I bought a Heat Pump

Reed_Richards

I think with any heating system you have to be pragmatic, @akwexavante.  First make sure it is set up to give you the comfort you need.  Then try to find the most economical way to achieve that level of comfort. 

Of course in these times of high energy costs that may be a bit idealistic but there may well be ways to reduce your costs without compromising on comfort.  Getting the right weather compensation settings should help to minimise your costs.  My installer used quite conservative settings and I have been able to improve on these, so that the Leaving Water Temperature is lower, which should make my heat pump run more economically, but I still have the same level of comfort.

akwexavante

Reed_Richards said:

I think with any heating system you have to be pragmatic, @akwexavante.  First make sure it is set up to give you the comfort you need.  Then try to find the most economical way to achieve that level of comfort. 

Of course in these times of high energy costs that may be a bit idealistic but there may well be ways to reduce your costs without compromising on comfort.  Getting the right weather compensation settings should help to minimise your costs.  My installer used quite conservative settings and I have been able to improve on these, so that the Leaving Water Temperature is lower, which should make my heat pump run more economically, but I still have the same level of comfort.

I will do this, but it'll be 24/25 before i'm ready.  Firstly, i'm modernising / updating the home throughout.  Nothing's been done to it for decades, and it's in need of some repairs too.

I'm finding that pipework is old and a mix of cobbled together pipework of all sizes and routes between radiators etc.

Different boilers in different locations done by different installers, cobbling together new systems to old existing pipework.  I've shortened the route the pipework takes from entry into the home to the upstairs radiators by nearly half by re-routing the pipework upstairs.  Downstairs next summer, i know that there is some uninsulated 28mm pipework under the ground floor to remove along with three 22mm spurs that have just been capped off, one is nearly 3mtrs long!  What underfloor pipework i can see (which is limited) is not insulated yet.  This can explain why i struggled to get the rads downstairs warmed up, perhaps.  So i'm slowly removing excess pipework, re-routing, shortening travel distances, removing spurs and insulating and i'll have to re-adjust things as i go and then perhaps explore more advanced tweaks for next winter.  When i do the bathroom, i'll be removing the electric shower and swapping to the DHW tank too.

I'm hoping you will be able to offer some guidance when i'm ready.

Netexporter

If you are doing major renovations would that not be a good opportunity to install underfloor heating? There are a number of overlay systems that will add no more than 50mm, including a 15mm timber/tile finish. The lower flow temperature required will ensure a good COP.

Reed_Richards

Whilst underfloor heating throughout the house on both floors would ensure a good COP, a mixture of UFH and radiators may give you no benefit at all.  That's because you need the high flow temperature for the radiators so the fact that you have some UFH as well gives you no economic benefit. 

A very few heat pumps allow you to have two different zones with different target LWTs for the two zones.  That's only physically possible if the zone requiring the higher LWT is off, so you could turn your radiators off overnight whilst running the UFH more economically during that time.  But my LG heat pump is not sophisticated enough to do that and I don't think many others are. 

akwexavante

Netexporter said:

If you are doing major renovations would that not be a good opportunity to install underfloor heating? There are a number of overlay systems that will add no more than 50mm, including a 15mm timber/tile finish. The lower flow temperature required will ensure a good COP.

This is something that i'll explore and price up in the new year whilst i'm doing the bathroom.

Ooooops! Just read Read_Richards most recent post.............. won't happen, a decision made, thank you.

grahamm

Reed_Richards said:

So, your heat pump is controlled by the thermostat in your bedroom.  Set it at 24 C and the heat pump will try to make your bedroom 24 C.  Set it at 22 and it will try to make your bedroom 22. 
           

Thanks for your reply, but I do not think this is the case.

I've just remembered that I have a video that I took of my Installer explaining the system when he was commissioning it and, having looked at it again (with a bit better understanding of how the system works!), he says "The thermostat is not a thermostat and don't treat it as a thermostat", he goes on to say that I should set it to 24, but the house is designed to be at 21 degrees, however if the temperature did get up to 24, it would then turn the system of, but it shouldn't because the Weather Compensation will do its job and modulate the heat/ water temperature to keep things at 21.

The Thermostat in my bedroom (there's a receiver for it under the worktop in the kitchen) is manually set at 24 degrees (a temperature that the ASHP can manage) but it's actually 22.2 degrees and has been staying close to that for the past few days since I changed the Target Temperature on the main controller to 40 degrees.

The main LG controller (with all the fancy graphs) is in AI (automatic) mode which will have maximum water temperature at -2 degrees outside and taper off as it gets to 21 degrees, but that it was difficult to get it right straight away because it was 19 degrees outside when they installed the system.

I can adjust the curve slightly in AI mode to +/-5 degrees, however as mentioned, the original curve was set to maximum of 49 degrees which was clearly too high, so I've dropped it to 40. I may tweak it down another couple of degrees at some point, but it seems OK for now.

