Anyone monitoring a new R32 Ecodan?

Its about 4 degrees. 17lit/min. Its an oddity with Ecodan since they always say dt should be 5 degrees, but the spec suggests 50% output is possible. If so, dt could go down to 2.5. My old 5kW is quite happy with this variation in dt. If they really want 5 degrees you would expect a speed controlled pump like other models have. Anyhow, I think you are right about new ones being sensitive to dt.

1 Like

Well the good news @johncantor is that if anyone can work out what’s going on it’s going to be you!

Please keep sharing your experience with us. It’s helpful to watch you diagnose it and maybe we might even be able to help.

2 Likes

I notice that your flow temp and dT drops at about the same time. Where does ‘heat_calc’ come from? Is it calculated from the dT, or is the flow temp reacting to the drop in heat being generated?

Also, how come the FlowRate drops off at 04:27, and yet input power and flow temperature continue to rise. Some metering issue there?

I don’t have your diagnostic vision. I am more an in-the-moment look and see sort of person. between us all, we should do OK.

1 Like

The heat is simply a flowrate X dt. The flowrate, flow temperure and return temperature are from the mbus heat meter, so should be accurate.
I think the heat output drops, and the result of this is the flow temperature drops.
Well spotted and diagnosed. The heat meter has a weird fault and the flowrate goes to zero when temperure goes above 40 or so. I have a new meter now!

1 Like

John, I see you posted a similar looking chart that crashed back in January in another thread.

I’ve reviewed my own Ecodan 11.2 kW over the past week (since getting a Sontex meter fitted), and I’m not seeing anything similar. :man_shrugging:

1 Like

Is yours R32?
I just had a look at mine for today. This shows one of the worst I have seen. It goes to dhw at 15:03. Thereafter COP is chronic. Flow rate is 16lit/min which is about right, and would give dt of about 5 if 5 to 6 kw output. Refrigeration wise, I am struggling to fathom out how the COP can actually drop so low

Yes, mine has the new R32 refrigerant - I think many manufacturers have switched over to it.

Here’s a snapshot from my own system during a similar scenario: at 18:20 it switched to heating DWH and the flow/return temperatures jump up to match the tank temperature then gradually increases up to 50 degrees at 18:35. COP is pretty poor (between 1 and 2), but not quite as bad as yours. I do note that the dT is pretty small at this point (2 degrees) - not quite sure what that means.

I’ve only had a heat pump for 3 months, and written no books about it, so I’m not sure I’m qualified to advise on your situation John. :smiley:

Your chart shows the flow temps steadily rising after 15:03 at about the same rate as mine, which make me think it could be the heat_calc that’s off rather than the heat pump itself.

Interesting graph. Your dt’s are quite close. You flowrate looks greater than Mitsi recommend.

I did a test with mine at lower flow rate. The 1st graph is flowrate slower than recommended, and COP is fairly consistent with the data sheet (my red line).


The 2nd graph is a repeat of the earlier with an approximate COP on it (my red line)
I still am no wiser as to why this should be happening.

1 Like

Hi
I’ve just installed an 8.5kW ecodan with R32. Ive only got the monitoring up and running over the weekend and currently think my flow and return sensors might be a bit to close to the low loss header or my primary pump flow is way too high as I’m getting very low delta T and lower CoP than I expect. I have my own sensors (in the same place as the Ecodan ones)and ive piggy-backed onto the flow meter output with an ESP8266. I was logging my gas boiler heat output for a couple of years before installing the ASHP, so i’m pretty sure (having compared) its a heat flow reading /calc issue rather than poor ASHP performance. I’ll post some charts when I’ve explored tye current issues!
Rachel

Hi Rachel,
I think its quite possible that your primary flow is too high. I have come across this a few times. If its only pumping to a low loss header, then resistance could be very low. If water is flowing, then it should be OK putting the sensor very close to the LLH. So…, if the dt is low, then the heat measurement will not be very accurate. Are you taking the voltage output from the Sika VFS flow sensor? . I guess your temperature sensors are not in pockets? I tend to feel you can probably get away with it if your dt is say around 5. If its 2 degrees, the temperature sensor error is becoming significant. Interested to know how you get on.

Hi John
Thanks for your thoughts…

No pockets for the sensors and since I got them under some proper insulation, the delta T has dropped to about 2C!!

