@marzipan71

Hi Steve,

Did the alleged project manager give any reason for installing a high temperature system?

Hi @derek-m no none at all. This was the one area of our build that I left in his hands, perhaps foolishly. We previously had a gas boiler with steel rads (legacy upon purchase). He knew we wanted UFH in the bedroom zone where the floor was coming up anyway. In the day zone, we thought oversized aluminium rads was more sensible given he wanted an additional 20k to install UFH in that zone. For aesthetic reasons we rejected his suggestion of air to air splits for that zone - plus cost of course given we'd/ he'd already bought the ASHP kit. I did suspect it may have been some kit gathering dust at the back of the Daikin warehouse (like some dusty glow in the dark rubber diving fins someone tried to sell me once in a dive shop when they found out I was a novice).

We do have a letter from Daikin validating the install fwiw. Subsequently we had an interesting interaction with another Daikin rep who admitted our outdoor unit which was positioned 15m from the house in an open field with strong winds should have had some kind of protective housing which the first Daikin chap had said was perfectly OK fully exposed to the elements on all sides - we are on top of a hill at 500m asl.

Question for you would be - under what circumstances would you usually need such a HT system over a non-HT ASHP install? I don't think there's anything remarkable about our property given we had an entirely new install of UFH in half the house, and rads in the other half with legacy 12 and 15mm piping which was never commented upon. We are running it now with the new settings with a flow temp in the low 30s. Have we paid for the convenience of a HT system which was inappropriate do you think?

As you've probably guessed our PM is not on our Christmas card list anymore. That's another story that would make your hair curl... 

@marzipan71

Hi Steve,

I failed my observancy test when you posted the details of your equipment earlier.

As the Daikin brochure, that you posted earlier, clearly stated, a HT system would remove the need for replacing radiators and possibly small bore piping, so making the install much easier. But since you don't have small bore piping, and replaced the original radiators with larger radiators and UFH, then why would you need a HT heat pump.

The only reason that I can think is that the outdoor unit also supplies both heating and cooling to your AC units.

As is shown, on page 4 of the brochure, there are in fact two refrigerant gas circuits, a R-410A from the outdoor unit to the indoor unit, and an R-134a within the indoor unit. This of course means that you also have two compressors, one in the outdoor unit, and one in the indoor unit, so hence could be using more electrical energy than a more conventional LT heat pump system.

Hi @derek-m the outdoor unit only connects to the indoor unit. We are about to install some AC but that will be entirely independent of the ASHP (the house was predisposed with piping). Is 12mm and 15mm piping for our rads not considered small bore? Our PM would have happily (imo) sold us a system that meant he had to do less work - i.e., replacing pipe work. From memory we were committed to rads in the lower daytime zone and his knowledge of what was needed seemed very limited (I had to do the energy calcs and source the suitable rads). They seem reasonably happy at 34C - that zone is staying a constant 21C.

We are also aware the ASHP system can cool in summer, but we're told it was highly complex and don't ask. A different plumber told us that was nonsense and it was relatively straightforward. I've also subsequently learned there are specific thermostats that can be installed for our system that connect to directly to the UFH, and also the wall mounted room stat, neither of which were discussed. I wouldn't have started from here etc. but we have obviously paid for the kit we have (with no grants or subsidies) so we are kind of stuck with it. The consumption doesn't seem too bad with the new settings you've helped with - averaging 1.6kw per hour.

Posted by: @marzipan71

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Hi @derek-m the outdoor unit only connects to the indoor unit. We are about to install some AC but that will be entirely independent of the ASHP (the house was predisposed with piping). Is 12mm and 15mm piping for our rads not considered small bore? Our PM would have happily (imo) sold us a system that meant he had to do less work - i.e., replacing pipe work. From memory we were committed to rads in the lower daytime zone and his knowledge of what was needed seemed very limited (I had to do the energy calcs and source the suitable rads). They seem reasonably happy at 34C - that zone is staying a constant 21C.

We are also aware the ASHP system can cool in summer, but we're told it was highly complex and don't ask. A different plumber told us that was nonsense and it was relatively straightforward. I've also subsequently learned there are specific thermostats that can be installed for our system that connect to directly to the UFH, and also the wall mounted room stat, neither of which were discussed. I wouldn't have started from here etc. but we have obviously paid for the kit we have (with no grants or subsidies) so we are kind of stuck with it. The consumption doesn't seem too bad with the new settings you've helped with - averaging 1.6kw per hour.

I suspect your project manager would be more conversant with AC type heating and cooling systems rather than A2W, which I think are more often used in the Mediterranean countries.

Not many people have the HT, double compressor, system, so I can't state for definite whether both compressors need to run together, or just the outdoor one is needed when running at lower LWT. You could try putting your ear near to the indoor unit and see if you can hear the compressor running, though it may be well soundproofed with it being an indoor unit.

Will your proposed AC units also provide heating?

Hi @derek-m yes that's probably true about his knowledge and experience. I'm not going to try and unpick how we got here too much as we are where we are, but needless to say if I was doing our renovation project over again I'd do a lot of things differently.

