delta T = 10 (Daikin)
I saw this article that mentions that Daikin recommend delta T =10 for radiator circuits. Does anyone know which of Daikin's ASHPs this applies to? (I asked Daikin, but they said to ask an installer, which didn't help much...)
https://renewableheatinghub.co.uk/heating-technology-heat-pumps-2025/
That's hysterical that a manufacturer would defer a question like to this to an installer.
@grahamh do you have any words of knowledge here?
Buy a copy of the The Ultimate Guide to Heat Pumps
Subscribe and follow our Homeowners’ Q&A heat pump podcast
Posted by: @editorThat's hysterical that a manufacturer would defer a question like to this to an installer.
That was Daikins answer to every single question I asked them during my discovery phase.
...Which is one of the reasons I discarded them from consideration.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
@rhh1, I’ll contact Daikin’s brand manager tomorrow and see what they say.
Buy a copy of the The Ultimate Guide to Heat Pumps
Subscribe and follow our Homeowners’ Q&A heat pump podcast
That seems like a large number. Our Grant Aerona 290 15.5kW is running with a Delta T between outlet and inlet of 2.7C at a current flow temperature of 28C. We have 30 radiators. During the hot water Legionella cycle the flow temperature of 61.3C has a Delta T between inlet and outlet of 4.1C.
Grant Aerona 290 15.5kW, Grant Smart Controller, 2 x 200l cylinders, hot water plate heat exchanger, Single zone open loop system with TRVs for bedrooms & one sunny living room, Weather compensation with set back by room thermostat based load compensation
Posted by: @grahamfThat seems like a large number. Our Grant Aerona 290 15.5kW is running with a Delta T between outlet and inlet of 2.7C at a current flow temperature of 28C. We have 30 radiators. During the hot water Legionella cycle the flow temperature of 61.3C has a Delta T between inlet and outlet of 4.1C.
Crazy large and unexplained so far as I know, I had heard Daikin recommend this. 10% efficiency penalty compared to DT of 5 (because average emitter temp is 2.5C lower for any given flow temp) unless somehow the Daikin pump works better with larger DT. Perhaps daikin fit undersized water pumps so need to run slower hence higher DT?
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
@jamespa Ours is a Daikin EDLA03 8 kW and the Delta T = 5, as I mentioned before; the pump starts a cycle at ~28 l/m and later drops to ~15 l/m. The DT seems to stay pretty close to 5 at all times. We have an LLH and secondary pump which I have set at ~15 l/m. Regards, Toodles.
Toodles, heats his home with cold draughts and cooks food with magnets.
@jamespa That's an interesting point! I was thinking that having a delta-T of up to 10C would be a useful degree of freedom to avoid having too high a flow-rate, and hence a high pressure-drop, through microbore pipe-runs. But if their reason for supporting a delta-T of 10C is to circumvent an undersized water pump then I'd be back to square one...
Posted by: @rhh1@jamespa That's an interesting point! I was thinking that having a delta-T of up to 10C would be a useful degree of freedom to avoid having too high a flow-rate, and hence a high pressure-drop, through microbore pipe-runs. But if their reason for supporting a delta-T of 10C is to circumvent an undersized water pump then I'd be back to square one...
So far as I can tell designing for DT5, which is 'the norm', is a convention not an absolute. I have seen people argue that a higher DT is preferable or that, due to some unspecified mechanism in the heat pump, no lower than 3C DT is desirable, but none of these arguments have been supported by any coherent explanation at least IMHO.
Thus, in the absence of a coherent explanation I fall back to the physics which is that:
- lower DT = Higher average deltaT (emitter-room) for any given flow temp = good (because of heat pump efficiency)
- higher DT = lower flow rate for any given heat delivered to the emitters = good (for water pump efficiency, pipe erosion and pipe noise)
Thus its a trade off which in principle is specific to any given house, but one where DT about 5 is reasonable in many cases, which does not mean that you shouldn't depart from that. Openenergy monitor did once have a thread on the trade off which suggested 2-3C was optimum for the specific conditions in question (but not for other conditions)
So you are right that a higher DT does avoid high flow rates and if thats a problem feel free to accept a higher DT. However if it isn't keep DT as low as you can within reasonable parameters. Or, put another way, dont get too hung up about it if departing from the norm or a manufacturers recommendation makes the design work!
