chrisru

Thanks all, and yes as you all suggest the system is not sufficient to warm the house in winter but they run a very large log stove and leave doors open, and the EAHP will recycle that heat as well. I think the ASHP as a first step is the obvious one, and it's just whether to go with something like the Sunsystem as a EAHP DHW solution alongside it - they are pretty good value for what you get.

I'm currently looking at a house purchase and a bit puzzled by the heating system. It's a 15 year old Nibe Fighter 360P (https://www.manualslib.com/manual/1240673/Nibe-Fighter-360p.html) which the original builder admits is a little undersized, the property is well insulated but 200m2 rather than the 160m2 suggested limit, they suggest it outputs around 5kW. We are looking to extend and would end up with 250m2, I also understand that the 360P is end of life and spares getting harder to come by so a replacement makes sense on all fronts. The house has the vents to capture warm air from the lounge and bathrooms and an exhaust chimney, with vents in the rooms for fresh air to come in (see diagram), UFH throughout and TRV to bedrooms. The house is very well insulated and fairly airtight. The options I see are 1. Replace the 360P with the updated model - the Nibe F370 this will be supported for longer, is a more efficient model and MCS registered so would qualify for RHI. However it still have the existing limitation in terms of output. With the Nibe systems in Winter mode then it will try to augment the heating using an electric coil and this proves expensive. The current owners supplement the heating using a wood stove, the heat from which is then captured and recirculated which is an options and I could go for a pellet stove which could be automated to some extent. 2. Replace the 360P with an ASHP, this will be more efficient and capable of heating the house without supplementary log stoves etc. This would leave the existing vent system so I had though that I could add an exhaust heat pump like the SunSystem TDA S 200 Sunsystem Exhaust Air Source Heat Pumps - Green Phoenix Ltd which would improve ventilation in the house and recover heat to compensate for the vents in the rooms, this would then provide DHW and as this unit has a coil it can be heated by the ASHP as well. I'm not quite sure how I would control these two together and whether this is overkill, all the houses I've had before have been sufficiently leaky to not require a ventilation system. Any input and thoughts welcome. Attached is a diagram of the 360P and vents, and the TDA S 200 manual. Thermopump_Exhaust_Heat_Pump-TDA_v0.2_EN.pdf