Installing an enclosure cooling solution for a water or wastewater treatment plant will protect valuable electrical equipment and prevent the breakdown of critical operations.
Here are the answers to 10 Frequently Asked Questions about enclosure cooling systems and their use in water treatment facilities.
1. Why does a water treatment plant need an enclosure cooling system?
Electrical equipment used to operate water treatment facilities must be protected from excess heat. Components such as programmable logic controllers (PLCs), transformers, and variable frequency drives (VFDs) which are housed in electrical enclosures will begin to suffer in performance, reliability, and lifespan if they remain above their maximum allowable temperature for too long.
Choosing the right enclosure cooling solution, sizing it correctly, and maintaining it properly, will ultimately save money, reduce downtime, protect the environment, and ensure the safety and purity of the water exiting the plant.
2. What conditions must an enclosure cooling system located in a water treatment plant be able to withstand?
The cooling system must be shielded from the harsh conditions commonly found in these locations, due to corrosion and/or contaminants. For example, many enclosure air conditioners utilize aluminum filters that are not built to withstand the chlorine cleaning chemicals sprayed on enclosures in wastewater treatment plants.
3. What NEMA type should be used for a water treatment plant enclosure?
The National Electrical Manufacturers Association (NEMA) has specified different ratings for protective electrical cabinets, based on the environment in which they are located. Enclosure cooling systems fitted to these cabinets should have the same NEMA type rating.
Because of the harsh conditions often found in and around water and wastewater treatment plants, electrical enclosures for these locations should typically meet the NEMA 4X standard.
NEMA 4X is specified for indoor or outdoor use, providing protection from extreme weather and climate, and exposure to dust and corrosive materials. This type of enclosure is also watertight and designed to tolerate the high-pressure spray that occurs during the cleaning process.
NEMA 4X is the ideal electrical enclosure type for applications that are subject to corrosion and wash-down with cleaning solutions, or other sterilizing chemicals, and where high pressure cleaning equipment is utilized.
Enclosures with a NEMA 4X rating are especially suitable for use in hot, humid environments, such as found in Florida, and in coastal marine environments—a typical location for desalination plants—where equipment may be exposed to salt water and the corrosion rates of mild steel equipment are high.
4. What are the requirements for a NEMA 4X enclosure?
Though enclosures with a NEMA 4X rating are sometimes referred to as waterproof, this is not strictly correct because a NEMA 4X enclosure cannot be submerged in water. However, it should be water tight, and should not allow water to accumulate in places where mold could grow. Additionally, all NEMA 4X enclosures must be dustproof and resistant to damage caused by the formation of ice.
The NEMA 4X rating also specifies that the enclosure will meet minimum conditions of corrosion resistance, though they may not necessarily protect the enclosure completely in actual site conditions where long-term exposure to corrosive vapors, such as chlorine and other chemicals used for sterilizing water/wastewater treatment facilities, is present.
5. What type of cooling system meets the NEMA 4X requirements?
Once the NEMA type for an enclosure has been determined, an enclosure cooling system can be selected from one of two basic types: open loop or closed loop. An open-loop cooling system is one that allows ambient air to circulate through the enclosure, for example with a forced air fan.
A closed loop cooling system is one in which air inside the electrical enclosure has no direct contact with outside air. Rather than blowing air into it, a closed-loop system removes heat from the air inside the enclosure and transfers it to the air outside. This insures that the enclosure is not contaminated with ambient air, dirt, chemicals, dust, moisture or foreign matter so that sensitive components are protected and are kept at the required operating temperature.
NEMA 4X enclosures must be sealed to prevent contaminants, corrosive gases, solids, or liquids, from reaching the electric components within. For this reason, closed loop cooling systems are required for these enclosures.
6. What types of closed loop cooling systems are available for water treatment plant enclosures?
Two basic types of closed loop cooling systems are air conditioners and air to air heat exchangers. Both have benefits and drawbacks to be considered when selecting a cooling system for a water or wastewater treatment plant enclosure.
In the case of an air conditioner, hot air from the electrical enclosure is drawn out, passed through an evaporator coil that cools it, and is then returned to the enclosure without ever encountering the outside air. The same method is used in the case of an air to air heat exchanger, except the heated enclosure air is passed over the evaporator side of a heat pipe.
7. Which type of closed loop cooling system is right for a water treatment plant enclosure?
A heat exchanger can only approach the same temperature inside the enclosure as it is outside, so if the ambient temperature is higher than the maximum allowable temperature for the components, it will not protect them from excess heat. In that case, an enclosure air conditioner is the only choice for maintaining a safe temperature inside the enclosure.
An enclosure air conditioner represents an extremely effective method of cooling an enclosure and will work efficiently even if the ambient temperature is much higher than the enclosure’s air temperature. It will also control humidity much better than a heat exchanger, which may be important for sensitive electrical components.
8. How should an enclosure cooling system for a water treatment plant be selected and sized?
Selecting a properly sized cooling system is critical for optimal operation and maximum efficiency. Specifying too large a system will result in higher costs than necessary, and may adversely affect the operation and efficiency of the system. A system that doesn’t have enough cooling capacity, however, will impact the reliability and lifetime of the electrical components.
An online Enclosure Temperature Management (ETM) calculator can simplify the process of selecting and sizing an enclosure cooling system. The calculator gathers information about a specific application and then calculates the cooling capacity of a suitable air conditioner or heat exchanger.
An ETM calculator takes into account metrics such as:
· Enclosure dimensions
· Desired temperature
· Ambient temperature
· Heat load
· Enclosure material
· Enclosure color
· Location of the unit
9. What are some options available to protect an enclosure cooling system in a water treatment plant from corrosion and contaminants?
Although not mandatory, NEMA 4X enclosures are generally manufactured from stainless steel as this provides the ideal substrate to resist the corrosion and weathering tests required to achieve the NEMA rating. If the enclosure will be located in a marine environment, 316 stainless steel is preferable to 304 stainless steel, due to its increased corrosion resistance.
Some manufacturers offer optional stainless steel air filters to help the enclosure withstand chlorine exposure. It’s also important to ensure that any exposed copper refrigeration tubing is protected with a corrosion resistant coating to prevent premature failure.
10. Where can I get assistance in selecting an enclosure cooling system for a water treatment plant?
Thermal Edge works with wastewater treatment facilities and many other types of industries to provide enclosure air conditioners that are both reliable and efficient. We also offer a suite of options and accessories, including corrosion protection and specialized filters, to ensure the best protection of your valuable electrical equipment.
For more information and help selecting and sizing an enclosure cooling system for a water treatment facility, contact Thermal Edge today.