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Problems with Daikin 18 kW High Temp ASHP

Bramshot · 2022-11-29T12:38:25Z

Firstly, the description, it turns out that it is not an 18 kW heat pump at all, but more like 12 kW with a 6 kW so called ‘ backup heater’. So feel cheated by that to start with. DHW, claims it can produce leaving water at up to 70 C, so DHW at say 60 should not be a problem, right? No, it cuts out at DHW 55. OK , not the end of the world and 55 is more than adequate but if you can set 60 ( you can set higher) it should be able to do it! No apparent reason for it to shut down. Disinfection cycle uses immersion ( ‘booster ‘ in Daikin speak) to get it up over 60. Despite this, in general, it has been working well until the colder weather came along. I now find that when ambient drops to 2 or 3 it starts to freeze up on the evaporator, and has to do a defrost cycle once an hour. This takes around 15 min, so it’s on for an hour , off for 15 min. It never reaches its set leaving water temp, so heating the house is suffering. And we haven’t had any really cold weather yet. I am sure it would be ok, it it could only last longer than an hour between defrost cycles. Are these things designed for our relatively humid winters as opposed to cold dry continental winters. Have I been sold a ‘pup’? Has anyone else had experience of these units?

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Air Source Heat Pumps (ASHPs)

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Bramshot

(@bramshot)

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Topic starter 10/04/2024 4:30 pm

@haggistrap Mine is ok until ambient gets down nearer freezing, say sub 4 degrees. Be interesting to hear how yours performs with a full charge of refrigerant but I suppose we will have to wait until next winter to find out now! I wonder if they will put it out as something that should be checked on all units?

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HCas

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11/04/2024 2:05 pm

@bramshot Interesting work-around you created with Hive, smart!! It still remains an on/off control, but you've essentially reduced the number of on/off cycles.

Did you also set a schedule in Hive?

Are you using the smart TRVs, or just the thermostat?

CEO and co-founder at HavenWise

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Bramshot

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Topic starter 11/04/2024 5:00 pm

@hcas I use schedules both with the wall stat and TRVs.

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HCas

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12/04/2024 8:40 am

@bramshot Interesting! Do you know what COP you get?
I'd imagine you prioritise control over minimal cost then?

CEO and co-founder at HavenWise

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Terry Nolan

(@haggistrap)

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12/04/2024 8:51 am

Just curious on COP. Mine is sitting around 3.3 -3.5 with outside temp 8 to 10c. Don’t want to get in to mine is better than yours but I think that’s about standard, or rather it looks acceptable.

I just leave my hive On, I.e. it’s just an easy way to zone / schedual heating on/ off. TRVs set to max mostly through house, with bedroom ones limited to around 19 20c.

set ASHP to weather compensation mode now.

if any one interested, the gas report from engineer came back. It was missing 840g of R32 gas. Now it’s back to 4.2kg of r32. Time will tell if it helps.

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Bramshot

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Topic starter 12/04/2024 10:36 am

@haggistrap I have no idea what the COP is mine does not tell me anywhere.

The HP is effectively on most of the time. I only use Heat on Demand for a couple of the TRVs, the ones with the Highest demand. The room stat schedule is mainly used for part of the day where I want to make sure the heating is on to get a boost during my off peak electricity period ( 00:30 to 04:30) when hot water has done for the day, so there is no heating required for a while and my battery lasts a bit longer in the on peak time.

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