When evaporator coil surfaces become coated with foreign particles, dust, dirt, pollen, bacteria, and mold, the ability to transfer heat is greatly reduced. Coils with a layer of dust the thickness of a dime lose up to 21 percent in efficiency. The build-up of these migrated or growing substances insulates the surfaces, which degrade the cooling capacities.

Living pathogens may develop, such as salmonella or listeria that could transfer to the area food processing equipment surfaces. Dirty evaporator coils increase discharge head pressures; reduce compressor capacities, increase delivered supply air temperatures, cut the system’s refrigeration effect, and overall increase energy usage.

Food processing area evaporators and HVAC unit evaporators need to be deep cleaned to reduce operating costs and avoid contamination risks.

All the equipment in the area of the evaporators must be protected, checked, and cleaned after the evaporator coils deep cleaning is completed. An unfortunate issue occurred at a food plant when an overhead coil had not been visually inspected or cleaned for a period of time.

The room temperature became a challenge to meet, so the coil was visually inspected. The maintenance personnel were surprised to find the coil fins were plugged with contaminants and airborne debris. The in-house sanitation crew was scheduled to clean the coil that night during the area sanitation period and following production.

The sanitation crew cleaned the production equipment during the routine sanitation period and then they proceeded to clean the evaporator coil. Unfortunately, the coil cleaning procedure caused contaminate particles to reach the surfaces of conveyor belts below. These surfaces were only rinsed off during the cleaning process.

A few days later, an outbreak of contamination occurred, which caused many illnesses and even deaths of customers who consumed the product that touched the conveyor belt surfaces.

Deep cleaning of the coil surfaces needs to be done with trained personnel and should be completed before the production area equipment sanitation period occurs.

All production equipment must be cleaned and sanitized after the coil cleaning is done to assure the sanitation procedures are not compromised. The sanitation process needs to include a systematic approach that is proven and effective in removing surface containments that are both visible and not visible.

DEEP CLEANING

So what does it mean to deep clean? Simply put, deep cleaning allows coils to operate as designed without major losses in efficiency. For most industrial cooling systems, the process involves cleaning equipment that utilizes high-volume heated water and specialized cleaners.

It’s not the pressure that is important, but the technique that is used. Small pressure washers, that use 1 to 3 gallons per minute at 2000 to 3000 psi, generally cause more harm than good. One of two things occurs: coil fins are flattened over, and due to the high pressure, that causes a further reduction in the coil heat transfer performance. From the outside, the coil appears to be clean to the first tube, but a dissection of the coil would reveal that a lack of water volume actually causes dirt to be pushed into the coil, and creates more of an impaction. The coil performance is again degraded and the risk of contamination of the production line is further increased.

Don’t forget to clean fan blades and squirrel cages. Dirty fan blades can reduce up to 25 percent in airflow efficiency and allow for the contaminants and airborne particles to be spread throughout the production area.

CLEANERS

Coil cleaners fall into four basic categories: acids, alkalines, solvents and detergents. It is important to use the right chemical for the right application to ensure the coil surfaces are not damaged and to provide proper cleaning. No matter what recommendation a chemical manufacturer makes, it isn’t a good idea to leave a chemical on any surface without thoroughly rinsing the coil prior to returning to service.

Continued use of caustic chemicals will shorten the useful life of your equipment. Many maintenance personnel are given the “it’s a non-acid cleaner, so it’s safe” line. Don’t be misled by claims that a product is safe for your equipment. Rinse it, then rinse some more to protect the service life of your equipment.

PROTECTANT COATINGS

The HVAC/R industry continues to expand the use of coil coatings. Epoxy-based coatings have been around for some time but a new process known as nanotechnology is making an appearance. Nano-coatings offer the advantages of: self-cleaning, antimicrobial protection, anti-corrosion and moisture control, to name a few.

Nano-coatings on HVAC/R coils look promising in extending equipment life and increasing overall energy efficiency over the life of the equipment. While the chemistry of these Nano-coats may vary, they fall into two basic categories: water attracting and water repelling.

They both have their pros and cons and ultimately depend on the end user’s needs. Some coatings have added components such as zinc to inhibit microbial growth. An entire article can be written on their antimicrobial properties, but for the sake of this article, any microbial claims should be recognized by an EPA registration. For more information on nano-coatings, contact a specialized coilcleaning contractor.