sharpener

AFIUI the anti-islanding is provided by the Gateway not the inverter itself. N.b. since that is >16A (3.68kW) it does not qualify for install-and-notify so I think (rules vary) you will have to get your DNO's consent in advance, they will check it is on the ENA database which requires anti-islanding relay operates within ?5 secs of grid failure. Also if they are like WPD were, they will not grant approval without de-rating the inverter to the 3.68kW - which is my case is not too bad since inverter has 50A passthrough which gives it a max o/p of 12kW when grid is up. The SunSynk was only 32A passthrough which IMO is defo on the small side esp as I have electric cooker (or I would have gone for the cheaper 3kVA Victron). But sthg you should perhaps check for the Giv, I can only find mention of 25A cont, 32 pk so maybe those are the upper limits. Incidentally I note it has an integral bypass at B below and also provision C for EV charger.

There seems to be some awareness to judge by recent postings on Heating Design f/b group. Someone else mentions the Fernox but it is well over £100 and looks just the same as the ones on Amazon which others swear by Many have a crankcase heater for the compressor and some have trace heating for the condensate drain as well. But only as good as your electricity supply. I am just 200m from a substation but I would still prefer a passive solution.

Interesting experience! Both the Victron I have and the GivEnergy @JohnMo is proposing have automatic anti-islanding which will disconnect in a power cut so are safe for the repair crew. I was talking about fitting an (optional) manual bypass in addtion so you can - when the grid is present - take it completely out of circuit in case you want to maintain the inverter or it has a fault which would otherwise leave you in the dark. This is a sensible option if you have the whole house behind the inverter, as opposed to just one or two wired emergency circuits or as some people do a twin 13A socket for plugging a table lamp and the TV into. This last option with the really cheapo Chinese inverters is non-compliant because of the inadequate earthing arrangements.

By coincidence have just had a call from "Tony" at EdF. He looked up the EPC and after the usual questions about construction and # of beds/baths he tells me they cannot quote because the solid walls mean the heat loss is too big for the largest HP in their range which is 22kW. So I responded that as I have had 3 quotes for fitting a 12 or 15kW unit I thought their process was overly conservative and would lead to them unnecessarily ruling out a significant part of their target market - which he said he would pass up the chain.

How does that give you stratification then? BTW @JohnMo did you see my latest on this thread?

No personal experience (as yet) but I do not like the idea of returning after a winter break to find house cold and HP inoperable because water has been dumped to drain. Or finding the valves were stuck shut and the HP is a write-off. Cost is about the same order anyway.

Has anyone found a complete description of how the Harlequin works? From reading here and (scant info on) H web site it seems they have one coil at the bottom to input heat and another at the top for DHW flow to abstract it in real time. If the water cooled by the latter falls to bottom of tank without mixing then there will be stratification and you will get hot water at constant temp until the cold level reaches top coil. If so what is the gubbins on top of the tank (flexi-hoses, solenoid valve are visible), how does the ?stagnant body of water keep free of nasties, what are the different overfill options referred to? H are a longstanding mfr of (polythene) oil tanks etc so this looks like a logical diversification for them. Polypropylene has been used for washing machine tubs for many years so should be an appropriate material to use for the inner and an interesting change from metals.

Annual HP maintenance will include checking the glycol concentration with a refractometer. Don't know about chemical degradation but if it incorporates inhibitor I would imagine a life of many years just like water with inhibitor. Also the HP does not reach the same temps as a boiler. Some mfrs have warnings (no idea if anyone pays any attention) about dissolved oxygen, pH and hardness e.g. Vaillant Arotherm Plus - but the following appears actulally to have been cut-and-pasted from a boiler manual. pH 8.2 is quite alkaline, mains drinking water pH only has to be >6.5:

Yes but nothing to do with the heat pump per se. I would say you need to have 50l per person min at not less that 50C. One installer has quoted me some rule of thumb of (# of bedrooms + 1) x 50 as the min vol, I think this came from a cylinder mfr. Are you differentiating between a conventional HW tank and TS? The problem with having a TS with HW flow through a PHX or secondary coil is there is no stratification so as you say the temp will fall steadily as you draw off. Is this a TS as just described where the temp falls, or a conventional HW cyl in which case I would expect 250l should be adequate stored volume, and 9kW input would provide a (not very generous) shower on a continous basis.

Dunno. I checked and it has various errors for the Vaillant products I am interested in. Seems to be a version of the ENA spreadsheet which is also not very good. I don't imagine they do any testing, and rely on mfrs data which is only as good as the test houses they use. Maybe there is an EU database which is better but I have not looked.

My 1.9m was assuming you can therefore change any point by +/- 1m so you can excavate a 0.95m hole and then build a 0.95 high bund round it.

If the whole house is behind the inverter it might be worth installing a switch like this anyway to allow bypass of the inverter for maintenance/in case of fault. Will go in an ordinary CU and much cheaper and neater than the free-standing ones often fitted. I have a second one for the garage as well, allows me to have the EV charger direct on the grid while I am using it. They are in the CU on the rhs of this pic However I wish now I had made the house switch a changeover relay so it would fail over to the grid automatically, to keep the freezer, alarms and router going if the inverter packs up while I am away. GivEnergy gateway is a good solution as it gives much more freedom with equipment placement and IIRC has got a built-in bonding relay. So much to think about, will have to evolve further to accomodate the HP...

