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?
Get a copy of 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.
Get a copy of 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."
Get a copy of 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
- 2,242 Topics
- 49.9 K Posts
- 436 Online
- 5,903 Members
Join Us!
Podcast Picks
Latest Posts
-
@majordennisbloodnok Good explanation I thought ὠ...
By bontwoody , 5 hours ago
-
RE: Mitsubishi Ecodan R290 10kW performance
I am using my Powervault electricity monitoring App to ...
By Ecoste , 5 hours ago
-
RE: Daikin Octopus installation update - I saw my first defrost. 😍😂
After installation the system did develop a noise in th...
By RadWhisperer , 5 hours ago
-
RE: Help me keep the faith with my air source heat pump installation
@jamespa it doesn’t seem to matter the outside temp it ...
By AdamK , 6 hours ago
-
Apologies as my post clearly interrupted this flow. Whe...
By Batpred , 7 hours ago
-
RE: One room is colder than the rest of the house
I would personally be sceptical about reaching any conc...
By JamesPa , 7 hours ago
-
RE: My experience with 3 heat pump surveys: Heat Geek, British Gas & Octopus
If you paid for any of the assessments try asking for t...
By JamesPa , 9 hours ago
-
@drei Thats a nice designer radiator which it would ...
By JamesPa , 9 hours ago
-
I've created a separate post here, wondering about radi...
By DREI , 10 hours ago
-
RE: Air source heat pump roll call – what heat pump brand and model do you have?
@ecoste, @walnut-tree-cottage these are both great piec...
By JamesPa , 11 hours ago
-
RE: New build installation query
That suggests to me that you have loss of heat in the p...
By Transparent , 13 hours ago
-
RE: Solar inverters - where does the energy go when clipping?
You will, of course, check the dimensions and weight be...
By Transparent , 15 hours ago
-
RE: Midea ASHP – how to set weather compensation
@pash44pump - there may be other ways you can improve t...
By cathodeRay , 16 hours ago
-
RE: What should we do with our Aga?
@annahickson We had a similar dilemma with our oil-fire...
By Morgan , 17 hours ago
-
RE: The Hidden Secret to a Successful Heat Pump: Pipe Size Matters
17l/min is enough for only 6kW at 5C DT, not surprising...
By JamesPa , 18 hours ago
-
@bontwoody The extra battery capacity is the solution f...
By Toodles , 19 hours ago
-
RE: End of Summer Time Reminder to Ecodan owners
As I understand it....ha....Melcoud will over ride any ...
By Abernyte , 19 hours ago
-
Finding flow temp data from Samsung 16kw HP
Hello, I have a Samsung MIM-E03 16kwh heat pump, and ...
By martingale , 1 day ago
-
RE: Faulty Clivet heat pump out of the box
We would never win these projects as we spend 1 whole d...
By ASHP-BOBBA , 1 day ago



