@derek-m - on the leaflet that came with the meter under Performance Criteria it says "Accuracy: Class 1 / Class B" which needs translation...

@batalto - having done some more reading, I think the connection may be impossible with current hardware, because what is needed in both HW and SW is not on the PC. It seems to be that you can network a second PC wirelessly via a wired router (which I have done) but networking a wifi/smart  device isn't possible using the same set up. I may need to get a USB wireless adapter (<£10 these days) which may also let me add bluetooth. Still working on it...

PS posted as you posted your last reply - yes, but I think the problem is the PC can't see a wifi connection, so the emulator can't see one, ie can't see what isn't there. The PC doesn't know about or if it does, can't read the wifi connection the router can see.

PPS this may explain why the router can see the Icarus Illumina wirelessly (I know it is the Illumina because the MAC is the Illumina's MAC) but the PC can't, its basically the same connection failure as with the Midea Controller: PC can't see anything wireless.      

Hi @cathoderay 

Accuracy Class 1 means that the measurement is +/- 1% of the full range reading under unity power factor conditions.

A meter with a full operating range of 100A should be accurate to +/- 1A, but this means that when only 10A is flowing the recorded measurement would be between 9A and 11A, so the accuracy would be +/- 10%.

@derek-m - interesting. Another example perhaps where quoted figures aren't always applicable to everyday conditions, as most of the time the meter will be operating in the range where it's accuracy is nowhere near +/-1%. If my heat pump draws 100A, the house will probably be a lot warmer as well, and the heat won't be coming from the heat pump...

Posted by: @cathoderay

@derek-m - interesting. Another example perhaps where quoted figures aren't always applicable to everyday conditions, as most of the time the meter will be operating in the range where it's accuracy is nowhere near +/-1%. If my heat pump draws 100A, the house will probably be a lot warmer as well, and the heat won't be coming from the heat pump...

It is standard practice with instrumentation to quote accuracy at Full Scale Deflection (FSD), though when greater accuracy is required the range may be split into sections with different accuracy specified. In the case of electricity power meters in domestic situations, as far as I am aware it is normal to fit class 1, but it is possible to have 0.5% or even 0.2% accuracy meters installed. From the accuracy point of view, the main problem with electricity power meters, is the fact that they are required to operate over such a wide range, from less than 100W to possibly 24kW. 

@derek-m - point taken about the wide operating range. 

Some observations this morning taken from Midea controller:

Compressor current 9A, Heat pump capacity 6.6kW (implies COP of 3.06)

LWT 48, RWT 42, outside ambient 6 (was 3 not so long ago)

Rad temps (warmest spot, measured using IR thermometer) 25/30/21/29/37/29/38/35/37 (and some rooms feel a bit chilly)

A few days ago the rads were reasonably balanced, all TRVs fully open, heating room stat is set to 18.5, no timing, and continuously calling for heat (except on sunny afternoons when there is some solar gain).  

Comments/questions:

(1) COP makes sense, LWT and RWT make sense (based on weather comp curve) but why only 6.6kW output when it is chilly outside?

(2) how can the RWT be 42 degrees when all the rads are cooler (crude average temp 31, 11 degrees below RWT)? There is no bypass that I am aware of, so this appears to be defying the laws of physics!

All in all system appears to be under-performing.

Any thoughts much appreciated.

@cathoderay you might have a low loss header stealing the warm water...

@batalto - I have a plate heat exchanger. Initially the installer or rather plumber had the flow going in the same direction on both circuits ie no contraflow (bit worrying they didn't know about this) and the heat transfer was abysmal, got that corrected, and for a while it seemed the heat transfer was good. But you have pointed to the reason why the rads can all be at lower temps than the RWT, they are not on the same circuit. Silly me...

But that still leaves the problem of why the heat transfer has gone back to being so poor. And why is a 14kW heat pump only outputting 6.6kW when the house clearly needs more? I think that is probably because the heat pump thinks it is putting out enough heat, because the RWT is high, so it looks like that too boils down to poor heat transfer across the heat exchanger.

The Midea app - I'm weighing up the pros and cons of getting a USB wireless adapter for the PC (<£10, keeps everything on the desktop with large screen and storage and ability to do things with data etc, but may not work) against getting a cheap basic smartphone or tablet (>£20, should work, but small screens, data transfer hassles, yet more gadgets to contend with).

@cathoderay,

Do you know where the flow and return temperature sensors are?  Are they in the ASHP or on the external pipes?  Can you use your thermometer on the flow pipe near the ASHP? That would give you an idea. A pipe with water in the mid 40s will feel distinctly hot to the touch. 

One of the features of my ASHP is that the flow temps can have an offset applied, i.e. you can add X degrees to the sensor readings and that's what the ASHP will use.  Might be worth checking.

Maybe switch weather comp off and try a fixed flow to see what happens?  You'll then know for sure what flow temp you should have.

Hi @cathoderay 

How accurate is your IR temperature sensor? Can you check it against a known reference temperature?

