Very likely, yes. Or more specifically, the heat pump is too large for the emitters you have. Ensuring you have as many radiators open as possible will help. I’m not sure balancing will necessarily improve things, unless there are a couple rads short-circuiting hot water to the return. Restricting lock shield valves too much could have a negative effect.
There is an optimal flow temperature for your system where your heat pump will settle into a steady state, when the radiators can emit the heat that the heat pump is producing. The more (bigger) radiators you have, the lower that flow temperature will be, and better performance.
These are the settings that can influence Auto Adapt:
Dropping the Lower limit and/or increasing the Interval can increase the time between cycles, allowing the system to cool down some more and potentially perform better. Probably not enough to make a big difference, TBQHWY.
My own 11.2 kW system (link in bio) also has a minimum flow temperature of about 40°C.
Just a quick reply without looking in any depth… I guess you have a fixed-speed circ pump. (not one that adapts to dt), so the dt will vary with heat-ouput power. Its normal, and not a problem. The rev-up is annoying isnt it? why speed up so much, then stop, then re-start so quickly after. What model is this? I think Mitsi realise they set the algorythm with too much ‘panic’ for adequate heat, with not enough concern for running costs. This should be able to run in a steady state.
I have been experimenting with controlling the pump to try and achieve a constant dT but very early in the tuning of the PID controller. That’s why I was experimenting with Weather Comp again.
You’d think the ramp up at the end of the cycle could be beneficial in increasing the gap between cycles a bit but doesn’t appear to do that.
It’s a pitty there doesn’t appear to be software updates to refine the algorithm.
I still don’t really get why the heat output is low to start with then suddenly jumps, it doesn’t look like the return is going up just that the flow temperature starts ramping up. Seems to happen before the HP decides to up the input power.
I keep coming back to a thought about how the flow and return temperature sensors connected to the FTC would effect performance / behaviour of the system (in my general clutching at straws to try and explain the difference in performance of different Ecodans).
ASAIK the thing the controller is controlling is the flow temperature from the outdoor unit, and also maybe the dT between that and the return? If so the temperature sensor placement and how they are installed could be very significant.
So I’m wondering if in systems like mine, @Timbones’s and others, where the outdoor unit is quite a distance from these sensors whether the lag in temperature measured on the flow when the compressor modulates and the potential heat loss between the return and flow sensors could have an impact on how the algorithm used by the controller acts and reacts to changes.
If there is significant heat loss from the pipes between the sensors the unit will also potentially be measuring a different dT to that at the outdoor unit.
I might be wasting my time thinking about this as the controller might account for variation in the position of these sensors in the system and might react to these readings slow enough that it isn’t an issue.
My sensors are probably around 8m of pipe away from the outdoor unit. I believe @Timbones yours is about 10m away.
I think the distance isnt a problem. Surely Mitsi have thought of this, and they dont specify a distance restricion. I recall seeing one at a great distance, and no obvious control diffrence.
My old 2009 ecodan (fitted on a friends house) seems steady as a rock, and i do feel that in trying to ‘improve’ things, in certain conditions, there seems to be problems. I will be meeting Mitsi in a couple of weeks, and yours is actually a good example for me to discuss with them.
Oh excellent, good to hear they are engaging.
Let me know if you need any information about my system or if it would be useful for me to try any settings to get data to show them.
My DHW woes (where heat output collapses but while the compressor still draws power before having to resort to immersion) have come back again now that it has gotten a bit colder at night again. I have it in Eco hot water mode that I don’t think helps. I did raise a ticket with them about it and after we ruled out flow rate haven’t heard back again.
I’ve always had the black SD card icon with white letters, indicating abnormal behaviour, rather than the white one with black letters indicating normal behaviour.
I replaced my SD card on Wednesday and the icon has gone white. Will see if AA gets better at adapting using a longer history.
Back in cold weather and I’m still struggling with my DHW runs again.
As background when it’s cold weather my Ecodan R32 8.5kW Monoblock heat pump struggles to complete DHW runs. It gets partway through the run then the heat output drops off a cliff while it still consumes input power then eventually gives up and uses the immersion.
The Room temp is actually cylinder temperature and the target is the hot water target.
I’ve shown with a red arrow when the immersion was active (need to fix my immersion feed to show this in future).
I have an ESP controlling my PWM pump’s speed to attempt to get 5K delta T hence why this varies.
My maximum DHW run was set to 60mins so I guess that’s why it eventually stops does some space heating and goes back to hot water again. It is able to do this bit solely with the heat pump.
I’m wondering if I should disable my pump speed control. But then do you think it would perform better with a lower constant flow so the dT is greater or higher as it appears to struggle when the flow rate is too low.
Well your flow temp is getting high enough, there’s just not enough heat energy getting into the tank to rise it’s temperature fast enough. Heat energy transferred is a function of the delta t and the flow rate. So my thought would be the flow rate not being high enough, at least towards the end.
I’m not convinced that low flow rate is the root cause here, but switching to a fixed flow rate will at least remove one variable from the equation.
The heat output drops off when flow temperature goes above 51°C. My guess is that refrigerant cycle isn’t performing properly at the higher temperatures. John may have better insight into this sort of thing.
Thinking it over, if you’ve got a pump that’s trying to target delta t 5c, what happens when the heat pump reaches it’s max flow temp (which is enough to get the tank up to target temp) and the delta starts to narrow as the tank reaches the target temp… The pump will slow down to to maintain the 5c delta, which in turn would reduce the heat output.
Disable the pump speed control, ensure the flow rate is within spec and see if the problem persists.
Ok, once I manage to remember how I set up my ESP I’ll change the logic to have a fixed speed on DHW.
Shouldn’t be too hard as I already have different PID controller values when it’s doing hot water from those used for space heating.
Then we will see what happens. @johncantor has had a look in the past at my system when it was doing this last winter.
Its odd. The flow temperature seems to rise to about 51c, then the system throttles back, then finally stops at about 57. My 6kW keeps going to at fairly high power to 57, and I’m on DHW ‘eco’. there used to be dip switches that limit max flow, but I think this was the old 410a units.
The flowrate seems well within bounds, so I would not expect that to be a problem. I cannot see its a flowrate issue. Have you tried ‘eco’ and ‘normal’?
I found earlier in the year that it did it in normal and eco modes.
However I’ve just remembered I have it in quiet mode although I don’t know if that applies to hot water and it did manage to get to 3kW input power at it’s peak.
Maybe I should turn that off or select the middle option.