I think both compressors do run yes but couldn't say for sure. The indoor unit isn't that quiet, even with the system on quiet mode 24x7. We were down to 2C overnight and it's 5C outside today but house is nice and warm with a LWT of 34C. Seems to be running ok. My main concern was that our units might struggle to operate at low flow temps if they are designed for high temps but hopefully that's not the case and we just have functionality that we are unlikely to use. I'm thinking we will have Daikin install the 'missing' solar thermal element and that should give us better efficiency for DHW and (presumably) space heating also. 

The AC units will heat yes. They are the Daikin Stylish units (FTXA) -we are putting one in each bedroom/ office; the external unit is a Daikin 4MXM80N2V1B9 unit here. The idea is to supplement heating in the shoulder seasons and provide cooling in summer (running off our PV). 

@marzipan71

Hi Steve,

Sounds like a good plan.

As you may have noticed from many of the forum posts, it is not just in Italy where designers and installers are supplying systems that are far from ideal. Long gone are the days when companies prided themselves on providing good service and that the customer is always right. We trust people to be competent and know what they are doing, but unfortunately that is not always the case.

I assume that besides having comfortable temperatures within your home, you are also seeing less energy consumption and lower bills. There may be room for a little more fine tuning, but I think that your system could be working close to optimum.

Please keep the forum informed of your solar thermal install and how it performs, since there are very few forum members with such a system.

Hi @derek-m - thought I'd provide a quick update on consumption using the new settings based upon weather compensation, using the room stats as temperature limiters, and running the system 24x7 with setback from 10pm until 7am.

House has been a nice constant and comfortable temperature for us – room temperatures vary between 18C and 20C, with the poorly located zone thermostats saying around 21C. Both zones have been showing more or less equal temps which is impressive as we only have the radiators in the lower zone, and the UFH in the upper zone. We are keeping all the doors open and have all the TRV’s on the rads at maximum so presumably that’s encouraging a stable temperature across the house.

I tweaked the WC curve on 1/12, so its currently set at 40C at -10C, and 25C at 15C.

Average daily consumption in November prior to switching on the ASHP was 16.7kWh per day. In the past full 7 day week, we have averaged 47.7kWh per day. Assuming the difference is the ASHP consumption, then we are using 31.1kWh to run the ASHP per day, or 1.3kW per hour, on average. At current prices that’s about 21 euros per day on the bill; at 2021 average prices, 5 euros per day on the bill. As I’ve read elsewhere, if we were using a plug-in electric heater to help heat one room we’d be using more than 1.3kW per hour, and for that we are heating the whole house. Seems impressive to me, unless my calculations are way out!

For comparison, we use around 400kWh in ‘background’ and DHW consumption per month; I’d project around 1400 kWh consumption for December using the above. In December 2020, our consumption was 2340kWh, and in December 2021, 2382kWh. So around a 40% reduction compared with previous years when I’ve ignorantly been using the system like a gas boiler – but with much more comfortable and stable house temperatures.

January and February are the coldest months for us so it will be interesting to see how the system works when we have consistent freezing night-time temps and damp, misty, cold days, and consequent reduction in PV solar. But looks promising so far.

@marzipan71

Hi Steve,

Thank you very much for the update. It is always useful to get feedback, both good or bad, and it also helps other forum readers to identify where their systems may benefit from a good dose of TLC.

You, like many others, appear to have suffered from a far from ideally designed and poorly commissioned system, which it would appear is now operating 40% more efficiently than previously. The goal of many of the forum members is to help reduce global warming and in the process to bring down the cost of energy for all. Even if we have to do so one heat pump at a time. 😎 

I am sorry to have to inform you that my wife and I will not be coming over to give your system a full inspection (which could take up to one month) until your weather drastically improves. 😋 

Hi @derek-m indeed the weather is relatively cold for us but nowhere near as cold as the UK right now! Of course it would better to wait for better weather before that much needed system inspection 🤣 

I've been tracking the behaviour of the system for the past few weeks and its really interesting to see how its performing, to me at least, with the 'new' WC curve from 1/12 (40C at -10C, and 25C at 15C) and to compare it with the 'old' curve I was using when I first turned on the ASHP in late Nov (50 at -5, 25 at 20). I've obviously got a limited dataset and I've been a bit brutal in assuming that our (grid) electricity consumption for everything other than space heating (DHW and background) is equivalent to the average for November before I turned on the ASHP (probably neglecting things like reduced PV these past few days and increased background usage elsewhere as we are spending more time indoors etc). However, the two curves look like this - WC1 being the original settings that we found too warm, and WC2 being the current settings.

Consumption of grid electricity for space heating seems fine to me comparing with data from that reported by other people on this forum - something like an average of around 1 kW per hr for the past couple of weeks, and generally between 1 and 2 kW per hr. Unfortunately I can't easily quantify how much our PV is contributing to running the ASHP. In terms of our absolute grid consumption, it looks like we'll hit something like 1200 kWh for December, compared with 2340 and 2382 kWh in Dec 2020 and Dec 2021 respectively when I was using the ASHP like a gas boiler - admittedly temps have been pretty mild so far this December but even so the system seems to be running massively more efficiently thanks to your help and the terrific advice from other generous folk on this forum.