When you buy appliances, there are two things you

01) Appliances shop like Jintex, ESH, D-Legend, etc all they do is sell appliances, they are not good in installation, and usually outsource to 3rd part when come to installation like fans, AC, Heater and some complicated stuff, some small things they do install them-self like TV rack, HiFi they will do it. Don't expect to have good installation quality.

02) Big shop like Seng Heng do have their own installation team, but still the quality are so so.

If you want to have good installation, get your own trusted installer, the shop installer really depend on luck. If you know how to do it, is best to do it your own.