Posted by: @craigh

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Cheers @majordennisbloodnok, an excellent and informative answer without getting too technical so I could understand it easy enough.

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Not a problem, @craigh. Glad I managed to get the balance right this time - I have a tendency to waffle and get too tied in detail.

Posted by: @craigh

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My head was a bit blown off when I had the heat pump installed, got a snippet of info on how to use the room thermostat to operate it and kept having to get up in the night to turn it down.

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I can imagine. I remember when we had our heat pump installed and, although our installers did a great job of handing over enough - but not too much - detail, it was still immediately obvious there'd be a bit of a learning curve.

As for the room thermostat, you'll probably have read enough already on this forum to know that under most circumstances our collective recommendation is to make your life easier and not use the thermostat at all (i.e. set it a few degrees higher than you'd like your room to be so that it acts as a backstop that's pretty much never activated), tinkering with the weather compensation curve instead until it delivers just the right temperature on its own.

Posted by: @craigh

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Yes I am the type to tinkle, I really just want to know that the heat pumps running efficiently and that my changes to the WD curve aren't running it in a way that will cause excessive wear on components and it sounded like one of these gadgets was the way to go. I do struggle with technology but I'm always willing to try. Many thanks.

The weather compensation curve won't cause any excessive wear at all. What'll have the potential to do that is your heat pump cycling - stopping and starting - too frequently. As a rule of thumb, more than four stops and starts in an hour is too many, and it's far more likely for a thermostat (with it's on/off nature) to get the heat pump doing this than the weather curve that's encouraging longer runs at lower temperature.

Whilst you've got your crampons on and are clinging to the cliff face halfway up the learning curve, I would suggest you just get used to the figures being provided to you by your heat pump's app and/or web portal. I'm well aware Onecta (the app) is a bit simplistic but once you get used enough to it to see its limitations you'll have a better idea of what problem you want to fix with your next step. And in the meantime, if you're really concerned about whether the heat pump is cycling or not, your most low-tech option is to grab a cuppa and spend 15 minutes or so sitting or standing next to the outside unit and noting how often it stops doing its thing - I know, with someone with me, I can happily spend more than that time having a chat, so it doesn't have to be a chore.

Once you do decide the standard tools are inadequate, then's the time to pop back here and start picking a few collective brain cells. We've a wide range of approaches taken by a wide range of people so there'll be plenty of choice for you.

@majordennisbloodnok I'm just brewing up, putting my thermals on and heading outside for a while, It takes me about 15 minutes to write a reply so that will help time fly, lol. It's definitely turning on and off now rather than running constantly as it has been. Is it best to put the WD curve back to what it was the other day and have the house slightly too warm but not cycling? I'm running on leaving water mode, yep I'm the type of idiot who likes to run before he can walk. Thanks for taking time to reply, your advice is greatly appreciated.

@toodles, thank you for the info. That looks a serious piece of kit!

Posted by: @craigh

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@majordennisbloodnok I'm just brewing up, putting my thermals on and heading outside for a while, It takes me about 15 minutes to write a reply so that will help time fly, lol. It's definitely turning on and off now rather than running constantly as it has been. Is it best to put the WD curve back to what it was the other day and have the house slightly too warm but not cycling? I'm running on leaving water mode, yep I'm the type of idiot who likes to run before he can walk. Thanks for taking time to reply, your advice is greatly appreciated.

To put things into perspective, a few weeks of short cycling still won't be a big problem. You've plenty of time to get used to the system.

Your home should be at the temperature that is right for you. That should be non-negotiable. Right now, the outside temperature is warm enough that you should expect some cycling, so now is the best time to find out how your heat pump is reacting. Use this time as information gathering rather than too much in the way of active control. Under ideal circumstances, your heat pump will try to keep operating constantly and turning the flow temperature down as the outside air temperature rises. It'll only stop altogether when it's hit its lower limit for how low it can turn the flow temperature and stopping is the only other way to avoid putting too much heat into your home.

