Annoying issue with Daikin Altherma 3M Disinfection

rjmachin

Hi,

I am hoping you may be able to assist in finding a solution to an issue I have been having with my heat pump (Daikin Altherma 3M) disinfection that runs once per week.

My setup:
I have the heat pump, solar panels (not relevant), and battery (partially relevant).

The issue:
The issue is that the disinfection starts as scheduled, but it does not stop until I notice and then have to restart the system to stop it.

My battery is set to allow discharging after 5:30am (outside of the cheap octopus rate), and if I don't wake up early, the heat pump virtually empties the battery.  This helps rather than paying higher costs, but it should not need to as I aim to do this in the early hours when it is cheaper anyway.

I have tried several things over the last few weeks.  I get the disinfection mode active icon in the top right corner of the house


This is the house after I have restarted the system (the above icon no longer shows as I restarted):


The disinfection is set (currently) to start at 4am, at 60 degrees for 30 minutes:


The installer said to heat the water via the heat pump prior to the disinfection so that it does not need to use the backup heater as much, which makes sense.

So for this morning, I set the hot water tank to heat up for 2 hours between 2am and 4am:


I know the heat pump can only do DHW or Heating, so I scheduled to drop the climate temp to 16 degrees between 2am and 5am:


This is the message I get in the app, which I know is the disinfection mode failed.


Own thoughts / Questions:
Is the water pressure okay at 1 bar?   Should it be higher and would it affect the hot water tank?

Are there any changes to the schedule / settings above that you can suggest?

I can provide any other screenshots or details you would like from the MMI or App if it helps.

My aim:  I just want it to be automated to run the disinfection and stop when complete (hopefully after a short time).

Thanks for reading and your help

matt_drummer

What heat pump is it?

mebu60

matt_drummer said:

What heat pump is it?

Daikin Altherma 3M according to the header and first sentence. 

matt_drummer

mebu60 said:

matt_drummer said:

What heat pump is it?

Daikin Altherma 3M according to the header and first sentence. 

Thanks for that!

They make more than one model of heat pump in the Altherma 3  Monobloc range.

In order to help I need to know which particular heat pump it is.

But maybe I don't need to help if you know the answer?

rjmachin

It is the Daikin Monobloc - 9kW (EDLA09DA3V3)

The MCS certificate show it as EDLA09D(3)V3

matt_drummer

Thanks.

Who installed it?

Now we know the model I know that you have a booster heater (immersion) and a back up heater (for heating)

First, you don't need to adjust anything with the heating, the DHW takes precedence.

The DHW cycle will start as scheduled and when the tank is at the desired temperature heating will start again if required, no set back required to allow DHW to heat.

Are you sure it is the booster running and not the back up heater? They use the same amount of electricity and the back up heaters have a mind of their own in my experience, I turned it off. Maybe turn off the back up heater at the mcb, you should have three mcb, one for the heat pump, one for the booster and one for the back up heater.

Not an answer to your question but do you need the disinfection cycle? Mine is turned off and many others do the same.

The 30 minutes in your setting is the time it will hold 60c for if I remember correctly, it is not a limit on the time taken for the disinfection cycle, but check the manual to be sure.

The DHW schedule in the app is not the only limit on DHW cycle.

You also need to check on the MMI, the app is limited and does not show everything. Your DHW might be on for longer than you think.

1 bar of pressure is a bit low, it is normally 1.5 bar and mine runs at 2 bar.

There is obviously an issue due to the warning message but that isn't necessarily related to the electricity consumption you are seeing.

There could be a conflict between settings on the MMI and those in the app, maybe the disinfection cycle doesn't complete because the DHW isn't on for long enough in the MMI even though the schedule shows it is.

On the MMI your tank is at 47c, do you ever see it at 60c?

rjmachin

Octopus installed it, but I have been adjusting the settings, so maybe I broke it.

I didn't realise the DHW takes precedence, that's good to know I don't need to reduce the heating.

The issue is only occurring when I try to complete the disinfection cycle, so I guess it is the booster heater (immersion).   How can I confirm this?

Where should I check in the MMI for the DHW?  The schedule?

I will top up the water pressure.

When I successfully complete the disinfection cycle (I have managed this before) then the warning goes away.  I am not overly concerned with the consumption itself, I can see it is due to the disinfection cycle running for endless hours (until a force restart) instead of 0.5-1 hour, but this itself.

Maybe it is not reaching 60 degrees and trying until it does.

I will check the MMI, but the app shows consumption (I think):
02:00-04:00 - 1 kWh
04:00-06:00 - 3 kWh
06:00-08:00 - 2 kWh

I have see the tank at mid 50s when the tank it heated up mid afternoon.

Reed_Richards

I presume you are on a clever TOU tariff where you can import cheaply at night and export for more money at other times?  Otherwise I would suggest that you do the Legionella cycle in the middle of the day when you have the most solar power. 

PK12

I had this. It was the booster heater (emmersion) not working.

FreeBear

rjmachin said: I have see the tank at mid 50s when the tank it heated up mid afternoon.

If you are running the disinfection cycle over concerns about legionella, you'll be happy to know that mid 50s is plenty hot enough if maintained for a few hours. You don't need 60°C every day - Once a week is more than enough.

rjmachin

I am on Octopus Intelligent Go (I have an EV) so get 11:30pm to 5:30am at 7.5p per kWh.

I am not trying to heat to 60 degrees every day, it is only once per week, but is not completing and just keeps running until I force it to restart (this is my issue)

Does anybody have any ideas why it is not completing?

The tank is due to heat up (normal) between 3pm and 4pm, so if it gets hot enough, I will set it to run the disinfection afterwards.

The installer set it up to run at 4am initially, but I could do it in the afternoon if it works and take the hit on cost.