Steve W

It would be really wonderful if it managed to get to 40C, depending on the humidity I have seen it to struggle to get to 35C and a really bad day it only just makes 33C. What I really want to know is whether the rumours are correct that the first generation Daikin Altherma is better or worse than any other heat pump. The unit was installed in October last year as stated above and I have been pursuing the installer who is a big name player as to what action they are going to take to remediate it. After all I bought a heat pump that I expect to keep the house warm not a device that may or may not work when the temperature is below 5C and it is humid. When it is not humid the heat pump works well and maintains a good temperature throughout the house.

The unit has an external sensor on the North wall of the house to ensure that it shaded from the sun. I have attached the pictures from the 27th January - 9 p.m. (this was the fourth cycle of the morning). The temperature was 2.5C and sunny - the humidity was probably greater than 95% (this was before I bought my weather station). The frost started to be apparent after approximately 8 minutes and by 25 minutes the unit was labouring just before it went into its next defrost cycle.

The question is simple, are some makes and models of ASHP more prone to frequent defrost cycles. I have had an ASHP (Daikin Altherma 7kW) fitted in October last year and it works well until you get the -2 to +5 temperatures with high humidity - recently humidity has been in the high 90s. Under the above conditions the unit was going into a defrost cycle every 25 minutes even at 9pm with an outside temperature of +2.5C. The interval between cycles is so little that the unit struggles to get to 35C before the next defrost. Essentially the average temperature is around 27C which doesn't make any impression on heating the house. As I have a mixture of UFH and rads the LWT is set to 45C. Hence the question are some units more prone to icing or are some units more prone that others.

As part of a different problem I had a visit from a Daikin Engineer. The problem with constant cycling / pump running / electricity usage, when there was no demand, has been corrected by altering one or more frost settings. No idea which settings - just glad it no longer happens

The system is fitted with anti freeze valves instead of using glycol to ensure that the system is protected against freezing. It would be useful if the protection could be configured as the water is quite warm.

There appears to be a threshold whereby the ashp heats and circulates hot water when there is no demand, even when heating and water are off. This morning the outside temperature was around 5C and the pipes were warm, other mornings they were cold. As this doesn't seem to make a lot of difference to the running costs I've moved this to mild curiosity from being a concern. It would be useful to have a definitive answer along with the cut in temperature.

I have Solar PV coupled to 18.5KWh of batteries and Economy 7. At this time of year the ASHP runs between 12.30am and 8.30am (and 7.30pm to 8.30pm upstairs only) and the batteries are also charged as necessary. The average temperature is around 20C when I get up, peaks around 21.5 and falls back over the evening. My average consumption for everything is around 30KW at 14p/kw. The heat pump is showing at about 13KW with COP of just under 3 - this includes hot water and running it at night. I'll be sticking to E7 / Solar

It appears that it periodically heats the water up and runs the pump. If I knock the water temperature down to 15C it doesn't appear to do anything other than circulate the water (I may be wrong but there aren't any significant blips on the power consumption). It also appears to do this regardless of whether it is switched on or not. I will keep an eye on it. Mechanically the unit seems to work well. From a control point of view it is bizarre, for instance you can program different time periods with temperatures but there isn't an off - best you can do is set it to 15C which means the pump runs constantly pushing around 15C water.

There is also a video on YouTube Connecting a 3rd party thermostat to a Daikin Altherma unit - YouTube (later part) that definitively confirms that it is 1 and 2 and it is volt free. I have checked that the relay is definitely working (more than once). I probably need a warmish day as at the moment the ASHP is running intermittently (without the display showing its running). Left hand side shows the batteries charging pink and the ASHP running in blue. At 7.30 the system swaps over from Economy 7, hence the pink areas above the line. at 8.30 the heating switches off (as expected). There are then a number of peaks (including the toaster), the later ones correspond to the heat pump running up. It may be the intended operation when the weather is cold?

