Proper Design of a HVAC Bacterial Control System
Using UV Technology

By James A. Hart, P.E.

There is much discussion today about the quality of home air. It seems everyone now is touting the latest UV technology to provide clean air throughout a household. UV technology is nothing new -- it has been around for years, and properly applied, it does work. Lately there have been a number of companies making claims that their particular device will purify the air for a marginal cost. The literature provided by these companies show purified air circulating through the house, providing air "as clean as the great outdoors", and killing germs throughout the house. While these claims sound good to the uneducated person, in fact, they are bogus.

UV Technology is very simple: take a known quantity of UV light, expose a surface or substance to the light for a specified period of time, and a percentage of the bacteria are killed. The product of the UV light intensity, multiplied by the length of time of exposure at that intensity, is termed the "CT Value". Tables of CT Values have been published and are well known. To properly determine what values to use, pick a microbe from one of these tables, then read the corresponding CT value and design the system around that CT Value. Sounds simple, doesn't it? Well, yes and no.

A proper understanding of the CT Value is essential in designing a HVAC cleaning system. High UV light concentrations will result in short exposure times; low UV light concentrations result in long exposure times. The proper balance of these two variables is what is at the heart of good design. High UV light concentrations are accomplished simply: provide more lamps per volume of space. The downside of this is the cost. The other way to meet the CT value is to provide a long "residence time". Residence time is the time a particular volume of air is in the presence of UV light; the "T" in CT. Residence time is almost always a fixed value in most home HVAC systems. Typical HVAC home systems operate around 2000 ft3/min for a 2,000 sq. ft. home. Typical ducting in such a home is on the order of 6" x 8" or 8" x 10". The plenum attached to the air handling unit is typically on the order of 2 ft by 2ft in cross section. With these values, it is easy to determine the velocity of air leaving the unit. For our example, 2,000 ft3/min will have an exit velocity of 500 ft/min, or 8.33 ft/sec. From this value, the proper residence time can be evaluated for specific CT values.

Selection of the proper HVAC treatment will depend next on the type of mold. Typical molds found in households are in the Aspergillius family. Aspergillius has CT values for 90% kill ranging from 44,000 to 132,000 m W-sec/cm2. Bacillus subtilis spores, a common bacteria, has a CT value of 11,600 m W-sec/cm2. For our example, we will use the Bacillus number, because as we will see, that relatively low number will mean a relatively high residence time. CT values higher than Bacillus will require an even longer residence time.

Designing the Proper HVAC

Diagram for designing a proper HVAV UV light system For our example, we will use the HVAC system previously described, a 2,000 ft3/min unit, with a 24" x 24" outlet plenum. These parameters will provide a velocity of 8.33 ft/sec. We will use low-pressure UV lamps, which typically provide about 800 m W-sec/cm2 at a 12 inch radial distance, a lamp typically sold by HVAC contractors. The lamp is placed at the outlet of the coils. However, at this flow rate, you will only have a residence time of 0.24 seconds. That is only 1.7% of the required 14.5 seconds for 90% kill. This is not even close to the required CT Value to kill Bacillus. In fact, this value is so small, the UV will have no effect on any airborne pathogen.

To provide a 90% kill, your system will need to be designed accordingly. For a 12 inch UV radius, a duct no more than 12 inches high will be used. Standard 30 inch lamps will be placed every two feet (an estimate for this example only) for the desired residence time of 14.5 seconds. The duct cross sectional dimensions are 12" x 30", for a cross sectional area of 5 ft2. To maintain 14.5 seconds residence time, a length of 95 feet will be required. This is beyond the normal HVAC unit in most houses. This simple example shows the absurdity of any claims that a single UV bulb can clean, much less sanitize, the typical household air system.

