The BUH equipped models need the LWT temperature sensor at R2T after the BUH as if the BUH is in use the LWT will be higher than it is coming out of the heat exchanger at R1T.
R2T measures the temperature of the water leaving the heat pump.
R1T measures the water temperature leaving the heat exchanger.
There is a temperature drop because the pipes and equipment are not insulated, the water is bound to cool down.
My app, MMI and heat meter all report the water coming into my house at the temperature recorded at R2T.
If there was less of a temperature drop between R1T and R2T that wouldn’t increase the temperature at R2T, it would reduce the temperature at R1T.
The heat pump is working to get the flow temperature requested as it leaves the heat pump, the last place that is measured and reported is R2T.
This is my understanding looking at pictures of the heat pump and the schematics.
Do you think something different is happening?
As long as the temperature of the water going into your house is that recorded at R2T and you use that in your heat calculation then everything is good in that respect.
If the temperature of the water entering your house isn’t that shown by R2T then what is it?
I think we’re all agreed that R2T is the most sensible place to monitor outbound flow temp for BUH-equipped systems - no need to discuss that further
What the HP/MMI should use and what they actually use for various values from the sensors are quite different things; I might be barking up the wrong tree, but it’s a combination of very complex hardware/software, and as a software developer who has struggled with co-ordinating different teams and many cubic metres of intractable code, I am very cautious about assuming anything!
As far as I can see the MMI and the app report the value at R2T as LWT, do you agree?
The value of R1T is reported in the MMI and I see a value, like Stephen, that is about 1c higher than that reported at R2T, there is a reported temperature loss, whether that is true or not I don’t know but there’s lots of uninsulated pipework there. I think there is a loss.
I don’t know how the MMI calculates heat produced but none of us use that, it’s of no concern to me.
The temperature loss is though.
I worked out yesterday that the extra 1c or so at the heat exchanger costs around 150wh of electricity at a COP of 5, quite a lot of electricity to waste.
I think there is value in adding insulation and mine arrived today.
I am going to give it a go.
I too have contacted Daikin to arrange a visit to check my heat pump. I am convinced that something is not right.
Various R1T/R2T differences reported, attributable to a) heat loss b) thermistor calibration/performance variation - agreed. I’m interested in finding out why mine seems so much greater than e.g Stephen’s; that extra 1.2C I experience constantly makes all the difference to heat output calculations at dTs around 5C
I don’t use the MMI’s calculations, but since they seem to correspond to my calculations using R1T, and not R2T, there is a distinct possibility that the MMI is using different sensors outputs for different calculations/displays, especially as the BUH is an option that requires sensor usage to be configured in the depths of the software
I’m really looking forward to your feedback from the new front opened in the war against unwarranted heat loss AKA insulating the BFPs in the HP case; details of insulation, ease of application and resulting dT is of great interest
It will be interesting to see if Daikin a) reply b) provide a date within the next 6 months!
But if we get R2T close to R1T you won’t see greater heat output, this is what I am trying to get across, what you will see is reduced electricity consumption, possibly anyway.
It is a subtle difference. I would not expect any insulation to increase the temperature at R2T, I expect it to reduce the temperature at R1T as with reduced or eliminated heat loss between R1T and R2T the compressor wont have to produce such a high temperature at R1T to achieve the requested LWT at R2T.
The only caveat I have is that at minimum electrical input even though the R1T temperature is lower it may not actually use any less electricity as it is already using the least it can.
Once I get to a certain level of electricity consumption it doesn’t matter how much I lower the flow temperature, it never uses any less electricity.
What we may be able to do is use a higher flow for no less electricity and generate more heat.
I am really curious now to see what affect insulation has.
Maybe there is a reason Daikin didn’t add it that is not related to cost?
I f you look at Stephen’s picture with the covers off you will see some insulation on some pipework, whether Octopus added that or it comes like that, I don’t know. I don’t know if mine has it, I wonder whether yours does, maybe that would explain the difference you are seeing between your data and Stephen’s?
I really need to set my monitoring up like yours and Stephens, I am sure we would all like to know what differences there are between the data direct from the heat pump and from a heat meter.
I really need to set my monitoring up like yours and Stephens, I am sure we would all like to know what differences there are between the data direct from the heat pump and from a heat meter.
