On the 16th Nov the mixergy tank dropped below the min threshold and a heating cycled automatically kicked in at 01:32 with a DHW cycle provided by the Daikin and the Mixergy HP interface, 5% to 100% full and a success completing at 02:42. See picture.
Perfect. (also following was the daily mixergy heating schedule, 03:30, again this was successful even with a small tank recharge).
Last night however, the mixergy tank did similar 01:26 (coincidentally similar time) but the Daikin failed to do what it had previously done, I think because we hit two defrost cycles part way through the DHW cycle and systems got confused and out of sequence? See picture.
The DHW cycle stopped at 03:13 with the tank only at 72% full. The then daily 03:30 scheduled DHW cycle didn’t kick in either to complete the remaining 28% to full.
Instead the Mixergy tank itself decided to use its immersion heater giving a cycle from 03:30 to 04:02 until 100% full.
Does anyone have any theory as to what might have been going on please or have seen this before? If it wasn’t for the monitoring equipment I’d be even more confused as to what was going on.
many thanks
David My Heatpump
Thanks Sam, something like Maximum Running Timer looks a likely candidate.
I can see the whole DHW cycle by the ASHP was 95 mins EXCLUDING the defrost cycles which lasted 5/6 mins each, or 110mins including defrost.
It’s likely that space heating was being called for too at the end of the 95/110 mins, room temp was targeting 18 and the OEM room thermometer shows we were at 18 at the time, therefore CH takes priority. Which is what I can see happened. Mixergy then took over as DHW cycle was not available and defaulted to immersion.
Feeling comfortable with that diagnosis, very grateful for your pointer, thank you
David
I emailed Mixergy about this as having a shower during a heating period caused the same issue.
They changed the timer from the default 15min to 45min.
I also now have a new line in the event settings entry - “heatpump_flatline_period”: 45,
Thanks Sam,
In conclusion then, reading back through the anti-recycle section, the default time is 0.5hrs/ 30mins between DHW cycles, and the time between my two cycles would have been 20mins, hence why it didn’t fire for that second cycle.
And the reason it didn’t complete the first DHW cycle was it hit the maximum run timer caused by 2 defrost cycles and associated start/stop lag of system getting back up to temp.
Does that sound like a sensible conclusion?
Thanks Mick &Gary, that too is a useful to know re. the mixergy timer for immersion kick when it thinks the ashp can’t hit temp. On this occasion the internal temp was an appropriate length of time I feel and it certainly finished the job giving a full tank ready for our morning.
