Has anyone seen their Daikin (8kW) choose to use the immersion heater to top up the hot water tank instead of using the heat pump?
Twice now over the last week our unit has done just that. The “powerful” option on the app is disabled, so I was wondering if there was an upper outside temperature that would limit operation, as on both occasions it was a warm day with external temps in the mid 20’s.
The 2nd screenshot shows a sudden and steady 3kW electrical input which looks like an immersion heater.
Could this be a legionella cycle? What’s your DHW set point? If set the point is higher than 50C it will need to use the immersion heater, R32 heatpumps mac flow temperature is around 55C. Usually a set point around 45C is plenty hot enough.
Apart from the use of the immersion heater above 50C or 55C, depending on your model, it will also use the immersion heater if the measured outside temperature is above 25C. This frequently happens if the sun shines on the sensor, and also if the sensor is in the shadow but the sun shines on and heats the entire outside unit. I think it will also use the immersion heater if the difference between setpoint and tank temperature is below a certain threshold.
Yes this is the resistive heater being used instead of the heat pump starting a cycle.
Legionella cycle is disabled, set point at that time is 50C and only recently have I moved the 50C DHW cycle from overnight to mid afternoon in the thought that running it when warm outside would result in better efficiency.
@Arnold I think you have hit on the reason. External sensor was showing 24.4C at start of yesterday’s DHW cycle but the unit temperature was recording 25.5C - It is supposed to be another warm day today, I’ll see what happens at the DHW cycle then.
Oh I see it now. On my unit, the 3kw resistive element is used in conjunction with the compressor during the disinfection cycle (DHW runs at 1am), so I see a clear 3kw jump up in addition to whatever the compressor is using. Here, it seems to switch from compressor to resistive which I’ve never seen mine do. Looks like it’s an outside temp issue, more Daikin madness!
I too have my legionella and immersion disabled. On my Octopus-installed system there is an electrical interconnection box near the cylinder and this box has a rocker switch that makes/breaks power to the immersion element.
The software can do what it wants, but if this switch is “off” the immersion element won’t get any power.
Check your field codes - (not the same as the ‘breadcrumb codes’ mentioned above but accessible in the installer menu).
As mentioned above the booster heater field code 4-03 should be set to Zero (restricted). Also it pays to make sure the more obscure codes are set properly too;
8-00 = 1 min (min running time for HP doing DHW)
8-01 =75 mins (max running time for HP doing DHW)
8-02 = 1 hour (anti recycling timer)
8-03 = 60 mins (booster heater delay timer)
8-04 = 95 mins (additional running time)
6-00 = 14 (Heat pump on hysteresis)
6-01 = 0 (how close you let the HP get to HP max temp)
I’m sure that someone will say that these have no effect if 4-03 = 0 but my experience is that the installation manual has lost something in translation on these settings and so the heat pump does not always do what the manual says it should. I have arrived at the above settings by trial and error and they have worked well for me for more than 2 years without the immersion coming on - except for when the HP is out of range. (ie the flow temp is higher than HP max) or if I choose ‘powerful’. Incidentally the HP max temp varies with the outdoor temp and could be as low as 50c in mid winter and as high as 60c in summer. Clearly if you want a 65c tank temp then you will need the immersion in any event.
