We have 261 units on our complex with technicoated evap coils , they range from 9,000 to 30,000 btus they have been installed for about 3 years ,we continue to battle growth on coils ,cleaning them about 3 to 4 times a year ,its a white growth that spreads over the entire coil and into the drain pan clogging drain pipe ,anyone having any similiar issues ,thank you for your help the units are Trane models Geve water source heat pumps