I’m going to assume John’s graph was from 2022-01-04. I was struck by how it looked like my graph from the same time range. (Ignore my measuring hiccup at 20:00).
My 14kW ranged up to a max of 10kW output and was around the nominal CoP at the flow temp (the gold line on Efficiency). Of course a CoP of 2.74 looks pretty dreadful considering the outside temp was 2 °C. The only saving grace is the hour it was switched off meant it wasn’t using any power during that time - it averaged 1.64kW consumption over the 3hr time window and 4.49kW output).
@johncantor As we were discussing, I think that turning mine off at 18:55 meant I avoided the defrost you had at 19:17. However, I still had a defrost about the same time as your second one.
This evening it’s colder at -1 °C and I’m seeing longer runs with two defrosts (19:43 and 21:03). You can see the algorithm resets the desired flow temp after a long defrost which caused it to ramp back up gently.
Your graphs are mind blowing David. I need time to understand them properly. I offer you 2 graphs. 1st is my old 5kW unit on FTC3. It seems to modulate as I would expect wrt tracking the fixed flow setting. It has served me well for 10 or more years. Same unit as Trystan’s.
2nd is 6kW R32 unit on FTC6. It seems to be behaving oddly… Not worked out why yet.
I wanted to correlate outdoor temperature with behaviour so that’s the extra complexity on my “Space Heating” graph.
I was also too lazy to work out the ratio between input and output so I created the “Efficiency” graph to show it for me, then I added Mitubishi’s opinion of the CoP so I could see if I was even vaguely close.
I didn’t want to wreck yours / Trystan’s existing app so I ended up with the other app.
That’s really nice to see.
Do you know what happened at 13:58 and 15:02 to cause it go back up so much when was looking like it was going to settle down?
Judging by the way the deltaT gets smaller from 13:40, it looks as though it was starting to get to the point it couldn’t scale down further. I was getting about 1.7kW solar then so maybe you had some sunshine and the house started to get warm on it’s own.
Gosh, it certainly does.
Those crashes look like defrosts from where I’m sat. I use the OperationModeDefrostMode attribute in the MELCloud data to tell me. There is a report on the operation mode in the MELCloud UI but it’s a pie chart so not really useful at all. Is there a way to grab the operation mode using your mbus setup so you can see when the defrosts occur?
BTW a ten-minute defrost (at 20:55) does look long, but I’ve been seeing those today too; you can see it in my chart at 19:42 - 19:56. The effective temperature here at the moment is -6.1 °C. The heat pump (next to the house) thinks it’s -1 °C and my weather station (about 5 yards away) thinks it’s -3.6 °C.
Well it looks like my code is using DefrostMode to decide to leave the system alone due to it defrosting.
However there are some other exciting nuggets of code I have hanging around:
# For a summary on a portal...a little snowflake appears
if deviceInfo["OperationMode"] == 5:
fp.write(
" <img title='Pumping water round so the heat pump does not freeze, it is currently "
+ str(deviceInfo["OutdoorTemperature"])
+ " °C outside' style='width: 32' src='/web_icons/ashp/anti-freeze.png' />"
)
and also this little puppy:
class TryToStopAntifreeze:
"""Notably, it seems wasteful to just pump it around so it goes outside and gets cold"""
@staticmethod
def tryToStopAntifreeze(deviceInfos: DeviceInfos) -> Generator[Action, None, None]:
deviceInfo = deviceInfos[-1]
if int(deviceInfo["OperationMode"]) == 5:
newTargetTemperature = TemperatureThresholds.maxFlowTemp(deviceInfos)
currentTargetTemperature = float(deviceInfo["TargetHCTemperatureZone1"])
if newTargetTemperature > currentTargetTemperature:
yield Action(
"SetHeatFlowTemperatureZone1",
newTargetTemperature,
"Nudging target flow temperature up from "
+ str(currentTargetTemperature)
+ " °C to the maximum temperature of "
+ str(newTargetTemperature)
+ " °C to try and stop the system wasting energy doing antifreeze",
)
Looking at 2022-01-05 we can see it doesn’t hit 5 very often or for very long:
Ha, yeah, I see that in my charts and my head goes “defrost!”
