Starting my journey with a Daikin ASHP

During the summer I had a Daikin EDLA06E2V3 installed under the BUS scheme. It wasn’t until the weather cooled that I discovered that it wasn’t performing as expected.

I have tried following the instructions to make appropriate adjustments but it still isn’t generating enough/any heat.

I have the installation manual and operation manual. They could be written in a foreign language for all the good they do me. I suspect that the installers using a third party room thermostat isn’t helping.

Does anyone know of an idiots’ guide, or something even easier than that?

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Daikin service staff have diagnosed that my house thermostat is not communicating with the heat pump controller. This is where the games begin as my installer used a third party thermostat and so far, just half a day, neither party will accept responsibility.

Hey Tim,
Yeah your third party controller is likely the problem, HPs are very picky about which controllers they work with (many use proprietary control signals), so unless your heat pump and 3rd party controller both support OpenTherm you may not be able to modulate output.
If you share the model of your HP and of your controller, others on the forum might have some tips?
We generally find Heat Geek to be good for optimisation advice, here’s their advice on optimising the daikin.
Hope that helps,

Not third party controller but third party thermostat. The wireless thermostat has lost contact with its own receiver, that is connected to the Daikin controller.

Hi Tim - I’m really sorry to hear that. Sounds like you need to take it up with the installer, clearly it’s not fit for purpose - can you use the MCS compaints process? What to do if things go wrong - MCS
I know that won’t get your heating working, but it might be enough to get the installer to come and sort it out…

I don’t know what my thermostat can do, when it’s working, that the Daikin one can’t. I would prefer everything from the same supplier as it avoids finger pointing and avoiding responsibility.

As it isn’t that cold where I am I’m not desperate and will try to keep on good terms with the installer. My wife, on the other hand, is from Zambia and does feel the cold.

Sorry I don’t have any specific help to offer, but out of interest, is your HP producing hot water ok (presumably stored in a tank)?

I have the hot water function turned off at the moment as I have a little end of season solar thermal and solar PV excess insufficient to run the HP. That will change as the weather gets colder.

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Today an engineer from the installer turned up and after a few hours work got the system up and running. Most of that time he was working on the thermostat/controller interface.

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@matt, after getting the heating system working (see above) I reviewed the video link you sent. Twice. I then used snippets from it to amend my settings.

I have now bypassed the troublesome thermostat by using only weather compensation with the room and all radiator thermostats set to 30°C. The house maintains a comfortable 20-21°C 24/7. There are no cold surfaces to radiate “coolth” and I am contemplating reducing flow temperature a degree or so to reduce electricity consumption and improve COP.

The current stage is to use the eTRVs in the bedrooms to limit the temperature where we are sleeping and increase flow temperature during our nightly 6 hour off peak electricity period. I am still experimenting but the hope is that I can preheat the house enough for the heating to cut back during the initial peak hours. This will doubtless increase our electricity consumption but may well reduce the cost. The cost difference between peak and off peak is over three fold.

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The next stage.

I have set a hot water schedule, which I can do with two target water temperatures, plus “stop”.

I have set a short lower temperature heat up as off peak rate starts, and I typically shower. Then I have a longer higher temperature heat up at the other end of the off peak period. Separately I have set the immersion heater for the end of that heat up in order to fully charge the thermal storage of water.
I like a warm shower, so lower temperature suits me. My wife typically showers late morning, after her exercise routine and likes the shower to practically take her skin off. There then needs to be enough hot water left for three children.
I do not use the heat pump to achieve maximum feasible temperature as it will badly affect COP. I would rather revert to space heating at a decent COP and let the immersion heater do its thing while electricity is cheaper.

For those new to heat pumps, a word (well, sentence) of wisdom. Heat pumps cannot heat your house and the hot water at the same time.
I was quite concerned when I found out, which is why I didn’t use mine for hot water until I’d finished experimenting with the heating.


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Tim, v. interesting to hear of your new-HP experiences. What temp-difference do you get now, between the In and Out on a typical radiator, eg living room? (I’m sure the gap/difference I see [on two magnetic thermometers] has decreased since I lowered our maximum flow temp, which bothers me; that’s from a gas boiler.)

I don’t have a way to measure the temperatures and as my radiators are all aluminium you solution won’t work

It is natural for the temperature gradient to reduce as the closer to room temperature the radiators get the less heat they lose. That is why big is beautiful for radiators in low temperature systems.

That’s big as in big surface area.

Ok. I’ve been looking at bigger rads (probably aluminium) as a further step towards low-temp operation, and HP; difficult to size them tho, different methods/online calcs give different ‘answers’…

In theory you should be able to choose a flow temperature, subtract target room temperature to get Δt and then look up the performance of radiators based on that Δt. However, there are few, if any, radiators with low enough Δt s defined. They are all based on gas at “normal” temperature ranges.

I just looked up Stelrad and they go down to Δt 20°C

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Returning to my heat pump journey:

Most of you may have noticed that we are having a rather cold snap. I was a comfortable temperature at 20.4°C (according the display in the hall). Other rooms were reporting similar temperatures. However it seems that Zambians like it warmer, so I raised the flow temperature a tiny bit using the weather compensation. At the same time I realised that the flow temperature remains constant above the warmest and below the coolest outdoor temperatures specified. I therefore extended the range by changing the lowest specified temperature from -4°C to -10°C and increasing the maximum flow temperature to 49°C. The COP won’t be particularly good at that temperature but at least we shouldn’t freeze.

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Hello again Tim, you probably know the answer to this: Are domestic radiators plumbed in ‘in series’, ie one after the other? Are radiators upstairs ‘in series’ with the ones downstairs? And related to this, if a TRV is set v low or at zero, say in a room that’s not used much, how does the warm water reach the next downstream rad? - does each rad have a diverter hot water pipe that can bypass the radiator? Or maybe zero on a TRV is not literally zero, but just minimal-flow?

So many questions!

There are 2 pipes that circulate heated water, one outbound and one return. Each radiator takes heated water from the “feed” and deposits cooled water into the return. Shutting down any or all radiators does not change this, although zero on a TRV isn’t actually zero, it is “frost protect” and comes on at about 5-8°C.

In the event that all radiators are off there is a bypass valve that directs water direct from the feed to the return and when the return temperature exceeds a set limit the heat source shuts down until it next tries a while later.

Ahaa… Thanks for that.