Makeup air

Makeup air is meant to replace, or “make up” for, the air that has been removed through exhaust fans. It works by pulling fresh air from the outside into the building to replace air that that has been removed. In the past two years, in light of the pandemic, this kind of solution has become more appealing for spaces that need greater measures of ventilation.

Good indoor air quality requires the building to both intake and exhaust air. When a space is ventilated but not replenished by another air source, it results in a negative pressure in the building. If the space is well-sealed, the negative pressure will make an exhaust system work harder and pull in unconditioned air through any means possible. A positively pressured building is best, and makeup air within VTAC systems can be a key component in effective building air management.

VTAC technology incorporates makeup air capabilities that help companies meet building code regulations. The technology has the ability to sense occupancy, running the makeup system only when necessary.

UV Systems

One accessory that will be a natural addition to VTAC in the future is the incorporation of ultraviolet light systems. Currently available for the packaged terminal air conditioner (PTAC), UV technology actively destroys microbial growth and viral loads from reproducing and spreading. Mold and fungus can, at best, affect the odor of an indoor space, but at worst, can lead to poor indoor air quality and have a negative impact on occupant health.

Using a high-powered LED array for maximum intensity and efficiency, this new technology applies UV-C light (the region of the UV spectrum most useful for disinfection) to air as it passes through the unit, focused and channeled where most air movement occurs to reduce airborne virus concentrations. The UV-C kit is customized to the latest VTAC technology and can be installed into existing products. The ultraviolet light in this air treatment system continuously cleans the coil and drain pan of the system, helping it run more efficiently and removing harmful pollutants.

UV systems have become more popular and seen more development over the past year and a half since the first U.S. shutdowns of the pandemic in early 2020. As people return to work or find new places to live, systems that can proactively fight pathogens have become not just a stop gap between pandemic times and “normal” times, but a solution for the long term. Building owners must come to accept the idea that prevention is key and that guests and residents now expect more technologies that will ensure healthy buildings.

Standards and testing

Testing, adjusting and balancing (TAB) is necessary for all air conditioning systems so that they perform optimally and provide occupants comfort, safety and health at low cost. Performance tests include energy efficiency testing, which makes sure energy usage is as low as possible without lowering comfort levels. Acoustical and airflow testing checks the airflow within the building to make sure it is working to its highest level, while maintaining a comfortable noise level. Finally, air cleaner testing examines how well the system cleans the air, aiming for the best possible indoor air quality (IAQ). The test is important for all occupants but especially those who have respiratory issues or developing bodies, such as children.

Accessibility compliance

VTAC products are tested for compliance with American with Disabilities Act (ADA) and the Uniform Federal Accessibility Standards (UFAS) in order to help make appliances and architectural elements accessible to people with disabilities. The five requirements for air conditioner accessibility includes standards for forward reach, forward approach, side reach, control operation and location of controls. Maximum high forward reach for controls and operating mechanisms is 48" and minimum low forward reach is 15 inches. Controls and operating mechanisms must be operable with one hand and should not require tight grasping, pinching, or twisting of the wrist. The force required to activate controls should not be no more than 5 pounds.

Testing standards

Air conditioning units such as a VTAC system is tested in accordance with ANSI/ASHRAE Standard 37 using the operating conditions specified by the manufacturer’s installation instructions.

For single package vertical air conditioning systems, the testing must show that the unit can provide air-circulation, air-cleaning, cooling with controlled temperature and dehumidification, and may include the function of heating, humidifying and ventilation.

In addition to what Standard 37 requires, the test data is only valid for tests conducted when the atmospheric pressure is greater than 13.700 psia. In addition, there are requirements for how condenser air temperature for air cooled products must be measured, how indoor airflow and ESP is set, how air enthalpy is specified, and what the secondary method for capacity measurement for all full-load cooling and heating tests is. Conduct secondary measurements in accordance with the provisions in sections 7.3, 7.4, and 7.6 of ANSI/ASHRAE Standard 37 that are applicable to the selected test method.

When using the outdoor air enthalpy method as the secondary method for capacity measurement it’s important to first conduct a test without the outdoor air-side test apparatus connected to the unit (“free outdoor air” test). Then attach the outdoor air-side test apparatus and conduct a test with the apparatus connected to the unit (“ducted outdoor air” test). Use measurements from the free outdoor air test (i.e., indoor air enthalpy method capacity measurements and power input) as the applicable measurements for determination of efficiency metrics, in accordance with the standard.

The free outdoor air test involves connecting the indoor air-side test apparatus to the indoor coil; but not connecting the outdoor air-side test apparatus. The test room reconditioning apparatus and the unit being tested must operate for at least one hour. After attaining equilibrium conditions, the following quantities are measured at equal intervals that span 5 minutes or less: The evaporator and condenser temperatures or pressures, and the parameters required according to the indoor air enthalpy method. These measurements are continued until the applicable test tolerances are satisfied for a 30-minute period (e.g., seven consecutive 5-minute samples).

To measure evaporator and condenser pressures, a thermocouple is soldered onto a return bend located at or near the midpoints of each coil or at points not affected by vapor superheat or liquid subcooling. Alternatively, if the test unit is not sensitive to the refrigerant charge, pressure gauges are installed to the access valves or to ports created from tapping into the suction and discharge lines. The alternative approach is used when testing a unit charged with a zeotropic refrigerant having a temperature glide in excess of 1°F at the specified test conditions.

For the free outdoor air test to constitute a valid test for determination of efficiency metrics, the following conditions must be met: For the ducted outdoor test, the capacities determined using the outdoor air enthalpy method and the indoor air enthalpy method agrees within 6%. Second, the capacity determined using the indoor air enthalpy method from the ducted outdoor air test and the capacity determined using the indoor air enthalpy method from the free outdoor air test needs to agree within 2%.

After collecting 30 minutes of steady-state data during the free outdoor air test, the outdoor air-side test apparatus is connected to the unit for the ducted outdoor air test. The exhaust fan of the outdoor air-side test apparatus is adjusted until averages for the evaporator and condenser temperatures, or the saturated temperatures corresponding to the measured pressures, agree within ± 0.5°F of the averages achieved during the free outdoor air test. Thirty minutes of steady-state data is collected for which the applicable test tolerances are satisfied. During the ducted outdoor air test, at intervals of 5 minutes or less, the required parameters are measured according to the indoor air enthalpy method and the outdoor air enthalpy method for the prescribed 30 minutes.

For cooling mode ducted outdoor air tests, the capacity is calculated based on outdoor air enthalpy measurements as specified in ANSI/ASHRAE Standard 37. For heating mode ducted tests, the heat capacity is calculated based on outdoor air enthalpy measurements. The outdoor-side capacity is adjusted to account for line losses when testing split systems. The outdoor airflow rate is used as measured during the ducted outdoor air test to calculate capacity for checking the agreement with the capacity calculated using the indoor air enthalpy method during the ducted outdoor test.

Why is this important? The reasons are mostly obvious, but important to note that beyond the goal of keeping occupants safe and comfortable, resolving any issues beforehand means reducing the probability of issues getting worse, leading to more costly repair and downtime.