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Heat pump delta T too low - 2c

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(@derek-m)
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Posted by: @toodles

@derek-m Indeed, I agree with you entirely! This is the initial set up and although the installers have made a good neat job of the physical installation, they have suffered from a project manager’s ineptitude to the degree that after two weeks, some of the radiators had not been fitted due to non-arrival (Not ordered in time I suspect), finally all the radiators arrived but I am still awaiting the arrival of the Eddi relay card to control the dual fuel towel rail in summer. The electrician didn’t bother to check though I had written it all down for the project manager to pass on; he wired the towel rail to the secondary circuit on the Eddi - didn’t think to ask me why I had specified the relay card!

At one point, I enquired when the system was to be commissioned and the radiators balanced and was told they had balanced the radiators - there were still three missing at this point! Little things like lagging the pipework to and from the Sunamp Thermino had not been carried out and when I requested it be done, they asked me what needed lagging? There are still exit holes where they brought out power cables through walls that havent had repairs to them and with all the delays, they have been anxious to leave after a full days work so commissioning has not been given the attention it might have.

I am investigating the fitting of a Homely controller when a compatible version for Daikin is rolled-out and this will enable me to take greater advantage of Octopus Agile variable tariff rates as well as run the pump most efficiently. I don’t think I will be asking the installers to do this and I will be going directly to Daikin for annual servicing and fault insurance. One more visit from the electrician is booked for tomorrow when it is hope, he will complete his work. Regards, Toodles

Sorry to hear about your troubles, but I am afraid they are not unique.

I am not that familiar with the Eddi power diverter, but with my Immersun unit I can change the priority from Output 1, to Output 2 or even Output 3. I assume that your towel rail has a thermostat control, so the towel rail could have been set as the primary output, with the Eddi switching over to the secondary Sunamp load once the towel rail is up to temperature. It would periodically switch back to reheat the towel rail for a period of time.

What function does the relay card perform? Does it make it possible to supply available solar generation to both the Sunamp and the towel rail at the same time? The Sunamp via the Eddi and the towel rail via the relay card from the mains supply, but only when there is sufficient solar generation, so that no power is imported.

 


   
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Toodles
(@toodles)
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@derek-m That’s fine Derek, I don’t regard them as ‘troubles’ as such, just a slight failure on my part not to have chosen an installer who might have done the job properly without many interventions from me! I’m 75, retired with time to indulge where I wish and have a modicum of technical knowledge and am happy to read up before embarking on large expensive projects. To be fair to myself, I did consult 19 or 20 installers who were at minimum, MCS registered and thereby likely to be at least competent. Only 4 companies showed any interest at all and one even quoted and then told me the didn’t install in my area. A company I would like to have used based in Wilshire aren’t working as far afield as Toodle Towers though Emilie was very helpful to me.

Regarding the Eddi relay card; this has two switching circuits so is able to separately control two other circuits and will switch a supplied live feed to each. My idea is that I can then programme it to supply power to the towel rail at times and conditions of my own choosing. This may mean using PV power and / or grid power as required and at times / seasons of my choosing. The secondary circuit on the main Eddi control is used once the primary circuit has finished supplying power to the primary load. Regards, Toodles

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@ajdunlop)
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This post was modified 1 year ago by ajdunlop

   
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(@ant87)
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@derek-m Hi Derek, just to catch up is this a second pump on the system? As the Daikin EDLA08 has a built in PWM pump that works on the DT of the system and is adjustable in the controller from DT 3-10 I believe.

 

Thanks

Ant


   
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(@derek-m)
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Posted by: @ant87

@derek-m Hi Derek, just to catch up is this a second pump on the system? As the Daikin EDLA08 has a built in PWM pump that works on the DT of the system and is adjustable in the controller from DT 3-10 I believe.

 

Thanks

Ant

Please indicate the post to which you refer.

 


   
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(@ant87)
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@derek-m sorry that was meant to be to @toodles (I clicked reply on the wrong post)


   
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(@sunandair)
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Posted by: @ant87

As the Daikin EDLA08 has a built in PWM pump that works on the DT of the system and is adjustable in the controller from DT 3-10 I believe.

Hi Ant87
Im trying to understand how various manufacturers address control of DeltaT. Some heat pumps operate with external primary circulating pumps and others have internal primary pumps.  
From what you’ve written does the Daikin internal pump give the customer the option of setting the deltaT and then the HP regulates and modifies the flow rate to achieve the targeted deltaT? In other words does the flow rate vary during operation? For example if the DHW cycle starts on the Daikin system, and it needs a slower flow rate to maintain the targeted deltaT, than the main heating circuit. Does the controller automatically adjust the flow rate?

