Soldato
- Joined
- 14 Nov 2002
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- 7,805
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- Under the Hill
My property has been held at 22 degrees for the past week, 24/7. 100kw of energy used at unit rate of 15p (Ovo discount) and COP of 4.6 (long term average of 5.5).
Heat Pumps: anyone have one/thought about it?
- Thread starter fish
- Start date
Yes.
This is a transition house. By that I mean plan to sell next year. So no way going to spend the cash on a heat pump. And new windows/insulation and radiators.
You'll never get the money back.
This house leaks heat like a sieve. The cost to get it to heat pump spec would be insane.
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is that using a octopus heat pump tarif - I did the cost calculation with more capish 26p a unit w/o solar/batteries that comes in about the same £6 price,
your avg unit price seems to be 10p ish.
Because they have batteries so are using cheap overnight rate. Of course the cost is not really 10p because of the upfront cost of the battery but that is another discussion really.
I have a Daiken 9KW heat pump fitted by Octopus last year, the engineer left the install set to 50C @ -3C within the WDC setup. I also changed it to 45C, I see flow temps to 34-36C.
This is the only setting I changed. I am seeing a COP of 3.8
Can you find out how many defrosts was carried out on the Daikin unit or do you need to use the installer menu settings to see this information.
The only issue that I have with the Daikin is with the room thermostat keeps over shooting
Any tips in how to improve the setup on the Daikin would be appreciated
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170m2 detached house, Arotherm plus 7kW with a unitower tank. Temperature is set at 20.5°C 24/7. Hot water is set at 50°C and just reheats when the tank temperature drops by 6°C. WC is set to 0.45.
There was no radiator or pipework changes apart from for the tank and heat pump.
We are on IOG, have solar and 29kWh of batteries.
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If you are overshooting in this weather (you can’t change the thermostats operating range, it’s -0.5 below and +1.5c above target temp) either lower your compensation curve a bit or enable the modulation settings.
Doing it via the WC curve is the ‘correct way’. Modulation is a bit of a sticking plaster and should only really be used to compensate for solar gain which you can’t predict.
Edit: the other thing to make sure you do is lower the thermostats LED brightness they are renown for causing it to over read the actual temperature.
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Simple answer is to use an AI agent like Grok (xAI) and describe your system in as much detail as you can. Then describe your symptoms. The AI agent should then be able to parse documents and support posts etc.
Defrosts will be a more visual/audio thing to spot. You can also see the 10-15 min power draw spikes in the Octopus app if you are still with them and have no other monitoring like me. Having the Octopus Home Mini dongle helps so you can see additional 5 min & 30 min readings in 10 sec intervals.
Check emitter type. The Daikin default would be radiators (assuming no UFH) which automatically sets the Delta-T to 10C. Very safe and responsive but not as efficient. Highest pump speeds. You might find Octopus have selected fan coils which sets the Delta-T to 5C. Medium pump speeds. If so you can leave it as the closer the WDC gets to the actual house heat loss the less pump modulation and temp overshoot should occur.
What I suspect is your WDC curve is still too high and maybe too steep too. You can leave the warm set points for now and just lower the cold set points down to say 40C @ -3C. Worst case the house doesn't reach the thermostat set point. If so bump it up to 42C. If you reach the thermostat set point with less overshoot then next would be to nudge down a degree and test again. Larger houses take longer to see the results so high 30s will probably be fine because you also have modulation to help. Assuming large rads and decent insulation.
Final step would be to enable the Daikin thermostat modulation which can move the WDC curve up and down on the fly to account for other influences such as humidity and wind. I think default is 5. Higher allows more control but also allows more overshoot and pump modulation. With rads about 4 is as low as you want to go at first.
Installer menu is 5678. To get back to Advanced User you enter 1234. Must do that to allow the new settings to work (App will nag anyway). Many settings will force a restart.
I learned a lot in a couple of weeks by adding as much info as possible to the AI "conversation" and then kept asking questions.
Avoid any changes that require codes entered in the field settings! The AI might be a bit too over confident about making changes. Stick to the menu options.
One last thing, I believe there is a bug in the Daikin firmware. After making a change that forces a restart there is small chance the water heating schedule won't start. Don't panic as another reboot usually starts it. I remember the installers said that after they leave there was a chance with new installs the legionella cycle might fail. Didn't think anything of it at the time as mine worked first time.
That's always a good one to do as I have a -1C offset to my Madoka thermostat to get it to read the room temp accurately.
How have you got your pump set up on yours?
I’m having issues with ‘hunting’ where the heat pump can’t decide what modulation level to stick with and it swaps every 60 seconds or so.
The AI have been sending me in circles and asking me to change settings which simply don’t exist. The things they have suggested I change which do exist made it start cycling.