I’m sure we’d all really appreciate that! Thanks in advance…
My only interest is in getting accurate data on the cheap - I want to be able to make adjustments against a reasonable baseline. So getting to understand the sensors and software’s actual performance etc. is important, rather than absolute cost/efficiency/whatever.
Maybe there is a reason Daikin didn’t add it that is not related to cost?
Haha, you jest! It’s a big corporation… although there may be some other reason, I’m not sure what it would be - keeping parts warm in the winter?!
I think it unlikely that Octopus do anything besides install the units, unless they do that in the warehouse prior to sending it out, in which case they carefully wrap it up in the original packing and transport labels. They certainly didn’t on mine. The manual pictures look pretty much like Stephen’s.
i am an accountant, I understand that they will want to save money, they did this by building one heat pump and turning it down to make three `smaller’ ones!
However, they have fitted some insulation and for only a tiny extra cost they could have insulated the whole lot and get much better performance.
Either they are really stupid or there was a reason, I am not sure I can discount either option!
I’m not sure the data needs to be entirely accurate to make improvements to our own heat pumps in isolation, but it does need to be consistent and reliable for sure.
The last time I looked, which was weeks ago, my MMI reported similar electricity consumption to my meters but the heat production was lower than that reported by my heat meter.
I will try and check again later…
Just looked at my MMI, it’s not very easy to read but the energy used and heat produced look to be almost identical to my heat meter.
This behaviour is not what I expected from a heat pump. I really want to be able to run the heat pump for shorter periods but stuff like this stops me doing it. I don’t think this is how a heat pump should behave.
It was working fine from 13.57 to 18.08 when I turned down the flow from 36c to 35c which stopped it.
It started back up at 18.12 and went through the same strange prolonged heating process until 18.52 where, just as it is about to settle down it decides to defrost even though it is 8c outside and no sign of ice on the heat pump.
Then it goes through the whole heating process again with the `Daikin Dip’ as I am now calling it!
Is this really how it should be, is it me, am I expecting too much?
I have changed nothing for days, it runs really well at times and at other times I think it is not right.
My DHW doesn’t seem right, and the DHW cycle seems to mess things up, it was fine yesterday morning and then the problems started after the DHW run yesterday, the heat pump didn’t resume heating like it was in the morning and it was worse this morning than it has been for the last few days.
This is well documented, but at the same time very annoying even the big companies with decades of history here haven’t nailed this still.
In mild weather like today, mine defrosts every 5-6 hours even with no frost buildup almost like there is a timer countdown.
This is a good read on it:
My dads Panasonic whole house Etherea Air to Air multi-split (1 outdoor unit and 4 indoor “heads”) had a few issues last winter where his unit (I also monitor) was (and still is) more reluctant than our Daikins to defrost. He can sometimes go through the night with maybe one defrost, where our units won’t last more the 30 mins.
This led to a couple of days where conditions led to a cascade effect and death spiral where each defrost did not fully defrost the unit, leading to a thick ice buildup, power use going up and up and heat output dropping……I had to force a manual defrost for him by putting the unit into cooling mode for 20 mins as he complained it was getting cold, yet I could see power ramping ever higher and well outside “normal” range.
The installer has been out, as have Panasonic and spent a whole day on it, to find no problem at all. (That said, he hasn’t had the issue so far this winter which is the 2nd with it)
Most of the time though, his unit barely defrosts, so efficiency is great relative to ours.
My point is: get the algorithm wrong, and it’s bad news and possibly physical damage through ice buildup.
My guess is Daikin err on the side of caution with defrosts for this reason.
Daikin should be best placed to explain the detail of how the product behaves here. The only contact I had there (Darren Manley) jumped ship to quantum earlier in the year though.
It’s still relatively rare to use heat pumps for heating; and air to water units whose performance one could actually hope to measure (and complain about) are rarer still.
It’s also not really picked up on the efficiency tests so no incentive to do too much (quite dry air); and with UK not in EU that continental winter test standard head even less reason to change?
Regarding the varying flow rates - the heat pump modulates them to try to maintain the delta t. Faster flow rates mean less time for the emitters to shed the heat so the return temperature will be higher and vice versa.
My heat pump is running much better now I have got my head around things. I am still having a couple of issues though, probably me as usual but I have to ask.