Or does the flow rate stay the same for both circuits? 

Any thoughts on this?

(My burning issue with variable speed primary pumps is the problem it might cause if there is a secondary room heating circuit installation…. In other words the problem of increased mixing between flow and return water through the hydronic separation leading to increased inefficiency.)

 


   
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(@ant87)
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@sunandair hi there.

 

The Daikin heat pumps will regulate their flow based on the return temperatures etc. So it might drop down to 15l/min for the heating and increase if the differential starts to increase i.e if its set to DT5 and the return drops in temperature the pump will increase.

(If the heating needs 35l/min it will then increase and so on). 

In the controller you can set your DT to between 3-10 degrees I think.

When it goes in to hot water mode or defrost it will then ramp up (I think between 80 to 100% pump power) the once satisfied it will then ease off to coast along with the heating. 

If you use their Madoka room thermostat it will then have an internal reference point and can adjust its own weather comp offset so if the weather comp is set to 40degC but the room is getting to temperature to quickly it will adjust its flow temp to say 38degC instead. 

The problem is when there's pre-plumbed cylinders or buffers etc. as the primary side is then PWM DT but the secondary side is fixed and so mixing of the secondary return can badly affect the heating system so the heat pump will likely have to run much hotter to compensate.

Cheers 

Ant 

 

 

Edit:

(The last part of your response coincides with mine I think) 


   
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Toodles
(@toodles)
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@sunandair Hello Sunandair, FWIIW, here’s my two pennorth worth on the subject: I have a Daikin EBL series 8 kW monobloc in the garden which feeds into a low less header in the airing cupboard. There is a secondary pump to control flow to the 9 emitters plus dual fuel towel rail, the pump is a Wilo variable speed jobbie (set fairly low as this not only gives a good Delta T for the emitters but runs very quietly too). My installer told me the Daikin monobloc pump is good at self regulation and with the LLH, the Delta T for the emitters is less critical this way. I have weather compensation in use and a Heatmiser thermostat / controller but, as I only had the installation in February, have yet to finesse the settings and use the stat as a limiter for warmer weather only. The WC has worked pretty well for us so far but come the winter, I can refine it. Was hoping to have a Homely stat / controller but as yet, their systems don’t cater for such a pump setup so I am waiting on a hoped-for workaround ‘some time’. Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@sunandair)
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Posted by: @ant87

If you use their Madoka room thermostat it will then have an internal reference point and can adjust its own weather comp offset so if the weather comp is set to 40degC but the room is getting to temperature to quickly it will adjust its flow temp to say 38degC instead

That’s interesting so it sounds like it allows the HP to modulate to a lower output? It’s a little similar to the Mitsubishi Auto adaptive function. 


   
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Toodles
(@toodles)
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@sunandair Well, I am impressed with the system so far anyway!! Next winter, when the system is working under full stress will be the final arbiter I suppose but, so far, so good. Our DHW is handled by a Sunamp Thermino ePV210 unit which is Eddi-fed from our solar panels or the grid. BTW, the secondary pump ‘jobbie’ is a Wilo Pico but i couldn’t remember that earlier (I’m nearly 76 y’know!) ;-))) So the heat pump is not labouring under our hotwater needs at all. The whole system is very quiet and unless I feel a radiator / emitter, the only way I can tell at a glance without opening the airing cupboard is that the power consumption rises 500 - 1000 watts as seen on the Tesla app. Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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(@ant87)
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@sunandair pretty much but I think the mitsi uses external pumps (I might be wrong) whereas the daikin is more of an all in one, very similar I guess to the Vaillant. You can operate with either the Daikin room stat, leaving water temperature only or via third party stats (the latter being less favourable).

The only reason to introduce LLH's etc really would be that the pump was not capable enough to deal with the system however I know on the 9,11,14,16kws they have something like a 12m head pump. The 4,6 and 8kw use something like an 8m head pump which usually has enough grunt to handle a radiator circuit.

The Madoka stat is really good, it has features such as solar PV room buffering so if you have PV, to save exporting it you can heat rooms to a temperature in excess of the stat (say 23degC) so when you get home the house has done most of the work via the PV. . .  but it can't control a zone valve or anything like that so when there is 2 zones or more you have to look at 3rd party thermostats etc. 

 

Cheers 

Ant 

 

 


   
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