Any buffers or hydro-separation?
I couldn’t talk BG out of installing one, so we have one and a pump in the house - I’m teaching myself plumbing so I can pipe in bypass valves with the aim of being able to cut it out and see how it performs without - then if it shows improvements, tidy the piping layer.
I’m looking at this because currently we are hitting just over cop3.5 but curve is set at 0.3 holding internal temp’ of 21. I think this should return better efficiency. 100sqf with areotherm+ 5kw (underfloor heating) modern build etc.
No buffers, no volumiser as far as I'm aware, just took the boiler out, removed my zone valves, installed the uniTower and heat pump, adapted original radiator feed and return to the new system.
Sounds simple, but installer made a right hash of it, it's all in my solar build thread linked in my signature.
Plumbings pretty easy, I replumbed the entire house just over 20 years ago, installed several other systems prior to that as well, did have my fair share of leaks though!
Sounds simple, but installer made a right hash of it, it's all in my solar build thread linked in my signature.
Plumbings pretty easy, I replumbed the entire house just over 20 years ago, installed several other systems prior to that as well, did have my fair share of leaks though!
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Yeah, it doesn’t seem too difficult - I can’t decide between soldering, or renting a compression tool… but also I’m going wait for warmer weather!
Will have a read of your thread later - sounds interesting!
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Its Octopus Intelligent Go EV Saver, so 6p/kWh from 2330 to 0530. The majority of the units used were off peak or from the battery/solar, hence the low average cost.
At price cap prices (25.5p elec, 6.25p gas and no gas SC) its approximately a SCOP of 3 required over the year to break even with gas for us, so even in this cold weather its cheaper (yesterday COP was 3.5ish).
The house has been 20-22C the whole time. Our highest use yesterday when the temp was below 2C for the whole 24 hours was 26.3kWh on heating.
Daikin specific of course
I'm back to Fan Coil emitters with Delta-T set to 4C (modulation lowered this to 2C this morning).
I did try UFH set to 3C which was very steady and quiet but basically too slow to respond to changes when using rads.
I settled on WDC + Thermostat with Daikin room modulation set to 4
Pump mode is Request default for WDC.
Pump speed in sample mode 60% - This affects Request & Sample mode which is used by the HP controller to test the average system water temp when NOT actually heating.
Above this (15 l/m) in my house is audible above my bedroom in the early hours.
My WDC/LWT curve is quite compressed plus I have a small house with low heat loss and big rads. Octopus calculated 3.2kw at -3C but even that is overstated by the MCS process.
2 point mode
33C @ -5C
25C @ 12C
Very specific to my setup. Not entirely happy maybe too aggressively locked down. May bump the cold temp 1 to 2 C higher to allow faster temp recovery from cold.
In Fan Coil mode there are firmware limits to LWT of 55C & 25C but this shouldn't affect 99% of installations.
I do have quiet mode enabled from 10:00PM to 07:00AM but as I have plenty of capacity in my setup it's an easy 20% cap on the maximum power draw and flow rates (25 l/m to 21 l/m).
Does not affect DHW heating which will use max power/flow to heat by default.
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Ive gone back to fan coil with a delta T of 5 as I can hear the pump at night aswell. I think its when it does a defrost cycle as there's a sudden rush of water sound and then you can hear the pump noise from the radiator. Outside it doesn't sound any different
So fancoil is lower pump rate than radiator?
Pure weather compensation has worked well for us during this cold spell. Using the Madoka doesn't work well for us as its too affected by draughts and cooking/sunshine in the kitchen.
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I watched the Heat Geek YT vid about setting the Daikin MMI. Not well edited I was a little confused about UFH/FC/Rad description.
After playing with settings and some feedback from the AI agent searching I believe the following applies
UFH - Very slow response (partly to protect from screed cracking) Delta-T limited to 5C (see below)
FC - Medium also allows Delta-T to be adjusted 3-7C I think
Rad - Fast response but minimum 10C
Lower Delta-T values should slow the pump speed and modulation rate. Quite significantly if the AI agent is correct. Perfect to protect UFH from rapid temperature changes.
Having a flatter WDC was one suggestion from the AI to help reduce pump flow rate changes. LWT changes the flow rate so keep the range (as) narrow and the logic slow by selecting Fan Coil. Cap the maximum flow rate with a lower Delta-T if this makes sense. Keep the modulation reasonable so there is scope to adjust the WDC on the fly but not too rapidly.
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I'm curious as logic would suggest the opposite - fan coils transfer heat faster than radiators, so require higher pump speeds to hit the target delta T. Radiators are slower, so need a higher delta T and therefore less pump speed??
It's not clear anywhere really. How do you find quiet mode? Does it make a difference overnight?