MattB67

I'm reserving judgement about the Speed Comfort for now, because temperatures have been in the double figures for a while here in Bristol. The reason I decided to give it a go is that downstairs I have 3.2kwh rad behind the sofa and 1.4kwh rad at the dining room end, and the other way to get the flow temp lower would be to fit a triple radiator and lose even more space. The sofa is very close to the radiator, so I think this is helping get more heat out into the room, instead of just warming up the sofa itself. The room definitely warms faster, and this is with flow at 40C instead of 43-45C I was using before. So although it might require the ASHP to deliver slightly more heat overall, that should be at a better COP because I've been able to drop the flow temp. Anyway, we'll see.... I wondered about that but at 40C flow it's switching on and off when I'd expect. It comes on after the heat pump has been running for 15 mins. Probably at lower flow temperatures it would hardly ever be on, so not suitable for all ASHP setups. The main problem is the noise, it's as noisy as an old skool pc fan. It's made of two pieces of plastic clipped together which vibrate, so I've put bolts through which has helped. But also the whirring is exaggerated by being in contact with the radiator, so today I've put it on some bits of wood instead of fixing it to the radiator with the magnetic clips. Also I wondered if it might be annoying having it blast air up the back of my neck when I'm watching TV. In fact the airflow is not all that noticeable.

Yep, and I've given a lot of detail there, but hopefully it might be useful to someone in future.

Time for an update here, as I've managed to sort out all the issues I was having with the Daikin Altherma 3. Shortly after installation I was getting a COP of 2.5 in a mild autumn. I managed to get this to 2.7 by being more careful with target temperature, etc but still way below the target scop of 3.7. The dining room radiator that was cold at the bottom was clogged with sludge. I took it off the wall, emptied and hosed it out. There was a lot of thick black water and it probably collected in that radiator because of its shape, being a column radiator, and is the last rad on the circuit. I think the installers should have done a powerflush, but at least now it's sorted. The installers said this about the Zilmet vessel, ""We have installed a Volumiser vessel which provides additional water volume to the central heating system, this is required when the system goes into de-frost." They offered to lag it, but I just went ahead and did that as I had some leftover from lagging the water tank. See pic below. Also I replaced heating circuit pipe lagging in the loft with all 25mm wall, instead of the standard 9mm they had fitted. 9mm pipe lagging makes a huge difference compared to bare pipes, but using this calculator https://kalk.pro/en/heating/pipeline-heat-loss-calculator/ I realised it would be worth upgrading to 25mm. It cost about £50 to buy but I reckon I'll reduce heat loss by 3kwh a day. If that's 1kwh consumption, that's about £6-7 a month saved, so it pays for itself pretty quickly. Still no idea why the DHW cylinder loses heat so quickly. That hasn't changed. I finally found the leak! After checking nearly all pipes, I noticed the copper below the lockshield valve in the bathroom was a bit stained. There was no feeling of damp, but I cleaned up the copper and tightened the lockshield, and finally the pressure stabilised. Luckily I didn't have to resort to Roger of SkillBuilder's YouTube suggestion - putting poundland purfume in the system and waiting a few days until one room "...smell's like a Tart's boudoir!" (that's a quote) After much badgering I finally got the installers to agree to move the condenser unit in mid December, so it's now 300mm from the back wall and 250mm from the side. However they did also say they've found Daikin send out the condensers pre-charged with refrigerant, but haven't been putting enough in. So he weighed the gas out at 1.35kg, but put back in 1.6kg. Both these things would have been contributing to low COP, so in a way I'm lucky they put it in the wrong place and had to empty out the unit anyway, because if the cop had been a little bit better I might not have persisted in getting it moved. After this fix the COP improved 25% overnight. One other important point was I miscalculated radiator capacity downstairs. I basically increased capacity x 1.5 throughout the house, but I'd forgotten that the open plan lounge/diner/kitchen was always a bit cold, which I used to overcome by turning the gas boiler up, and the upstairs radiators down. When I checked the heat loss calculations it was clear I needed more capacity, so changed one rad from a type 21 2.2kwh to a type 22 3.2kwh, and that's made it much easier to keep downstairs warm. With all these fixes the cop is probably now around 3.3ish. I'm now testing dropping the flow to 40c to see what's the lowest flow temp that will keep the downstairs warm. I'm also trying out a thing called a Speed Comfort, which is a bit noisy, but I think a good idea - it's basically 3 computer fans in a block with magnetic catches, and a thermostatic switch. You put it at the bottom of the radiator and it blows air up through the convectors to distribute heat into the room better. I've only got one on a 1800mm rad, (they say you need three) and it was £55, but I think it might prove to be worth the money because so far the room feels warmer and heats up more quickly, even at this lower flow temp. I'll reserve judgement for now, and we had a lot of very mild weather so I won't know how good the cop and consumption is until we've had some cold weather to compare. Before the fixes listed the system was using 16-17kwh daily average. In similar weather I reckon that's more like 10-11kwh now, so a huge improvement. Thanks again for all the advice given, and happy new year to you all.