Kill zone for an ordinary UV Lamp

Proper Duct Length for 90% Kill

 

New and Improved AirOasis Generation 3 (G3) Air Purifiers:
Same Superior Technology, Same Sleek Design
Now More Energy Efficient with Lower Ozone Output

Air Oasis G3 Induct HVAC Air Purifier image

The ONLY Induct Air Purifier with Rotational UV Shield Technology

Since UV lamps were first used in HVAC systems, there has been one constant complaint from HVAC engineers and contractors. UV light can degrade many of the rubbers and plastics used within an HVAC system, causing premature system failure. Air Oasis has created the perfect solution. With the development of their proprietary Rotational UV Shield you can control how little or how much UV light is emitted from the unit, while allowing for a constant stream of air to pass through the AHPCO Cell for treatment. The Rotational UV Shield can be rotated 360 degrees exposing more or less of the UVC lamp.

The new Air Oasis G3 commercial and residential induct series offers these new enhancements:

  • Significantly more energy efficient, reducing energy consumption by more than 50%.
  • Can be powered by a 110-240 VAC wall outlet internationally.
  • Lower ozone output compared to the previous models (call 866-75-4386 for higher ozone options).
  • New operational indicator lights to identity system failures and lamp replacement.
  • Proprietary Rotational UV Shield technology that prevents premature HVAC system failure caused by other induct UV systems that break down rubbers and plastics.
  • Automatic overheating safety shut-over. When that happens, the thermal protector opens the circuit, disconnecting power to the ballast. The circuit will automatically reset when the ballast cools.

Air Oasis Induct is the Affordable SOLUTION
for Whole House or Building Indoor Air Pollution

The Air Oasis G3 Induct UV Air Purifier easily installs in your HVAC system to ensure the duct work in your house or building stays free of harmful contaminants such as mold and bacteria. This UV air purifier also allows your home or building to be covered more evenly due to ions being forced throughout the duct work and into each room or area with an air outlet.

UV PCO Air Purifier Technology Developed by NASA.

Air Oasis G3 Induct HVAC Air Purifier imageMore than 20 years after NASA put the first man on the moon, NASA began to prepare for future man missions into deep space by growing their own fruit and vegetables in space. They had to find a way to reduce ethylene gas, which was destroying the plants and vegetables when they would ripen. NASA developed an ethylene scrub air purification machine using a titanium dioxide catalyst in conjunction with UV lamps to remove the ethylene gas. Subsequent tests revealed that this PCO/TiO2 air purifier technology also helped destroy harmful organisms such as bacteria that passed through the system.

Air Oasis has utilized this early NASA UV PCO air purifier technology to develop a revolutionary line of air purifiers. Every Air Oasis air purifier contains a PCO Cell coated with their proprietary nano Nickel HCT catalyst that is permanently bonded to the PCO cell structure. When photons from the germicidal UVC lamp excite water and oxygen molecules on the catalyst surface, redundant oxidizers, including hydroxyl radicals and hydro peroxides, are formed. Organic compounds that collide with the catalyst are greatly reduced. Air Oasis air purifiers have been tested by Nabarun Ghosh Ph.D., Associate Professor of Biology, Department of Life, Earth and Environmental Sciences at West Texas A&M University. They have been proven to greatly reduce mold, bacteria, VOCs and other aeroallergens. Read Air Oasis Studies and Test Results

nano Nickel PCO Technology

The proprietary patent-pending Air Oasis nano Nickel HCT catalyst is superior to any PCO catalyst currently on the market. Imitation air purifiers use titanium dioxide (TiO2) alone as a catalyst. TiO2 is the cheapest, most available catalyst metal on the market. It's often used as the white pigment in standard house paint and costs only pennies. In contrast, the nano Nickel HCT contains five rare catalyst metals. We also use nano size metals to increase the kinetic rate of reaction. Read about Air Oasis Technology

Air Oasis G3 Whole House/Building Purifiers Via the HVAC Duct

Air Oasis G3 nano HCT HVAC Induct Air Purifier image

Air Oasis G3 nano HCT 6" UV Air Purifier

The Air Oasis nano HCT HVAC 6" Induct UV Air Purifier is for smaller sized homes, offices or buildings up to 1000 sq. ft. per air handler, assuming an 8 foot ceiling and depending on cubic air space and contaminant sources and levels.

