Yes you can have two or more indoor units to one outdoor condensation unit, they are called split units.

BTU stands for British Thermal Units, which is an old empire unit. The proper term should be joule. You'll find a conversion table here:

http://www.simetric.co.uk/sibtu.htm

Split units really refers to the cooling unit and the compressor being separate.

Running two or more indoor units with one outdoor compressor evaporator requires special valves and piping. I believe Mitsubishi has a a unit available in Thailand.

I looked around a bit and found this and other sites with dual split, triple split, multiple split.

I checked the shops in Udon - nobody had ever heard of it. So I go for the singele split unit for the bedrooom and the open door to the living room. Then I buy a second unit next year.

Thanks for the answers.

philo

Daikin do also have spit units and they are conciderably cheaper than Mitshubishi whos spit units are made in Japan whereas Daikin's are locally made.