Multi split air conditioner in a single-family house

Hello! We moved into our newly built single-family house in 2019 and I am currently seriously considering having a multi-split air conditioning system installed because especially the last two summers were really borderline. We had an indoor temperature of around 27 degrees almost constantly in the living room downstairs (many patio doors, southwest orientation). Upstairs in the bedrooms it was even worse at 28 degrees, of course. All the clever tips about ventilation and exterior blinds eventually stopped making any improvement. Once the heat was inside, we couldn’t get it out anymore. We had previously lived in an attic apartment and I had been looking forward to the house for that very reason, but unfortunately it is not much cooler there either now. So I am actually willing to spend what is probably a five-figure amount and indulge myself with the luxury of an air conditioner. I would now like to brainstorm here or gather experiences/tips/suggestions from people who may have been or are in a similar situation. In my initial research I came across multi-split air conditioning systems and am now trying to find out what kind of effort that would involve?! Standard floor plan with utility room, guest room, guest WC, living room downstairs and bedroom, bathroom, 2 children’s rooms upstairs. What should be considered? Who is best to consult? What (cost) traps could be lurking? I am grateful for all suggestions!

If you don’t already have suspended ceilings everywhere to run the cables, I would rather install oversized decentralized single split units at critical points (bedroom, living area). With controlled residential ventilation, the cool air gradually spreads throughout the house; if there is no controlled residential ventilation, the doors just have to be left open. It is 1. cheaper, creates less mess, and is sufficient in most cases. I don’t have more tips yet, as we are still planning this ourselves. First, though, a photovoltaic system and many other things are to be installed, and for that the piggy bank must first be fattened.

It really depends on the rooms to be cooled which option makes more sense. Price drivers in this matter, besides the sizing of the system—where a professional should plan appropriately—are especially the piping routes. The refrigerant lines cost, if I remember correctly, about 30€ per meter, and since you need both supply and return lines, they are quite significant price drivers.

Then, of course, the manufacturer comes into play. We ourselves have a multi-split from Daikin with 4 indoor units and are very satisfied. Incidentally, we also use it for heating during the transitional seasons. We have (feeling-wise) been very lucky that our heating installer is a trained air conditioning master technician and only afterward completed his master training in heating technology. So I would definitely consult a professional with a setup like this, even though theoretically, you could mostly install it yourself.

They should also be able to advise you on whether it’s better to install several single-split systems or if you can manage well with one multi-split system. We simply didn’t want 4 outdoor units on the house; the current one is (since the 3 of the 4 rooms are there) on the roof.

Not all indoor units are multisplit capable. Often several outdoor units are cheaper than one large one. Get advice from a specialist. The most beautiful indoor units currently are Mitsubishi Diamond

From personal experience:

- Pay attention to line lengths, it is really a cost factor
- Count necessary core drillings
- Avoid condensate pumps (but then pipe installation with continuous slope is required)
- Rely on brands/quality
- Avoid oversizing, often a mistake is made
- Single splits are preferable to multi splits, but it gets expensive in large quantities and space must be available
- The fewer exposed pipes inside, the better, not really nice to look at
- WLAN is a must
- Technology over design
- Check size ratios of indoor units
- Sketch indoor and outdoor units once in the floor plan, a good test

Not all cable lengths are possible without further ado. We had to position the outdoor unit differently and make another wall breakthrough because the cables would have been too long from the initial location.