Has anyone replaced an old ASHP with a new one?

Pressure · 2024-12-17T17:18:46Z

I have a first-gen Daikin heat pump which was installed in 2008. It looks like the compressor in the external unit might be failing and a new one will cost in the region of £2.5K. I talked to a Daikin engineer today and he suggested that it might be worth buying an entire new system rather than sticking with 16 year old technology. I am a little skeptical, simply because £2.5K will be a lot less than a full new install. On the other hand, a new unit might be cheaper to run, and certainly would be easier to understand and control. Has anyone else faced this kind of dilemma and what did you do?

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Air Source Heat Pumps (ASHPs)

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Mars

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15/02/2025 10:20 pm

@pressure sounds like a positive outcome and glad you’re happy with it so far. Keep us posted on your progress and whether running costs are better than with your old unit.

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Tim441

(@tim441)

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16/02/2025 4:30 pm

@pressure very interesting read - thanks for posting. A lot of us will have such decisions in coming years. Hopefully mine is still 10 years away.. LG installed 2020.

How did you decide on 9kw? Did you do heat loss calcs as if new install? Of use actual data from existing heat pump? Or??

Mine is currently 16kw which I think is probably about "right size" on paper but with the way we run with cooler bedrooms and some other rooms also cooler I suspect we could drop to something like 10 or 12 kw.

I don't know how much improvement there might be to COP over the years?

This post was modified 11 months ago by Tim441

Listed Grade 2 building with large modern extension.
LG Therma V 16kw ASHP
Underfloor heating + Rads
8kw pv solar
3 x 8.2kw GivEnergy batteries
1 x GivEnergy Gen1 hybrid 5.0kw inverter
Manual changeover EPS
MG4 EV

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Pressure

(@pressure)

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Posts: 12

Topic starter 29/03/2025 10:18 am

I settled on 9 kw after:

1. Doing heat loss calcs using free online calculators to give me an idea of the likely requirement

2. the installer got a proper, detailed calculation done based on the house plans etc.

In the end the calcs said 8kw would work but the 9 kw model has a back up immersion heater, which recent experience indicated we definitely need!

I think the new system is more efficient but I won’t have the data to demonstrate that properly for a few months. It’s been quiet and trouble free so far.

This post was modified 10 months ago by Pressure

Built house with 16kw gen-1 Daikin heat pump in 2008. Installed replacement 3rd-gen 9kw Daikin heat pump 2025. 5.6kw solar. Heat recovery and ventilation. UFH. Massive insulation.

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