Fan types available with USA Air Handling Units are housed DWDI forward curved and airfoil fans, plenum fans, in-line fans and twin fans. Forward curved fans generally provide the lowest first cost option and are used for lower static pressure applications. USA housed forward curved fans will typically operate up to 6.0” of static pressure. Airfoil fans have a higher first cost, but are more efficient, quieter and can handle higher static pressures. USA housed airfoil fans will operate up to 9.0” of static pressure.
Plenum fans save space by eliminating turns in ductwork. They also provide a high degree of flexibility when locating the outlet ductwork. Plenum fans are also very good for blow through applications as they generate a uniform outlet velocity profile. Both belt drive and direct drive plenum fans are available.
In-line fans are quieter and more efficient than most standard fans. In-line fans are most beneficial in VAV applications.
Twin fans (two housed forward curved fans mounted on one common shaft) are excellent in both retrofit units and stacked energy recovery units. Twin fans can handle high CFMs in very low profile units.
These different types of fans are available in numerous wheel diameters per unit size. The fan size selection is always optimized and identified by the software selection program. The program offers a number of fan sizes to select from, considering performance, efficiency, sound generation and first cost. Fan and motor assemblies can be provided with 2” spring, rubber in shear, or rigid mount allowing the customer the option of isolating the fan and motor assembly internally or isolating the entire unit.
All fans are dynamically balanced at the plant as an assembly including the motors and drives. All fans rotate on a solid steel shaft of uniform diameter that has been ground, polished, and coated with a rust inhibitor. Fan shafts are selected to have a maximum operating speed well below the first critical speed.
Belt guards are available on plenum fans and in-line fans. Seismic restraint is also available for applications requiring additional fan support.
The fan bearings provided will have a minimum L50 life of 200,000 hours, and are available as high as 1,000,000 hours. Bearings are selected for minimum noise levels and minimal service. Bearings are self aligning and pre-lubricated for immediate use. Bearings are mounted on rigid frames and positioned to provide proper balance. All bearings include copper lubrication lines that are extended to the access side of the fan cabinet with the grease fittings located near the access door opening.
All fan motors are internally mounted. The appropriate motor size will be selected by the selection software program. Motors cannot be undersized, but may be oversized if desired. Motor options include open drip proof, totally inclosed fan cooled, 1 speed/1 winding, 2 speed/1 winding, and 2 speed/2 winding. Motor efficiencies available include standard efficiency, high efficiency and premium efficiency depending on the motor type.
B. COILS
USA Indoor Air Handlers offer broad application flexibility in the coil sections and coils. Coils can be arranged in draw through, blow through, or multizone configurations. Heating only, cooling only, or cooling and heating sections are available. All coils are installed with space between each coil to allow for access for cleaning and mounting of controls.
Cooling coil sections, and cooling and heating coil sections, are available in seven different section lengths to accommodate every application requirement. Drain pans extend the full length of the section. Removable access panels or doors may be provided in the deeper sections that will not interfere with the piping connections extending through the unit side panels.
All cooling coils are mounted over a double sloped drain pan. The cooling coil rests on coil supports located over the drain pan. The drain pan extends beyond the leaving side of the coil to help recover condensate. The primary drain pan also extends under the coil headers and return bends to help remove condensate from the unit. A full thickness of insulation is always provided between the drain pan and the bottom outer panel. The drain pan is sloped in two planes to promote proper condensate removal. The galvanized drain pan is coated with an antimicrobial treatment as standard to further inhibit the growth of algae and fungi. A stainless steel drain pan is also available as an option.
Coil Connections always extend through the unit cabinetry, allowing for easy connection of valves and piping. Water coil vents and drains are located outside the
cabinetry.
A range of different size face area coils is available, including small, medium, medium extended, large, extended and staggered. Generally small face area coils are used for heating applications, the large face area coils are used for heating applications with bypass, and the extended face area coils maximize the unit cross section for restricted space applications. The extended coil is intended to be used to maintain coil face velocity limitations without going to a larger cabinet size. This ultimately saves valuable floor space and money.
