Keeping the coils running at factory efficiency

INDOOR Air Quality (IAQ) is only too easy to overlook when thinking about new building designs, and it has not been very well addressed in existing buildings.

The causes of poor IAQ are always pretty much the same; however, the single worst cause and probably the most dangerous is a contaminated AC cooling coil and air conditioning ductwork. The mould and bacteria that grow on the coil get into the air flow and cause health problems for the people receiving the contaminated air, as well as causing technical problems for the equipment.

The dirty coil also has a knock-on effect on other aspects relating to bad IAQ, such as excess moisture and poor air flow, leading to inadequate heat and moisture removal from the air. Insufficient ventilation, particularly untreated air, also exacerbates the situation, increasing the level of airborne pathogens, to which we also must add the external pollutant ingress that happens every time a door or window is open.

In existing buildings, the possible solutions are not limitless; this, however, does not mean that they must be limited in their result capabilities. A small number of well-executed measures can help improve IAQ considerably and make indoor environments safer, as well as better protect the equipment and extend equipment life.

These targeted interventions must include the installation of germicidal UVC lamp systems, which will continuously disinfect the coil and help keep ducts cleaner by reducing microbial growth. Using UVC lamp systems will serve a double purpose – they will deep-clean the air-handling unit coil to remove even the toughest microbial accumulation with no human intervention, and will help keep the equipment efficient, reducing wear and tear as well as impacting on operational costs. An ASHRAE member study supports the fact that a clean coil saves energy.

Good filter maintenance is also essential and should be carried out in a timely and responsible manner; if possible, increasing filter efficiency is also a step in the right direction, if the equipment permits it.

As far as ventilation is concerned, the treating of incoming air with UVC lamp systems in the ducts will help reduce the incoming level of pathogens. These systems will treat the air as it passes and are designed to flood the duct with Germicidal UVC for efficient incoming air decontamination

For smells and in-kitchen exhaust systems, photocatalytic oxidation technology can be used. They are easy and simple to install, using a UVC lamp as the activator. This measure will complement the work done on the coil face as well as in the ducts. Current IAQ monitoring devices focus on CO2, PM2.5, humidity and VOCs, enabling proactive action to be taken in the face of these non-microbial contaminants.

For new buildings, the problem can be addressed in the design stages, and the measures stop being preventative and become proactive. The installation of germicidal UVC during the installation of the AC system will help keep the coils running at factory efficiency; and if the lamps are changed as suggested by the manufacturer, this status will not change. A clean coil will keep the equipment efficient with optimum heat transfer as well as maximum air flow, for less equipment effort. The requested room temperature is reached faster, and the equipment operates at optimum efficiency. It is worth noting that a new coil after only three months of use will have sufficient biofilm accumulation on its surface to start affecting operational efficiency.

A great example of forward thinking when designing a building with IAQ in mind is Torre Mayor, the tallest building in Mexico City and the second tallest building in Latin America. The building was designed to be sustainable, green and intelligent, where attention to people was paramount as a goal. There are 46 coils that are taken care of with germicidal UVC lamp systems. Added to this, the HVAC system has reservoirs, where the clean condensate is accumulated and repurposed, being used in bathrooms as well as cooling tower replenishment. This can be called the safest and healthiest building in Latin America.

Other aspects that should be given attention to when designing new buildings include the design and layout of ventilation systems and exhaust systems, making sure these are efficient and independent of each other. Adequate maintenance and cleaning of air handlers is essential, aided to a very large extent by the implementation of germicidal UVC systems. Material selection will also be very important to make sure that low emissions are achieved, as well as avoiding mould growing components, so that no hidden design flaws come to light when it is too late. Energy-recovery ventilation is also suggested to reduce the cost of fresh air injection. Again, designing UVC systems into the air handlers from the beginning is essential. And correct sizing of the equipment for worst-case scenarii is crucial.

There is no doubt that for existing and new buildings a well-executed IAQ strategy not only improves occupant health and comfort but also boosts productivity, reduces absenteeism and extends building system life, all leading to increased financial gain.

The writer is International Sales Director, UVTronix. He may be reached at <tghiraldo@uvtronix.com>