Through the cooler months we have noticed different freeze protection techniques. The most common of these is overflowing. The following will point out some of the problems associated with this practice.
While overflowing the tower addresses freezing of condenser and make-up water, it also creates a few problems. Overflowing causes conductivity to drop. If the tower has a feed/bleed controller, once the system is returned to normal, the inhibitor level will be low. It must be brought back into range to prevent the build-up of scale and to control corrosion. If your system has a proportional feed system, while you overflow water, you also waste chemical. With this in mind, you may ask yourself, “How do I properly protect my system from freezing?”
Water only freezes at 32° F or less, and this can be extended much below that if the system is recirculating. Most chiller manufacturers recommend you do not start your system if your condenser water is below 65° F. As a result, many towers have basin water heaters and/or tower by-passes. If the forecast indicates freezing weather, turn on the basin heaters and circulate the water or by-pass the tower. If the make-up line needs protection, heat stripping or insulation is recommended. These actions will eliminate the need to readjust the make-up float as the weather changes.
Many preventative maintenance programs recommend overflowing, but, as already pointed out, this may cause more problems than you anticipate. If you have any specific questions or concerns regarding your system, please discuss them with your Water Treatment Consultant.