My DHW production doesn’t seem right most of the time, the heat output just doesn’t seem as high as others.
Also my heating doesn’t always resume particularly well after a DHW cycle, it struggles to get going at times.
I am running a fixed LWT but the heat pump is struggling to achieve it at times and if I ask for an increase it’s reluctant to do it, it often fails to raise the LWT
Finally I am seeing my flow temperature decay over time, not all the time, but quite often and that is when I try and raise the flow temperature with little to no response.
My requested LWT is 36c but it will not sit at that and steadily decays. The app and the MMI show the LWT at similar to my heat meter, ie requested is 36c but I am only getting 35c or less.
The flow temperature is reducing, the electrical input has increased, the heat output and COP are falling. It feels like it is struggling to produce heat, like something is holding it back. The radiators cooled noticeably.
I don’t think this is a problem. The drop is only by 0.5° and the return is dropping by the same amount. This just means that the heat pump is trying to match the heat loss, but hasn’t quite managed to lock it in perfectly, so output is a bit less. Around 22:00 it notices, and ups the heat output a little to compensate. COP is a steady 4.0 between changes in input.
This looks to be working as it should, within the capabilities of the controller. If you want the flow to be exactly 36°C, you may need to increase the target by a degree.
It’s not looking great, no, but your experiment from cold showed that good performance was possible.
The drop in flow temperature is more than 0.5c, the requested flow is 36.0c and it had dropped to 34.7c. It is 1.3c below target and continues to fall unless I take action.
This is not in a short space of time, it happens over two hours or so.
I would have thought the heat pump would not take more than two hours to notice the flow temperature is not as requested.
It does have quite an impact though, I know the return is dropping too but so is the dT between the flow and room temperatures and therefore my potential heat output is impacted.
I try to raise the flow temperature but the heat pump doesn’t respond, I don’t expect it to be instant but I would have thought if the requested flow is 36.0c and the actual is 35.0c or less and I ask for 37.0c I would have thought to see some increase in 30 minutes or so.
In respect of the DHW, it does work better at times, probably related to tank temperature.
What I don’t get is why I am not seeing a higher heat output than 6kW or so during the DHW cycle?
Does it drop below R1T sensor (you know the one…)?
What if there is faulty logic here with Daikin somehow? I know it’s unlikely, but worth tracking your issue with regards to allowing flow temp to drop, and seeing if it correlates to the higher temperature of R1T.
My water coming into the house is the temperature as measured by the heat meter so that is that.
My temperature measured by the heat meter decays but it is roughly what is reported by R2T (I can only see round numbers on the MMI and app) and so is the same in the MMI and the app, but they are both below the requested.
As R1T is always higher than R2T then my flow temperature is always below R1T.
All I know is that R2T is reporting lower than my requested flow temp, my requested flow temp isn’t what is asked for and that my flow temp slowly decays over a couple of hours to at least 1.3c below what is requested.
I see this whether I use radiators with a fixed dT of 8c or fan coils with a lower dT.
I thought it might be because it cannot get to the dT of 8c at that flow temperature and rate but it behaves the same at times when I have a lower dT set.
At other times the flow temp just increases as the overshoot allows.
I don’t understand why it decays and fails to respond to requests to increase flow temperature.
I don’t have any leaks as I don’t have to add any water to the system.
I do notice the radiators lose their heat as it is struggling to raise the flow temperature, it is quite pronounced, you can really feel the heat disappear, like it has been sucked out of the house.
I also believe my DHW cycle isn’t producing the heat it should.
I remember in the early days it was suggested that it could be lacking refrigerant.
I don’t know that it is but what would be the symptoms of a lack of refrigerant, how critical is it?
R1T flow temp: 36.5C (we know somethings not right with this sensor where BUH exists)
R2T flow temp: 35.5C (you’ve said this closely matches your heat meter)
Your heat meter: 35.5C (what your heat meter is recording so we know it is very accurate)
In this example, the unit will allow (if minimum output allows) the flow temperature to drop if for some silly reason it’s using R1T (and not saying it is, just does the behaviour correlate to the sensor or not)
Have I misunderstood your numbers? (Quite possibly!)
- I want to be able to make adjustments against a reasonable baseline. So getting to understand the sensors and software’s actual performance etc. is important, rather than absolute cost/efficiency/whatever.
