Eileen

There was a just slim line of ice down one side a bit earlier. The PHE temp had already reached about 36 from about 26 before the defrost started, and the outside temp was good, so I thought we were all good to continue and get up to 45. Yes, i think we have a buffer cylinder, I remember we had an extra £1000 worth of plumbing a year ago in our attempts to get a solution, which I believe was adding a buffer cylinder. That fixed an error code we were getting. I’m pretty sure it was defrosting because the little snowflake symbol was presenting on the main display of the ashp. It only last a few minutes so I don’t see it unless I’m standing there forever, but I was triggered to go and check because the house power consumption went down to about 1.44 instead of the 2.58 it was previously running at, yet all thermostats were still calling, so I knew none of rooms had reached temp and turned off any pumps. The refrigerant temp had dropped sharply to -7.6 from 36 by the time I got to it, then the snowflake symbol went off and the refrig temp started rising again

FYI, if it’s a useful case study for anyone, it’s just gone into a ‘normal’ defrost right now at 12.48, outside temp 7-8C, now doing its thing trying to get the PHE temp back to where it was. When it’s in this mode it drops back before it ever reaches the required temp (we have set it to 45 since the original 36 made zero impact on the room temperature). If we’re lucky it will reach 35 before it defrosts again, on repeat, so makes no dent in the room temp.

Steamy Tea, it’s a certified passivhaus so low heat loss. It’s a Daikin Altherma LT Split EHBH08CB3V wall-hung indoors, ERLQ006CAV3 outdoors . It uses a Sunamp for DHW but that doesn’t use the ASHP (that’s another story, we initially hoped it would. But for 9 months the sun is enough to fill it and then direct from the grid for the other 3.) I think we suffered a bit from being early adopters 3 years ago, different tradesmen for the different techs, and no local experts in marrying all the technologies. It’s taken us this long to know that it’s a real issue and not just user error or teething troubles, because it’s only on for 3 months of the year and needs a run of frosty nights. Finding an expert is the hard bit. No-one we called can tell us if a bigger unit will make any difference. Any tweaks an engineer has done can take a year to reproduce the conditions that cause it, and every experiment to see if it works differently with different usage patterns needs the same conditions for days/weeks. Apparently the next size up would fit our current pipe work, but there’s no guarantee it would make a difference, but we’d need whole new pipe work if we went a size above that. So do we go one size up and risk failure or rip out more and possibly over-engineer it in the hope of fixing it. If anyone knows any Daiken heat pump experts in Devon, and ideally know Sunamp too, who can say ‘X is the problem and Y will fix it’ and is willing to take on maintenance of an installation they didn’t put in, I’d love to hear. DPmiller, I’ll check on that, I know when it was first installed Daiken sent a man I believe he disabled an heater within the internal unit because being in the plant room it would never need it. if the external unit has one would it explain this occasional power usage surge? I see lots of defrosts but this spike is very rare, only saw it once or twice, each time for about 20-30 mins, and it sticks out like a sore thumb on the solaredge app household power usage. Thank you both for your help, I am going to contact Daiken direct now that I have the confidence to say it really is an issue that needs to be fixed.

Thanks Steamy Tea, yes sorry, kW, forgive my schoolgirl errors. Thanks for confirming that something is not right, we’re finding it very hard to get anyone to advise us, no-one seems to know what to suggest, We don’t know if putting in a more powerful unit would guarantee to resolve the problem so are reluctant to try it and find out it that ot makes no difference. At the moment it’s not fit for purpose, but we are obviously very committed to this type of heating. Do you know if the rare 5kW spike is a normal thing, or if that in itself is also an indication of a problem?

I have the same issue with defrosting. If it’s below +6C outside we reluctantly turn the ufh off because it still burns power but provides no heating (water never gets to temp before next defrost cycle). We are a passivhaus so we can survive comfortably without heating for a day or so. I’ll keep reading this thread for suggestions, but I have a general question. Very occasionally, when starting up, I notice the power consumption running at 5kwh for about 30 mins. it’s normal run rate is about 2.5kwh. It’s related to low temperatures, I assume a defrost, but has happened when first turned on, often at noon when I’ve waited for the outside temp to get above 5. Is there some process that explains a 5kwh usage. It’s very rare and not part of its general heating or defrosting pattern of power consumption.

Oh no, I never achieved those! Running yes, swimming no...

This was all a long time ago, but we are now one of the 3 "small projects" shortlisted for the Passivhaus 2021 awards, with the shootout being on June 30th. See https://passivhaustrust.org.uk/passivhaus_awards/uk-passivhaus-awards-2021/ We are also finally getting visited by the RIBA jury as they have moved their 2020 awards to 2021.

Hi Nick - our ASHP is 6kwDaikin Altherma and was installed by the plumbers, and the UFH separately bya specialist sub-contractor working with our plumbers. This is entirely separate from the electrically heated Sunamp, which we just use for DHW and which was also installed by the plumbers. At the time Sunamp really weren't geared up to supporting people like that with no previous Sunmp experience (as opposed to highly-motivated diy self-builders) but I think that's improved now. We recently had to replace our Sunamp under warranty as it leaked PCM material. Apparently that was a known problem with V1 of the new range (a missing O ring , now fixed. A specialist installer came and did that.

I sent you a message, Conor.

Congratulations! I'm not sure how hand on you're intending to be, but with our Passivhaus build, the really important thing was to have a "Passivhaus champion". Our project manager got enthused and went on the training and then indoctrinated all the subcontractors and was on their case the whole time. He personally did much of the taping. He was even disappointed when we "only" got 0.56 on the final airtightness test!

We've now been shortlisted for the RIBA regional awards - so awaiting the jury visit "some time"!

One thing to watch out for - we also built on a virgin plot so my wife (Eileen that is, as this is her husband writing), who did the garden design, was very keen. However, we found that some quite large areas had been really trashed by the groundworkers. Having moved away the topsoil at the start it was then pushed back, but beneath it the sub-soil was very compacted and had lost all its structure and if we dig into the topsoil we often find puddles underneath. As a result, several trees have died, although we did belatedly dig some drainage trenches near them. I guess we should have kept a closer eye and had them do a bit of breaking up of the subsoil before re-laying the top soil, but of course everyone was rushing in a mid-December period. BTW I'm not the gardener so this is a layman's description!

We have a Daikin!

On batteries - we have a 10kWh LG DC battery (originally ordered a Tesla AC battery, but that caused a problem because of the limit set by Western Power). Over 2019 we used 4.95MWh of our solar power, of which 2.25 came via the battery. We are on the lowest feedin tariff as we only just made it before the cut-off, so we save in the order of 10-12p per kWh by avoiding the roundtrip to the grid for those 2250kWh. I can see that a little more capacity, such as the 13kWh offered by Tesla would be optimum, and that's about where some research I read put it for the normal domestic situation. We're switching to a variable tariff this year so I hope we'll be able to time-shift the cheaper power then. Even at the crappy feed-in rate our net electricity cost was zero (we are all electric, including borehole water and sewage treatment pant, so that's the only utility bill). In the summer quarter we were asked by the electric company to provide photos of our feed-in meter to prove we were telling the truth about how high it was, and by another part of the same company to check our readings on the consumption side because they were so low!

@kayeCIL came along just after our new-build but we paid some S106 charges that were relatively low. However, on looking at our local planning authority site it confirms that new builds are exempt, BUT it says that you must apply for and recive an official exemption certificate before you commence development, otherwise you will be liable for the full charge. So it would definitely be worth checking if your authority is the same.