Posted by: @batalto

@adaml there is one in my signature. It's very straightforward, just make your own copy and off you go

Thank you - I ended up using this!

@derek-m

I have put in all of the data into your excel and for a 21° indoor temperature get 50°C flow @ -5°C and 25°C flow @ 20°C. If I increase the insulation building regs so as to reduce the heating demand (which I think is probably nearer the true values) then the result is 48°C flow @ -6°C and 23°C flow @ 20°C.

@adaml 

Hi Adam,

No two ASHP's coming off the production line are going to perform exactly the same, just as no two installations are going to have the same operating parameters. The aim of the modelling tool is to provide reasonably accurate initial values, which can then be fine tuned to provide the best overall performance.

@derek-m 

Thanks Derek, that makes sense.

The installer had the weather dependent curve set at; 55°C flow at -5°C and 35°C flow at 20°C when we moved in. I had little data to go on and decided to bump this down slightly to 50°C flow at -5°C and 30°C flow at 20°C, which actually fits nicely with the data I now have. I will leave this set for the Spring, along with the reduced DHW temp of 48°C. The schedule is also now set to 21°C from 05:00 till 23:00 and 16°C overnight.

I have left this here for reference and so if anyone else with a similar setup wishes to start on the long and very interesting road of optimising ASHP usage they have some data to go on.

Thanks for everyones help so far, I am very grateful.

Happy New Year everyone 😊 

I have been continuing to monitor my system and believe I've managed to make some improvements. I found the setting that was allowing the ASHP and gas boiler to fire simultaneously and have now disabled this.

The Daikin stats are difficult to pull as you can only look at month to date, so as it's a new month I thought I'd take a look. Today's COP is 3.5, which seems a little low.

I have one potential concern that I'd appreciate some feedback on, the compressor shows as having been running for 2 hours today with 27 starts. This seems rather high? I wonder if this indicates anything in particular?

The December average COP was 3.47. On the 6th December this was 1.6 average so the warmer end to the month and no doubt tuning have definitely helped. I have lowered the curve to 45 at -10 and 25 @ 18 and have the adaptive LWT enabled to off-set this curve not necessarily being optimal.

I've been looking through the installer settings and the Delta T is currently set at 10°C

Posted by: @adaml

I've been looking through the installer settings and the Delta T is currently set at 10°C

The range is 3~10°C, step: 1°C

The default is 5°C.

Would it be possible for someone to explain this setting and the rationale for the optimal setting?

Hi Adam,

I am not certain I know as to what you are referring when you say Delta T. Do you have a manual reference or page number?

Your ASHP should not be switching on and off (cycling) so frequently, what are the various settings and temperatures?

@derek-m 

Thanks so much for getting back to me, really appreciate your time.

Description

[A.3.1.3.1]

[9-09]

Heating: required temperature difference between entering and leaving water.

In case a minimum temperature difference is required for the good operation of the heat emitters in heating mode.

Range: 3°C~10°C (in steps of 1°C; default value: 5°C).

It is currently set at 10°C - what do you think?

The outdoor temp tonight is 9°C. The thermostat on the Daikin controller is set to 21°C. The desired flow temp was showing as 31°C. I bumped the thermostat up to 23°C to see how the unit would respond and the desired flow temp then changed to 34°C which seems to be using the maximum modulated LWT value of 3°C. The weather dependent curve is currently set to 45°C at -10°C and 25°C @ 18°C.

The values were climbing, below is a snapshot;

Leaving water 27.3°C

Leaving water (PHE) 27.1°C

Inlet water temp 22.3°C

Refrigerant temp 22.5°C

Flow rate 13.0l/min

Could the cycling be affected by the weather dependent curve being sub optimal?

Hi @adaml 

I can't remember who was the manufacturer, but they were stating that for optimum operation of their heat pump, the Delta T should be in the 4C to 5C range. So you could give this setting a try.

I would have expected that with an outside air temperature of 9C, your heating would be provided by your gas boiler.

