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Updating Buildings with Old Induction Systems…

fm_induction_unitInduction HVAC systems were very popular in the 1950s and 1960s. They were used in large buildings where space was at a premium and the small ductwork used with the induction systems was an advantage. The induction units were typically mounted on the floor or the wall in the building’s perimeter zones, and concealed under enclosures built to suit the size of the units selected.

With the emergence of variable air volume systems in response to the energy crisis in the 1970s, induction system fell into disfavor. There were energy cost concerns as the old induction units required very high inlet static pressure (often 1.5 – 3.0 in. w.c. or more) which imposed a significant penalty of the systems fan energy consumption. In addition, the old induction units produced relatively high noise levels.

Many of these older building are now in need of updating. Rather than simply replacing the old induction units with like units, there is often an opportunity to significantly improve the performance of the old induction HVAC system through the use of new induction units which incorporate the latest induction nozzle technology, while re-using much of the buildings existing infrastructure (ductwork, piping, etc).

Lower Noise Levels

Very low noise levels can be achieved when the new induction units are sized at relatively low inlet static pressures. With the new units selected at typical inlet static pressures of 0.5″ w.c. or less, room noise levels can be dramatically reduced as the new technology nozzles are whisper quiet. DADANCO’s patented nozzles rapidly induce room air to reduce the momentum and height the primary air jet, which significantly reduces the noise generated.


Increase Cooling Capacities

In many buildings the cooling loads have increased from what was anticipated when the building was originally designed and built. This is often due to the use of more heat-producing electronic equipment within the building such as computers and equipment in offices, medical equipment in hospitals, etc. The old induction units were not sized for these increased cooling loads and often cannot now adequately cool the rooms.

If increasing induction unit cooling capacities within the same unit space constraints is an objective the new induction units can be selected at inlet static pressures and primary airflows close to the original conditions, while providing more cooling capacity through the new induction unit’s water coil. As there is normally excess water chiller cooling capacity available in most buildings, the room temperatures can now be maintained at acceptable levels.

Gain Floor Space

Many building owners want to remove the unsightly old induction units and enclosures from the floor. Depending on the heat losses along the buildings perimeter it is often possible to replace the old floor-mounted units with new concealed ceiling-mounted models.

The net result is a gain in floor space and overall improvement to the room’s appearance.


Lower Energy Consumption

With the new nozzle technology available today the induction systems supply fan static pressure can be dramatically reduced (often by 1.0 – 3.0″ w.c.) when retrofitting an entire system with new induction units. In addition the primary airflow can often times also be reduced (within the constraints of the ventilation air requirement).

The net result of these decreases in static pressures and primary airflows due to the use of the new induction units is lower fan energy consumption and operating costs.

Frequently Asked Questions

What is an induction unit?fm-induction-drawing
Primary supply air from the central system air handling units is introduced into the induction unit through a series of nozzles (2). This induces room air (3) into the induction unit and in turn through a secondary water coil (4). Induced room air is cooled and/or heated by the water coil to the extent needed to control the room temperature. Induced room air is then mixed with the primary supply air and the mixed air (5) is discharged into the room.

Induction Units Product Range

DADANCO’s Induction units have been developed using our patented nozzle technology. We offer several designs that can fit into the existing enclosures of most brands and models sold in the past and which may be in need of replacement or updating.

Our standard units are the FMTBY (approximately 20” high x 7” deep), the FMLBY (approximately 12” high x 9” deep), and the FMFBY (approximately 11 ½” high x 11” deep).

All models are available with unit lengths from 24 inches through 96 inches and with either a 2-pipe or 4-pipe configuration.

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