My ASHP Journey in Bonnie Scotland.

cannugec5
cannugec5 Posts: 403
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edited 5 February at 8:37AM in Heat pumps
We have our new ASHP - just three weeks now and I want to get the best from it. 
As it was part funded by a renewables grant we also had a phenomenal amount of additional insulation put in the attic. 

We have 2 zones - upstairs and downstairs. I have so far left the settings as put by the installer. 20 downstairs 18 upstairs. I’m finding it far too hot at night but wonder if I need to give it time for me to adjust? ( Our previous oil heating was set to 13 overnight) I do understand that it works best on a static temperature. What temperature do others have their ASHP homes set at? 

I noted that Octopus (my supplier) offer the Cosy Octopus tariff and I thought about asking to switch to that ( if they can get my smart meter into smart mode). However I see that @matt_drummer doesn’t recommend it and I’d like to understand that a bit more. I get that you don’t want to put a timer on the heat pump but I thought I could shift other electricity use onto the cheaper periods and sometimes the pump would be on at the ‘right’ time, particularly if I’m careful about the timing of hot water use. We are both retired so home all day. 

Ive also not yet been brave enough to connect the thermostats to the Hive Hub. It requires me taking out the batteries for the thermostats to link them and I’m worried about getting it wrong. However I should know how to do it as I will have to if there is an issue ( or when the batteries die although I’ve been promised they last ages!). Once I have the Hive set up properly I feel I will be able to monitor temperatures better and see on the app whether the house really is too hot or if it’s just me (without constantly running up and downstairs) 

Other than ‘not fiddling with the settings’ are there any other tips or tricks to getting the best out of an ASHP?
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Comments

  • Cosy Octopus may work for you, it depends on how much electricity you use in total, when and what you could move into the lower rate periods and away from the peak.

    Assuming a heat pump is used to keep a home warm for most of the day a tariff that gives three hours low rate electricity at 04.00 to 07.00 and another three hours between 13.00 and 16.00 is not going to help much.

    Just concentrating on one of those periods the idea must be to get your home as hot a possible in those three hours and then use nothing and let the home cool down waiting for the next three hour period.

    Running the heat pump at a higher flow temperature in those three hours means that the heap pump is running less efficiently than it could meaning that the `cheap' rate of 18.43p per kWh isn't really that cheap.

    What happens between 16.00 and 19.00? You probably can't cook, your heating is now off and your home is cooling down. The heat pump will need to come back on at 19.01 to heat the home back up to get through the night, or at least later depending on the desired nigh time temperature.

    Then you have to wait to 04.00 to heat the home again on the lower rate.

    Somewhere in all of this you need to heat your hot water.

    Basically, not a lot of heating at the low rate each day 

    My svr from Octopus would be 27.93p per kWh

    On the coldest day running my heat pump at a low flow temperature I could use 30kWh plus say 10kWh for the house

    40kWh @ 27.93p = £11.17

    If my heat pump on this day was 300% efficient I have produced 90kWh of heat.

    If I used Cosy in the same way (even use spread over 24 hours) my cost would be

    (40 x 6/24 @ 18.43p) + (40 x 15/24 @ 30.72p) + (40 x 3/24 @ 49.15p) = £11.98 


    So on Cosy Octopus I need to run a higher flow temperature to generate the same amount of heat using the cheap periods so lets say it is now 200% efficient.

    My heat pump would use 45kWh to produce 90kWh of heat in 6 hours. 

    That is 45 x 18.43p = £8.29

    There is also my house load which if I split equally over the day as before would cost £3.00

    My total cost is now £11.29


    Cosy and the SVR produce similar results cost wise.

    But Cosy isn't great, my heating is limited in cost terms to 6 hours and I really need to avoid 16.00 to 19.00 hrs.

    I think you would spend similar amounts of money but suffer more inconvenience and will be too hot and too cold at times.



    The example is made up but based roughly on my house and heat pump. You can play around as you wish with your own figures.

    But that is why I don't like it, no real saving and a load of hassle to make sure you don't spend more.

    Maybe some other people have different ideas?
  • FreeBear
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    matt_drummer said: So on Cosy Octopus I need to run a higher flow temperature to generate the same amount of heat using the cheap periods so lets say it is now 200% efficient.
    During the hours of 04:00 to 07:00, the air temperature is going to be quite a bit lower than it would be later in the afternoon. So the ASHP will have to work even harder, and you might not even get to 200% efficiency.
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  • I just had a check and I remember you had a topic about your heat pump and the HIVE system.

