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.
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.
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?
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.
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?
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.
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.
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
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…
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.
Economiser I think is something old - it’s role is to preheat suction vapor before the compressor. It should tick or the rectifier should work above 40 degrees of liquid line temperature when a mixture of vapour and liquid appear in the liquid line. The temperature depends on type of refrigerant I think. This is only my opinion though…It’s quite complicated to understand the refrigerant direction in heating and cooling mode and what is the idea behind this without some measuring on site…
sorry, not very good at coping with lots going on here. For me, i see this as an occasional issue, like a cough and splutter from a performance car. Many units dont do it at all. For others, 95% of the time it looks fine. I think that the refrigerant control can be tricky to control, and occasionally it ‘crashes’. Manufacturers obviously dont want to spend more than they have to on development, so this is a case of us haveing to press them to take it serious. Unfortunately, this development work probably happens mostly in Japan etc. My hunch is that these issues will dissapear with new models… but I dont know. I feel they need to sample and modify the EEV more often. However, it could be something else… I dont know. Looking at the EEV pulses should enlighten us about what it might be.
Hi Matt, The internals of my heat pump have clearly not changed since my installation this summer.
What may be happening is that the operating environment (the ambient outside temperature and humidity) may be dipping into a zone where, as Marko suggested, the hp making poor assumptions becomes more likely.
I notice that the screenshot examples in this thread are happening during similar, lowish outside temperatures. Temperatures that my hp is experiencing for the first time.
In the last couple of days, when the weather has been milder, the problem has not exhibited.
perhaps you should change your name to Marko_Cynic…
