Luke1

It reduces the compressor Hz, and the power use drops fairly significantly. The cycling conditions it would peak at 1.0kW and in similar outdoor conditions it would run at 0.550kW approximately. I will check the exact figures. If I calculate that would make sense because running for 35mins at 1.0kW would be approx 580Wh if my maths are correct? Compared to 550Wh with no cycling running for 1hr. It appears to work to a deltaT of about 5C and controls the flow rate through the heat pump to maintain this.

I'm not sure of the ability of other heat pumps, however I have the ability to adjust the compressor curve in the service menu. (It has an auto setting) From what I understand, it is generally better to run a heat pump for a longer duration, and that is certainly how you can see "Heat Geek" using their heat pump. https://emoncms.org/heatgeek My system in auto mode would generally cycle the heat pump 35 mins on, 20 mins off. In which time the flow temperature would go from 32C to 42C as the 'degree minutes' catch up. Now I have adjusted my compressor curve for heating so that the maximum output it can generate is generally only 1-2C higher than the required flow temperature, leading to much longer run times. So do we think I will get a better COP this way, or by letting the controller manage the compressor curve itself? Im tempted to think manually controlling the compressor curve is better because I can get a better COP if the system doesn't have to heat way over the required flow temperature to catch up the degree minutes. (I have noticed that is the degree minutes still end up over 150mins then it does go above the compressor curve to catch up with the degree minutes again)

If you were being serious, a simple solution would be to use a Switchbot on timer function for this. Or via your phone from the comfort of your sofa!

Just to add, the Nibe installer menu says this for the F2040 models: You can also see that the 8kW model uses approx 30W in crankcase heater mode. Even in the middle of summer I've not often seen my system use anything less than the 30W, and Nibe won't confirm what conditions must be met for the system to enter standby or thermostat off mode. I have only ever seen power usage drop when the outdoor unit air temperature exceeds 42C (In the sun during the heat wave)

Where abouts are you based? I used a company called K A Stripp Ltd based in Headcorn. Installation was great, and worked around my timescales. I had to tune the Weather Compensation curve myself. Living in the house makes this much easier than someone coming in trying to do it though. Given that you are on this forum then you will be able to to tune it yourself and you just need to make sure the calculations are right and they have specc'd a heat pump that you want to use. I chose this company over other companies on the basis that they were happy to install the full system (house was previously storage heaters), all other companies I tried only wanted to fit the ASHP and I would have to find a separate plumber to do the UFH, Radiators and ancillary H+C pipework.

I agree that this is borderline criminal from Vaillant and its UK Suppliers. It would be nice if someone were to request an explanation from Vaillant as to the price disparity from Europe in particular! It would be good to setup a table of pros & cons for various heat pumps for future reference. Recently this forum discovered the high standby electricity use of certain systems and now this from a different supplier. These are certainly points that savvy interested prospective buyers would like to know about.

I've kept both at the minimum 3C. Because the heat pump only runs for 10-15 mins at a time I thought that it would run at its lowest modulation for longer (and more efficiently) if the delta was lower. I have no idea if my logic is correct though!

I've just had a similar error. The unit is south facing and it is sensor BT28 which causes the unit to shut down above 43C. I have now shaded the unit and BT28 is back to 40C with outside shaded air temp being 38C and the unit is working again. Inside temperature is currently 24C which has steadily increased from 22C this morning.

That's impressive service from your installer! Where in the UK are you based? I'm sure now its enabled, you can adjust the minimum flow line temperature as you wish in the heating settings menu. The Nibe recommendation is 18C and if you put anything lower it gives a warning about condensation, but it will still let you set a lower temperature. To prevent condensation build up, you need to know the RH and current temperature. The dew point here is around 11C right now. I am currently running my system at 11C and some condensation is forming on the supply from the heat pump (around parts not insulated in the cupboard such as valves) The radiators and floor obviously never get as low as 11C and therefore are not forming condensation. (Albeit there is a slight misting on the radiators) (There is also a risk of any un-insulated pipe runs between radiators etc forming condensation. Once this heatwave has passed I will up the flow to something around 18C and see how the house performs.

I have the SMO 20 controller and F2040 8kW heat pump. I had to enable cooling in the Service menu (Holding the return button for 7 seconds brings up this menu) (At your own risk) I have no idea if the SMO 40 controller is the same? https://www.nibe.eu/assets/documents/23958/231765-5.pdf (See page 32, your system would be 2 pipe cooling) I couldn't see anything on the SMO 40 controller about how to enable cooling mode. There was a simple check box on the SMO 20 controller.

I'm currently running my ASHP (Nibe) in cooling mode with flow down to 11C. The pump runs for 10 mins dropping flow tempt to 11C and then creeps up to 15C until the unit comes back on again after approx 20 mins. So far today the UFH has been working exceptionally well. The downstairs is curently 23.3C and this has not moved since 11 o clock this morning. Current outdoor temperature 31.4C in the shade. The radiators are also cool, however they don't help really help to keep the room cool. I did experiment by putting a tower fan on its side under the radiator however it causes a significant amount of condensate to accumulate and then drop off the radiator. So unless you can mix the upstairs water to keep it above dew point, or somehow collect the condensate then the fan assisted radiators would cause issues. I was getting condensate when running the flow as high as 15C-18C, at which temperature the cooling effect for the UFH and radiators is minimal.

