Something has gone quite wrong with my 8kW Daikin today!

dmajwool · 2024-11-29T19:25:52.504Z

johncantor:

it might be David’s one that has a varible flowrate/variable pump

Hi @johncantor, Hi @matt-drummer, Hi @alibloke, Here are a couple more instances from today where some “phantom electricity usage” occurred. I’ve included a trace for flowrate which remains constant through the 15 mins of abnormal output. See how for these 15 mins the simulated carnot trace is so much higher than the heat meter readings.

Screenshot 2024-11-29 1905241112×729 132 KB

This one when the system is waking up on a chilly 4C morning after being idle for 45 mins

Screenshot 2024-11-29 1903441113×727 117 KB

And this one after the pump had been idle for 90 mins in 7C outside temp.
Could there be a trigger connected with these idle periods in lowish temperature?

My system is Lindfield 8kW Daikin, but please ignore the rather severe air errors during DHW which I’m trying to purge with limited success. But that’s for another thread

matt-drummer · 2024-11-29T19:57:19.169Z

Hi David,

This is my one today, caught me by surprise, I was awake but driving to an airport so couldn’t do anything about it.

image1120×1167 236 KB

I haven’t been able to link this behaviour to any particular set of circumstances, mine had not been idle here. It had defrosted but I haven’t seen it after a defrost before and thought I was safe if it was running.

matt-drummer · 2024-11-29T19:59:48.273Z

This is another 8kW this morning.

image1150×997 159 KB

Looks awful and we didn’t see anything like this when they were installed last winter.

It is worrying me a little I have to say.

johncantor · 2024-11-29T23:03:33.703Z

This is quite dramatic isnt it? Its not at all good. When I first saw this type of thing on my 6kW Ecodan, I fitted a sensor of the discharge pipe from the compressor. This would at least confirm that liquid refrigeant is entering the compressor. Mine was. The next question is … what is the expansion valve doing at that time. I had an idea to look at the Expansion valve (LEV or EEV). I got as far as very carefully putting something like 2kohm (I think) resistors on the LEV signals, straight onto LEDs. This gives opening and closing pulse flashes. Next stage would have been an EmonTH with optical pulse sensor to count pulses. To know it the valve is opening or closing, a 2nd optical is needed… e.g. If ( LED2=on 10ms after LED1 pulse ; LEV opening; else LEV closing. It would be nice to see what a LEV was doing… but what will it tell us?? I would expect the LEV to be closing quite rapidly when the discharge temperature is so low (when heat output drops). However, maybe the sensors are oblivious to conditions, and the valve is opening up, making it worse. I dont actually have the knowhow to be able to configure an EmonTH with 2 optics, and the ability to read the state LED2 10ms after sensing LED1. How easy would this be to achieve? Can LEVs stick?? I dont know. However, if this were the case, we should see closing pulses with no response. Its still a thing I would like to complete. I’m sure something would be learnt

[Discussion about monitoring the Expansion Valve continues here:
Heat Pump Expansion Valve behaviour ]

dmajwool · 2024-11-29T23:28:55.630Z

If I’m understanding you correctly John, I think you are not suggesting that the refrigerant is leaking out of the heat pump (ie. escaping into the atmosphere), but rather that liquid refrigerant is likely finding an internal short-circuit into the wrong part of the compressor pipework - into a part of the cycle where it should be vapour - and it then takes some electrical energy to heat it up to correct the situation. Is that more-or-less what you are saying?

These screen shots and stories from at least four Daikin 8kW pumps are all showing the same behaviour. It seems unlikely that these are random experiences, and likely that the pattern will continue and be present in other systems using this pump.

So what to do about it? Perhaps if those other of us with this model of heat pump could scan our data for similar patterns we can approach Daikin / Octopus with some evidence and ask for a joint investigation and explanation of why this seemingly unproductive electricity is needed. If there are several unrelated installations with similar performance, it becomes difficult for the manufacturer to shrug it off.

Robert.Wall · 2024-12-01T23:14:05.370Z

6 posts were split to a new topic: Heat Pump Expansion Valve behaviour

John · 2024-11-30T10:59:47.516Z

Does anyone suffering from this problem have ESpAltherma installed? That would provide lots more data, at least as much as the HP itself has. That would be pretty useful, I know it includes lots of info on refrigerant temp and so on.

I’d be happy to assist someone if they are interested.

Marko_Cosic · 2024-11-30T22:46:41.212Z

@Ivailo_Stefanov summaries this nicely I think.

These units “fly blind” (inadequate sensing to truly know the state of the refrigeration cycle) and guess at the state using proxy information.

Sometimes they guess wrong.

Given how long the model has been about it’s either unfixable or the vendor doesn’t care because it doesn’t show in the official performance tests and people will keep buying them anyway?

Ivailo_Stefanov · 2024-12-01T07:06:13.097Z

The fix is quite easy. They just need to put pressure sensor for evaporation pressure and change the code. Almost every big chiller or heatpump has a controller that measure both pressure and temperature. Check Danfoss superheat controllers for instance. I think it’s just an old practice for small air conditioners and heatpumps for households. The producer prefers to change the refrigerant but not to fix all holes on a domestic heatpump systems.