I've attached the wiring diagram from the Daikin installation Guide, the connections inside the controller and the external shot of the 0V relay. There is a green LED that lights when heat is called for. The 0V end has been metered to verify the on/off and that the relay is acutally working. EBLQ05-07CV3-EDLQ04-07CV3_4PEN405544-1D_Installer Reference Guide_English.pdf

Screenshot from the Daikin App eith LWT SET TO 35C, no demand heat. Not sure why there are two temperatures, climate control 27.1 and heating to 35C.

Copy of the commissioning settings. Commissioing Daikin - EDLQ.pdf

Ideally I would like the UFH to be at 35C and then radiators at 45C. I currently have the system programmed to heat the hot water to 45C between 12.30 and 1.30 which it does. I have the UFH set from 12.30 to 6.30 to 35C. If the hot water finishes early, which it does when it has been a sunny day, the UFH starts early. The radiators get heat between 6.30 and 8.30 at 45C as I manually up the temperature. I also give the upstairs a couple of hours from 8.30 and 10.30p.m. The overall performance is good for the time of day that the pump runs. The "Unit Control Method" is set to "Ext RT control" which is "ext RT is used when the system has more than 1 zone, requiring a 3rd party controller. The pump operation mode is set to request. Temperature range us set to 15min and max 55. Emitter type is set to slow UFH. I have a copy of the installation parameters which I will post.

The controls are largely irrelevant as the final output is a zero volt relay which when closed activates the ASHP external control. The external controls comprise 6 x TADO smart radiator valves and 6 TADO room stats that operate the UFH. Each control is capable of demanding heat. To verify the operation the second pole on the relay switches an LED to provide visual confirmation of the operation.

As I primarily use my ASHP using Economy 7 / Solar / Batteries I use external controls to determine when the ASHP should produce heat. The external control calls for heat and the ASHP starts and the rotating arrows show the pump is working - this is all as expected. When the house is up to temperature the external control switches off and the rotating arrows stop as expected. The problem is that the ASHP continues to heat the water and circulate it through the bypass valve. No indication is given that the ASHP is running but it cycles and consumes significant power from the batteries. If I turn the water temperature down to 15C this mitigates the problem as it is not hearting the water. The downside is that when the house calls for heat it only gets water at 15C. Am I missing a setting as this is making life very awkward or expensive.

Balancing the radiators seems to have fixed the problem and all rooms are achieving the correct temperature.

It wasn't getting anywhere near the radiator set point temperature before the flow from the ASHP drops ro zero. With all the radiators on this morning the problem doesn't appear to occur in that all radiators got hot water and the rooms heated to the correct temperatures. I have also adjusted the lockshield valves on a couple of the radiators at the end of the pipe run.

There is a 10 litre buffer tank in the return leg from the heating circuits. So when heating the DHW the return water doesn't go through the buffer tank. There is an ESBE valve which takes priority - the DHW is heated between 12.30am to 01.30am followed by the UFH and finally the radiators. There is no overlap between the functions.

I have recently had a Daikin Altherma 7.5Kw heat pump installed in place of a bosch gas boiler. The downstairs is UFH with 8 zones and auto balancing flow controllers. The upstairs is radiators with individually controlled radiator valves (TADO). There is an ESBE valve which controls whether the tank gets the hot water or the two heating circuits (2 x 2 port valves). The UFH and DHW work as expected and I've been getting a COP of 3.5 (heating / DHW). As the weather has been mild the upstairs of the house has required little or no heat and hence not paid any real attention to it. Tonight was quite cold so I turned on a couple of radiators. Which got to a reasonable temperature - enough to warm the room. After about 10 minutes the flow and return temperature converged and the flow rate dropped. The flow rate dropped to zero and essentially there was no more heating. I will be ringing the installer tomorrow but would like to have an understanding why this has happened. Looking back this is probably not an isolated occurrence. I should add that the reason for individual controls is that it is extremely easy to overheat the rooms given the level of insulation.

Hi, I have built a four bedroomed house that is energy efficient, has solar panels, batteries 18.5Kw/hr, UFH and MVHR. Recently had an ASHP installed in place of Bosch gas boiler.