However, my algorithm uses the effective temp based on the weather station readings so the micro-climate fun around the heat pump itself doesn’t bother me.
Those bumps only last a couple of minutes, but it does show a lot of heat is being used to melt the ice.
David, I have lost your question (what happened at ? time) . mine does defrosts and you can see the flow temp drop below return (briefly cooling). At other times, the water temperature drops if radiator actuators opens, and the compressor responds accordingly.
Have either of you used ‘request codes’,/ 'running information on the mitsi control? My old one shows 014 (condensing temperure), but new one has dashes. David, are you getting Discharge superheat (request code 004) Mine is low than expected at times. Also, my SH (code 012) varies from 1 to 31… Interested what yours are.
Seems to be controlling better tonight, but still dont know why it suddenly stopped (when not at minimum) at 10:53 tonight, then restarted 6 mins later.
No. Is it in the spanner menu? I have been very cautious about going in there for fear of upsetting the MMSP/RHI things. Some of the few things I did try to look at seemed to say the heat pump would be shut down before display, so I chickened out in case I couldn’t restart it!
Yes, its in the spanner menu, and its one that does not need a shutdown. i.e. you can see readings when its running. Its ‘running information’ , and in there somewhere. If you put in 016, it will give you the compressor speed, for example. Its a useful diagnosis tool.
if you do need to shutdown, it restarts easily by pressing the big button. Actually, I think it restarts in time. e.g. it will recover from a powercut
Many thanks David. Fascinating… lots of interesting numbers in there. I dont think any of the ‘Running Information’ values are in there (values from temperure sensors etc). Unfortunately I dont have Melcloud. Have you investigated what info is on the SD card on the FTC panel?
Still finding my new unit ‘revving up’, and flow temperature creeping up, when I would not expect it to. Not got to bottom of it yet.
If you look at Swift3, you will be bombarded/baffled by graphs… I am!!
I have never seen the compressor discharge pipe oscillating like Bart Simpson! I guess you dont have access to the discharge temperature? It’s code 004 on ‘running Information’
I actually borrowed a melcloud module, but not bothered to look at it really… it seems a bit limited.
I might ask others to look at the discharge temperature… not sure what we would lean from it though
I look forward to getting to the bottom of it
I might put something publically on the forum, but am mindful it may not be a good idea to criticise Ecodan. Or at least… I should criticise thoughtfully
I have now put (non intrusively) a few sensors around my refrigeration circuit. My old 5kW has a steady discharge temperature (‘running info’ code004) but the new one is modulating regularly with dramatic swings from around 50 down to 35C. Not seen anything like that before. I look forward to getting to the bottom of it.
I am loosing the will to live now! My old model has been there for 10 years, and always done what I expected and what I wanted. This new one seems to do what you least expect. Maybe I am missing something, and I hope is a fault. Swift3 is an emoncms account.
I fear it may be a fault in the latest firmware update. Mine also seems to increase the flow temperature aggressively if left to do what it wants, which I think then causes it to go above the target flow temperature, try to modulate down aggressively, then the temperature difference falls below 4° and it shuts down for a few minutes before starting another cycle. If I spot this, I can often stop it cycling by reducing the flow temperature 2°, waiting for it to steady and then stepping it back up, but I’m not always watching and I haven’t automated this yet.
That is interesting observation. I did get mine to go steady-state minimum for 10 minutes! then it ‘revved up’ and cycled. If I could get mine to at least steady state at 50% of output rating, I would be mildly happy.
Given I got COP 5.25 yesterday during a steady period (mostly 3.5 to 5.5kW), and the discharge temperure was oscillationg between 50 and 35, I am no longer worrying about the discharge (code 004) dropping so low… maybe its normal?
