Adding ultraviolet air treatment to an existing HVAC system is rarely a matter of choosing a germicidal lamp by wattage alone.
The available installation space, duct geometry, air velocity, humidity, operating temperature, electrical connections, and maintenance access all influence the final configuration. These factors become particularly important when an air-conditioning and humidification system has already been assembled and there is no room for a separate factory-built UV section.
This project involved selecting a compact UV light kit for installation inside the mixing chamber of a private home’s central ventilation system.
Project Background
A homeowner in the Istra district contacted UVL to add ultraviolet treatment to an existing ventilation, air-conditioning, and humidification system.
The HVAC installation was already complete. Its mixing chamber provided only limited free space, making it impractical to add a conventional bactericidal section or rebuild the entire duct assembly.
The customer therefore needed a compact UV kit for self-installation inside the existing ventilation enclosure.
The initial project conditions were:
facility: private residence;
system: central ventilation and air conditioning;
installation point: HVAC mixing chamber;
additional process: air humidification;
expected environment: elevated humidity inside the duct;
principal limitation: no space for a separate UV section;
installation format: retrofit into the existing enclosure.
Why a Standard UV Section Would Not Fit
A complete UV section normally requires sufficient straight duct length, mounting flanges, service clearance, and access for lamp replacement.
None of these conditions could be guaranteed at this site. The ultraviolet module had to be placed directly inside the existing mixing chamber, where the remaining space was restricted by previously installed HVAC components.
This changed the selection criteria. The most important factors were no longer only UV output and lamp power, but also:
the physical length of the lamp;
clearance between the lamp and the chamber walls;
access for inspection and replacement;
secure positioning in the moving air stream;
protected electrical connections;
cable routing from the humid duct to the external power supply;
compatibility with the operating temperature inside the ventilation system.
Humidity was another significant consideration. Because the UV source would be installed downstream of a humidification stage, an open electrical contact assembly inside the chamber was undesirable.
The customer also needed a clear installation concept that could be implemented without redesigning the complete HVAC system.
Selected UV Lamp and Installation Kit
UVL selected a retrofit kit based on the UVL 19170-144-W2000 FLOW germicidal lamp with a rated power of 170 W.
A longer lamp had initially been considered. After checking the actual dimensions of the mixing chamber, the design was revised to use a more compact 392 mm lamp. This provided sufficient installation clearance and made future servicing more practical.
The selected lamp was designed for operation in an active air stream and for air temperatures between 10 and 35 °C. It is an ozone-free, low-pressure amalgam UV lamp with a stated service life of up to 16,000 hours.
Instead of an exposed contact group, the lamp configuration uses an integrated ceramic connector and insulated outgoing wires. The cables can be routed outside the humid chamber through sealed cable glands, while the electronic ballast remains in a more suitable external location.
This arrangement reduces the number of vulnerable electrical connections inside the humid airflow and simplifies access to the power unit.
Kit Components
The supplied in-duct UV light kit included:
one UVL 19170-144-W2000 FLOW lamp;
rated lamp power of 170 W;
ozone-free low-pressure amalgam technology;
expected service life of up to 16,000 hours;
one L-220-1×200-2201-15 electronic ballast;
three T5 lamp clips with 20 mm mounting feet;
wiring required for connecting the lamp to the external power unit.
The result was not a complete ventilation section, but a set of matched components for building a bactericidal treatment zone inside the customer’s existing duct enclosure.
Selection and Installation Process
The project began with photographs of the HVAC system and a consultation about the intended mounting point.
The customer then visited UVL to explain the configuration of the mixing chamber, the humidification stage, and the physical restrictions in greater detail. This made it possible to compare the proposed lamp dimensions with the actual available space before the equipment was supplied.
UVL recommended the compact FLOW lamp and explained:
where the lamp could be positioned inside the chamber;
how the three clips should support it;
how the wires could be routed through sealed cable entries;
why the electronic ballast should be installed outside the humid airflow;
how sufficient access could be retained for maintenance.
The supplied solution matched the customer’s original requirement: a compact retrofit kit rather than a separate UV duct section or a major reconstruction of the ventilation system.
The order included the lamp, electronic ballast, and mounting hardware. The customer collected the equipment directly.
Practical Benefits
The selected configuration gave the homeowner several advantages:
UV equipment could be added to the completed HVAC system;
the existing mixing chamber did not need to be replaced;
the compact 392 mm lamp fitted the restricted installation area;
the lamp was selected for operation in an active air stream;
electrical connections could be routed away from the humid zone;
the ballast remained accessible outside the duct;
the supplied clips provided a clear and straightforward mounting arrangement;
future lamp replacement could be performed without rebuilding the ventilation system.
Important Engineering and Safety Considerations
An in-duct UV air purifier must be designed around the actual airflow and chamber geometry. Lamp wattage alone does not establish the UV dose delivered to the moving air.
A complete engineering assessment should consider:
air volume and velocity;
duct cross-section;
lamp output and orientation;
exposure time;
air temperature;
relative humidity;
reflectivity of internal surfaces;
target microorganisms;
required level of microbial reduction.
Germicidal UVC radiation can damage the eyes and skin. The lamp must not operate while the chamber is open or accessible to occupants. The installation should include appropriate access controls, warning labels, electrical protection, and, where applicable, an interlock that switches the lamp off when a service panel is opened.
Electrical installation and grounding should be completed by a qualified specialist in accordance with the equipment documentation and applicable electrical requirements.
Conclusion
This project shows why a retrofit UV installation must be selected according to the real HVAC layout rather than lamp wattage alone.
A full-size bactericidal ventilation section could not be installed because the residential system had already been assembled and the mixing chamber offered limited space. The compact UVL 19170-144-W2000 FLOW lamp and matching installation components provided a practical alternative.
By using a 392 mm lamp, protected wiring, sealed cable routing, an external electronic ballast, and dedicated mounting clips, the customer could integrate an ultraviolet module into the existing ventilation system without reconstructing the entire duct line.
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