USA unit coils can be selected from a full range of coil options. With USA being a major manufacturer of heat transfer coils, the coil options are virtually unlimited. The USA coil line has many different coil types, ranging from hot and cold water, evaporator and steam coils. Standard USA coils are ARI certified. In addition to a broad range of circuitings, fin spacing and row depths, coils can be constructed of different material types for fins, tubes, connections and casings. This provides the ability to specify the coil to exactly meet the application needs.
For more information on USA Coil & Air coils contact the factory.
C. FILTERS
Good air quality is of utmost importance. A key ingredient in maintaining good air quality is air filtration.
The USA Indoor Air Handler has been designed to house flat, angular, bag, or cartridge filters. These media types range in efficiencies up to 95% and MERV* 15. In addition to offering a full range of efficiencies, the filter media can be provided with an optional antimicrobial treatment. Antimicrobial treatments are highly recommended for a complete filtration system.
An optional filter pressure gauge may be ordered with each filter section to help promote regular servicing and prevent clogging.
Both bag and cartridge filters are provided with a prefilter. Bag and cartridge filters can be either side load or front load, and access can be from either or both sides of the filter section. An access door is provided on either side or both sides of the unit Filters can be positioned any place in the unit and as many filter sections as required can be used. In many health and food industries, stringent filtration is required. Often times there a need for a filter section to be the last component in the air stream. The USA Air Handler can meet these needs by providing a filter section located as the last component in the air stream and with full sheet metal liners.
D. STANDARD FILTER TYPES AVAILABLE
5700 - 2” depth. Flat panel filter designed for heavy dust loading conditions.
PerfectPleat - MERV 6 (30% efficiency), 2” or 4” depth.
Made from pleated, self supporting DuraFlex™ by AAF.
AmAir 62plus - MERV 8 (70% efficiency), 2” or 4” depth.
Standard AAF AmAir pleated filter with two layers of added polypropylene laminate to increase efficiency.
VariCel II MH - 95%, 85% and 65% efficiency, 4” depth, 1” track requirement. Mini pleat filters with metal cell sides and headers that provide superior moisture resistance.
VariCel SH - 95%, 85% and 65% efficiency, 12” depth, 1” track requirement. Steel interlocked header and cell sides hold the corrugated aluminum separated pleats allowing optimum airflow. Rated UL Class 1.
VariCel V - 95%, 85% and 65% efficiency, 12” depth, 1” track requirement. Mini pleats held in a V-bank configuration providing greater airflow capacity and longer service.
DriPak2000 bag - MERV 15, 14 and 11, (95%, 85% and 65% efficiency), 36”, 30” and 22” depths, 1” track requirement. Extended surface pockets made from high-loft, layered synthetic media. Rated UL Class 1 MERV 8 efficiency DriPak2000 filters also available in 19”, 15” and 12” depths.
E. *WHAT IS THE MERV RATING
Minimum Efficiency Reporting Value (MERV) - ASHRAE Standard 52.2-1999 entitled “Method of Testing General Ventilation Air-Cleaning Devices for Removal by Particle Size” provides a methodology for determining filter efficiency at removing various sizes of particles as the filters become loaded. There are three ranges of particle sizes that define the MERValue.
Range 1 - .03 - 1.0 um particle size
Range 2 - 1.0 - 3.0 um particle size
Range 3 - 3.0 - 10.0 um particle size
The Table below shows a comparison of the MERV rating to the average arrestance percentage by the older ASHRAE Std. 52.1 method.
F. ULTRAVIOLET LIGHT OPTIONS
USA Air Handlers can be factory-equipped with ultraviolet (UV) light options that are pre-engineered for placement to provide maximum effectiveness. Two UV light options are available. The first can be mounted on the downstream side of all cooling coils and above the unit drain pan for surface kill applications to comply with the GSA Facilities Standard for federal buildings.
The second can be mounted in the air stream prior to filter(s) for “kill on the fly” applications. Both applications are agency approved to UL Category Code ABQK specification, HVAC Accessories, Air Duct Mounted, in addition to the ETL listing of USA Air Handlers.
