Did they repressurise after the settling in period? My Vaillant shut itself off when it detected the low pressure. Our installer warned us that this was going to happen and was on the scene as soon as it did. 

@lfranklin. I've a similar system to you, 2 x 12kW Samsungs controlled by Hive and 5.6kW PV array, south facing. 

The trouble with PV and ASHPs is the yield from the first is tiny just at the time the demand from second is greatest. These last couple of months have been similarly challenging for me, with a PV average for Jan 2kWh/day and December 1.5kWh/day although come the summer I'm expecting 10x these. I reckon yield and demand will be much closer matched in Spring/Autumn and then around 4 months of free power in summer. You should see similar so don't despair juat yet.

It sounds like your radiators aren't balanced. I had a load of air in mine for weeks after the ASHP commissioning so if you're not regularly bleeding them I'd start there. Make sure you keep repressurising or you'll find water not reaching all the extremities as well! Also worth checking how your system is controlled - is it in 'weather compensation' mode (the controller will say 'Water Law' if it is) and what the temperature settings are - the manual should tell you how to do this but if not please repost. Your radiators won't feel hot like with a gas boiler but should feel warm and - in weather compensation mode - should get warmer as it gets colder outside. 

@dunlorn can I ask how many KWH you're using roughly per day for each 12kw system?

What system are you using for monitoring.. I have shinephone app. 

 I've found my graph shows massive spikes of power regularly through day and thermostat only set to 17° 😭

@lfranklin

Consumption is very much dependant on external temperature. In the recent freezing spells in December and early Jan (we're in Scottish Highlands) our system had a few days with a truly eye-watering 120-130kWh! A more typically cold day, say 1-3°C, will use around 60-70kWh and if it gets to a balmy 5 or 6° or more we'll see 50kWh or lower. In October/early Nov we were using 20-30kWh. I generally only use a single unit as not at all convinced that the second has any value other than increasing bills - it's something I've asked the installer to look at.

The consumption range has come as something of a surprise but, if you consider a single ASHP drawing around 5kW at low temperatures and on for 15-20hrs per day, then you can soon get to these numbers. At milder ambient temperature the unit may only draw 3kW, and be on for less of the day, so you can see the difference. Part of the reason for the drop in efficiency when you get near to freezing is the regular defrost cycles. Mine were happening around every 45 mins at peak and - whilst they need to happen - they do end up drawing heat from your system and can mean you never get up to set point water temperature.

I don't think your spikes are defrosts, more like on/off cycling. The Hive only has to drop 0.1°C from its target to start the heat pump. This isn't ideal. A lower water temperature may help but this is a matter for experimentation. I also tried moving my thermostat to different locations as I found some were very prone to generating on/off cycles.

I've deliberately not changed my installers settings for weather compensation (yet) but I think these are too high, 50°C at 2° ambient and 42°C at 15° ambient. Notwithstanding that, I've never seen my unit discharge water at more than 44°, even when freezing outside, so we never get near the set point!

There's no monitoring btw, just me popping my head in a few times a day and making a note. I certainly don't want to be doing this for the rest of my days! 

Posted by: @dunlorn

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@lfranklin

Consumption is very much dependant on external temperature. In the recent freezing spells in December and early Jan (we're in Scottish Highlands) our system had a few days with a truly eye-watering 120-130kWh! A more typically cold day, say 1-3°C, will use around 60-70kWh and if it gets to a balmy 5 or 6° or more we'll see 50kWh or lower. In October/early Nov we were using 20-30kWh. I generally only use a single unit as not at all convinced that the second has any value other than increasing bills - it's something I've asked the installer to look at.

The consumption range has come as something of a surprise but, if you consider a single ASHP drawing around 5kW at low temperatures and on for 15-20hrs per day, then you can soon get to these numbers. At milder ambient temperature the unit may only draw 3kW, and be on for less of the day, so you can see the difference. Part of the reason for the drop in efficiency when you get near to freezing is the regular defrost cycles. Mine were happening around every 45 mins at peak and - whilst they need to happen - they do end up drawing heat from your system and can mean you never get up to set point water temperature.

I don't think your spikes are defrosts, more like on/off cycling. The Hive only has to drop 0.1°C from its target to start the heat pump. This isn't ideal. A lower water temperature may help but this is a matter for experimentation. I also tried moving my thermostat to different locations as I found some were very prone to generating on/off cycles.

I've deliberately not changed my installers settings for weather compensation (yet) but I think these are too high, 50°C at 2° ambient and 42°C at 15° ambient. Notwithstanding that, I've never seen my unit discharge water at more than 44°, even when freezing outside, so we never get near the set point!

There's no monitoring btw, just me popping my head in a few times a day and making a note. I certainly don't want to be doing this for the rest of my days! 

I would suggest that you consider adjusting your weather compensation settings and then set your hive to 1C or 2C above the desired temperature. Doing so should hopefully reduce your consumption.

@derek-m thanks what setting would that be please ..in 201* &

202*

And what settings would you suggest I enter at first?

I work from home full time so tend to have at around 17-18° max through day and maybe 19-20° on an evening (well in a perfect world where its working ok)

@derek-m Thanks, I'll give that a go.

The installer (along with an engineer from Joules) has promised me a visit on 23rd Feb and I've a loooong list of questions. Most pressing is what controls the second (slave) unit, why it sends out water around 6° cooler than the master (when set-up appears identical) and why it makes no difference to comfort levels. Also, we've now had two days where for some reason LWT is stuck around 30°, and the system on constantly as it never reaches our 18 ° internal target. The list is getting longer. 

@dunlorn what does your compensation settings currently say in 201/202?

Posted by: @lfranklin

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@derek-m thanks what setting would that be please ..in 201* &

---

202*

And what settings would you suggest I enter at first?

I work from home full time so tend to have at around 17-18° max through day and maybe 19-20° on an evening (well in a perfect world where its working ok)

I'm afraid that I have to go mow the grass (she who must be obeyed has spoken), so I will formulate a reply shortly.

Posted by: @lfranklin

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@derek-m thanks what setting would that be please ..in 201* &

---

202*

And what settings would you suggest I enter at first?

I work from home full time so tend to have at around 17-18° max through day and maybe 19-20° on an evening (well in a perfect world where its working ok)

Now that I am back with the 'living', so that there is no confusion, could you clarify what is meant by 201 & 202 and to which manual you refer. I don't have a Samsung heat pump to play with and have downloaded a number of Samsung manuals.

Using the reference number and the text description would probably be best.