NightMail

Even though the cold weather that was forecast failed to arrive in any strength, it is looking likely that the recent adjustments to the heat pump settings have resolved the problem with excessive use of the immersion heater.

As predicted the immersion coming on had nothing to do with a lack of gas, a point also made by the service man when he arrived. As far as I understand the situation there were two settings that contributed to the immersion being turned on. Firstly, the ambient temperature setting was set to 5 degrees C and secondly, the length of time that was allowed for a temperature increase in the flow and return pipes was set at 30 minutes. The former setting was reduced to 3 degrees C and the latter increased to 60 minutes. Another period of sub-zero temperatures is forecast to start on Sunday February 11, which should test the above explanations.

Thanks for your responses and my apologies for not replying before now. Since the weather became somewhat milder I have noticed that the immersion heater was in use only once, on Tuesday last, for space heating, while the DHW was at the required temperature, water heating was in standby and the outside temperature was approximately 5 degrees C, see attached photo. The ex "mid 90's double glazing" salesperson is to call tomorrow so hopefully a resolution will be found! Best regards.

Unfortunately, at this stage no clear resolution yet. The installers have suggested two possibilities: firstly, that a service may be needed, as the initial installation was in February 2023, and, secondly, that the quantity of gas in the system may be a bit low. The service company is to to pay a visit. Also, the ratio between delivered and consumed energy has dropped to ~2.91 for January 2024, which is down from ~3.49 for December 2023 and ~3.42 for 2023 overall. It seems to me that the increased immersion use probably contributed to the drop for January 2024 but the need for a service or low gas in the system might be factors too. Best regards

Many thanks to you all for your responses. The company that installed the heat pump is to pay us a visit, as the system is still within warranty, so I should have a better idea of the situation in a few days time. With regard to your various queries: Kelvin & PhilT: When the installer calls I will ask if the heat pump software should be updated to the latest version. joth: The DHW temperature is set to 50 degrees C. It seems to me that the heat pump does not have an inline booster heater, only an immersion heater. There is an external switch labelled "immersion" which may be the simple way that it is controlled. I will ask the installer if it can be switched off. Best regards & thanks again for the responses.

Hello all, I am based in Ireland and signed up to the BuildHub forum yesterday. We have a Mitsubishi Ecodan air source heat pump and I have noticed that the immersion heater was used quite often during a recent cold period, when overnight temperatures ranged from about -4 degrees C to -8 degrees C. The multitude of manuals that came with the heat pump refer to the immersion as a booster heater but I have not been able to find any explanation, apart possibly from Legionella prevention, of the conditions that cause the immersion heater to be switched on. Any comments or suggestions appreciated.