Air Oasis G3 nano HCT 9" Induct UV Air Purifier

The Air Oasis G3 nano HCT HVAC 9" Induct UV Air Purifier is for average to large sized homes, offices or buildings up to 3000 sq. ft. per air handler, assuming an 8 foot ceiling and depending on cubic air space and contaminant sources and levels. This model works well in small commercial applications like kennels, pet shops, medical and dental facilities, business offices, etc.

Air Oasis G3 nano HCT 14" Induct UV Air Purifier

The Air Oasis G3 nano HCT HVAC 14" Induct UV Air Purifier is designed for large commercial or industrial applications where higher contaminants are known to exist and need to be reduced continuously. HVAC blowers should be over 6500 CFM. Read about Air Oasis G3 Induct Models

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Need help determining the right model? Call us toll free at 866-875-4386.

Nano HCT Induct Technical Specifications

The following specifications apply to all nano HCT induct models:

  • 12 VDCUL, CE, TUV, CSA, FCC, PSE, TCA, and CCClisted power adapter (included in price)
  • Warranty: 2 years parts and labor
  • Material: Aluminum and Polymers
  • Approvals: Conforms to Standards: UL-867 and EN-60335

Air Oasis Approvals imageAir Oasis Approval image

Nano HCT Induct Air Purifier Power Source

The Air Oasis nano HCT Induct is powered using a 26 VDC power adapter with a rated input voltage of 100 - 240 VAC and 6 foot supply cord. The adapter connects to a 110 or 230 VAC 3 amp power cord that is 5 feet in length. The AC power cord is detachable and interchangeable to meet global requirements. For safety and to ensure proper function of the nano HCT Induct we recommend that ONLY the power adapter included with the original purchase be used.

The Air Oasis nano HCT Induct air purifier was designed for continuous operation. For maximum effectiveness, operate the unit 24 hours a day, 7 days a week.

Optional 24 VAC Internal HVAC Power Source Wiring

Most forced-air heating or cooling systems have a internal 24 VAC power source to which the nano HCT Induct can be safely connected without overloading other circuits.

Nano HCT Induct Indicator Lights

The Air Oasis G3 nano HCT induct unit has two indicator lights that tell specific information about the unit.

Operational Indicator Lights

  • Green - Unit has power, ballast and UVC lamp are operating efficiently.
  • Red - Unit has power, UVC lamp is defective or not properly connected. Contact an Air Oasis representative.
  • No Lights: There are two possibilities.
    • The unit is not properly connected to the power supply.
    • The ballast exceeded the operating temperature of 105C. When that happens, the thermal protector opened the circuit disconnecting power to the ballast. The circuit will automatically reset when the ballast cools.

UVC Lamp Status Lights

  • Blue Solid - The UVC lamp is within its two year life span. No action is needed.
  • Blue Flashing - The UVC lamp is outside its two year life span and should be replaced.

Low Maintenance

The nano HCT Induct was engineered to be virtually maintenance free. The AHPCO Cell should be replaced every two years. A blue flashing light on the panel indicates that the UVC lamp is outside its two year life span and should be replaced. At two years of age, the UVC lamp performance drops by 20%, and continues to drop during the third year of use until it is no longer effective.

To maintain the outer housing, never use harsh cleaners, chemicals or abrasives on the plastic polycarbonate housing or anodized aluminum. Only a dry micro fiber towel or a towel lightly moistened with water should be used to remove any dust or other debris from the outside of the unit.

Made in the USA

Air Oasis is made in the USA with quality American engineered parts. From durable light weight titanium anodized aluminum, down to the polycarbonate ballast housing, every part of the nano HCT is made with pristine quality and assembled and tested by hand. Air Oasis offers quality you can count on. (Read More about Air Oasis Quality)

Nano HCT Induct Placement Options and Applications

The nano HCT Induct units are designed to be installed within the ductwork of an HVAC system. They can be mounted in either the supply side or return side of your HVAC system. The nano HCT Induct unit should be placed within 10 feet of an electrical outlet. To help you determine the optimal placement of your new nano HCT Induct we have listed a few examples below. We recommend that you always work with an authorized Air Oasis dealer and licensed HVAC engineer or contractor when deciding optimal placement.

