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Daikin Altherma 3 Steady State Operation

Air Source Heat Pumps (ASHPs)

Last Post by Toodles 2 years ago

4 Posts

2 Users

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pj_preston

(@pj_preston)

New Member Member

Joined: 2 years ago

Posts: 4

Topic starter 06/11/2024 5:55 pm [#1839]

New Heat Pump Owner and First Post on the Forum

We had a heat pump installed in September by Octopus Energy. The initial operating settings didn't meet our requirements and I have adjusted the WD curve and changed the control from the Madoka unit, to LWT - WD

The WD curve I have selected is set at:

2 Point Curve

40C Max @ -8C OAT

25C Min @ 15C OAT

Because the Daikin OneEcta app doesn't really show when space heating or water is actually being called for and because I thought it could be useful to indicate and confirm consumption of the new system, I decided to install a Shelley EM and add it into my Home Assistant instance.

I have added an Image of the data screenshot for a 24 Hr Period and also a 2 Hr period, just to give a bit more detail. It isn't quite the sort of operation from the heat pump that I was expecting and I would appreciate any feedback and comments.

I can confirm that the water pump operates for 4 minute cycles with 4 minutes rest until I presume the temperature being sampled drops to the required level it is looking for, whereby it then applies heat for another variable amount of time, again I presume until the water returned reaches another expected threshold temperature and the signal to turn off the heat is applied?

I was expecting something that showed a modulation up and down, not this On / Off display.

Thanks in advance.

24hr_Heat_Pump_Power_Graph.pdf

2hr_Heat_Pump_Power_Graph.pdf

👍

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Toodles

(@toodles)

Famed Member Contributor

Joined: 4 years ago

Posts: 3031

07/11/2024 4:03 pm

With my limited vision, I may be missing the finer details of your graphs but the ‘timings’ look very ‘mechanical’ as though despite your needs, the pump has a setting based on time rather than needs. I too have a Daikin with the MMI and the Onecta app is of little merit or use to me other than to report an approximation of consumption. Homely presides over the operation of my system so is not a direct comparison by any means but I am attaching a graph from the last 24 hours indicating OAT, IAT and pump cycles in case this is of any assistance. If you look at the list of available data and you notice any that you would like me to include, please ask. I tried to reduce the amount of values on any one chart for clarity - it looks rather busy otherwise!

Regards, Toodles.

Toodles, heats his home with cold draughts and cooks food with magnets.

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pj_preston

(@pj_preston)

New Member Member

Joined: 2 years ago

Posts: 4

Topic starter 07/11/2024 5:13 pm

@toodles Thanks for the reply and data. Mine does look very mechanical. I found a setting in the MMI for the Pump and it was as I thought set to "Sampling". I changed this at 14:00 to "Continuous" and have added an extra screenshot below. It has flattened out the sampling cycles between the calls for heat and made it a little easier to see how the heat pulses have variable times of duration. My system is based purely on outside temperature and I presume this is what is affecting the pulse width. I have plans to add external temperature measurement and also flow and return temperature measurement. I just need a little time to get up in to the loft to add the sensors.

My main concern was to try to establish that the Heat pump is working correctly and as the manufacturers, intended. I think I have read that the pump is set to sampling to save costs. I will leave it on continuous for 24 hours to evaluate what happens.

I was very interested in Mars's video regarding heat pump monitoring, with Homely and the other contributors.

Could I take you up on your offer to supply another graph?

Could it include: Inside Temperature, Outside Temperature and Estimated Power Input. (My Shelley device is just a current clamp with mains voltage sensing so it may help me to understand a little better.

Is the Homely device connected to your heat pump via an interface, which it can then access all the heat pump data in real time and adjust the settings of the heat pump to maximise comfort and minimise costs, based on your energy suppliers tariff?

Regards, pj_preston

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Toodles

(@toodles)

Famed Member Contributor

Joined: 4 years ago

Posts: 3031

07/11/2024 5:40 pm

@pj_preston The Homely smart controller is connected to the Daikin via the MMI and uses Modbus (they use a D.comm unit to accomplish this). If you read my review on RHH, it describes the control it provides but basically it takes over from the WC settings, compares temperatures OAT and IAT, monitors losses, weather, solar gain etc. and ‘micromanages’ the whole system. From installation, it takes a week or so to ‘learn’ your system and your needs then just gets on with the job. Regards, Toodles (graph as requested attached).