EVAPCO LSTE Forced Draft Centrifugal Fan Cooling Tower

Low-sound forced draft cooling towers for indoor and ducted plant rooms

The EVAPCO LSTE is a factory assembled, forced draft, counterflow cooling tower driven by centrifugal fans. Because the fans sit in a sound-reducing housing at the base of the tower and air leaves vertically through the top, the series is positioned by EVAPCO as the standard for low-sound, low-profile open towers that can be placed indoors, ducted, or on height-restricted sites. EVAPCO also lists it as suited to exact replacement projects where an existing footprint must be matched.

Warm water from the heat source is pumped to a pressurized distribution system at the top of the tower and sprayed over PVC wet deck fill. Air is forced in through louvers at the base, rises through the fill against the falling water, and a small portion of the water evaporates to remove heat. The cooled water collects in the basin and returns to the process. Because the discharge is vertical and well separated from the fresh air intakes, the warm humid air is directed up and away from the unit, which reduces the chance of recirculation.

Technical specifications

Model range and engineering data

The engineering bulletin groups the series by cabinet footprint. From the printed footprint table, the model code can be read as cabinet width in feet, a size digit, and cabinet length in feet: LSTE-416 is a 4 x 6 ft unit, LSTE-4118 a 4 x 18 ft unit, LSTE-5718 a 5 x 18 ft unit and LSTE-10636 a 10 x 36 ft unit (derived reading, confirm on certified drawings). The 8P and 10 foot wide units use large centrifugal fans. A selection of printed rows follows.

The bulletin states that an adequately sized bleed line must be installed to prevent the build-up of impurities, that catalog drawings are not for certified prints, and that for external static pressure up to one half inch the next larger fan motor should be used.

Installation, winter operation and options

EVAPCO recommends structural I-beams under the outer flanges running the full length of the unit, level to within 1/360 of the unit length and not more than one half inch before the tower is set. The unit should not be levelled by shimming between the tower and the beams. When a centrifugal fan unit is installed indoors with ducted intake air, a solid bottom panel is required so that the fans do not draw air from the room; for elevated units the bulletin recommends adding bottom screens.

For idle periods in freezing weather the bulletin describes a remote sump inside the building as the surest protection, with electric basin heaters sized by footprint as an alternative; for example a 4 x 12 ft unit lists one 3 kW heater at 0 F, 5 kW at minus 20 F and 7 kW at minus 40 F. Hot water pan coils are another option. Water lines and the spray pump piping should be heat traced and insulated up to overflow level.

Optional equipment printed in the bulletin includes an electric water level control (make-up supply pressure 5 to 125 psi), stainless steel basins and units, a vibration cutout switch, vertical ladders and sound attenuation packages: discharge attenuation, end and side inlet attenuation with solid bottom panels, and fan side inlet attenuation. EVAPCO water treatment options for the series are the Smart Shield solid chemical system and the chemical-free Pulse-Pure system.

Using the LSTE in Oman and the GCC

Cooling towers in the region must be selected for high design wet-bulb temperatures, which can be well above European or North American design values in coastal summer conditions, so the selection should use the project’s design wet bulb rather than a catalogue standard condition. The LSTE suits indoor plant rooms, basements and ducted installations in hotels, hospitals and commercial buildings, where low sound and centrifugal fans that can work against duct static pressure are needed.

Make-up water quality varies widely, from desalinated water to treated effluent, so a water treatment programme, blowdown control and regular cleaning are essential, together with a Legionella control plan. Dust and sand enter towers easily, so plan for basin cleaning and consider side-stream filtration.

Information to send with an enquiry

• Heat load, flow rate and inlet and outlet water temperatures
• Design wet-bulb temperature
• Indoor or outdoor installation and duct static pressure
• Sound limits and quantity

Documents and quotation

The LSTE and LPT engineering data bulletin is attached to this page for dimensions, weights and connection sizes. Seven Star LLC is an independent supplier based in Muscat; send the process flow, entering and leaving water temperature, design wet bulb and site constraints through the quotation form and we will request the selection from the manufacturer. See also our cooling equipment range.