@crustydoodle

Do you have a buffer tank within your system?

I presume your installer did not supply a list of all the controller settings?

I presume that your heatmiser sends a signal to start and stop the heat pump? How many thermostats do you have on your system?

Looking at your graphs, though I cannot read the scaling, it would appear that your heat pump is raising the Leaving Water Temperature (LWT) until it reaches an upper limit. The LWT then cools until it reaches a lower limit, at which point it reheats the LWT. It is therefore operating in a similar way to your hot water cylinder, which heats up, cools down, then reheats.

I would suggest that you provide photo's of the different controller screens so that it may be possible to ascertain how your system has been set to operate.

@derek-m Thanks for all the responses on this.  See attached the current summary settings in the pics.

The heatmiser does start and stop the heatpump - I have just turned all 11 stats on to test things out more thoroughly and the ASHP is active with the flow temp running at about 32°C.

You assessment of the charts is the same as mine.  When the flow and return temps drop to around 30°C then the ASHP kicks in and raises the temp to 60°C.  The flow target is 55°C so it is overshooting a little.  I think it is just heating what is in the loop and bypassing the DHW and the UFH or maybe sending it around a bit of the UFH loop and not into any of the actual zones - I can't prove that as far as I can see.

@crustydoodle

A photo of the main screen may indicate the mode of operation.

Here you go.  Heating is on as I took this photo with the ASHP active.

@crustydoodle

The photo shows that your system is operating in WC mode, so I would suggest that you watch the video below to see what settings have been applied.

https://www.google.com/search?q=setting+ecodan+weather+compensation&rlz=1C1OPRB_enGB514GB552&oq=setting+ecodan+wea&aqs=chrome.4.69i57j33i10i160l3j33i22i29i30.20475j0j7&sourceid=chrome&ie=UTF-8#kpvalbx=_JcANZdzOOMSDhbIPhNOn6Ag_34

It's set at:

40°C @ -2°C

30°C @ 17°C

Posted by: @crustydoodle

↑

It's set at:

40°C @ -2°C

30°C @ 17°C

Those seem reasonable for UFH, though you may wish to optimise the settings during the heating season.

I would suggest that you now go through all the controller settings, both in the user and installer menu's, noting down each setting, for future reference, and to possibly locate the cause of your present problem.

@crustydoodle,

this definitely isn't normal.  My Ecodan doesn't do this; nor does any other I have heard of.  What is puzzling is that it all does look perfectly normal when the heating and water are working normally; it's only when idle that it behaves strangely.  

From the traces it looks like your LWT and RWT are increasing by about 35 deg in 15 minutes.  It definitely won't be heating the entire volume of water in your ufh system in that time as your 11.2 kW Ecodan physically couldn't do that so fast (look how long it takes when the heating is working normally).  I don't know much about ufh but most/all of the ufh pipes must be shut off and a small amount of water is circulating and being heated to create the effect you are getting. The fact that the flow is not losing any heat also supports that it's not being circulated around the ufh pipes.  

Perhaps you could ask the supplier to explain exactly what the traces are showing based on your system, rather than just saying (or repeating Mitsubishi saying) that it's normal.

I wouldn't be so quick to dismiss the F9 error message either. Any error message indicates something not having functioned correctly. A quick search tells me it is to with pressure switch contacts – not that I can explain that any further.  I would speculate that these are located in the outdoor unit. I presume this error message caused a complete shutdown?

The identical flow and returns temps show that the heat being put in to the primary flow through the outdoor unit is not being taken out by circulation through the heating or hot water circuits, it is only the primary pump that is working until the flow temp reaches 60 which is the maximum that the HP is designed to get to, when it stops. The question that can't be answered from the MelCloud charts is what is the heat pump itself doing? Is there any noise coming from it when it isn't supposed to be doing anything? Is it actually running at full pelt when the water temps are climbing so quickly?

(This scenario is entirely of my own devising but, for example, if the compressor was continually running at a low level and generating heat in the exchanger but no water was being circulated then the heat could build up to the point where it triggers the FTC to set the primary circulation off to remove the heat in order to protect the unit.)

