Punggol differs from older towns because so much of its aircon work is installation, not repair. New owners collect keys, plan a renovation and decide how many rooms to cool.
HDB expects outdoor units on the designated ledge, fitted by a BCA-trained air-conditioning unit installer, with an installation report afterwards. Timing is the real constraint: installers are asked to fit systems after carpentry and before move-in, and the renovation contractor often controls the schedule.
A year or two later the work turns to servicing plans, first repairs and the question of who covers a fault after installation. Singapore's humid weather, with no winter, means units get heavy use once the family arrives.