Posted by: @treewizard

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just replace with a wireless third party thermostat?

I wouldn't replace with a wireless third party thermostat, thrid party controls and heat pumps are generally best not mixed.  If you do contemplate this you need to be careful which you pick, simple on/off not smart control.

Posted by: @treewizard

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- Automatically modifying the thermostat temperature offset using another wireless thermometer

- Automatically adjust the leaving water temperature offset, to effectively apply an alternative weather compensation curve.

- Wireless serial bridge, so I can move the Modoka anywhere

Obviously if you like tinkering these are in principle possible, but personally I stick to the rule that mission critical things in a house need to be operable by the least techy person in the house and repairable by a reasonable third party.  Thats not to say I dont have some home automation, I do, but everything will work without it.  Obviously this is a personal choice influenced by age as much as anything else.

Does Daikin do a wireless controller instead of the wired one, that would be the best option by far if its available.

Another option is not to rely on the temperature sensor in the Madoka at all and run on pure weather compensation (which is what I do with my Vaillant, and many other heat pump owners do).  This is going to be the most efficient and there is a good chance the most comfortable!

Thank you for the advice.  Pure weather compensation would be a much simpler option, I'll check over the manuals and give it a go. 

For the time being, I've just set the offset to the maximum delta between the coldest and warmest points in the house. 

Posted by: @treewizard

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Thank you for the advice.  Pure weather compensation would be a much simpler option, I'll check over the manuals and give it a go. 

For the time being, I've just set the offset to the maximum delta between the coldest and warmest points in the house. 

If you do go for pure WC you may need to adjust the WC curve down (which will anyway improve efficiency) and possibly balance emitters.  Feel free to ask for guidance.  

If this is a recent install is there any point in asking the installer to relocate the Madoka to a sensible place where it can properly sense the IAT (even if you decide not to use that function) or is this water under the bridge?

The switch from WDC to LWT i.e. pure WC is fairly straight forward. Your current WDC will apply to the LWT mode except now your thermostat is a read only sensor. Your app will show Inside Temp, Outside Temp & Leaving Water Temp. Also the current offset if you get as far as using the scheduling which is off by default in LWT mode.

Your water pump will switch from OnDemand to sample. You might hear the pump operate periodically, if it's annoying there is a setting to limit pump speed in sample mode.

You will likely find the house gets too warm so you can start to lower the cold weather (LWT) temp to closer match the heat loss of your home.

If you don't like it then just switch back to WDC and change the slope back to your previous values.

Our Daikin is due to be installed next week. 

Today is very sunny day and the solar gain is substantial on our south facing side, which all living and bedrooms face (bar 1 bedroom).

Our Heat Pump will be installed on the other side of the house, North facing and in the shade all day.

It is significantly cooler there.

Our house is lovely and warm with no heating running today. North facing wall where the thermostat will be is 3c.

The issue we may have is the placement of the outdoor thermostat and the indoor room thermostat.

The room thermostat will be in the hallway, which only has a north facing window, so isn't as warm as the rest of the house.

We are aiming to run at 21c 24/7 with a small setback overnight for a few hours.

I am a little concerned that if I can get the WC curve right, the HP will run all day on low power and would only switch off if the hallway temperature hits its set point and the south facing rooms will continue to heat up.

Does anyone have experience of solar gain and how in practice this might work?

It's annoying that the Daikin thermostat is hard wired, otherwise I'd move the thermostat on sunny days to a south facing room.

@bash We have a Daikin EDLA08 Monobloc standing by our rear wall which faces SSW ‘ish’ and the wall has cavity filling beads in it. The pump thermostat is as you say, on a fixed position at the back of the bodywork and for most purposes, in the shade of any sun.

At time of installation, we had the MMI control connected to a NeoStat which communicated wirelessly. I didn’t want ‘bang-bang on or off’ control for the pump so set the NeoStat above the temperature we required and used WC via the MMI controls. The only reason I had the NeoStat was that the Homely smart control was a few months off from integration with the Daikin model we have. Using the MMI to set the WC required better sight than I have to get the finessing of the low and high points in the curve spot on but Homely then solved that for us.

As to the siting of the heat pump on the north side in the shade, I doubt that would be an insurmountable problem - better there than with the solar gain interfering. Perhaps judicious use of TRV’s to limit the highest temperature in any problematical rooms. I know this is not ideal as open circuits are so much more efficient and kinder to the heat pump. You may find careful setting of the LSV.s in the solar warmed rooms will go a long way towards reducing any need to throttle the flow with TRV’s.

As to the internal thermometer (can’t recall whether you said it was actually a ‘stat’ or not), does this sensor have to be sited in the cool hall rather than perhaps a living room environment? Regards, Toodles.

@toodles 

Yes, it's the Daikin hardwired room stat that comes with the HP.

Our HP is the same as yours, the 8kw.

I have considered the option of having the room stat in the lounge as an alternative. Thg only downside is it's at the other end of the house and would require the cable to run around 4 doors, the hallway and the stairs, which isn't very appealing!

We are fortunate that all our rooms are south facing (other than 1 bedroom, bathrooms and the utility).

If I rely on trvs I could end up with most of the radiators shutting down, which probably isn't ideal either.

@bash Sounds as though esthetics are not working in your favour then. Perhaps you might consider a wireless sensor for the job, I have a NeoAir kit lying idle but I wouldn’t even suggest this route. As most of your rooms face for solar gain, it sounds as though careful setting of the LSV’s is likely to be your first move. The rooms on the cooler side may require their LSV’s to be fully open as a starting point and only start closing those in overly warm rooms. You may be able to use a lower flow temperature once you have the radiators balanced. Regards, Toodles.

@toodles 

I'd come to the conclusion from (too much) reading that third party thermostats aren't the best way forward, so had already discounted them at this stage.

I had considered balancing the radiators to allow for solar gain, however I don't think this will work as when there is no sun the rooms go cold and I'd only have a limited amount of flow to those radiators,  so would then under heat.

We may need some floorboards lifting as part of the install, so I might have to be a bit persuasive and get the cable run under the floorboards.

My gut feeling is the room thermostat, which ideally will only be needed as a failsafe if we overheat, should be in a room that gets the solar gain (which is pretty much all of them.

@bash Yeap, that sounds like a good plan, the occupied rooms at the right temperature for comfort; the ‘cold rooms’ are these rooms having new (larger emitters) that would compensate for the greater demand than the sun-soaked rooms? This would help you to ‘even out’ the demand and enable you to use a lower flow temperature, then when the sun has gone shy on you, the WC would compensate. Regards, Toodles.

@toodles 

Yes. British Gas seems to have done an excellent job with the heat loss calculation.

Our hallway radiator, which is the coldest room, will be getting a radiator with triple the output of the current one.

All the others are being upgraded significantly as they designed to 45c @-2.

I'm pretty confident knowing our house as it is we will be running lower than that.

I reckon the curve will be somewhere around 40c@ -2c to 32c @10c