J1mbo

It sounds like the meter monitoring is dependent on some external piece of hardware. Contact the installer as having some form of metering for the heat pump is a requirement for the RHI. They should have shown you this as it is part of the RHI annual declaration.

@Hogboon - possibly on the main controller there is an 'energy' menu with the electric consumption data: Information Of Meter Interface - LG Therma V series Owner's Manual [Page 36] | ManualsLib

The other issue is that the heat demand is listed as 12.3kW. Assuming you want the heat pump to deliver DHW, there is no power left to do so with a 12kW ASHP. Maybe it would be worth looking at a 16kW ASHP or use 2x 8kW-ish outdoor units, which would also give some capability to survive breakdowns.

I don't. But, radiator output is a function of surface area and surface temperature. Looking back at your spreadsheet, your requirement is going to be quite challenging. No heat pump will work with what you have and qualify for RHI. Radiators are usually rated at DT50. This means, the average surface temperature of them being 50°C higher than the ambient air temperature. i.e. at flow of 75°C and a return of 65°C at 20°C room temperature. To get decent running costs the heat pump probably wants to be run at 45°C flow and 40°C return (or maybe 50/45). Therefore the target DT from a radiator perspective is just 22.5°C. Hence, the surface area needed is much, much greater and the water speed needed also double (since the radiator is being specified to give up 5 instead of 10 degrees or water temperature). Looking in particular at the lounge. The heat demand is 2.8kW. Some of the most effective radiators are aluminium fin style such as Faral Tropical 95 (datasheet is available from here). The 672mm high FT9-672 provides about 50W per section at dT=22°C. That would mean a total of 56 sections needed for this room. At dT=30° (52.5 flow / 47.5 return) it's 76W, requiring 37 sections. The piping may also need some thought. To deliver 12kW with 5° across flow and return the heat pump will need to deliver 2,100 litres per hour or so, meaning 28mm flow and return there as usual. But the way the radiators are linked should be considered. The lounge will need 500 litres per hour so if the radiators are on the end of a run serving others, this might be a problem. The plan calls for 2 radiators but it might be worth thinking about more if the room design allows for that and have that room served from 22mm pipe going back to the 28mm. There also won't be anything like enough water in the 12 panel rads specified, so a larger buffer tank will be needed - reckon on total water volume of 240 litres being needed in the system to avoid short-cycling mid-season. If there is anything you can do to reduce the thermal load, such as maybe updating glazing or adding wall insulation, it would be a good idea to do so.

Yes it will give 55 degrees all day long but it will cost you much more to run like that and it won’t achieve 3.6 in practice. Really, spend the money on the radiators. And also be sure to specify Vaillant’s own controls, like Ambisense.

The heat pump should also have meters either built in or connected to it assuming it was installed under the RHI.

It’s a nightmare tbh with all these “smart” controllers being hooked up to simple contact inputs on heat pumps. It should not even be allowed in my opinion, for whatever that is worth. I feel sure that it is precisely these controls that will further hurt heat pump reputation as unresponsive and having poor output. Anyway, the hive won’t start doing the TPI thing until the temperature is within 1 degree of the set point. Yes the room will overshoot, and that’s what you need to find out so that you can tune the weather curve to your particular home by turning down the min/max temps based on observations. For now obviously making sure it heats enough is however the priority. To minimise running costs, the heat pump compressor ideally would run continuously and the radiator temperature be just enough to keep the temperature up. If either are not true then the COP is impacted and the running cost increases. Obviously there are too many variables (how much the property is heated, amount of hot water demand, how much solar heat gain ie sunshine, how much other thermal output in the house like cooking, just people being there etc) to have a perfect setting at all times but right now the heat pump is very likely set much too hot. So you need to monitor it for a few weeks and see how much the settings can be tweaked to reduce overshoot whilst providing adequate warm up. If you get to the point that you’re happy with it with the Hive controller and aren’t trying to squeeze every last percent of efficiency from the system then fine. You might even be able to log a ticket with Hive to have them turn off TPI for yours if the setting is not in the app. I suspect that the system will cost less to run and be more responsive with LG controls though, but will need yet more configuration.

TPI is an algorithm used to reduce overshoot by on-off thermostats. Basically it cycles the heating on-off periodically as the set point is approached, thereby reducing the average surface temperature of the radiators. Heat pumps with weather compensation are always controlling the surface temperature and hence the two conflict. Short cycling is the compressor running for short intervals. Since there are losses in the pre-run and as the pressure builds, each compressor start costs efficiency. Running the compressor for less than about 10 minutes each cycle will reduce COP and therefore increase running costs. The TPI programme probably only takes effect within 1 degree of the set point (either side). Therefore you want the Hive to be at least two degrees above your actual desired temperature to eliminate the short cycling risk. The house temperature dropped initially because the heat pump was heating the DHW.