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
@rhh1, got a reply from Daikin. There brand manager was way on holiday. He's replied saying, "The delta of 10 for the radiators applies to all our air to water heat pumps. Please let me know if you require more info on this."
Buy a copy of the The Ultimate Guide to Heat Pumps
Subscribe and follow our Homeowners’ Q&A heat pump podcast
Posted by: @editor@rhh1, got a reply from Daikin. There brand manager was way on holiday. He's replied saying, "The delta of 10 for the radiators applies to all our air to water heat pumps. Please let me know if you require more info on this."
I think, based on what others have said here, that the Daikin adjusts its water pump to get the required DT. Others have said that you are asked somewhere in the menu to tell it what type of heating you have (UFH/Rads) and it decides the DT to control for based on this. If thats all true then the recommendation has surely got to be tell it UFH no matter what you have unless there is some other reason not to or the setting has other 'effects'.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
- 26 Forums
- 2,208 Topics
- 48.7 K Posts
- 70 Online
- 5,868 Members
Join Us!
Podcast Picks
Latest Posts
-
I'm assuming you're referring back to this post by @edi...
By Transparent , 3 minutes ago
-
RE: Air source heat pump roll call – what heat pump brand and model do you have?
Panasonic Model WH-WDG05LES 5KW Thermino ePlus 210 Li...
By Darrell P , 10 minutes ago
-
RE: Samsung Heat pump with Yonos Pico circulating pump running all the time
@pirate-rich thank you, I will pass this onto the elect...
By LCH07 , 1 hour ago
-
Thanks for that clarification @majordennisbloodnok - mu...
By Transparent , 2 hours ago
-
RE: Forum updates, announcements & issues
We've had a slight glitch with our security software fo...
By Mars , 3 hours ago
-
@bontwoody I rather feel that this drawn out episode is...
By Toodles , 3 hours ago
-
RE: The Hidden Secret to a Successful Heat Pump: Pipe Size Matters
Er...no comment!
By JamesPa , 4 hours ago
-
RE: 4 Year Ongoing Heat Pump Battle With Poor Heat Pump Installation
@fiona sorry to hear that, and I sympathise with you be...
By Mars , 4 hours ago
-
RE: Samsung Heat Pump – Can't Activate TW2 Pipe Sensor (for Delta T Control)
If you do suggest you consider repurposing it as a 2 po...
By JamesPa , 14 hours ago
-
RE: Say hello and introduce yourself
Fully agree with @cathoderay. My journey took 2 years ...
By JamesPa , 16 hours ago
-
RE: RDSAP10 effect on existing heat pump EPC rating?
Tim, Yes ChatGPT thought I could get another...
By Mike Patrick , 1 day ago
-
RE: Enabling WiFi: Samsung ASHP on Smart Things App
No problem, @richdorm; glad it helps.
By Majordennisbloodnok , 1 day ago
-
RE: Help me keep the faith with my air source heat pump installation
If that makes you feel happier then go ahead, but it wo...
By JamesPa , 1 day ago
-
RE: Testing new controls/monitoring for Midea Clone ASHP
I do already have the same basic setup, all room influe...
By cathodeRay , 1 day ago
-
RE: IVT Greenline high pressure switch and electrical cassette errors
OK. You dont say whether it is from the feeds to/from ...
By JamesPa , 1 day ago
-
RE: How can I programme a setback for my Samsung Gen6 8kW heat pump?
Yes, and probably also Adia although the latter has a m...
By JamesPa , 2 days ago
-
RE: How to Understand Wiring Up a Heat Pump
Morning, On top of what everyone else I would deffo loo...
By Grantmethestrength , 2 days ago