I’m looking to the outdoor_P feed storing the power consumption measured by SDM120 MID approved meter part of the the emonHp bundle.
Compressor power will depend on frequency (speed) and how hard it’s working (pressure head for want of a better word)
Electronic expansion valve hunting @johncantor ?
This discusses things quite well https://www.youtube.com/watch?v=RXV-35gfQrk&t=59s
I think that in certain conditions, the control overreacts, basically swinging between closing too much and opening too much (hunting). I’m sure they could stop it happening with a bit more development. Its possibly only people like us who are trying to get the highest COPs where it strays into this erraticness
Interestingly, Ecoforest slow down the circ pump, thus inctreasing flow-return dt, in certain low water temperature conditions. I wonder if they have done this to avoid unstability.
Now that it is much colder outside and I’m getting continuous running with AA it thought I’d see what happens by switching to WC. This is what I’ve gotten:
I’m confused as to why AA can achieve continuous running but WC appears to just keep ramping up until it overshoots and cycles.
I’m also controlling my pump speeds as of about 2 hours ago . I’ve been building controller for about a year (it’s never really been a high priority). It’s all happening in an Arduino/ESP8266, which also has 4 x DS18B20 to monitor the ASHP flow and return and the radiator loop flow and return. I’m also monitoring the flow meter and state of the DHW 3-way valve.
The controls are all happening in the Arduino and I’m sending data directly to emoncms (Emoncms - dashboard view ) . The chart is my first heat-up cycle with the PWM controls working, they are both trying to achieve a delta T of 5C with the radiator PID controller operating faster than the ASHP ccontroller. They both need a higher gain though I think, but I’ll leave it be for a bit and see what happens. The chart also shows it doing a defrost cycle, which had a rather instantaneous impact on the pump speed .
My ASHP is also on the heatpumpmonitor web site (West Yorks 8.5kW Ecodan) but it looks a bit rubbish as the flow meter stopped working a while back and I only got that going again a couple of weeks back. It managed a CoP of about 4.0 over the first year, mostly running in weather comp mode. This year, I’m running it in autoadapt, but changing the target setpoint remotely from NodeRed according to time of day and Agile Tariff.
(PS the pump speed signal - forgot to start logging it until nearly 8.30 - is the %PWM to the Grundfos pumps - it’s inverse - 0.1 or less is max speed, .84-.91 is min speed)
Are you able to make your flow rate feed public? I assume it isn’t and that’s why ‘Show flow rate’ isn’t an option when I view your MyHeatpump app.
I’m just interested to see how the flow rate changes as your heat pump runs.
My flow rate is public … available here Emoncms - app view
I’ve added it now - I set mine up before it was an option in heatpumpmonitor! I’ve also added my DHW relay state - but that’s quite obvious anyway.
@Rachel nice work on the pump control. Adding the DHW relay state gives the added benefit of automatically calculating energy consumed/generated in heating vs dhw mode which can obviously really skew CoP figures for households with no vs heavy DHW requirements.
@Dan_Nichols - I found the DHW/Heating CoPs just after posting last nght - very useful!
Any idea what is going on with this hot water run?
The same thing happened earlier. Looks like the compressor is working really hard but getting very little heat output so struggling to get the last degree of hot water. My hot water target temp is 49 degrees.
For context the hot water cycle this morning took so long that all showers were done so at the start of this cycle the hot water was probably still fairly hot.
Can you plot tank temperature and pump frequency for the same time? It looks odd but is hard to tell from that.
This looks like the classic thing we see occasionally with Ecodans. I bet the discharge superheat was zero around that dip. It always seems to happen when dt is small, BUT this can always happen with fixed circ speed pump. I dont think the dt is the cause of the problem, but possibly the close dt is causing an EEV control issue… I dont know… Is this the only occurance like it?
Here is the whole run
Here is tank temperature in black, ignore the power values in this one as they are inaccurate ones from Melcloud.
So only going from 48 to 49.5.
I don’t record the frequency in a feed
Here is on earlier in the morning
This one needs a bit of explanation. Earlier, the hot water temperature got nearly up to target temperature, but had been going on too long so was interrupted by a period of heating. So the part shown was again only needed to raise the temperature by a few degrees and got into this situation of lots of input for barely any output.
The spike then is when it decides it needs to resort to immersion. For some reason at that point, it flipped the three port valve and continued to run the pump around the radiators while the immersion hit of the tank.
And even more to complicate things the FTC output for immersion actually goes to an Eddi to actually power the immersion and that was set to stopped so the immersion didn’t come on at that point until I realised. But I don’t think that has anything to do with why I’m getting no output for lots of input.
A bit weird. looks like there is water circulation. HP is using power… what are we missing? where are the sensors?
The same thing can be seen happening on Sunday → Emoncms - app view - dT collapses at 05:20.
Was this also a) attempting to run the immersion but Eddi was off, and b) was then interrupted by the heating cycle? It would have been more efficient to have let the immersion run for that last little bit.
Another drop in dT can be seen here → Emoncms - app view @ 05:09.
I’d suggest maybe reducing the tank target to, say, 47C, and see if that problem goes away.
Consider increasing the “DHW max. temp. drop” setting so hot water runs less frequently.