comply with MCS standard. For new builds IIRC this is 45C flow max and for retrofits 55. This is probably how they will beat the independents, I have contacted 5 cos and none of them will design for flow >45C - as if I cannot be trusted to make my own capital cost v running cost decision. Current preferred choice is coming back with his Tech Dir next week and I hope to get them to re-visit the rad upgrades which are a significant part of the end price after BUS. Originally they said "do nothing for the first season and see what rad upgrades are really needed" and it would be good to get them going down that path again. Meantime I have a plan to cascade larger rads down to the smaller rooms but that doesn't save anything on the labour.

Still looks mighty complicated. Can you post a link to this magic manifold so we can see what it is supposed to do? Also you have got two check valves in series in the return from Manifolds 2 - 4.

wrong sign I think, try if (0AT<20) then heating_output = 20 + 0.8*(20-OAT) else = 0 which simplifies to 36 - 0.8*OAT for OAT < 20 Edit: Or in your specific case @SteamyTea (now I have read your other post) 46.8 - 0.8*OAT <g>

Missed that on first reading, thought you were referring to gas. You should be able to get WC for that now. I have a 25 y/o oil boiler which has an economiser in the flue, but won't run in true condensing mode because low temps would cause the flue to rot. So my alternative to WC was a wireless TRV setup. Now that has been very problematic and I wouldn't recommend Honeywell Evohome. The old oil boiler is now reaching end-of-support, and a new one will require an expensive new lined flue through the roof, so given the grant available an ASHP is a sensible choice. But as with many retrofits it has not been a straightforward project.

A bit over-dramatic. Today WC is pretty much standard fare for a new gas boiler and I think more or less mandatory. I agree it wasn't always like that. 15 years ago the installers hadn't heard of WC, but I insisted they find a small boiler (20kW Vokera Mynute) that could do it. Then I had to fit a relay so WC would be disabled by a call for HW. Would have been beyond most plumbing firms. Has needed a bit of tweaking and I have recently had to replace the outdoor thermistor, the front has never been off the boiler though. 30 years ago I had to buy an aftermarket Boiler Manager unit made by Danfoss which modulated the boiler on and off in response to the return temp. Saved about 1/3 off the gas bill. Pity they are no longer made. Whether WC is set up properly is another matter, I have read they deliberately do not do this on mass newbuilds to avoid callouts, which is a scandal (as so much about the housebuilding industry). The difference is, it goes unnoticed because a gas boiler is much more forgiving than an ASHP.

If the bends are too tight then the new pipes might well fail in the same way in due course. But you could re-work it with bigger radius bends by looping to the next-but-two or next-but-three etc instead (like the tops of hooped iron railings), this would require digging up both ends of the array though. Hence (assuming my understanding that the GSHP itself is OK) my suggestion of a vertical loop which would have a much smaller footprint.

But maybe drilling a hole for a vertical loop would avoid this, and although expensive would still be cheaper and less disruptive than replacing the whole shebang.

I seem to have heard somewhere that with the Vaillant figures the yield does not include the input power so you need to divide it by the input power and then add 1 to get the CoP. Don't know if this is true or not.

Yes, the advantage of plastic is you may be able to get away with bends, and it is good for angles that are not 45 or 90 deg. But when new CH was installed in previous house they still had copper mentality and used lots of elbows quite unnecessarily. This calculator is quite useful for various comparisons.

DHW settings: if tank is big enough run only once per day and ideally on offpeak electricity set DHW run time and anti-cycling time so as not to interfere unduly with heating target temp as low as you can tolerate, 43C sounds fine flow temp limit max 10deg higher (so 53C) hysteresis 10deg or more turn off legionella cycle if you are regularly using most of a tankful every day Heating: Open all TRVs fully (if any) to start with, then use only as backstop for any rooms that overheat Run HP 24/7 Increase setpoint by 1 or 1.5 deg during any periods of cheap electricity Setback 3deg (at most) at night and (if on Octopus Cosy) during evening peak electricity period. Use WC, check curve is not still on default setting (or worse, set up for a boiler), try 0.8 and reduce (or increase) no quicker than 0.1 every 24hours. Disable load compensation/room temp sensing to begin with Set max flow temp, min flow temp and OAT HP off threshold to sensible numbers.

WRT my own (successful) planning application it seems I have got away very lightly. The report says (p36) On the whole, LPAs treated planning applications for ASHPs as they would for a general industrial noise source and require a noise assessment in accordance with BS 4142 [11] or similar. There was an inconsistency about which threshold (-5dB or -10dB below background) from BS 4142 LPAs required. If my LA had used this process I would have had to jump through the same hoops as @JamesPa, and I don't think it would have passed as the night-time background noise is v low (I would guess 30dBA or less). Perhaps they didn't bother because the neighbours wrote a letter in support saying they approved because of low carbon emissions and were not concerned about possible noise. Or perhaps because they are notoriously undermanned, overworked and incompetent. [As I write a van has been idling outside for several minutes, this is bad for both carbon emissions and noise. Occasionally I have gone out and turned off the engine in an unattended vehicle.]

For starters: Well matched to the heating and hot water requirements of the house and its occupants Not over-specified or unnecessarily complicated Installed in accordance with manufacturers' recommendations Proper frost protection and lagging Set up correctly to achieve best attainable performance Controls that are fit for purpose, easy to use and properly explained to the customer

That's the catch, if you have a fixed (highish) flow temp from the HP and then temper it during the day you will not get the same CoP benefit as lowering the flow temp at source somehow during the daytime. For that reason I would guess that separate timed setpoints or conventional night setback setting would give better CoP. 0.5 is quite a big hit if you were to get that. If you mean the entire HP I wouldn't have thought so. Recovery from off would take a long time as many ppl have found. Maybe during the 1600 - 1900 peak would be viable for someone on Cosy (which you are not). Will be interested to learn what your conclusions are in practice for someone on E7.

Yes, I am wondering whether plain old Economy 7 will be best for me for that reason. Will have to do some spreadsheet modelling. The 10kWh battery will bridge the gap for usual domestic loads but would not get a 12kW HP through to 0400. Planning to switch to Octopus to give me a choice of tariff when the HP is installed in the spring.

https://octopus.energy/smart/cosy-octopus/ So peak is 160/60 = 2.67 x "cosy" rate.

From reading yr post in the UFH thread it would seem you have a lot of setback, 3 deg would be more normal. Also many ppl increase the target by 1 or 1.5 deg during the cheap periods to provide a reserve of heat so the HP runs less in the peak. Whether you can do this with the setpoint or the WC will depend on how yr controls work.

To expand on that a bit, the hot water will have priority and so the heating will go off while it is doing it. Hence to get the best efficiency you need to heat the hot water to the lowest acceptable temp and at times when the other demands on the hp are going to be minimal e.g. the last hours of the off-peak window. Heating needs to be on weather comp as others have said, not programmed to a fixed temp. Once you have got that right the HP will automatically run at the lowest temp that will meet the house heat demand and so with the highest possible CoP.