Blendworth

Just a thought, have you read the Domestic Ventilation Compliant Guide? Link below domestic_ventilation_compliance_guide_2010.pdf (publishing.service.gov.uk)

I dont fully understand your issue but things to note, For vertical separation, exhaust wants to be above FAI (fresh air intake) to reduce the chance of recirculation. Horizontal separation, if I remember correctly, the minimum recommended separation is 1.5mtr. Try and avoid having the FAI n a area where pollutants will be absorbed into the building, and also avoid area where any external 'hot-sports' of air may be brought into the building, eg intake within the recess of the south facing roof may lead to hot air being drawn into the building. Zehnder make an approved external combined stainless steel intake & exhaust terminal that allows both to be routed out the building directly adjacent, well below the 1.5mtr minimum separation.

Has any one had issues with the FTC6 not powering the remote controller? Having installed many heat pumps over the last 15 years, my preference because Mitsubishi Ecodan units for the built quality and the connectivity with bespoke system. I had a W85 on my last house and having recently moved house, I went for the same arrangement, a Mitsubishi Ecodan W85 with a FTC6. Ive fitted a fair few of these units over the last 10 years and for the first time ever, I have a issue with the one I am fitting to my house. I can not for the life of me get the remote controller to power up. Ive changed the wiring 3 times, move the controller from the preferred location to directly adjacent to the FTC6 panel with several inches of cable between them, played with the dip-switches and still nothing. I want to make sure I am not going mad before I go back to Mitsubishi with my issue because I've never had a installation issue with any Mitsubishi kit before. Items tested, checked and replaced; connecting cable replace, connecting cable relocated(in the case in interference), controller replaced, dip-switches moved on and off several times. No voltage on the controller connections but I am not sure what if any voltage I would see as the book appears to not provide any voltage for the controller, Incoming voltage to the panel is 238-244v. I've tried powering the FTC locally and form the outdoor unit. I've even stripped out all the other connection so its only the incoming power supply, the FTC6 itself, and the remote controller, still nothing.

Several things to check. 1. Has the system been commissioning, or even part commissioning? Insufficient ventilation rates could allow humidity to build up within the building as you are relying on the MVHR to provide cross-flow ventilation over a traditional extract system with passive supply air via trickle vents. 2. Has the system been completed in rigid ducting or flex? Flex just shouldn't be used as any movement in the ducting can affect performance and any 'traps' in the ducting can cause water to form and therefore restrict the free area of the duct. 3. Has the condensate been connected to the drainage system, and has a trap been provided to prevent foul moist air from the foul drainage system entering the supply air? With no condensate drain, any moisture that forms on the MVHR unit could leak into the supply air side of the unit, then evaporate increasing the humidity within the building. 4. Are there any extract points directly over a wet area, IE shower? Extracting from directly within a shower area can cause uncontrollable condensation to form within the ducting, and if no additional duct mounted condensation traps have been provided if extract directly from any wet area, this can also prevent the correct extraction from within the building. Any long vertical sections of ducting after extracting from areas of high humidity, it would be prudent to fit an a inline trap to prevent any issues, and have a dry trap. I have the same unit in my roof space. Its been perfect for me as the main reason I got it was to help reduce the humidity in the house.