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2.06 COP on LG Therma V 12kW ASHP – no idea how to improve it

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(@leo-ramos)
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Hey all, have been using an ASHP daily since it was installed 2 weeks ago.
 
Installer said that I did not need to change my radiators and recommended setting the flow temperature (attached a pic of my rads) to a fixed 60c or maybe 55c. I tried the first day with 55c and got 100kWh consumed on that day, with outside temps going from 15c to 6c.
 
Got to research a bit more and started to learn how to tweak my unit, what is weather compensation, etc, and decreased the flow rate (still not have found the perfect Weather Compensation curve and the house started to get cold), but the COP without DHW is averaging 2.06. Is this correct? It's not even peak winter so this will go even down?
 
Is there anything I can do to improve my COP?
 
About my home:
Single-storey 170m2, constructed in 2008
102 radiator elements
Wall cavity insulated with 4mm XPS
Double glazing windows
No loft insulation (yet)
ASHP LG Therma V 12kW
100L Buffer Tank
 
I really appreciate any help you can provide!

   
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(@jamespa)
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There have been some cold days recently so on those you would expect low cop.  However operating at a fixed flow temp of 60C is sheer madness and will guarantee low cop whatever the oat.  You need to enable weather compensation and adjust the parameters for lowest possible flow temperature both when it's cold and when it's mild, leaving trvs and thermostats open so they don't throttle the system (later you can adjust them to 1-2C above the desired temp to act as limiters not controllers).  Your installer is misleading you and probably didn't balance the rads either, which may also be needed. I'm worried that he may have set up the control in a way which defeats wc given you have a buffer tank,   Likely as not the buffer tank is badly set up too, but we can come to that later ( what can you tell us about it?)

And do get loft insulation, it's cheap and effective!

Where in the country are you, just as a reference for climate.

Some things about your fabric don't make sense - 4mm xps = 40mm, 102 radiator elements?

 

This post was modified 3 months ago 2 times by JamesPa

   
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(@leo-ramos)
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Thanks for the reply @jamespa !

 

I set it up on the Therma V control unit to run at 45c for now - I was trying to tweak the Weather compensation (or AI mode in this specific HP) but it kept using a Leaving Flow Temperature bellow target, not sure why (for example, had the system at 50c flow at -3 outside and 35c when 16 outside - the HP keep it at 35-38c even when it was 6 outside, so the house called down to 16c)

No, they did not balance it, I'm trying to do it on my own but I'm not sure it's ok.

Posted by: @jamespa

I'm worried that he may have set up the control in a way which defeats wc given you have a buffer tank

What do you mean by this?

What I can tell about the Buffer Tank, is that it has its own pump to circulate the system and a thermostat that enables the pump that circulate the rads (attached a few pics for reference)

WhatsApp Image 2023 12 03 at 17.21.43(1)
WhatsApp Image 2023 12 03 at 17.21.43
WhatsApp Image 2023 12 03 at 17.21.43(2)

I live in Portugal, so the worst I might see here in the Winter is around -3 at night!

Posted by: @jamespa

Some things about your fabric don't make sense - 4mm xps = 40mm, 102 radiator elements?

Yes, sorry about that typo, it's 40mm of that that blue polystyrene. The radiator elements I mentioned are each individual part of my aluminun radiators around the house. Installer said that I would not need to change it, but at this point they also recommended starting with 60c flow temp, so I'm not sure now.

rads1

Thanks a lot!


   
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Mars
 Mars
(@editor)
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Posted by: @leo-ramos

Installer said that I did not need to change my radiators and recommended setting the flow temperature (attached a pic of my rads) to a fixed 60c or maybe 55c. I tried the first day with 55c and got 100kWh consumed on that day, with outside temps going from 15c to 6c.

Hang on. Running your heat pump to a set point of 60C or even 55C with outdoor temperatures above 6C is insane, so no wonder your COP is so low. You should be running at 35-45C to make the heat pump efficient. Does your house get really cold? Setting the heat pump to 45C should make your rads very, very warm to the touch. Are they? At 55-60C, they should be extremely hot. Are they?

Based on what you've said, this heat pump is not running anywhere where it should be.

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(@leo-ramos)
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Posted by: @editor

Posted by: @leo-ramos

Installer said that I did not need to change my radiators and recommended setting the flow temperature (attached a pic of my rads) to a fixed 60c or maybe 55c. I tried the first day with 55c and got 100kWh consumed on that day, with outside temps going from 15c to 6c.

Hang on. Running your heat pump to a set point of 60C or even 55C with outdoor temperatures above 6C is insane, so no wonder your COP is so low. You should be running at 35-45C to make the heat pump efficient. Does your house get really cold? Setting the heat pump to 45C should make your rads very, very warm to the touch. Are they? At 55-60C, they should be extremely hot. Are they?