Bear in mind, however, that you've still got your room thermostat up and running. Whilst that is still playing an active part, if your weather compensation curve is still a bit too high and the natural balance for it is to maintain your home at a slightly higher temperature than the thermostat wants, your heat pump will be trying to keep going low and slow and the thermostat will rudely jump in at frequent intervals and say "No, that's too warm - heat pump, you've got to stop." There's no turning the heat pump down a bit; it's either on or off.

Have you taken a look yet at the recommended topics for new members? In particular, the topic worth your having a good look at is the ABCs of ASHPs. That gives a much better overall explanation about what's going on than I can give here and also gives a good pathway for how to set things up well.

@majordennisbloodnok I will have a look at the ABC post, thanks for the heads up👍

Can I ask people's thoughts on whether running in pure lwt mode is far more efficient than setting it up as a room thermostat using the madoka running weather dependent and using modulation and overshoots? Is this way less efficient or just a bit and does this also help reducing cycling as that was another problem I was having running the daikin in lwt mode. Thank you 

Posted by: @craigh

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Can I ask people's thoughts on whether running in pure lwt mode is far more efficient than setting it up as a room thermostat using the madoka running weather dependent and using modulation and overshoots? Is this way less efficient or just a bit and does this also help reducing cycling as that was another problem I was having running the daikin in lwt mode. Thank you 

In general pure LWT mode will be more efficient because it means you are operating at the lowest flow temperature.  It may well, depending on house, also be the most comfortable, however you can only determine this by experiment.   As a concrete example (and after several experiments) I run my Vaillant ASHP in pure LWT mode for almost all of the season, switching to what Vaillant call 'extended' mode only at the very end of the season, when solar gain begins to be significant in comparison with loss.  Extended mode is the Vaillant equivalent of what you are proposing, ie using the manufacturers temperature sensor as a limiter.  I find this combination by far the most comfortable, throughout most of the season running in extended mode leads to unwanted downside temperature swings and too long spent 'off' for comfort.  

In terms of what the efficiency loss is for departing from pure LWT mode, its about 2.5-3% for each degree that the WC curve is set above the optimum (the optimum being the settings for the WC curve that just heats the house when the heat pump is run on pure LWT.  So if you run in thermostat mode having first adjusted the WC curve to be near optimum, you wont lose much efficiency (and if you havent first adjusted it to be near optimum, then you should).

I think the message from this, applicable to most cases (there are alwawy exceptions) is - adjust the LWT curve first to just heat your house when the heat pump is run 24x7 and all or almost all TRVs/zone valves/thermostats are set to max.  Then (and only then) do whats most comfortable in terms of using or not using a thermostat. 

Cycling is principally dependent on house loss vs minimum turn down, not so much on the operating mode.  This is something you cant do anything about!  Cycling when the OAT is above about 11C is more or less inevitable in the UK; if your heat pump is cycling below about 8C then its an indication that its oversized.  Switching from pure LWT mode to thermostat mode will principally change the nature of the cycling, making the period longer or shorter depending on various factors.  If your system volume is low so that, in pure LWT mode, your cycles are short (say every 20mins or less for an on/off) then operating in thermostat mode may well lengthen them and be beneficial.  If your cycles are anyway long then its unlikely to be beneficial.  If you are suffering from short cycling then increasing system volume by adding a volumiser is probably the best bet, unless you are NOT already operating fully (or largely) open loop - ie without active TRVs or zone valves.  In the latter case switching to open loop operation and if necessary balancing radiators/loops is the best course of action in the first instance.

Some people set a minimum flow temperature that is higher than is strictly necessary to maintain room temperature, as a means to reduce cycling.  This means that, on mild days, the room temp will rise a bit above the desired (increasing the loss, hence why the trick works).  Some find this acceptable but I cant say that it is likely to yield savings.

Hopefully that helps.  Its not Daikin specific but I know of no reason why Daikin heat pumps will perform differently from all others given that the above is pretty much a direct consequence of the physics and they are subject to the same laws!

@jamespa Many thanks for your reply, a very detailed and informative response. I will follow your advice and keep persisting to get my wd curve optimised. Thanks again. Regards Craig