DC Sizing Instructions

The following guidelines pertain to sizing UVC lamp quantities where the main objective is to provide a degree of UVC irradiation to pass-by airstreams. American Air & Water, Inc. provides an Excel driven calculator as a means of determining the proper amount of high-output UVC lamps for pass by airstream irradiation purposes. Many factors go into determining the required amount of UVC energy and lamps to adequately provide this energy, when installed into forced air systems. These factors include airflow velocity and temperature. The Excel calculator takes into account these factors as well as duct area available for lamp mounting purposes. With this info provided, an exposure time can be determined which will determine the overall quantity of lamps required for a dose rate. The dose rate is a general term applied to the total amount of UVC microwatt seconds that a particle sees or is subjected to, as it passes through the UVC lamp section mounted in the duct.

Application objective and description:

The idea of placing UVC lamp fixtures in forced air ducts is intended as a means of controlling the spread of microorganisms throughout the air duct system and into the adjoining office or other living quarters. This inline duct installation along with subjecting any cooling coils to shortwave UVC energy offers the best means for inactivation microorganisms in the airstream. UVC energy will degrade and inhibit the growth patterns of these microorganisms which will prevent their spreading throughout the air system as well as clean the coil. UVC lamp fixtures can be placed in either the supply or return air ducts. Our UVC lamp fixtures produce the highest UVC intensities available anywhere on the market.

Steps and required information:

1. Record the overall height and width of the air duct that the UVC lamps are to be placed in. This information is entered into the Excel calculator. Enter these values as inches for the unit of measure.
2. Record the available duct length for installing lamps into. Enter this into Excel as feet for the unit of measure.
3. Record the airflow and temperature into Excel. List the temperature as degrees Fahrenheit and the flow rate as cubic feet per minute. (Important note: do not enter any temperature value greater than 60 degrees or less than 35 degrees, as the lamp intensity correction will be too high. For example, if the actual flow temperature is 80 degrees, enter it as 60 degrees.)
4. Specify the lamp length to be used. Typically the lamp length should be sized to span as much of the duct width as possible.
5. Determine the lamp output of the selected lamp from sheet (2) of the Excel calculator and enter it into the proper space. The intensity to be entered will be highlighted and is listed as ‘UVC Intensity @ 12”. Excel will then correct the lamp output based upon airflow listed.
6. Excel will calculate the number of selected lamps required to provide a dose of 2,500 microwatt seconds. This value will be displayed in the (J) column. Round this value up to the next even number and select the lamp fixtures accordingly. Lamp fixtures should be selected as (2) or (4) lamp fixtures.
7. The lamp quantity is calculated based on a dose of 2,500 micro-watt seconds. For other dose requirements, increase or decrease the 2500 value shown in the formula for column N.
8. Each series of calculations should be saved off as an individual Excel file with the customer or job description used for future reference.