Based on what you've said, this heat pump is not running anywhere where it should be.

Hey @editor !

After the weird suggestion of 60c from the installer, I changed the Flow Temperature to 45c, so this COP I mentioned (around 2) is with the Pump running at 45c fixed all day/night, The LG Therma V system gives me the energy, and the Heat output so I did the math to reach that number (this is the correct way of calculating this, right?).

Since the unresponsive weather compensation did not increase the flow temp, house dropped to 16c, right now it's 17c so I think it will take a couple of days to heat the house back.

Yes, I have a Thermal Leak detector and I'm reading the corresponding temperature from the flow to the entry valve of all radiators!

Thanks for the support!

 

 


   
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(@jamespa)
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Posted by: @leo-ramos

No, they did not balance it, I'm trying to do it on my own but I'm not sure it's ok.

Posted by: @jamespa

I'm worried that he may have set up the control in a way which defeats wc given you have a buffer tank

 

 

What do you mean by this?

OK step by step.  The bad news us that your installer is that clearly either ignorant about heat pumps or a cowboy or both.  The good news is that you appear to have  good components and a willingness to learn, so it can be fixed.

So, basic principle is work with as low a flow temp ft at any given oat as possible.  Use wc, adjust it so you are comfortable over a range of outdoor temps.  (Incidentally  I'm not sure ai is wc, I think this might be the next level of sophistication).

Have you got a system diagram? If so can you post it.  My concern about the buffer (which in a 170msq house is probably unnecessary) is that pump speeds etc may not be matched, resulting in mixing in the buffer costing 10% on your energy bill (and there are worse scenarios but the fact your house is warm suggests you have escaped those).  

Best approach with the rads now is suck it and see.  If you can get the ft down to a max of say 50 when it's cold and are still comfortable,  then no need to change them.  Otherwise it's a trade off between running costs and capital cost which you may need to consider downstream.

 

Ps I totally agree with @editor

This post was modified 3 months ago 2 times by JamesPa

   
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(@leo-ramos)
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Hey @jamespa, thanks for the comment! Yes, the AI is LG's new term for WC, I'll try again starting tomorrow, but I've seen multiple conflicting information on how to set this up. For example, should I set it outside -3c to 50c flow and 20c outside to 20c flow? Should I set it to my target temperature, like outside -3c to 50c flow and 16c outside to 35c flow? I'm still not sure what is the correct way to start testing.

 

Yes, I have this one:

WhatsApp Image 2023 12 03 at 19.03.32
WhatsApp Image 2023 12 03 at 19.03.32(1)
WhatsApp Image 2023 12 03 at 19.03.33

(added the other temp information for reference)

The external Pump has 3 velocities, as far as I understood, and it's currently on level II. I also had to change the Buffer Tank thermostat that was connected to the external Pump, as it was configured to wait for a 45c temperature to start the external pump.

It's currently at a fixed 45c, and the house it's getting warmer.

Thanks again!

 


   
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(@jamespa)
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Posted by: @leo-ramos

Hey @jamespa, thanks for the comment! Yes, the AI is LG's new term for WC, I'll try again starting tomorrow, but I've seen multiple conflicting information on how to set this up. For example, should I set it outside -3c to 50c flow and 20c outside to 20c flow? Should I set it to my target temperature, like outside -3c to 50c flow and 16c outside to 35c flow? I'm still not sure what is the correct way to start testing.

The setup is design specific and a starting point should be the design flow temp at the desing min temp, but I guess you dont have these (or they were never calculated).  However if its at 45 and the house is currently getting warmer then clearly it needs to be lower at current OAT.  If you don't know the design temperature then you don't have a lot to go on other than how the house responds.  Unfortunately I don't know the LG controller, so can only make general suggestions, and Im concerned that there may be other problems in the system which will obscure behaviour (eg I don't like 'no monitoring information' visible on the display).  Someone who does know the LG controller may be able to be more specific.

 

Ideally you need two periods when the OAT is stable for a couple of days, one at a fairly mild temp and one at a low temp.  You can then get it right at those two temps (making notes) and you have a line to draw between them.  You could start with whatever the temperature is currently (assuming its reasonably stable) and whatever ft you need to be comfortable at current temp.  Without more info its impossible to guess particularly as there appears to be little or no design and the distinct possibility that something isnt correctly set up which its difficult to tell without actually seeing it.

 

In the absence of any other info use the default WC parameters as a starting point, check WC is actually working.  If its not then something is amiss.

... or get your installer back and tell him to set up WC properly.  I don't know what the rules are in Portugal but here, if its an MCS registered installer (which most are) then WC is obligatory.

This post was modified 3 months ago 7 times by JamesPa

   
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