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Fan coil being installed in garden room to replace UFH, which really didn't work well unless at flow temperatures. Which wasn't an option with the ASHP and the main house heating demand. So Christmas eBay search led to me buying a Myson iVector MkII fan coil 1.2m wide. This unit can do heating and cooling and has a variable fan cut in temperature, so should allow me run weather compensation. Unfortunately the unit needs to placed on the opposite side of the summer house to the existing water entry point. So instead of running pipes internal, have decided to run them externally. Some photos of progress Unit wall mounted Cover installed The unit I got is a 4 pipe fan coil. This unit has a dedicated cooling and seperate heating heat exchangers. The heat transfer area of the combined heating and cooling HE's is about 50% larger than a 2 pipe fan coil. Have piped the two HE's as a single unit. I am using a Salus self balancing actuator to balance the flow rate through the fan coil. Have started the external piping using 15mm Hep2O and 25mm wall thickness insulation. The insulation to aluminium tape covered to keep mice away and UV to stop sun damage. The pipes sit on metal brackets 40mm off the ground and are galvanised banded into place.

An Excel spread sheet has been used to calculate the heating and cooling. One thing also calculated is that at peak energy the bungalow requires as much for the heating in the winter as for the cooling in the summer! So the hottest part of the hottest day and the coldest part of the coldest night need about the same amount of power! This is mainly because of the solar gain through the windows. The calculations were compared with what has been used for heating and it is reasonable good. The calculated heat requirement is down to -8C although I cannot find records here of colder than -5C. It is assumed that the ASHP will supply all heating and hot water when required. (hopefully mainly hot water heating from excess PV power) There is a back up immersion in the buffer tank but I hope to never use it. The cooling is another thing all together. The ASHP manufacturer informed us that if you run the cooling through the radiators below about 19C this will cause condensation - They were right. When running the ASHP in the summer in cooling mode at 18C the radiators began to get wet because the warm air was being cooled and the cooler air could not hold as much moisture.( the buffer tank also started to do the same and this has to be sorted as well) This is what is know as the dew point! Water coils are now designed to be added to the MVHR ducts to overcome this problem by cooling the air entering the building. The MVHR will be boosted with cooling to the east end of the building, or the west end of the building ( no south windows) when there is strong solar gain. As a trial the ASHP will be left on 24 hrs to see the effects. The temperature of the heating water produced by the ASHP will be turned down to the lowest setting which keeps the desired room temperature. Anything else let me know