Chemical cleaning for the condenser of chillers is required in case of hard scales on the heat exchanger tubes. Usually chiller are opened annualy and cleaned by rotating brush. howeverif hard scale exists you must use acidic solution.

The procedure is as follows:
drain the process water from the chiller and fill with fresh water, add acid chemical (like sulphadex powder, around 0.5 % concentration in water), the chemical must be added so that the PH of the solution is near 2. Then circulation should be as per videos, so that the solution from the barrel enters the chiller from the bottom (forced by pump) and leaves it from the top to go back to the barrel.
PH should be monitored hourly during circulatoin and chemical should be added whenever PH goes above 4, because scale removal will be non efficient. the circulation must be stooped when the PH becomes stable with time. The overall process should take between 8 to 10 hours and no more because heat exchanger pipes tends to corrode in acidic solution.