KevM has linked to Facebook groups (in some other thread recently I think) where Mitsi engineers can be found, it might be worth posting there.

@crustydoodle

Did you record the list of controller settings?

@derek-m Sorry - couldn't get to it yesterday.  Here we go (Many of these I do not understand:

DHW

• Max temp 50degC
• Max temp drop 10degC
• Max operation time 90 mins
• mode restriction 45 mins
• Recharge - Large
• Legionella
  • temp 60degC
  • Frequency 7 days
  • Start time 14:00 (27 september 2023)
  • Max operation time 3 hours
  • Duration of max temp 10 mins

Heating mode - compensation curve

• 40°C @ -2°C
• 30°C @ 17°C

Schedule timers - appear to just have everything highlighted

Holiday mode

• DHW - inactive
• Heating - Active
  • Room temp 15degC
  • Heating flow temp 35degC

Initial settings - mostly not included as the dates/time etc are correct

• Sensor setting - Main RC
• Room RC - all Zone1/Zone2

Service section

Function settings - Ref add 0, Unit GRP

Thermistor adjustment - THW1 (0degC); THW2 (0degC); THW5B (2degC); All others Invalid

Aux Settings

• Economy ON; Delay 10 min
• Electric Heater (Heating) - On; Delay 30 mins
• Electric Heater (DHW) - Booster On; Immersion On; Delay 15 min
• Mixing valve - invalid
• Flow sensor - RefAdd - 0;  Min 5L/min, Max 100L/min
• Analog Output - Normal; Interval 5 min

Heat source Setting - Standard

Pump Speed

• DHW 5
• Heating 5

Heat pump settings

• Heat pump flow rate range - RefAdd 0; Min 5L/min, Max 100L/min
• Quiet mode - unchecked for all days; Time - 0:00 - 23:45

Operation Settings

Heating operation - Flow temp range - Min 20degC; Max 40degC

Heating operation - Room temp control - Mode Normal; Interval 10 min

Heating operation - H/P Thermo Diff adjust - On; Upper +5degC, Lower -5DegC

Freeze Stat - Flow T 20degC; Ambient 5degC (NOTE - Have tried turning this off)

Simultaneous operation - Off; Ambient -15degC

Cold Weather Function - Off, Ambient -15degC

Boiler Settings - Invalid

Smart Grid Ready

• DHW - Off
• Heating Off (50-55degC
• Cooling Off (15-10degC)
• Pump cycles
  • Heating On
  • Cooling On
  • Interval 10 mins

Floor Dry Up - Off

Summer Mode - Off

• Ambient temp - Heating on 10degC; Heating off 15 Deg C
• Judgement Time - Heating On 6 h; Heating off 6h
• Forced Heating ON 5 degC

Water Flow control - Off

Energy Monitor settings

• Electric heater capacity
  • Booster Heater1 capacity - 2kW
  • Immersion heater - 0kW
  • Analog Output - 0kW
• Water Pump input 
  • Pump 1 - ***W
  • Pump 2 - 0W
  • Pump 3 - 0W
  • Pump 4 72W
• Delivered energy adjustment 0%
• Energy Meter (pulse/kWh) - 1000
• Heat Meter (Pulse/kWh - 1000

External Input settings

• Demand Control - Off
• Output Thermostat - Boiler

Thermo ON output - Zone 1&2

Commissioning wizard - lots of data i can share if it is relevant!

Thermistor Readings

• TH1A 18degC
• THW 56degC
• THW2 56degC
• THW5B 44degC
• TH7 18degC
• All others no entry

Error history

• l9 Errors on 4/9/23

Posted by: @harriup

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I wouldn't be so quick to dismiss the F9 error message either. Any error message indicates something not having functioned correctly. A quick search tells me it is to with pressure switch contacts – not that I can explain that any further.  I would speculate that these are located in the outdoor unit. I presume this error message caused a complete shutdown?

The L9 errors were from a loose connection to one of the pumps - the cable got knocked loose when replacing some of the insulation in the loft.

@crustydoodle

Thanks for the data. I will have a look through the list and see if I can make any suggestions.