East Midlands 11kW Daikin altherma 3 has some interesting data - the lowest power draw is really low, just over 600W. This is much lower than our similar (but 9kW) system, which rarely drops below 1000W.
I’d love to know more about this system and understand the difference to ours, and potentially what changes I could make. Common understanding seems to be that the compressor can’t run below 800W.
Here’s a link to that system: HeatpumpMonitor.org (#126) - I’m not sure they’re on the forum.
Note that the metering is not MID certified.
Thanks Tim, that’s where I noticed the data.
Now spotted that it’s a “spilt” system, with UFH. So even if it shares a compressor with the monobloc (EDLA09-16kW) range, my guess is that the metering might not include circulation pumps or controls.
I’m wondering how mad I go on installing new rads and re-piping, to get a respectable COP on our 9kW monster. It could be a busy summer.
Hi,
It’s not the standard monoblock outdoor unit to most of the Daikins on there. The EPGA011-016DV7 has 3.5kg of R32 compared to 3.80kg of the EDLA units so I would suspect a different compressor or setup. I also have around 950m of UFH pipes at 100mm spacing so probably able to maintain lower flow temp without overshooting quite as much as those on radiators.
The PZEM has voltage input and PF monitoring:
I’d be more worried about the accuracy of the thermal output from ESPAltherma - the return inlet temp (R4T) is only accurate to 0.5C on this model.
I could turn off some circuits so only the heat pump is on and see if my IHD/SDM230 matches the PZEM reading, but I’ve never had reason to question it’s accuracy before when it was doing whole house metering as it always tied in with IHD reading (granted that’s not going to be skewed much by motor/compressor PF).
Oh and the UFH is measured by a shelly PM and included in the readings - but its only 25W or so.
Just by coincidence, I have a similar PZEM-004T module in a case, that I bought to play with (!). The main chip is a Vango V9881 energy meter chip. Searching with Google, the chip data sheet is available online (284 pages!). It does all the normal energy meter measurements, including power factor, frequency etc, and has a specified active power measurement accuracy of 0.5% …
So it should be ok … 
YMMV
edited to add - assuming that the PZEM-004T module is correctly calibrated.
and - one further point - the voltage and current sensing on the PZEM-004T are both on the live mains side - one side of the CT is connected to the neutral terminal of the PZEM-004T. The PCB has mains voltages on it. The mains isolation is done on the data output side of the V9881, using optocouplers. The PZEM-004T schematic can be found on the web.
So you need to know what you’re doing for safety’s sake!
I also thought the whole point of having MID metering flag was to toggle the high accuracy data…
Thanks!
Like many, I’m struggling to bring my minimum power down on my EDLA09, so was interested to see your HP drawing only 600-ish.
I notice that the periods of 180W I see (controls 25W + pump 155W) isn’t evident on your logs, so is the circulation pump power draw included in your metering?
It could be that my system is so strangled that my pumping power is unusually high.
TIA
The circulation pump shouldn’t be on when you don’t have a call for heat unless you are using LWT control - and then it should sample every 15-20 mins afaik. The 155W circulation pump draw sounds like its at 100% continuous, rather than the 60% during sampling which should drop it down to about ~70W or so.
Is your pump setting to on request/sampling or continuous? And is it set to 50/60% on sampling?
As an aside if you look back at mine on the 23rd January the circulation pump came on between 430-0730 at ~160W for the water pipe freeze prevention (cold temps).
This then led to me to identify that the menu options for water pipe freeze prevention are labelled incorrectly and “intermittent” meant “continuous”. Got that fixed (see periodic sampling):
A second bug was then identified where the 50% during sampling actually mapped to the 90% during sampling value which was why the pump power was so high (and noisy). Reset the setting around 930pm and the circulation pump dropped down to 70W when sampling - also a lot quieter.
So you can’t always trust Daikin menu options 
Ah, I wondered why the CT was so tickly when I moved it 
Ok great, apologies for jumping to conclusions regarding the power meter, I could only see the CT sensor in the photos. It does indeed have Real Power, it claims 0.5% which if true is more accurate than MID meters! Impressive.
Hi, new to the forum but have been monitoring you people for a few months while I battle with my HP.
I have a 16 kW split outdoor unit ERLA16DW17 with a EBVX16S23D6V indoor unit, so not the monoblock that is often installed in the UK.
I have a buffer tank, which I plan on turning it into a volumiser before summer, so I reckon I can get a bit better COP, as I seem to lose between 3 and 1 deg to my rads/fancoils.
Anyway, back into this topic, I have also noticed that the dreaded 900w minimum input does not seem to apply to my unit. I have the indoor, outdoor and secundary circ. pump going through an energy meter and I have seen it run continously as low as 750W total, so about 680w for the heat pump units themselves.
So it would seem that the ‘beast compressor’ is not shared between the mono and the split units, and that I have ‘won’ the lotery.
Overall, extremely happy with the performance so far, with SCOP for heating and hot water since November of close to 4.5. Please note that I am north of Madrid, where Dec-March average is around 5-6 degrees, with cold nights (often subzero) and mild days (10-15).
Interesting.
What heating emitters do you have? UFH or radiators or other?
Simon
A mix of rads and fancoil units, LWT is usually between 28 and 40.
Glad to see I’m not the only one seeing those numbers 
I think my biggest breakthrough was with overshoot. With your milder temps I’d recommend trying the overshoot at 3-4. I’ve found when its milder that this allows the unit to settle and reduce compressor frequency from its initial starting point without unnecessarily cutting out. The average flow temp is slightly higher, but doesn’t cause any overheating. Would be interesting to see how that goes with the buffer.
Before - Jan 29th Outside 10.9C COP during day 4.88. Average flow temp 27.2
After - Feb 16th Outside 10.8C COP during day 5.57 average flow temp 28.7
Ruined a bit by Daikin’s 6 hour mandatory oil return/defrost cycle.
Ah, I am on the fence about getting monitoring hardware to publish my data here…
Yes, up until a few days ago I was running with overshot 1ºC and minimum flow temp 32, to get rid of cycling. I have since increased overshot to 2 and reduced min flow temp to 28. The result is more cycling (1 to 3 times an hour when very mild), but better COP, so a bit of a trade-off.
It is hard for me to know daily COP with the tools I have but I think my best so far has been around 5.5-5.7. Not bad for no UFH and 22mm pipework!
I am looking forward to the summer, when this will be reversed into cooling mode!
For a bit more data, so far this February (extremely mild vs average), the MMI reported COP for heating is 4.72.
For context, these are the meteo reported temperatures in the area. I usually see 2 to 3 degrees cooler than this where I live (as reported by my outdoor sensor).
I am tempted to get the reversible conversion kit (ours is heat only at the moment) to feed into a attic-mounted fan coil for bedrooms but my installer said it wasn’t available in the UK and would void warranty so may need to wait for warranty to expire.