Marko_Cosic · 2024-12-01T10:15:03.150Z

The fix is easy…if you want to spend £0.20?

This stinks of “let us improvise a cheap air conditioner into a monobloc heat pump as cheaply as possible” - in the air conditioner they can control how “easily” heat is removed (by varying fan speed) so they don’t need to worry about the situation where large radiators or underfloor heating can “sink” away the heat faster than their “lick the finger and guess at the state” algorithm assumes.

“Unfixable” for units out in the field… though perhaps if they half a brain they could use a flow rate sensor and the two temperatures to work out how quickly heat is being removed and “reset” the state (detect flooded evaporator) from there?

SarahH · 2024-12-01T10:36:30.252Z

perhaps you should change your name to Marko_Cynic…

(Afterthought - and keeping the trigonometric reference - that should be Marko_Sinic) S

Marko_Cosic · 2024-12-01T11:33:01.206Z

Unfortunately if it quacks like a duck… it’s often a duck.

Corporates rarely care. They’re probably furious at having been found out courtesy of open energy monitor. Whilst their design engineer wanting to spend £0.20 extra quietly mutters told you so…

I think I’d be filming the evaporator with a thermal camera, measuring discharge temperature, and asking octopus when they plan to install a product that’s of satisfactory quality and fit for purpose. After all, the MCS certificate they gave me is proof that the system is designed and installed to the highest standard.

Not because it’s material; but because they’re working together to prevent market access for better installers and better products. And a forcing them to fix one sets the legal precedent that they then have to go finish the rest of their homework and it’s no longer economic to do shoddy jobs with the cheapest products.

The only defence would be “this is as designed” but that would also be a clunker to put in writing.

meatballs · 2024-12-01T12:07:32.261Z

The sensors and diagrams can be seen on the installer reference guides (if you can find them). This is for the larger EDLAs.

There is a pressure sensor there on the refrigerant circuit (S1NPH) but is the suggestion that they need a second?

Screenshot_20241201-1205391080×1649 284 KB

matt-drummer · 2024-12-01T12:12:39.050Z

If this is a design fault why was this behaviour not evident from the start?

The Octopus/Daikin bashing is wearing a bit thin with me.

You are so good at telling us how bad they are.

I wanted a heat pump, I had many installers, including Heat geek registered, come to survey and quote, they either didn’t turn up, didn’t quote and one even insisted on a 14kW Daikin for my 100m2 house!

One wanted £25,000 for a Stiebel Eltron plus whatever radiator upgrades were deemed necessary. It would have been nice but beyond my means I am afraid.

What should I have done?

matt-drummer · 2024-12-01T12:24:40.793Z

I am sick of the Octopus bashing.

Out of any trades people that I have ever used they have been the best.

They replaced my heat pump along with many others with no fuss or cost. They respond to every request for help and engineers visit quickly.

Other companies, including Heat geek installers, can’t even answer enquiries let alone install heat pumps and deal with problems.

My installation is immaculate and I can’t see how anybody would have done a neater job.

And I have a SCOP of 5, as good as pretty much anything else.

How can any of it have been so bad?

Sour grapes that they rob `real professional heating engineers’ from exploiting the gullible like me?

And as for Daikin, are all the other manufacturers that great?

I don’t see any that are significantly better?

I didn’t have to pay hundreds of pounds for new hardware to update the firmware with my Daikin, they just came and did it foc.

We have an issue at the moment but it is not catastrophic and we just need to understand what has happened and how to deal with it.

SarahH · 2024-12-01T16:21:34.398Z

Hi @meatballs,
Have you figured out what makes the Economiser tick?
My Samsung has one, and from my PFD it looks like it produces a compressor suction sidestream, i.e. vapour injection (VI) at an intermediate pressure - plenty of info on the benefits of VI in the literature - but there aren’t enough instruments on it to allow reverse engineering, and the PFD in your post suggests that on the Daikin there isn’t even a suction sidestream. So what is it doing, and why?
Any thoughts welcome…
Sarah

meatballs · 2024-12-01T23:50:04.588Z

Way above my head sorry

Ivailo_Stefanov · 2024-12-02T08:29:23.363Z

Yes. They need second. Somewhere around R3T to monitor suction pressure. Also my opinion is they need to move R3T just before the compressor and position new pressure sensor there…

Ivailo_Stefanov · 2024-12-02T08:31:14.470Z

This type of pressure sensor is around 150 USD…

johncantor · 2024-12-02T08:33:28.005Z

Hi David. The refrigerant is ‘metered’ through from the hot high pressure side to the low pressure side through a modulating ‘throttle’ valve (aka expansion valve, TEV, EEV, LEV). if too closed, then the evaporator (cold side) only has liquid in say 1/2 of it. 2nd half of this heatexchanger just has vapour, so redundant. If the valve is too open, too much liquid flows to the evaporator, and this can then flow back to the compressor. Normally the compressor should only receive vapour. To be useful (energy wise), all evaporation should take place outside. if liquid vaporises inside the compressor, it robs heat from the wrong place.