G. ACCESS
The access section can be selected to meet specific application criteria. Access sections are available to be placed anywhere in a unit in a variety of depths.
Sections are available in depths of 16”. 24”, 30”, 36”, 42”, 48” and 54”. Typically access sections are used for field installed components, air monitoring devices or to provide ample space between components.
H. FACE & BYPASS DAMPERS
Face and bypass dampers can be provided for temperature modulation, by bypassing air around the coil. The opposed blades meter varying air volumes through the coil and bypass to attain the final air temperature demanded. USA Air Handlers offer only low leak dampers in their face and bypass sections.
Three styles of face and bypass sections are available. Internal bypass is available for use with medium face area coils. External bypass and external right angle are used when larger face area coils are required. The damper blades are fabricated of continuous galvanized steel with the damper rods rotating in nylon bushings. Damper shaft extensions are supplied to facilitate damper motor location.
I. INTEGRAL FACE & BYPASS OPTIONS
USA Air Handlers can be factory-equipped with an integral face and bypass coil that is pre-engineered to provide an accurate, reliable method of preheating and tempering air in standard or make-up air applications. Integral face and bypass coils maintain constant steam pressure or tube velocities through the coil to help prevent freeze-ups, while varying airflow through the coil using bypass dampers.
The amount of air bypassed or heated is determined by a preset leaving air temperature. It can vary from the bypass dampers being fully closed (all air passes through the coil) for maximum heat output, to the bypass dampers being fully open (no air passes through the coil) for minimum heat output. The air is then mixed at the discharge of the coil to achieve the desired leaving air temperature. Air pressure drop is maintained constant regardless of the position of the dampers.
J. BLENDERS/AIR MIXERS
Stratification occurs from the mixing box when the airflow of two different temperature air streams do not mix completely. This incomplete mixing can continue through the air handler, and subject an unprotected coil (no glycol) to freezing temperatures, damaging the coil. With the increased minimum outdoor air requirements as indicated by ASHRAE Standard 62, the likelihood for air stratification increases. An air handler must be able to handle the required amount of outdoor air, regardless of temperature, without risking damage to the coil.
Blenders/air mixers help to provide protection for coils from freeze-up due to stratification. Blenders/air mixers add additional turbulence to the passing air streams, boosting air velocity for improved mixing. Proper distance is provided immediately downstream to give the air streams enough time to fully mix before reaching the next air handler component. Because blenders/air mixers are static devices, they require no maintenance. Different blender/air mixer lengths can be selected to satisfy either the acoustic, space, pressure drop, or initial cost requirements. The USA Air Handler selection software will select the appropriate blender/air mixer for the application.
B. ELECTRIC HEATERS
(NOT AVAILABLE ON OUTDOOR UNITS)
Electric Heaters extend the wide versatility of USA Air Handlers. With negligible air pressure drop, accurate controllability, light weight, easy serviceability and inherent freeze protection, electric heaters are valuable alternatives to conventional steam and hot water heating coils.
ETL-approved electric heaters are available on all standard sizes (003-090) for horizontally-mounted draw through units in both left and right hand configurations. All units are open wire style construction, with automatic and manual backup limit controls, air switch, stainless steel terminals, power on pilot light, magnetic contactors and integral control boxes. Safety interlock switches, step controllers and vernier silicon controlled rectifiers (SCRs) are available options.
The heater requires its own electric service. Heaters are available in 208V, 240V, 480V and 600V (all 3 phase) and use an internal 24-volt control circuit. Standard ranges of kW are available for each heater size and are designed to give an approximate temperature rise from 20ºF to 60ºF, depending on the airflow through the unit. Typical pressure drops range from .01-.04 inches of water, depending on the air velocity and number of rows of heating elements.
An integral control box with optional door handle power disconnect is included with the electric heater. Insulated panels are factory installed behind the control box. Any standard motor may be used, although the discharge air from the electric heater must not exceed 104ºF since the rated ambient temperature of the motor will be exceeded. The heater is assembled into a separate section of the USA Air Handler. Standard section widths include: 30”, 34”, 42” and 46” and vary depending on the unit size, control type and kW used.