Mostly the doors to my rooms stay open (I don't have a family), so the temperature will balance out between them, although I could close them to check each room temperature individually at some point. BTW the sizes of the radiators were based on the measurements of the rooms and windows and the insulation I have which were used to calculate an approximate heat loss figure for each one.

I should also point out that I've been living here since 2005 and have no plans to move on (I'm in my late 50's) so I'm not worrying about what will happen with any future buyer.

So I think I'm going to leave things for a while and see how much electricity the system uses for the next month then, if it seems particularly excessive, I'll try changing things as you suggest.

Once again I'm very grateful for your assistance and explanations, because it's helped me to understand exactly what's going on

Reed_Richards

@grahamm, the explanation given by your installer is not any different from what I wrote; I guess I just did not make myself clear enough. 

Your installer was describing how things will work when everything is set up perfectly and correctly "tuned".  Unfortunately that's not the state he left your system in (it was too hot outside to run tests).  Your LWT was initially too hot and this forced the thermostat in your bedroom to intervene (as I described).

You have now modified your Weather Compensation setting to make the LWT less hot and it seems to work perfectly over the range of outside temperatures you have at the moment.  But it looks to me that the slope of the line is too shallow now, so I expect you will be too cold when it is really cold outside and/or too hot (i.e. 24 C) when it's milder.  But you will find that out in time.  Just try to make any further changes so that you keep the same LWT you have at the moment when the outside temperature is the same as you have at the moment.  To do that you will have to change both the Max and Min settings.

I also wonder if your target hot water temperature is set too high, particularly if you are on your own.  That won't affect your comfort but could cause you to use more electricity heating the hot water than you need to.  Most people with heat pumps seem to set the DHW tank temperature to be 40 to 50 C.  I have mine set to 50 C for the start of the day when we shower then, 44 C from mid morning onwards.

I hope things go well for you.

  

Reed_Richards

I had an eventful week this week. 

I'm retired, some mornings I putz around before getting dressed and so on Monday I did not shower until 10 am, when I noticed that the hot water was warm rather than hot.  Looking at the controls I saw that the heat pump had been trying and failing to heat the hot water since it came on at 06:30.  The reason it was failing was that the power to the heat pump was stuck at a maximum of about 2.2 kW, not nearly enough to heat my DHW cylinder to the desired 50 C.  Since DHW has priority I switched that off, so the heat pump could concentrate on trying to heat the house.  But it still could not manage more than about 2.2 kW input and an output water temperature of about 30 C (less efficient than usual).

I reported this problem to my installer and first thing on Tuesday morning I was able to generate a data file of the various heat pump parameters and email it to him.  His diagnosis was that I had a refrigerant leak.  By now the water temperature was about 27 C, it was 7 C outside and the house was maintaining about 17 C inside.  Fortunately my heat pump, which was installed almost exactly 3 years previously, has a 7 year warranty.

Refrigerant leaks are very slow and time consuming to repair.  I rate my installer very highly.  On Tuesday afternoon he phoned me with the news that he had persuaded the manufacturer, LG, to replace the heat pump rather than fund an expensive repair under warranty.

On Wednesday morning he arrived first thing and detached my old heat pump.  At about 11:00 a truck arrived with the new one and it also took the old one away (fortunately the driver was good natured and helped with the unloading and loading).  The replacement heat pump was attached, it was a newer model than my old one with a newer version of the controller.  Everything was finished by 13:00 and the new ASHP has been working fine since then.  The new heat pump has several new features for me to explore.

My installer tells me that in his experience refrigerant leaks are very rare with LG heat pumps.  I just feel incredibly fortunate that things worked out so well, and indebted to my installer.           

Reed_Richards

I started this thread two months after my heat pump was installed, which happened in December 2020.  At that time there were very few others posting about heat pumps on these boards; three years later and there are quite a lot of heat pump owners here now.  So this particular thread is probably of less interest to others now than when I started it.

I've just looked at my annual usages, which are:

27/12/20-28/12/21     6886 kWh
28/12/21-28/12/22     5117 kWh
28/12/22-28/12/23     5115 kWh

Before that I had an oil boiler and my best estimate of annual usage was 17935 kWh per year.  That is based on an optimistic assumption that my boiler operated at 90% efficiency.  I have no means of determining the Seasonal Coefficient of Performance of my heat pump other than through this comparison. 

One reason why my electricity usage might have been higher in my first year than in the next two was that I had not got my Weather Compensation settings optimised.  It must surely be a pure coincidence that the electricity usages for the last two years are almost exactly the same.

After what I am told was a very rare instance of a refrigerant leak, I am now on my second actual heat pump, a replacement under the 7 year warranty.  It is a newer model and seems to have a lower minimum power output, which could lead to improved efficiency.  Time will tell.

I would be happy to answer any questions posted on this thread.  Otherwise, I will come back in a year's time to report the 23-24 electricity usage.  

 


 

Reed_Richards

Looks like they didn't find this one.