sharpener

Many (?most) HP installations include isolating valves for the outdoor unit in case it needs to be drained down or even swapped out. So better if that is not the only place a PRV is fitted on the primary side. I think from various pix I have seen it is usually sited with the filling loop and pressure gauge. Typically all teed into the return pipework before it goes back out to the HP via the filter, which should be the last thing indoors.

And there is a big Mitsi factory somewhere in the Central Belt of Scotland, videos of operations there avail. on youtube.

I think you will find the warm-up curve will be spread out over time but the shape will be the same. So the CoP as a function of increasing temp will be identical and the overall efficiency willl be exactly the same.

Yes but that is what enables one to recharge batteries and thermal store several times every 24h. Admittedly it needs careful thought on how to program all systems to best advantage.

Standard calc for 4 beds gives 225 so installer will probably want to fit 250 min. Should be OK for a family if you are happy to top up in afternoon (when Cosy is cheap for 3 hrs anyway).

According to this discussion that advice is outdated, and plenty of ppl there say 5kW is compatible with 250 l cyl.

Why wouldn't the pump just push the air into the buffer, which presumably has an AAV at the top?

Maybe it was done this way deliberately so the flow to zone 2 came preferentially from the return from zone 1, so temp for zone 2 was lower as befits UFH. Problem is to adjust the 3 pumps so that it actually works like this. Try turning zone 1 pump down and/or primary pump up so zone 2 can suck a hotter mix from the LLH.

Yes or IIRC simply left in the system while running hot as normal for 72 hours, while you get on with something else. Powerflush very fashionable bc it needs expensive equipment and takes time so plumbers can charge more to do it.

Good to know, thanks. Is there any publicly available info on this? https://www.hvpmag.co.uk/New-AI-technology-signals-boom-time-for-heat-pump-installers-/18477 First of six paras near bottom of article says "Octopus Energy’s Kraken software already provides optimisation for its Cosy 6 heat pumps, which it manufactures itself, and for Daikin models through that company’s API. Octopus says it is also working to integrate with Mitsubishi, Vaillant, NIBE, and Samsung and hopes to make a series of announcements by this winter."

Cosy is fit and forget, you do not constantly need to seek out the best times. You can still use it to your advantage: Set target room temp 1 or 2 deg higher 0400 - 0700 and 1300 - 1600 and set back for the first couple of hours of the higher tariff periods. Make sure HW is heated 0400 - 0700 and/or 1300 - 1600 (higher OAT = slightly better CoP) Octopus have an online tariff checker based on yr recent bills which will advise which is better (but not taking account of the above hacks)

Seems to be, here you are. The supplied neutraliser provides this function with the DS40. Then inhibit with F1. Other products are available but these have served me well in several houses. Current heating system dates from 1995, last cleaned and inhibited in 2015, HP installers were surprised how clean it still was this summer.

I would read the Ts and Cs very carefully, you are giving them access to your HP's API in order to read its energy usage so they can credit yr account with the difference. The two schemes seem to be inextricably linked, the link says " * You’ll also need to be signed up to our Heat Pump Plus tariff and be an OVO customer." It sounds as though this is a necessary but also sufficient pre-condition for their "nationwide heat pump flexibility trial" as its web page name is actually "heat pump plus trial". Octopus have something similar in the works, I shall study it carefully but am not sure it would be compatible with my battery setup.

Fair enough, it's reasonable the electrician should want to check his work before he leaves. At a guess if he turns on the breaker the HP should come on in standby mode and the display should light up, that might be sufficient. Grant HPs are at the simpler end of the range of control options and are often wired up in a standard S-plan config but even so he will have to run it in heating mode to check the thermostat wiring and zone valve functions. Grant person may be happy for him to do this before he visits to configure heating curve etc. Fortunately my spark was an employee of the installers (they were actually a firm of electricians who had branched out by taking on plumbers) so didn't face this issue. He was very good, wiring neat and mains and low voltage all segregated, integration with legacy controls and battery inverter all worked. First time except for one missing perm live connection to UFH controls quickly rectified.

IME Octopus Cosy is better - I have batteries and so can charge them three times every 24 hours and run the HP off them during peak periods. Off-peak tariffs are comparable. The OVO HP integration AFAIR also potentially gives them control of your HP which I don't like the sound of even if they don't use it to begin with. If you haven't got batteries Tomato is also worth checking, there is a thread about it.

Open one valve to be in line with the pipe and just crack the other open a bit until you hear water flow. Then adjust the flow rate while watching the pressure gauge. If you open both valves fully to begin with the "whoosh" sound will swiftly be followed by the pressure relief valve going off and possibly water over your feet or elsewhere before you can react, particularly if you have not played this game before.

Depends on the contractual arrangements between the three parties. If you run it and it provides heat you are effectively commissioning it. The Grant guy may not be best pleased particularly if you don't do something that needs to be done in sequence, or fail to spot something which needs to be rectified before it causes a worse issue. I was very annoyed when before I got there the plumbers fired up a new type of boiler which I had specified but they had not installed previously. And when I was a laser systems service manager I could instantly tell if someone had been on site before me and tried to make things "better". In the extreme you could end up voiding the warranty.

Don't see why it wouldn't work from the heat transfer point of view. But the various sensors and software may view it as an error condition and it will be difficult to hack that. As a less elegant solution you could fit an external heat exchanger to do the HW and plumb it up as a second heating zone, then the boiler would not be able to tell the difference. Except you wouldn't want the WC to function when there is a demand for HW. I have had to get round that with an external relay as Vokera did not have a solution for this.

I have used the Fernox citric acid based cleaner for this with good results, need to neutralise well afterwards, don't know if it's still available though.

Nothing wrong with that - I used to specialise in analogue circuit design. The solar immersion diverter I made in 2011 has an analogue multiplier IC to compute the true rms value of the chopped waveform and close the feedback loop to achieve <100W export.

It's not an ideal location though, I have Pylontecs in a lobby on the N side of the house, even so I see cell temps of 28C on occasion. Also have fitted a linked smoke alarm, and on the other side of the kitchen door a fire extinguisher. Insurers don't mention battery systems so I imagine they are regarded as mainstream now. without a BMS how do they get balanced if they need it?

Fair enough. My first ones have silver frames but the later ones are all black, not too bad on dark grey slates. And I realised this week that a house near us has black panels on black slates, so inconspicuous I had no idea they had been fitted. Yes its the batteries that tilt the economics a good deal, the PV on its own would have a lot quicker payback.

When I got the system put in in 2009 the Vokera was the only small (20kW) boiler I could find that had it. The plumbers had never heard of WC, or Vokera (since acquired by Riello). I think the internal expansion vessel needs replacing now but other than that it has needed no attention. The HX is an extruded finned aluminium pipe hydroformed into a coil, which is quite neat. In the house before that there was an Ideal Mexico, I found an aftermarket WC box from Danfoss which allowed/prevented the boiler firing according to the measured return temperature and OAT. With zone valves it cut 1/3 off the gas bill.

I think solar installers are pushing batteries hard bc the panels have become a commodity item and there is comparatively little profit in them. Margins on the batteries are better (for now) and you can install them in the warm and dry. The economic case for the customer is harder to establish, though now e.g. Octopus Cosy will allow you to make three full cycles in 24 hours which is a big improvement. And if you can achieve round trip efficiency >80% you can even make a margin selling their own electricity back to them. But I can't quite.

Sounds like a soft error, you might be able to recover by doing a factory reset (having carefully recorded all settings first!).