Posted by: @cathoderay

@batalto - I have a plate heat exchanger. Initially the installer or rather plumber had the flow going in the same direction on both circuits ie no contraflow (bit worrying they didn't know about this) and the heat transfer was abysmal, got that corrected, and for a while it seemed the heat transfer was good. But you have pointed to the reason why the rads can all be at lower temps than the RWT, they are not on the same circuit. Silly me...

But that still leaves the problem of why the heat transfer has gone back to being so poor. And why is a 14kW heat pump only outputting 6.6kW when the house clearly needs more? I think that is probably because the heat pump thinks it is putting out enough heat, because the RWT is high, so it looks like that too boils down to poor heat transfer across the heat exchanger.

The Midea app - I'm weighing up the pros and cons of getting a USB wireless adapter for the PC (<£10, keeps everything on the desktop with large screen and storage and ability to do things with data etc, but may not work) against getting a cheap basic smartphone or tablet (>£20, should work, but small screens, data transfer hassles, yet more gadgets to contend with).

   

Why was a plate heat exchanger installed? Do you know if your radiators have been balanced using the lock shield valves?

Is your weather compensation correctly optimised?

Do you have your heat loss calculations and the output capacity of your heat emitters?

When operating in a balanced manner, the heat output from the heat pump should be approximate to the heat loss of your home.

@kev-m - The LWT and RWT are shown on the Midea Controller Operational Parameters pages, so are coming from the heat pump box, but I'm not sure where the sensors are in the box. @grahamh might know. The primary flow from the heat pump in the DHW tank cupboard does feel definitely warm at times, at others more tepid.

The weather comp is still on the standard Freedom curve, ie 55@-2/37@15 which assuming it is linear is as near as LWT 1 degree down for each 1 degree up in ambient temp. If it was about 5 degrees ambient this morning, then a LWT of 48 is where it should be. My concern was the rads were significantly cooler, average about 31 degrees. I'd 'forgotten' about the heat exchanger, what seems to be happening is the heat exchanger isn't transferring the heat, so the RWT remains noticeably higher as well. 

@derek-m - I think the IR thermometer is reasonable accurate on the rads (+/- a degree or two). Difficult to have a reference temp that I know is X degrees to check it against. I do have a thermistor on a multimeter as well and if I leave that to stabilise on the rads it shows the same temp +/- a degree or two as the IR thermometer. The IR thermometer is less accurate (repeated readings vary) on pipework, even with black insulating tape on the pipework to get the emissivity in the right ball park.  

"Why was a plate heat exchanger installed? Do you know if your radiators have been balanced using the lock shield valves?" Freedom require it, warranty void if you don't fit one. My (vague) understanding is that it is to protect the primary heat pump circuit from crud in the secondary rad circuit, allow easy rad venting etc. Again, @grahamh might know. It is not without a penalty though, not 100% efficient transfer even when working as it should, and it means another circulating pump clocking up £££. The balancing was done with the lock shield valves, all TRVs fully open. Nearer rads are mostly 1 turn or less open, further away ones mostly close to fully or fully open. It is about 90% there (when the rads are working). The odd thing is various rads just stop warming up on a whim: warm one day, cool the next. TRVs have remained fully open, venting checked on cool rads, usually no air or occasionally minimal air.  

"Is your weather compensation correctly optimised?" As above, it is currently on the standard Freedom curve.

"Do you have your heat loss calculations and the output capacity of your heat emitters?" Yes. The four original quotes quotes from over a year ago all had different heat loss calculation results, some were patently wrong, and one later one was almost bordering on the absurd. Some just had silly mistakes eg 2m external wall for the largest triple aspect room in the house with 12m external wall. I actually did the original heat loss calcs in the 1980s for a solid fuel then oil boiler, and so I have an idea of what the loss is, though heat loss calcs in the real world on an old building are a far from exact calculation. External walls vary in thickness, how much to add for the inglenook, insulating effect of the kitchen cabinets covering much of the kitchen external walls? With that said, I think the heat loss as the house currently is (I am slowly improving insulation/draft-proofing where I can) is something just over 12kW. The rads are matched plus ~10% to the room heat losses at a flow of 55 degrees.    

"When operating in a balanced manner, the heat output from the heat pump should be approximate to the heat loss of your home." You may recall we've discussed this before, because of the fall off in heat pump output at higher flow temps and lower ambients, the heat pump (using Midea's Engineering Data tables) does not match the heat loss in these conditions. It looks like it should in the Freedom heat pump calculator, but only because the outputs in that calculator at high flow/low ambient temps are over-optimistic. 

@cathoderay,

you do have a good reference temp in your own (or another person's) body temp.  The variation in healthy humans is low; even the difference between hypothermia and extreme fever is only 3-4 degrees.  

It's puzzling; if water is leaving the ASHP at 48 degrees and is in the 30s in your radiators, all that that energy must be going somewhere.

I think someone more familiar with Midea specifics needs to help.  My system's flow temp sensors are on the pipes external to the ASHP. 

Are Freedom Heat Pumps/Midea one and the same thing?  From what you say they at least seem to at least have a very close relationship.