@derek-m

@anng 

that is an astonishingly high amount of electricity. If I understand the pictures, you are burning through 4kWh in some 1/2 hours, which is 8kW. I'm not even sure your ASHP could consume that amount.  Is there anything else that could be consuming that amount of energy? If you turn the ASHP off for an hour, does the usage drop off?   

@kev-m I wonder the same. Maybe an immersion that's connected and switched on?

Posted by: @batalto

@kev-m I wonder the same. Maybe an immersion that's connected and switched on?

Good shout on the immersion. 🙄 

Also, Not sure if the LG is the same where it can only heat DHW or the UFH/Radiators, not both at the same time.

When my Vaillant ASHP was first put in, it was set to heat the water cylinder 24/7, and since DHW has priority, over the under floor heating & radiators, the house got cold, plus the backup immersion was also on so big bills... 

@colin that was my other suspect. Is it heating their hot water all the time. It's a good question to @anng.

Your heat pump should have a separate meter. Can you take a 24-hour reading from this and also post your smart meter reading for the same period.

@batalto 

we had our HW on 24/7 up until a week ago.  It doesn't make a lot of difference either way with HW at 50C.  Maybe if it's a lot higher.  Or the ASHP isn't heating the HW at all but an immersion is. But even then, Anng would actually have to be using the water. 

@anng

Sorry to hear about your experience so far. I’m no expert, just an interested observer, so I’m reluctant to suggest anything that may add to your worry, however If I’m interpreting  the thread correctly, then I would say that your installation may be undersized. The assessed heat loss for your property was quoted at 14.3kW at -3.56C (looks about right for your location), you indicate that the heat pump is an LG Therma V 16kW model, which sounds like it should be OK and that the outlet temperature is set to 50C. Looking at the LG website data sheet for the Therma V Monoblock HM161M.U33, which I assume is the right model, it quotes a performance of 16kW at 35C outlet temp and 7C outside temp, but only 12kW at 55C outlet temp and 7C outside temp. Due to the way this heat pump works, the heat power output will fall with falling external temperatures, and at the system design temperature it may well only be capable of around 10kW. This is below the requirements of the house, so it will probably be unable to provide adequate heat. The data sheet also indicates that the COP, coefficient of performance, is around 2.8 at that scenario and the pump will use around 4kW continuously, which seems to be your experience.

If you look at @batalto post and data for his installation, you can click on the system tab and see a graph that shows his installation is correctly sized, the pump output is greater than the design heat loss requirement at the design temp.

I would suggest that you ask the LG engineer to confirm that the installed heat pump model is capable of meeting your properties heat loss requirements.

If not, it could be made to work but only at 35C outlet temp, which would probably require oversized radiators.

Could anybody with more knowledge please verify my assumptions and reading of the LG spec sheet please, in order to assist @anng?

Sorry about the long post and technical detail.

@rusty 

Good spot.  I doubt I have any more knowledge but I agree with your interpretation of the LG figures as stated.  Maybe they don't tell the whole story; my ASHP also quotes 'nominal' figures but that isn't only output it can do; it can go higher ('maximum') and lower ('medium' and 'nominal') and can achieve its claimed 14kW in almost any conditions.   I don't know if the LG ASHPs are the same.  

I'm also a bit surprised by the 14.3kW requirement at design temp.  Even though we don't know the construction, that seems high for a 3 bed bungalow with a 18,000kWh/year EPC.  My 1990 bungalow is less than 8kW and its EPC assessment for heating was nearly 20,000kWh/year.  When it's 2-3C outside my ASHP consumes about 1.5kW to heat the whole house to 21C so it seems puzzling that this LG one consumes 4kW to not heat @Anng's house to what she wants.

If you're right though it would be concerning that LG's biggest domestic ASHP struggles to heat a 3 bed bungalow when it's not particularly cold outside.

Maybe @grahamh could comment given his recent article and knowledge of the different brands? 🙂  

@kev-m 

Kev,

The problems would not appear to be with the ASHP itself, but with the cowboys who installed it and the way it has been configured and commissioned.

@Kev M

I take you point about the spec sheet referring to nominal values, guess I’m used to more detailed specs! But how do you estimate performance and chose an adequate device without some more accurate information? Perhaps the installers have this information.

I was also puzzled by the size of the ASHP, the heat loss requirement and the annual heat energy requirements. It would be useful to see the heat loss calculations and the system design.

Looking at other heat pump specs, the LG one doesn’t seem that different, and the LG engineer indicated that it was working within expectations.

@Derek M

You may we’ll be right, I had overlooked Ann’s comment about the initial installation company as she referred to it as another story. There are so many things to consider, including the concerns raised about the radiators and the control system, siting, etc. I just thought best to start with the pump itself and the initial system design to eliminate this first.

Hopefully @anng will let us know the findings of the LG engineer report.

@rusty 

There are full performance test results that have been made available by Midea, (supplied by Batalto) and Mitsubishi (supplied by Kev), that have been carried out to EU Standards. They make interesting reading as to how the different sized units perform over the normal ambient air temperature range, and also just outside the normal range.

There may be similar data available from other manufacturers that I have not yet seen.