Posted by: @archibold

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I've spoken to the installer a couple of times and they are not sure, but would a simple solution to move the ecodan controller to the house (instead of with the integrated boiler unit in the garage)?  We have a cable conduit that we could use, but would appreciate any thoughts/ideas before I go back to the installers

In short, yes.

Then turn the hive (if it is connected which seems to be in doubt for some reason) up to a temperature about 2C above that desired, so the main temperature control is down to the heat pump.  You may need to adjust the WC curve and/or set it to auto adapt if this has not already been done, but it sounds like it probably has.

Posted by: @archibold

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@jamespa Thanks, appreciated.  I don't think it has been done correctly (e.g. the controller is in the garage and not the house, but easy to move - they had to do quite a bit of re-work on piping etc).  Pondering whether to replace the Hive with the Mitsubishi remote controller, so it is all on the same platform/system (it doesn't need to be hive). 

I think the installer is out of their depth as reading between the lines they have only done it before where the system is in the house and there was quite a bit of staff turnover during the installation/commissioning.  Also different staff came for different parts of the job (radiators versus ASHP) and I don't think they were talking to each other.  To be fair, I'd assumed that they were project managing things, but in hindsight I should have checked that or got our builder involved.

As far as I can tell the system is not running on weather compensation, so won't be as efficient as it could be.  It's all a learning curve!  I need to figure out whether to go back to the installer, or find someone else to come and review (I'm assuming Mitsubishi won't be much help, but I haven't tried that route).  Thoughts apprecaited!

You have various options.

If it is not too difficult the display part of the Ecodan controller could be moved into your home and located in the main living area, which would allow the auto adaptation function to be utilised should you wish to do so.

Alternatively you could leave your system as is, and use the Weather Compensation mode (WC) in conjunction with the Hive thermostat, provided that the Hive thermostat does not have a cycling function that cannot be disabled.

The objective should be to use any room thermostat (Hive or otherwise) as a high Indoor Air Temperature (IAT) limiter, such that it is normally calling for heating and enables the heat pump to operate. If the IAT should increase above the desired level due to solar gain or human activity, the room thermostat would disable heat pump operation until the room thermostat resets.

Normal IAT control should be achieved by the heat pump controller varying the Leaving Water Temperature (LWT) dependent upon the Outside Air Temperature (OAT), which in turn varies the heat loss from your home.

More information about your system may be helpful so that more detailed advice can be provided. Photo's are also useful.