Set the hive to well above where you want the room as well.

Progress! Since outdoor temp for auto mode min is -10, it will almost never reach the max flow and the general flow temp will be lower. Change it to -1. Indoor temp probably shifts the whole curve up and down. Try 18/23. LWT are the flow temps themselves. Change the min to something higher eg 30.

You are right. There is definitely a market for a heat pump troubleshooting and configuration service, though getting a reasonable rate of pay for that might be a challenge. The current trend of smart heating with individual room control is another enemy of the heat pump, since around 20 litres of water are needed circulating per kW of output at all times to avoid short cycling too. Longer term I suppose the products will have to evolve with higher compressor modulation ratios, enabling them to more readily match demand mid-season, and eliminate buffer tanks since many (most!) properties simply don't have the space for one given a DHW cylinder will be needed. And, there is no reason why the heat curves and pump speeds can't all be solved automatically with a continual feedback loop. All this manual configuration is representative I feel of the manufacturers not being software companies, it's a bit like the challenge the established automobile manufacturers are facing when compared to the new-entrants. It is obvious that the heat pump, with suitable interior sensors, can learn the heat curves needed with no user input and continually adjust these in relation to (for example) solar thermal gain.

You can find the Arotherm Plus SCOP values for all flow temperatures up to 55°C on the MCS directory here: Product directory - MCS (mcscertified.com) Search by manufacturer, 'Vaillant Group UK Ltd', then the 12kW is on the second page. The rating is 3.63 at 55°C (and 3.92 at 50°C). The increased SCOP will directly affect the RHI payments vs the Ecodan (i.e. they will be higher with the Vaillant). Personally I wouldn't skimp on the radiators. You want the flow temperature design as low as possible because this increases the declared SCOP for the product and in turn this increases your RHI payments, as well as of course reducing the electricity consumption in practice. I would aim for a flow temperature design of 45°C if you can or even lower. Radiators like Faral Tropical95 can really help.

@Hogboon - I've looked at some older threads and I think figured out the weather compensation settings. See here. Outdoor temp for auto mode - this defines the ends of the slope. Set min to -1°C and max to 12°C. LWT for auto mode - this defines the leaving water temperature, i.e. flow temperature, targets at the outside temperature points set above. Set min to 34°C and max to 55°C. The logic is: at or above the max outdoor temp of 12°C, the heat pump will use a target flow temperature of 34°C. This may be too high and could result in overshoot, but start here. at or below the min outdoor temp of -1°C (usually the point at which the property heat loss will be calculated in the UK), the heat pump will use a target flow temperature of 55°C. In between (i.e. -1°C to 12°C), the heat pump will chose a flow temperature between 34°C and 55°C based on a straight-line between the two points. The question is then how to activate this automatic mode, if @ReedRichards is still reading this forum perhaps he/she might be able to comment. I think the internal controller should be put in 'auto' mode and the desired temperature range configured in 'Indoor temp for auto mode' - probably min 18°C max 24°C or something like that. I suspect that this range is then used to control the offset that can be configured in the controller, in my example it would allow -3°C to +3°C, corresponding to room temperature targets of 18 to 24. Based on the photo of the controller earlier, you should be able to see pretty quickly what impact changes have. Inlet/Outlet were 28°C/32°C with a target (top of screen) of 32°C. That target, and after some time the outlet, should change according to what's been set and the outdoor temperature. The final consideration is the Hive controller. I suspect this is a big part of the problem. Anything with a TPI program is unsuitable for a heat pump with weather compensation as the TPI program will introduce short-cycling by design, which is the worst possible operating condition for a heat pump. My advice would be to replace it with LG's native controls. However, for now, just set it to something really high like 30°C all the time which will effectively eliminate the TPI as the room temperature will be so far from the target and let the heat pump weather compensation control the living space. I really hope this helps. Please do let me know how you get on.

Great. Can you post what is currently listed for: Temp. sensor selection Pump frequency setting(RPM) Heating only mode Seasonal auto temp: Outdoor 1, Heat Outdoor 2, Heat Re DHW: is the immersion is even connected to the heat pump? Or just straight to a switch in the usual way. Based on my own system I'd be inclined to set min/max to 28°/55° but it's not clear to me how these settings interact with the seasonal auto-temp settings. Does 'Set Point 1' through 'Set Point 8' appear anywhere in the controller under/near seasonal settings? Also, as noted previously the run time of the system needs to be enough. I think that the Hive will prevent the system using the interior temperature to adjust the flow temperature and therefore it will tend to be less responsive. For now, we need to match the heating curves to the property heat-loss and then worry about warm-up times and such later. On that basis, I'd be inclined to leave it running 24x7 at the moment.