Luckily not, no. Just standard TRVs. I think that's what it must be doing. I was misunderstanding 'curves'. I thought they were how the unit heats up the water over time to save power. Looking at the options in the system it looks like a curve is about setting the flow temp according to the outside temp? Weather dependent curves aren't enabled, it's in 'setpoint mode', so yes I guess it keeps running at 45C until it reaches desired temp. I was assuming the Hive thermostat was a bit more sophisticated than being an on/off switch. I was expecting it to send at least two signals to the indoor unit, to tell it the desired temp and the actual temp, and let the heat pump work out how it gets there. But maybe not. I could enable WD curves. The only problem is that the system was designed for 20C internal, 45C flow at -3C outside. But because the house has been struggling to get to 20C even when it's 10C outside, because radiators aren't heating up properly and there's some waste in the system, there isn't much room for weather dependent curve to use a lower flow temp. But once the other issues have been addressed, (heat pump location, flow speed, lagging etc), that could be something to look at.

Hmm. I don't think so. It's a standard Hive thermostat. I thought all the Hive is doing is replacing the thermostat on the indoor unit, because that's in the loft. There are menu options for editing the curves etc on the indoor unit, including weather dependent curves (not currently enabled). I was assuming the Hive is setting a target temperature, then the indoor unit decides how best to meet it. But maybe that's another cause of the problems. Overnight I have the Hive set to 18C, during the day I turn it to 20C. Depending on the ambient temp it could take 4-5 hours to get to 20C downstairs, if at all. I was thinking that would be a product of heat losses in the loft and the dining room radiator being cold at the bottom - plus the poor location of the inverter making the system work harder. For that morning warm-up, assuming the indoor unit is using a reasonable curve, I'm wondering if the Hive would have much effect on that?

Thanks J1mbo. Yes, I wondered if the diverter valve might be causing problems still (they called it a 3 way port, I'm guessing that's the same thing?). They did come out and fix one problem with that, but maybe it's still not right. I don't know the volume of the system. It's a smallish 3 bed Victorian mid terrace with about 9kWh worth of radiators (at Delta 50). The radiator that's most affected is in the dining room, right at the end of the CH circuit. The downstairs is quite a bit colder so I've got the downstairs radiators open full flow at both ends, and limited the upstairs ones as upstairs has been getting too warm. The system is controlled by a Hive thermostat downstairs, which I guess is just sending 'on' or 'off' signal to the Daikin indoor unit, and then that decides how to deliver the heat. The outdoor unit seems to be running more or less constantly, and is an inverter so hopefully won't cycle too too much. When you say 'anything limiting the volume circulating' - would that be reduced by having the pump run a bit faster?

ah, that's annoying. Once you have a winter's worth of bills, you might be able to get a rough estimate of COP with the energy consumed figure on your EPC. For instance, I know I use 5kWh electricity in the spring/summer per day. With eco bulbs it won't be that much more in winter. So I would subtract your daily 'background' consumption from your winter total, maybe then take something off if you run any electric heaters other than the heat pump, or have an electric shower etc. What's left is roughly being used for heating and hot water by the heat pump. You could then divide that consumption into your heat and hot water requirement on the EPC to get a ballpark figure? Also I wonder if EPC heating requirement figures are slightly high. I'm not sure if heating requirement is the actual amount needed, or the amount they expect an average gas boiler to consume so that the householder can estimate their bills? I've asked that question on a couple of other forums and no-one seems to know for sure. If an average gas boiler is 75-85% efficient maybe your heat + hw requirement should be multiplied by .75 or .85 to get the actual amount of heat needed. Divide that figure by your consumption and you'll have a very rough idea of COP. BTW, a reason I think EPC figures may be high is that last year my gas boiler broke down, so I used portable electric radiators as my main source of heating, until the Green Homes Grant came through and the heat pump went in at the end of Sept 2021. The EPC says I need 9300kWh heating, but my consumption went up by 6000kWh that year, with portable heaters that are 99% efficient. The house was a bit cold, and I lit the open fire quite often. Even so, that's quite a big difference.