That seem a good explanation. But what are the spikes in heat o/p at 0850 and 0905, there a corresponding dips in the F & R temps but nothing on the elec consumption, what is going on here?

Not much UK market for them as WC is mandatory under MCS. FWIW Midea is what Good Energy fit under their scheme. EdF seem to use Daikin.

Looks like from this there are a lot of connection options inc genny but I can't say I have got my head round it all! Seems they will need to fit an external relay for earth-neutral bond in island mode, also you will need an earth electrode if you are not on TT supply already. Lots of info and several Sunsynk users on this forum https://camelot-forum.co.uk/phpBB3/viewforum.php?f=11.

Out of interest does the Sunsynk provide the full 5.5kW to the house in a blackout or have you had to compromise with only a few circuits on the EPS output? I think if you put the CT on the grid side of the tee to the outbuilding the Sunsynk will manage the installation as one.

I have wondered about doing one of various HP courses e.g. this one from NAPIT, £550 looks very reasonable for a 3-day course. However like most of the others it requires a daunting array of preconditions including 3 yrs industry experience and a Water Regs certificate. Whether they would in practice turn down the extra £550 is another question.

I was told by LAPD in respect of the neighbour building up the level of his garden that changes of level of less than +/- 1m do not require PP. After 3 yrs it is "established" and so you can do it again ad infinitum. I guess if a 1.9m depression fills with water as a result of forces of nature they cannot argue that you must drain it.

Total rubbish solution. CoP of 1. Increases maximum demand. In what scenario would you do this? Might as well have instantaneous water heaters everywhere. My 80A supply has DNO approval for an HP only, not any supplementary heating.

Yes that's the one I have been using. Agree with your comments on interpretation of the boilerplate. I imagine that the degree of oversight by Vaillant will, like any other commercial relationship, depend inter alia on how long the installer has been on the approved list, how often he wants to install "specials", how much aggro there has been in the past, what warranty claims there have been etc. As installers get referrals from the Vaillant "Find an installer" service they will not want to do anything to prejudice this situation. That would include making lots of requests for design approval relative to the number of HPs they actually install, and putting in systems which may result in warranty claims or requests for troubleshooting. So as there is plenty of work around they can afford to play safe. Or so it would seem to me. Having been Business Manager of a contract R & D company I can see this from several different points of view.

Vaillant do. In addition they have a field engineer force who will come and troubleshoot installations done in line with HQ approved designs, whether generic or custom. You can also call them out to fine-tune your system e.g. after the first year, said to be well worth the £300 or so. Or so I glean from e.g. the facebook group. I think it's more about a priori risk reduction. No reason to suppose they don't honour the warranty provided it is installed by their own lights. One of my interests was analogue circuit design - which is why my home-made immersion diverter uses an analogue multiplier IC to get the real-time product of the voltage and current waveforms and hence measure the signed true export power flow. In this field it is maybe a bit different from digital ICs, as Analog Devices, National Semiconductor and so on published very extensive application notes with typical component values and pcb details. So the technician can build working circuits quite easily but also the professional engineer can study the examples, understand the principles and come up with novel designs. Vaillant's standard schematics are analogous to the application notes. I don't regard it as interference so much as a response to a complete absence of the involvement of professional engineers, in the domestic market at any rate.

Not so, wrt non-standard ideas like adding an HX or secondary pump, the installers refer back to Vaillant as discussed upthread for anything that is not in their book of approved schematics (which I have). It doesn't make much difference to the end user if this is bc it is a term of their approved installer status or just backside covering, it is what the 3 who have quoted all do. And there are constraints from Vaillant, the allowable relationship between HP output and (Vaillant) cylinders is published in the cylinder literature extract above - at roughly 7kW/m^2; the advice from their tech support is even more restrictive at 4. Whether they will accept any third party cylinder as compliant is conjectural, I can't demonstrate that the surface area of my OSO cylinder is 3 m^2 so they won't agree to it. No reply to my latest missive as yet (nor from the Guardian).

No, but following the option of "Bespoke Layout - speak to your Installer" imposes in practice whatever constraints they or the company choose to believe.

Can you give a link for that? I have got the installation instructions <arotherm-plus-230v-double-2626669.pdf> for the twin-fan units but there is nothing at all about constraints on DHW cylinders, only that they need min 150l of engaged volume (45l with the auxiliary heater fitted) - this would seem to be about defrosting though. Not if you want the 7 yr extended warranty which is only available via approved installers, and can't find an installer who will fit the HP to your existing tank without running it past Vaillant for pre-approval which to date has not been forthcoming. I am persisting with this bc their units are R290 and have an unusually narrow footprint (only 605mm including air space behind) but there will be rival products out in 2024. And it is already getting late for this season as the P/P is not due until 12 September.

But as you say, with an HP from Cool Energy who are much more relaxed about the whole thing.