    I have a  Daikin heatpump with their MMI controller and a Daikin Madoka thermostat.

    I do not use the thermostat as a thermostat though.

    I have set up pure weather compensation so that my heat pump controls it's leaving water temperature by reference to the outside temperature.

    At the moment the graph that it runs from is set with leaving water temperature of 45c @ -5c outside and 20c at 18c outside (20c lwt is basically off)

    This graph has a slope (obviously) so as it gets colder outside the heat loss of the house increases and therefor the leaving water temperature of the heat pump needs to go up adding more heat to the house.

    The aim is that eventually the heat pump runs as continuously as possible as the heat produced exactly matches the heat loss of our house.

    If the home is too hot at a particular outside temperature then our thermostat is used to reduce the leaving water temperature by however much is necessary to make us comfortable.

    I don't really care what the actual temperature is, our radiators are sized to run at 18c upstairs and 21c everywhere else. I leave all the trvs wide open, I don't want the radiators closing.

    Over time this graph is fine tuned so that the house is always at the right temperature for us compared to outside.

    This results in being able to run at the lowest flow temperature necessary and is most efficient for us.

    We set back by 4 degrees over night but I don't want the heating on and off like our gas boiler was.



    If you are hot at night then you can adjust the temperature in that zone and set it lower when you need it. 18c is probably hotter than most people want for sleeping.

    But if it is always too hot upstairs it could be that the radiators are too big, that is too big compared to those downstairs. That means you could fit bigger radiators downstairs and lower your flow temperature. Your bedrooms would be cooler whilst maintaining the temperature you want downstairs.


  • matt_drummer
    matt_drummer Posts: 1,312
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    edited 20 September 2023 at 12:49PM
    FreeBear said:
    matt_drummer said: So on Cosy Octopus I need to run a higher flow temperature to generate the same amount of heat using the cheap periods so lets say it is now 200% efficient.
    During the hours of 04:00 to 07:00, the air temperature is going to be quite a bit lower than it would be later in the afternoon. So the ASHP will have to work even harder, and you might not even get to 200% efficiency.
    Yes, could be, depends on the day.

    Also the heat pump may not be even that efficient on the coldest days at the highest flow temperatures at any time of the day.. There are also defrost cycles that I left out completely. Not only will they take away form heating time, but they would also be necessary during the peak periods.

    I chose the figures for simplicity and there's a bit of `artistic' licence.

    It is the first time I had written it down because to me, an accountant, it was obvious how it would work out.

    Maybe I have something wrong though?


    I don't think it is much of a heat pump tariff, I think it's pretty awful.


    I wouldn't go near it as I run my house (including my heat pump) from the sun and E7 electricity using batteries (a lot of batteries!)
  • QrizB
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    I'd always assumed the two cheap-rate periods on Cosy Octopus were intended to support water heating, rather than space heating. If you need a flow temp of 50C plus to heat your DHW tank, you'll have a lower COP and so cheaper electricity will be useful.
    But I could be entirely wrong!
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  • cannugec5 said:
    Other than ‘not fiddling with the settings’ are there any other tips or tricks to getting the best out of an ASHP?
    I'd say actually fiddling with the settings is the best thing you can do, once you know what the most important settings are and what they do.

    Main things to check are the hot water temp, how low it's allowed to go before heating up again, whether you want to schedule hot water and/or heating (i.e. allow it to kick in only at certain times - some models allow you to refine it by days of the week although probably less relevant to you than to people going out to work in the week), legionella cycle, whether there is a setback temperature for overnight, things like that.

    You'll also want to keep an eye on the energy consumption and output to see how efficient it's being, and in summer to see whether it's a vampire load model (you'd hope not, but better to know for sure).
  • cannugec5 said:
    Other than ‘not fiddling with the settings’ are there any other tips or tricks to getting the best out of an ASHP?
    I'd say actually fiddling with the settings is the best thing you can do, once you know what the most important settings are and what they do.

    Main things to check are the hot water temp, how low it's allowed to go before heating up again, whether you want to schedule hot water and/or heating (i.e. allow it to kick in only at certain times - some models allow you to refine it by days of the week although probably less relevant to you than to people going out to work in the week), legionella cycle, whether there is a setback temperature for overnight, things like that.