I had picked up on this a while back. Hence why I took an extract from the Nibe installer handbook. Given the fact that the book states a number of different standby states would suggest that the crankcase heater mode should not be the default standby mode that I have so far witnessed. I am unable to find out what preset temperatures and sensors are required for the system to enter standby mode, however you would have thought in these current warm conditions that the crankcase heater would possibly turn off? If it doesn't then perhaps Nibe providing standby consumption rates for modes other than crankcase heater mode is very misleading. The Nibe uses 0.72kWh per day in standby 'crankcase heater' mode, so whilst not as bad as other systems noted here, its still adds up to a significant sum over the course of a year based on current energy prices. (More than £60!)

I've got a NIBE F2040 8kW model. I have a shelly 3M monitoring the power usage. It would appear that when not in use the system is using 0.03kW. According to the installer manual this would suggest that the crankcase heater is operational. I do not see any settings to disable this and wondered if anyone else had found anything? I would expect the system to either be in Thermostat-off mode, or standby mode as per below table.

For reference I had a Shelly EM monitoring my Nibe F2040. When not in use the standby power required is 39W. This includes running the internal control unit, & display etc (Can't normally hear any circulation pumps running).

Kerosene has only recently spiked to 88ppl because of what is going on in Russian and Ukraine. If you'd bought in early February you'd have paid around 60ppl. Lets hope the spike is just temporary, however I fear it may not be! https://www.boilerjuice.com/kerosene-prices/

Could it also be that the system is compensating for a big change in your desired room temperature? Are you running the system in Weather Compensation mode and are you generally keeping the house at a steady temperature, minimising the use of any setback temperatures? UFH and especially ASHP benefit from longer run time and not in short bursts, but I'm sure you're already aware of this?

Are the sensors fixed in the correct locations and wired to the correct terminals on the control panel? Not unheard of for installers to mix these up. Also could it be that inlet temperature is a sensor further down the line from the ASHP. Ie. just before it enters the UFH manifold?

Are you sure this is true? The Nibe system works on degree minutes. In the settings there is an option to add additional heat (immersion) when the degree minutes exceed 700 or another defined number. I suspect other systems are similar, hence why so many people complain about running costs when they try to use an ASHP like a conventional boiler. I also note that the Nibe system will try and run the compressor until the degree minutes hit 0. If the system is started after a period of blocking then the flow temperature will continue to increase (reducing COP) until either the maximum flow / return temp is reached or it hits 0DM. It will then oscillate at the higher end of the flow temperatures until it reduces the DM to 0.

I’m not sure the house has to be EPC C or better to claim RHI. You do however need an EPC that is less than 2 years old and does not recommend further cavity wall or loft insulation.

Thats very interesting, my Nibe allows me to set a schedule which can increase the DHW to luxury for certain periods, likewise the heating can also be scheduled to move the setpoint up and down. I'm now also making much better use of night rate electricity to heat the DHW and put as much heat into the house over night as possible. (My night rate is over 2 separate periods hence the wild swing in flow temp) How do you determine an increase in number of people in the house, to increase DHW temp? Nice to see someone else using Home Assistant too. It can make some nice graphs to track use etc.

Yes both sensors are installed. I assume the hot water charging sensor is half way up the tank however I haven’t actually looked at it. I think this is the sensor the system uses when the temperature falls past a set point to re heat the tank.

I'll monitor it over the next few days. Perhaps I'll set the heating to be off so that it doesn't switch over and I can then get a better idea of the times just for DHW I'll upload some graphs to a new thread when I've done this.

That's interesting, whats your thinking behind the charge pump speed? I notice that 30% is only during 'wait' mode whilst the heat pump itself is not running. I've currently left my DM at -60, it seems to cycle 20-30mins on and 30mins off during the day, which apparently seems reasonable. I currently have WC enabled and I also have a room thermometer connected. It reduces the calculated flow temperature as the room temperature increases. Even though its not recommended for UFH due to slow reaction times it does seem to be working ok at keeping a steady temperature with a low ish flow temp. Sorry Ecodan people this has gone off topic!

Yes the SMO20 controller. I've fiddled with the priority and it is currently set at 90mins DHW and 30mins heating. Generally very happy with the unit and controller (It seems a lot more straightforward to adjust settings than some of the other systems people talk about on here). How long have you had your unit and is it performing as expected? Don't tend to see many reviews on them here.

I have an 8kW Nibe with a 200l UVC. Looking at last nights log at an ambient temp of 5C: Charging circuit: 2:40 - 33C 4:00 - 41C The system then switches over to do heating for 30 mins and then switches back to DHW at 4:30 4:30 - 41C 6:15 - 48C The top of the tank is as follows: 2:40 - 42C 4:00 - 42C 6:15 - 48C In the summer it was much quicker to heat the tank. I'm just wondering whether I should give the DHW full priority over heating to save the changeover time during E7 hours. That said, the flow temp at night for heating is around 40C so it wouldn't have had to wait for long to switch over I suspect. It seems your ecodan is much quicker to heat the DHW, but then I guess it also depends on your ambient temp and the frequency your HP is working at. Mine seems to work at 66Hz. Its generally never got higher than 80Hz, expect for one occasion where it hit 110Hz however this may be an anomaly. So its either operating at 83% or 60% of peak?? Does anyone know where you can find the maximum frequency stats for heat pumps?