One of the problems with domestic heating systems is the wide range of conditions over which they are expected to operate. With gas and oil boilers and the like, they heat the water in the heat emitters to a temperature above that required to meet the heat demand, and then shut off for a period of time whilst the heat energy is dissipated into the home. ASHP's on the other hand can operate more efficiently when running constantly at lower water flow temperatures, but as the outside air temperature increases there comes a point where even when operating at its minimum output, the heat pump is producing more heat energy than is required, and must be shutdown for a period of time.

The frequency with which the heat pump starts and stops, along with the length of time for which it runs, is dependent upon a number of factors.

The present heat demand.

The heat energy output at minimum operating conditions.

The produced water flow temperature.

The setting of the control parameters.

I remember reading that one of the manufacturers stated that their heat pump should not start and stop more than 6 times within a 1 hour period, and some manufacturers have incorporated a timer to prevent the heat pump from restarting for a certain length of time. I would suggest that you have a read through the manual to see if there are any specified requirements for your system. Also check to see if there are any settings that may need to be adjusted.

With thermostat control there is already a built in hysteresis, which means that by the time that the thermostat has sensed and reacted to the increase in room temperature, the heat emitters are already warmer than actually required to meet the heat demand. So the heat source is shut off until the room temperature falls to a level where the thermostat once more switches on the heat source. Most thermostats also have an inbuilt hysteresis of 0.5C or 1C, which means that the room temperature has to fall from say 21C to 20C before the thermostat switches.

 Try increasing the maximum modulated LWT value of 3°C to 10C, and see if this has any effect on the cycling that is occurring.

@derek-m 

Thank you. Delta T is now at the default of 5°C. I have increased the LWT max modulation to 10°C with the same curve set.

As you suspected the room temp hysteresis is set to 1°C.

It is interesting that you would expect the gas boiler to have taken over at 9°C. Due to the advice earlier in this thread I had the system setup to allow the gas boiler to function at temperatures below 5°C. Our fixed tariff has just ended and gas is now 4p/kWh and electricity 20.39p/kWh. The updated pricing is programmed into the controller. I raised the equilibrium temp to 15°C (the installer default, perhaps to allow the controller to work out most economical based on programmed pricing) and the ASHP is still carrying out space heating today. The outside temperature is co-incidentally 9°C this morning as well.

At what temperature would you suggest the space heating be provided by the gas boiler?

[A.5.1.4]	[5‐01]	Equilibrium temperature. Outdoor temperature below which operation of the backup heater is allowed. Range: –15°C~35°C (default: –4°C) (step: 1°C)

Hi Adam,

How are you getting the actual true COP, are you getting this from Daikin or external equipment monitoring it?

If it is from Daikin how are you achieving this? I can see on the screen under the Information menu you have a basic readout of the energy used and the heat produced (very vague graphs though) but cannot see a COP measurement. Yes you can divide heat produced by the energy consumed but the graphs are too vague to get accurate measurements.  I am really disappointed in my Daikin unit in this regard, for such a expensive device the monitoring is extremely poor. 

Thanks. Adam

Hi @adaml 

I was basing my assumption that your system would be running the gas boiler in preference to your heat pump, from the tariffs that you had provided, which indicated that your heat pump would need to achieve a COP of over 5 to make it viable financially. This would probably have occurred at an outside air temperature around 14C.

Based upon your new gas and electricity price tariffs, and assuming an efficiency of 90% or above for your gas boiler, it would be financially viable to run your ASHP when it can achieve a COP of 4.6 or above. This now sets the changeover point at approximately 7C, so it is quite possible that your ASHP could now be selected to operate.

I think that you may be confusing Backup Heater (electric heater) with Auxiliary Heater (gas boiler). The electric backup heater is an optional extra that may have been installed, it is designed to support the ASHP in very cold weather conditions when the heat pump may be struggling. You should only allow a backup heater to operate as a last resort, since it is basically like an immersion heater with a COP of 1, and will soon burn through your bank balance.

@adam-c 

Hi Adam,

Totally agree, the reporting is extremely poor - can only get month to date and previous months.

When you're looking at the graphs if you press the right and left buttons it goes month by month and the figured displayed at the top right is the kWh that month. The respective bar in the graph is highlighted black. As you say it's just a case of doing the maths.