I’m reading the voltage output from the Sika VFS directly on the ESP8266 NodeMCU input. Ive double checked my calcs and I seem to have a flow rate of 0.34l/s or 20.4l/m - thats reasonable for the pump curve given its a short run without many bends. It’s also within the range for the unit, but I’m only running at minimum load at the moment, hence low DT. Your point about accuracy is well made - just checked and those DS18B20 sensors have an accuracy of +/- 0.5C, so error could be huge at 2C delta!. I probably need to get a pair that are well matched even if running at 5C DT.

Rachel

Its interesting that some sensors go into external pockets. These are a little pipe soldered to the pipe you are sensing. the temperature conducts around the pocket pipe, and it seems to work well. I have sometimes wrap a bit of copper around the sensor. It helps, but not done a lot of comparitive tests. Speed response will be better too.
With respect to calibration. You could put the sensors together for testing and add a callibration shift. I have done this several times. e.g. +0.25 or whatever it needs. You could also run the pump (easy on an Ecodan) and see if the sensors come together with zero dt. be mindful of water temp… i.e. it might be different at different water temperatures. The other point… I always remove the heat-shrink on the sensor if going direct to a pipe… conductive paste also helps…

2 Likes

If I had my time again, I’d fit sensor pockets into the pipework as it was being installed. (JTM Pipeline Brass Sensor Pockets | Plumbing Superstore®)

I have a number of sensors taped to pipes with Aluminium foil, under a thick layer of EPDM insulation and I’m sure the reading is lower than if they were in proper pockets.

Calibration is one of my moans - what can you use as your calibrated sensor? I have numerous types of sensors around and they all read a different temperature (when in the same location :stuck_out_tongue_winking_eye:). Even the rates of change and response curves are different!

Calibration here isnt quite so critical as other applications as we’re only looking at a differential - as long as they’re both consistently in error to the same extent. The DT will still be Ok.

I’ve used pipe earthing tags to fix my sensors to the pipe.

Rachel

Pipe earth tags sound great…
I dont callibrate as such, but sometime elastic-band a few sensors together and put them in a thermos flask. They are usually no more that 0.3deg highest to lowest. I simply add/subtract a bit of correction to some to bring them closer. I suppose melting ice and boiling might be a good-enough way of doing a slightly better job.
I think the response time is to do with how much air is in with the epoxy in the pocket… it could vary in a similar batch of sensors.

1 Like

My beef is with different types of sensors; they all behave differently and it is impossible to know which one to believe!

I take your point. I tend to trust that PT1000 and DS18b20 are good enough. I try to ‘match’ calibrate around the range of use.

1 Like

Hi all

I’m still mulling over which ASHP to get for my location and still have the 6kW R32 on my potential list. Although @johncantor struggles continue to give me worries, especially with his observations that the 6kW unit is just the 8.5kW in the same box, so it can’t run really low.

Note: my heat calcs come out at 5.3.kW at -3 with a flow of 42C.
So at 8C i’d probably only need 32C flow (approx 700W in / 2.8kW out)
Will it do that low? And go lower for 10-14C range?

But saying that all of this, any COP of 2+ is way better than the 0.85 i’m getting from my Gas Combi right now. :scream:

How are you driving your unit?
My preferred method would be weather comp from the unit temp sensor and then use an overnight setback of 18.5C or something like that.

Does anyone use an internal room sensor to help influence the curve? Apologies if that doesn’t make sense, but I’m not sure that is even a thing. I’m still trying to work out the control mechanisms available for each model. Is there even a room sensor for the Mitsubishi?

How close are folks getting to the interpolated efficiency charts that @MyForest created?

COP charts on a spec sheet are one thing, but real world data is far better indicator of performance.

Cheers, Mick

Here is a ‘snip’ of my 6kW unit, operating with around +10 to+7 outside air. I actually took it out of my place and fitted it on a friend’s good underfloor heating (50mm spacing!) to see how it performed.


Anyhow, as you can see, it exceeds the 6kW, but that might be expected at such low flow/return temperatures. At just before 02:00 it ‘revs up’ where I would expect it to slow down, then it stops, then restarts only 4 mins later… annoying. The COP for first section is great, but at the end of the graph it cycles and the COP is considerably less. I have never seen it anything like the minimum output promised on datasheet. There is one reasonable section around 4am, but it doesn’t last long. Again, another unwanted ‘rev up’ followed by some messy operation. It is plausible that ‘rev ups’ are all to do with compressor lubrication, but they don’t seem to have done this control well. My 10-year-old unit does none of this.
Have you considered a 5kW unit?
What I don’t know is how well (or otherwise) Samsungs and Panasonics work. Not had the opportunity to properly monitor one yet.
My feeling is that few people are getting full potential… Maybe that is acceptable?? seems wrong to me.

1 Like