Above coils

The nano HCT Induct unit should be mounted directly above the coils with UV Shields rotated 90 to the open position. The unit should be orientated so that the UV light shines directly on the coils (air flow label should be pointing at the coils). Larger air handlers may require multiple units.

Reducing Contaminants in Ductwork

In residential or light commercial applications a single unit can be mounted in the plenum on the supply side of the HVAC system.

In Large Commercial Applications

Air can become recontaminated as it travels through the duct work. Therefore it may be necessary to mount several nano HCT Induct units throughout the ductwork. The UV Shield can be rotated to the closed position when installing the unit in close proximity to rubber seals and gaskets or electrical components to protect them from the UV rays. When possible, the UV Shield should be rotated in the open position for optimal efficiency to expose more contaminants to UVC radiation.

Reduce Airborne Contaminants in a Room

The nano HCT Induct unit should be installed in close proximity to the air outlet vent that supplies air to the room being treated. The UV Shield should be rotated to the closed position to prevent human exposure to UV rays.

Air Oasis Induct Installation Recommendation imageAir Oasis Induct Installation Instructions

Air Oasis Induct ACT units are installed directly into the plenum or other remote "down stream" locations. The following are simplified instructions. Please consult the installation manual for extensive installation instructions.

  1. Determine the best location for optimal mounting (see installation manual link below). The mounting location should be within 10 feet of an electrical outlet.
  2. Using a 4" hole saw, cut a 4" hole in the ducting where the nano HCT induct will be mounted. Center the hole ensuring there will be at least a 5 diameter of ducting around the outside of the hole.
  3. A trained service professional should be consulted to determine the extent of UV Shield rotation. Rotate the UV Shield to the desired opened or closed position. Place one hand on the Distal Cap and the other on the Outer UV Shield. Rotate the Distal Cap clockwise while rotating the Shield counter clockwise until the desired position is reached. Rotation will require firm pressure.
  4. Remove the wax paper from the gasket located on the bottom side of the Retainer Ring. Insert the nano HCT into the 4 hole, aligning the cross hairs parallel to the ducting. Press firmly on the Retainer Ring to adhere to the ducting.
  5. Firmly press the Ballast Assembly onto the four pins protruding from the AHPCO Module. The Ballast Assembly should be orientated with the air flow label running parallel with the length of the ducting to ensure the four pins are in line with the Four Pin Connector. Optional mounting configurations may vary this orientation.
  6. Using a 1/4 hex head screw driver, secure the nano HCT with four self tapping 3/4 screws. The screws should be slightly tightened being careful not to strip them.
  7. Using a 1/4 hex head screw driver, secure the power adapter with four self tapping 1/2 screws.

Once the installation process is complete, plug the included power adapter into the Nano HCT. Connect the power adapter to a 110 or 240 VAC electrical outlet. The Nano HCT will start, with the green lights and blue lights illuminating.

Additional installation instructions and options can be found in the manual. Read the nano HCT Induct Installation Manual

Call Us Toll Free at 866-875-4386 for Specials and Quantity Discounts
or for Help Determining Which Model to Choose

Combine an Air Oasis Induct Air Purifier with a
Venmar Heat or Energy Recovery Ventilator
for the Cleanest, Freshest Air Possible

The Venmar air exchange system is fabulous for recovering heat or energy, providing fresh air, controlling humidity and removing particulate (dust, pollen, dander, etc.), giving you the ultimate in clean air for your home. It is the perfect companion to the powerful broad-spectrum pollution purification abilities of the Air Oasis HVAC Induct Air Purifier, which destroys bacteria, viruses, pesticides, herbicides, mold spores, chemical fumes and gases, VOCs, odors and more. Click here for Venmar Ventilation HRV and ERV Systems.

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