    You'll also want to keep an eye on the energy consumption and output to see how efficient it's being, and in summer to see whether it's a vampire load model (you'd hope not, but better to know for sure).
    I know what the water temperature is set at and the legionella program, although I’ve no idea how to adjust these settings. 
    The little box with all the settings has a warning label that it is NOT to be adjusted by the householder and should only be used by the installer. 
    I am accustomed to doing monthly meter reads, submitting them and completing my own spreadsheet. I am looking forward to comparisons . Our oil bill had reached £1200 per year ( before the system died) so I can anticipate an extra £100 a month on electricity before it’s costing anything. 

    I’m surprised that you suggest it could be possible to refine the program by days of the week or times etc. I thought the whole point is to leave it as constant as possible so it isn’t trying to heat from cold. 
  • Reed_Richards
    Reed_Richards Posts: 3,977
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    edited 21 September 2023 at 6:58PM
    I know nothing whatsoever about Cosy Octopus but would disagree with the statement that a heat pump works best at a static temperature.  A heat pump works best, i.e. most efficiently, when the target water temperature is as close as possible to the outside temperature.  If you like your house to be cooler at night then if you can reduce the target water temperature that will have the desired effect and give you more efficient operation.  However you may find that the house warms up again quite slowly, in which case you need to ask for the temperature to be increased an hour or two before you actually get up.  My Drayton Wiser has a "comfort" setting that will do this automatically so I imagine a Hive controller will do the same.  Unless it's very cold outside, my heat pump just turns off between 22:30 and around 04:00 in order to maintain a set-back temperature on the thermostat because the house (fortunately) doesn't cool down too fast.

    Make the heat pump conform to your comfort requirements, don't sacrifice your comfort to conform to what you imagine the heat pump wants to do.  
    Reed
  • Here's how the temperature of my two zones varies over a few days.  They cool down at night then warm up gradually during the day to be warmest in the evening when I am most sedentary.  My heat pump manages this perfectly well and because the warming is gradual there is very little practical difference to maintaining a constant temperature.

      
    Reed
  • cannugec5 said:
    cannugec5 said:
    Other than ‘not fiddling with the settings’ are there any other tips or tricks to getting the best out of an ASHP?
    I'd say actually fiddling with the settings is the best thing you can do, once you know what the most important settings are and what they do.

    Main things to check are the hot water temp, how low it's allowed to go before heating up again, whether you want to schedule hot water and/or heating (i.e. allow it to kick in only at certain times - some models allow you to refine it by days of the week although probably less relevant to you than to people going out to work in the week), legionella cycle, whether there is a setback temperature for overnight, things like that.

    You'll also want to keep an eye on the energy consumption and output to see how efficient it's being, and in summer to see whether it's a vampire load model (you'd hope not, but better to know for sure).
    I know what the water temperature is set at and the legionella program, although I’ve no idea how to adjust these settings. 
    The little box with all the settings has a warning label that it is NOT to be adjusted by the householder and should only be used by the installer. 
    I am accustomed to doing monthly meter reads, submitting them and completing my own spreadsheet. I am looking forward to comparisons . Our oil bill had reached £1200 per year ( before the system died) so I can anticipate an extra £100 a month on electricity before it’s costing anything. 

    I’m surprised that you suggest it could be possible to refine the program by days of the week or times etc. I thought the whole point is to leave it as constant as possible so it isn’t trying to heat from cold. 
    Can you post a photo of your controller with the warning not to change anything?  Just want to be sure we're thinking of the same thing!

    The controller may have consumption/output data in kWh, which tells you the efficiency of the system.

    I'm not suggesting heating should be turned on and off (although we do turn it off overnight as we don't have a setback temperature - it was kicking in full pelt at 3am when it wasn't needed!) but the refinement by day can be useful for hot water if you don't need the whole cylinder heated every day.  If there are setback temperatures then there could be advantages for setting a lower temp in the daytime in households where nobody's home (not applicable to you though, of course).

    There is also the option of a weather compensation curve in order to have heating on most consistently and efficiently, but that's something beyond me.

    I'd recommend trying to have a look at the more granular settings even if you don't touch them yet, just so you know your starting point if you then have to troubleshoot.

    Unfortunately just leaving it on the settings the installer set can be expensive.  It's best to get to know your system if possible.
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