When tragedy strikes in the form of natural disasters such as hurricanes, tornadoes and other extreme weather events, time and resources are of the essence. Without reliable temporary cooling and heating systems, critical infrastructure can fail, resulting in important social services such as hospitals and other institutions unable to function as well as data loss. Moreover, evacuations require large populations to be housed in large tents or makeshift shelters and having appropriate systems can save lives. Furthermore, AC units that are sold on the retail market are simply not powerful enough to provide adequate relief to a large space or populace as retail units only go up to 14,000 BTUs. Therefore, it is imperative to have mobile, rugged and powerful systems that can reach up to 360,000 BTUs, such as Untitled Cool Air’s units. In addition, larger units are in development.

Built to last

An emergency unit must be built tough enough to hold up under harsh conditions and transport. Instead of cabinets built out of flimsy plastic, you will need a unit constructed from thick metal and quality parts. United CoolAir portable units are built in such a way, with each one tested before leaving the factory. This line of portable units under the name Therm~Air, are self-contained and built with various capacities and sizes such as air-cooled, water-cooled and heat pumps. For over 30 years these well constructed reliable units have been built in the USA.

Adapting DOAS To Your HVAC System

There is a proven method that will meet the challenges of complying with the ASHRAE Standards, delivering precise amounts of ventilation to spaces regardless of load size, and do it cost effectively.
Known specifically as a Dedicated Outside Air System, or DOAS, the outdoor air is conditioned separately from the air that controls the building’s space temperature (dry bulb). By having one system to provide and dehumidify all the ventilation air and a second system to control the space dry bulb temperature, both humidity control and space temperature control are improved.
By conditioning the outdoor air and recirculated air independently, a DOAS effectively separates the sensible and latent loads. The outdoor-air DOAS unit removes the latent load to control humidity, and the main HVAC unit removes the sensible load to produce a comfortable temperature. This is important because the primary source of building humidity in most climate areas is fresh outdoor ventilation air that has not been properly dehumidified. Additionally, the DOAS unit can assist the main HVAC unit by controlling smaller internally generated amounts of latent load that naturally build from occupants and other sources. It does this by providing air that is slightly drier than the target humidity level. Generally speaking, a DOAS provides “neutral” air of 70ºF to 72ºF @ 50% RH.
If desired, a DOAS unit can also provide the dehumidified air directly to the space at 55°F where it will offset some of the sensible load of the local HVAC unit. By delivering the air “cold”, this operation strategy doesn’t waste the sensible cooling byproduct performed by dehumidification but allows the local heating/cooling units to be sized smaller and requires less valuable floor space. A smaller main heating/cooling system means less energy consumption through smaller fans and compressors. A DOAS delivering cold supply air requires less reheat, but some reheat may be needed during periods of low sensible loads so the space is not “over-cooled” by the DOAS unit.
A DOAS doesn’t rely on totally new technology, but rather uses HVAC equipment configured to condition outdoor ventilation air separately from return air. The outside air conditioning system design consists of a cooling/dehumidification-reheat coil and supplemental heating system. The deep evaporator coil’s consist of 10 fins per inch/6 rows deep design, positioned in the draw- through air flow arrangement that provides the most effective moisture removal efficiency. It is this technique that differentiates it from conventional HVAC systems. This configuration will cool and dehumidify air in the summer and heat or cool it in the winter.
The operation is simple in design with the outdoor air first passing through an optional preheat coil (if used), which is sometime used for winter operation. When a heat exchanger is used, it brings the outdoor air closer to the temperature and humidity of the conditioned exhaust air.
A DOAS provides design engineers installation flexibility to meet the requirements of the application. Variables facing the engineer include, but are not limited to, if it’s new construction, retrofit or an installation having an existing system in place. Other considerations include the type of new or existing HVAC system installed such as constant volume, VAV and even the newer variable refrigeration flow (VRF) terminal units.
Delivering the conditioned OA from the DOAS to where it’s needed usually includes a separate ducting system running parallel to the HVAC supply air. For many climates, an independent duct system is considered the best choice because the ventilation air volume better meets the volume requirements of the project, and the DOAS ducting can be smaller than the conventional HVAC saving on the installation cost. Smaller ducting is also easier to manage in retrofit and existing HVAC installations.
A popular alternative ducting choice is a single duct system where the conditioned OA is blended with return air from the main HVAC system in a mixing box, or in a terminal unit that serves just one zone. If using a multi-zoned HVAC control system, individual zones are controlled separately and the DOAS will deliver the proper amount of outdoor air directly to each zone. In all cases, the DOAS can vary the fraction of ventilation to supply air, which can reduce the outdoor airflow rate by 40 percent by conditioning only the amount of air necessary for each zone.

The late sixties, early seventies ushered a new era into many facets of our lives. The rising cost of oil along with the uncertainty of supply made it necessary to evaluate what we had taken for granted for many years.
The October of 1973 Arab oil embargo sent oil prices rocketing while shortening oil supplies, causing building owners/operators to search for more reliable, less expensive ways to heat and cool large commercial spaces. The solution it seemed was to create a sealed building envelope thereby limiting the amount of infiltration and ventilation air to the minimum.
National energy conservation measures called for a reduction of outside air to 5 CFM per building occupant from 10 CFM. Most experts believed this would be sufficient ventilation to ensure adequate health and comfort, but they were quickly proven wrong.
The reduction in expensive OA resulted in a large increase in occupant complaints traced to their time at their workplace. Symptoms included nose or throat irritation, headache, dry cough, itchy skin, and sensitivity to odors, nausea, and eye discomfort. Sick Building Syndrome (SBS), as it was later known, caught the public’s attention with the sickening of 221 people and death of 34 others at an American Legion convention in Philadelphia through contamination in their air conditioning system.
Many studies have since proven beyond a doubt and established links between indoor air quality and human illness. When you consider the economic impact through lost productivity, lawsuits and increased insurance costs, building owners, HVAC design engineers and operators all take this issue very seriously.

OA is the Answer

ASHRAE Standard 62.1 – 2013—Ventilation for Acceptable Indoor Air Qualityforcommercialbuildings — quantifies the minimum ventilation rates and indoor air quality that will be acceptable to human occupants. 62.1 intends to minimize the potential for adverse health effects and has increased average ventilation rates from 5 CFM/person up to 20 CFM/person.
As a result, greater amounts of outside air must be introduced to the space, which also affects humidity levels. Humidity control becomes particularly important in the eastern half of the United States where mean dew point temperatures are 60°F e.g., 78°F/54% relative humidity, and higher during the summer.
These issues influence the need for an HVAC unit design capable of controlling ventilation, moisture levels and temperature in the space. To rectify the problem, traditional central station comfort cooling air conditioners must be “oversized” to handle peak latent load. To attempt to meet the new ASHRAE ventilation standards, a traditional air conditioning system generally requires 20%–70% more outside air than it was designed to cool, heat and dehumidify. Also, the traditional central HVAC must be set to provide the proper amount of outside air for the space with the greatest ventilation requirements. This ultimately causes over ventilating the rest of the building in the process and increasing the cost of conditioning that air.