Best solution is the ID coodinate with Aircon installers with owner presence.
no matter what company (GC,AB,BT or Cs) owners need to do due dilligue and be there..do not just leave them at their own accord. do some homework and know some installation pointers.
the sale person/ supervisor who talk to you maybe not the exact person who installed the aircon. so be there when they installed so there is no chances of error.

" he knows doesnt mean they knows as assumption is the greatest folly of oneself"