Thanks for the advice. Yes it's not ideal that it's all in the loft, but I think the heat loss can be reduced a bit more. I have bought 25mm wall pipe lagging to replace the 9-13mm they fitted because the lagging feels slightly warm to the touch. I'm going to tape seams and joins as well. But it seems a bit pointless if there's an uninsulated white metal vessel that is there to let heat out of the system. Interesting that there could still be air trapped. There was a problem with the 3 way valve they sorted out a few weeks ago - it was putting the HW into the CH circuit. I did wonder if they did an air purge afterwards. I can't find any leaks in the pipework and but there are a few floorboards I still need to pull up. I've bled the radiators a few times and refilled, and there doesn't seem to be any more air in the rads. But I guess air could be anywhere in the circuit. It's possible to make the unit do an air purge, but you have to go through installer settings, so I'm waiting to clear that with the installers in case something goes wrong. Could an expansion vessel that just needs recharging with air cause a pressure drop like that?

kWh heat produced by the unit and put into the central heating system presumably. From the front panel of the Altherma 3 there are two lots of stats, "Electricity Input" in kWh and "Produced Heat" in kWh. The Daikin app for some reason only shows Electricity Input.

Well, this is a brand new install of an expensive ASHP that is supposed to return an SCOP of 3.7, room temp 20C, flow temp 45C. According to the MCS calculations its saying I should get 12565kWh heat for 3396kWh electricity, making SCOP 3.7. We've been in a mild autumn and it's hovering around 2.5, so will get worse with the colder part of the winter, meaning the SCOP will be below 2.5, which apparently is the minimum requirement for an ASHP to be sold in the EU. Realistically I wasn't expecting 3.7, and thought anything around 3.4 would be fine. But 2.5 in a mild part of the year is not good. I posted the problems I'm having here, https://forum.buildhub.org.uk/topic/24036-advice-needed-before-i-tackle-the-installers/

Ah, that's a shame. Yes, there is quite a lot of useful information on the new Daikin, (installed in September). I think Stand By Me is the Daikin App I have. I got it working for a day, it's quite a complicated setup, and then it refused to work the next day. It's got the ability to set flow temp and desired temp etc, but no heat output. I wonder if it would have anything more useful than what you've already got from the Daikin controller?

I'm having a number of problems with a shiney new Daikin Altherma 3 installed in September (COP down at 2.5 already with intended SCOP of 3.7; radiators cold at the bottom hot at the top; system pressure keeps dropping). I've emailed the installers a couple of times and got no reply, so this week I'm going to start phoning them up. So I don't get fobbed off I'd appreciate some advice on three things. 1. There's a red expansion vessel, and a white Zilmet VSG Solar temperature reducing vessel (pictured). It looks like all the CH and HW is passing through the Zilmet. It is in the loft and permanently warm so I was thinking I should insulate it. From reading up it looks like this is designed to limit the heat from solar thermal, which can be as hot as 90C. But I don't have solar thermal and no intention of getting it. I have CH running at 45C and hot water around 50C, once a week 60C for the legionaries program. So isn't this thing just wasting heat as it's in the loft, not living space? Is the effect any different from leaving some pipes without lagging or could it actually have a useful purpose? Rather than me insulating it I think they should just take it out. 2. Part of the install was a brand new 125L indirect HW cylinder. From the max temp of 54C, it will drop to 44C within 24 hours, even if I avoid turning on any hot water taps all day. Is that heat loss normal? I thought modern cylinders were only supposed to lose 1-2% heat per day? 3. I have had to refill fill the system several times, because pressure drops from 1 bar to 0.2 bar within a week. I can't find any leaks from the radiators or pipework. So I guess the pressure dropping might be an expansion vessel problem? One thing I don't need guidance on though is whether they've put the unit too close to the walls. The Daikin installation manual says this outdoor unit should have at least 250mm clear at the back and side. It's been installed with 140mm and 160mm, so I am going to insist they move it, and will complain through MCS if they refuse. Lack of airflow has got to be contributing to poor COP. Thanks for thoughts on the above.

Do we need flow rates? The Daikin units give kwh in and kwh out. I have an newly installed Daikin Altherma 3. I've been going up and down the loft ladder because the Daikin app only gives energy input, not heat output (Doh!). On the Altherma 3 indoor unit you scroll through the menus to Information > Energy data > Electricity Input to get the kwh used. Then go back a level to Information > Energy data > Heat Produced Both of these display bar graphs which you can scroll through, and change using the left and right dials. Note that it shows Today/Yesterday, This week/Last week and This year screens. But also on the right hand side are three different symbols, a sun for heating, a shower head for hot water and a Greek thingy, which I guess is the two combined? So whatever your checking, make sure your electricity input and heat produced have the same symbol on the right, or you might be dividing the wrong figures. I thought all you needed to do was divide one by the other for COP? My system is not working properly, so on 31st Oct I got 11kwh used, 28kwh produced, 28/11 gives a COP of 2.54 - which is rubbish, and what I've just joined to post about!