That would be personal preference. Typically delivered as high-wall splits, the draft can we quite uncomfortable e.g. for contact lens wearers. I think it's fair to say that most prefer not to have a stream of warm air on their face, which is why cars deliver heating at foot level when set on auto.

Continual fan noise inside The puffing around of hot air

I don’t think the system needs a bigger pump based on the delta between flow and return.

See here at 1m34s - LG Therma V R32 Monobloc Heat pump | Installer Setting Guide - YouTube Could still be the software version number. Take a look at page 99, water heating temperatures. Maybe that's all that needs to be adjusted (min/max).

The oil use is consistent with 6kW load. it seems to me that this is just a system configuration problem and the original unit was sufficient.

It seems a bit 'translated' and I'm not sure I really follow it. My interpretation (fwiw) is that the system with the Hive controller attached should be set to "leaving water temperature" mode and water leaving temperature set via "Seasonal auto temp" as something like: Set point 1 - the flow temp on the MCS certificate (I guess 50°C) plus maybe 5°C (could also be LW1) Set point 2 - seems to be the minimum flow temp, go with 40°C (could also be LW2) Set point 5 - the outdoor air temp providing max flow, put -5°C in (could also be Out1) Set point 6 - the outdoor air temp providing minimum flow, put in +5°C (could also be Out2) Be sure to write down all settings before changing anything. Installer code could be 1001. What's not clear to me is whether these are configurable directly or set via Out1, Out2, LW1 and LW2.

I found the installer manual here in case you don’t have it @Hogboon: https://www.manualslib.com/manual/1580071/Lg-Therma-V-Ahuw096a3.html?page=124#manual

Also as a very approximate check. How much oil did you use per year before having the heat pump?

Based on the EPC numbers the thermal load in the property is about 6.5kW. It seems like the emitters (radiators and any UFL) are slightly undersized at the configured flow temperature, being only 6kW according to the assessors calculations. But that is a small difference and can easily be remedied by increasing flow temperature. Weather compensation (WC) is the adjustment of the radiator flow temperature based on outside air temperature. This increases the heat pump efficiency considerably as the flow temperature is lower for most the year. WC is based on a curve dictating the amount of flow temperature adjustment based on outside temperature along with configured minimum and maximum temperatures. Adjusting the curve and maximum temperature will enable the output from the radiators to be controlled based on the outside temperature. The display appears to indicate that the system is working with 32°C flow (and 28°C return). This would tend to suggest that weather compensation is enabled and, given the difference across the heat pump, that the radiator circuit pump speed is perhaps a little low as the difference of 4K (assuming the radiator circuit is balanced) would be more when the radiators are hotter (i.e. when it's colder). The display also shows room temperature of 22°C. Some controllers will use this additional data point to further adjust the flow temperature, which increases comfort by reducing overshoot, reduces cost by further reducing flow temperature when possible to do so, and increases system responsiveness by increasing flow temperature when there is a large difference between the current and target room air temperatures. The design flow temperature will be listed on the MCS certificate as this dictates the SCOP for the system in question based on the approved tables for the particular product, and also dictates the RHI payments for the EPC annual heat demand (of 16,000 kWh). This temperature is the hottest flow temperature that the system has been sized to produce to match the thermal loss of the property with the fitted emitters (radiators). In this case, the stated maximum flow temperature should provide 6kW or so of output from the radiators fitted, assuming the radiator system is balanced and the inside ambient temperature is about 20°C. Based on the information presented it seems that the original HP was adequate and that the issue is some combination of incorrect WC curve, maybe spurious room temperature based flow temperature adjustment possibly caused by the control panel being somewhere 'warm', and to a lesser extent undersized radiators and possibly low water speed. Finding the configuration is the most important step at this point. You are looking for configured min and max flow temperatures, the design flow temperature from the MCS certificate, the weather compensation curve setting, and if room and weather compensation are enabled of course. HTH

How is the system configured in relation to flow temperature - weather and room compensated, or fixed temp? What was the energy loss calculated at? What does the EPC show as annual energy demand for heating? What is the sum of the output of the installed radiators at the design peak flow temperature?

I don't know that's necessarily true. The overnight CO2e for UK electricity is generally lowest between 2am and 4am (real-time data here: Carbon Intensity), obviously heating the water higher does have an impact on COP and I'm currently getting about 2.5 for DHW in this configuration.