Monday, November 30, 2015

Immersion Heater Application Note - Cooling Tower Basin Freeze Protection

screw plug heaters
Screw plug heaters used as basin heaters on cooling towers.
Industrial electric immersion heaters, more specifically "screw plug" immersion heaters are used in many commercial and industrial applications for keeping gases and liquids flowing at required temperatures. Cooling towers use screw plug immersion heaters for freeze protection of the cooling tower basin.

Cooling towers are an important part of many HVAC systems, providing comfort or process cooling across a broad range of applications. They function to remove system heat by dissipating it to the atmosphere through an evaporative process. They are common in many industries such as chemical processing, power plants, oil refining, and steel mills, as well as many other manufacturing processes where process cooling is required. Another huge market for cooling towers are commercial buildings including airports, shopping malls, hotels, casinos, conference centers, and
cooling tower with basin heater
Cooling tower diagram with basin heater.
medical centers.

The purpose of a basin heater is to prevent water from freezing in the cooling tower basin during periods of shutdown or standby operation.

After the water passes from the top of the tower through the distribution system, it cascades down to the collection basin at the base of the tower structure. From the collection basin, the cool water can be pumped back into the system and begin the process all over again.

As a general rule, basin heaters are normally sized to maintain a 40°F basin water temperature at a 0°F ambient condition. When the system is running, the basin heaters should be powered off as the heater isn't required due to agitation and the heat load picked up during the cooling cycle. The heaters do need to be operational when the cooling tower enters standby or is shutdown for maintenance though. Thermostats, or other on/off controls, are used to tun the heaters on below 40°F  and when the cooling tower pumps are not running. The basin heaters are intended only to keep the basin water from freezing and not intended to act as freeze protection for other pumping or filling components.