AHU Series
AHU
  C Series

Air Handling Unit - AHU Series - Typical Specifications


GENERAL SPECIFICATIONS

  1. The unit shall be manufactured by Concepts and Designs, Inc., Owatonna, MN. Phone (507)451-2198 FAX (507)451-1177 E-Mail CDI.
  2. The unit assembly shall carry an ETL Label.
  3. The unit shall be completely factory assembled and tested and shall be shipped in sections (if necessary) to facilitate shipping and installation requirements.
  4. The unit shall be designed for roof (or indoor) mounting. The unit will have the capabilities of filtering, cooling and/or heating, humidifying and/or dehumidifying as required in the schedules and drawings.

MATERIALS AND CONSTRUCTION

  1. Frame Construction
    1. (a) Units over 8 feet to have an electrically welded 6" steel frame. Units under 8 feet wide to have an electrically welded 4” 12 gauge galvanized steel formed frame. All frames to be suitably reinforced and braced to permit the loading, shipping, unloading and rigging to the unit location and general handling of the completed sections without damage to external or internal components or misalignment of factory assembled components due to normal handling techniques.
    2. (b) The base frame shall be primed prior to the assembly of the unit.
    3. (c) The lifting lugs shall be provided on the base on the corners of each section of the air handling unit.
  2. Housing Construction
    1. (a) The casing shall be constructed of a minimum of 16 gauge, G-90 galvanized steel and the panels shall be fabricated into self-framing, double standing seam type construction. The panels shall form a self-framing casing with no additional structural support required. All joints shall be caulked airtight with a silicone sealant.
    2. (b) The exterior of the unit shall be completely weatherized with a minimum 16 gauge G-90 galvanized steel. The fiberglass insulation shall be completely enclosed. (Optional - Interior liners shall be perforated with 1/8" holes on 3/16" centers. When perforated liners are used, a solid liner shall be provided from the entering side of the cooling coil to 3 feet downstream of the coils.
    3. (c) Insulation shall be 2", 3.3# per sq. ft. rigid, rot-proof, non-combustible glass fiber insulation. Mount insulation in roof, sides, floors and interior partitions as required and in all service doors. The insulation shall be completely sheathed on both sides. No exposed insulation shall be permitted on the inside or underside of the unit. Insulation shall have a coated face when used with a perforated liner.
    4. (d) Roof panels shall have a minimum of 1 1/2" standing seams, caulked and sealed. Each standing seam of the roof deck shall be securely fastened at intervals not exceeding 24 inches. At unit section joints there shall be a minimum of a 1 1/2" high C-type standing seam with a field installed "C" hat channel forming the rain tight seal. The interior roof liner shall be of a minimum of 18 gauge, G-90 galvanized steel and shall be designed to provide the roof structure and support. The exterior roof panels shall be a minimum of 16 gauge, G-90 galvanized steel.
    5. (e) The floor decks of each section shall be composed of an underside sheathing of a minimum of 20 gauge, G-90 galvanized steel. Between the sheathing and floor surface shall be installed a minimum of 4" rigid, non-combustible, fiberglass insulation as previously specified. The top wearing surface on the floor shall be a minimum of 16 gauge galvanized steel. The floor shall consist of 30" maximum width panels. With a minimum of 4" deep 12 gauge C-Channels for support. This floor shall sustain the equipment loading and normal maintenance loading for the unit. Where holes are provided in the floor for duct and pipe, they shall be carefully cut and the exposed edges framed by angles for large openings or by steel sleeves welded in place for smaller openings. All floor opening sleeves shall cover the floor insulation and shall extend above the wearing surface at the floor a minimum of one inch.
    6. (f) Closures around all components, such as coils, dampers and filters, shall be provided and made airtight. Closures shall be a minimum of 16 gauge, G-90 galvanized steel and shall provide solid close-off inside of the unit housing walls. No air bypass or leakage around the components will be allowed.
    7. (h) Housing wall penetrations shall be provided with a finished cover plate both on the interior and exterior of the unit casing.
  3. Access Doors Construction
    1. (a) Access doors in the unit housing shall be provided to permit ready access to all internal components. The access doors shall be provided with an inner sheet of a minimum of 16 gauge, G-90 galvanized steel to protect the insulation. The exterior of the access doors shall be a minimum of 20 gauge galvanized steel. The doors shall be designed to swing against the fan static (outward on suction side, inward on discharge side). The doors shall be provided with a continuous heavy duty stainless steel hinge and two heavy duty latches, operable from both the exterior and interior of the unit. The door frame shall be of a galvanized steel construction with a replaceable gasket around the full perimeter of the door frame which shall provide an airtight seal. (Optional - 12" x 12" plexiglass viewing port shall be provided.) Outdoor units shall have drip shields over every door.
  4. Drain Pan Construction
    1. (a) The cooling coil drain pans shall be designed to extend the entire length of the coil, including headers and return bends. The depth of the drain pans shall be at least 1 1/2 inches and shall pitch toward the side of the unit. (Optional - drain through bottom of unit.) Drain pans shall be a minimum of 16 gauge and shall extend beyond the coil a minimum of 24 inches. An intermediate condensate drip pan shall be provided on all coils over 48 inches high and the intermediate drip pan shall extend a minimum of 6 inches in the downstream direction of the airflow. Each intermediate drain pan shall be piped to within 2 inches of the bottom drain pan. All cooling coils shall be installed in a vertical position, perpendicular to the airflow to minimize condensate carry-over.
  5. Shipping Splits
    1. (a) Shipping splits, if required, are to be mating angle design on unit interior walls and roofs. Unit base frames to be pulled together with 3/8 bolts. All fasteners, caulk, and gaskets required shall be supplied and shipped with unit.

SUPPLY AND/OR RETURN BLOWER(S)

  1. The blower(s) shall consist of centrifugal, forward curved (Optional - BI or AF) double width, double inlet blower wheels and scrolls. The wheels shall be supported by two outboard bearings which shall be of a self-aligning, ball bearing, pillow block type and shall be designed for at least 100,000 hours average life. The blower assembly shall be dynamically balanced.
  2. The blower, motor, and drive assembly shall be mounted on a heavy duty steel frame support. The frame shall be mounted on spring isolators designed for a minimum of 90 percent isolation efficiency. The isolation springs shall have a non-skid acoustical pad, locking screw and adjusting leveling bolt. The springs shall have a minimum of one inch nominal deflection (Optional - 2" or 3" deflection, earthquake provisions, or thrust restraints). The isolation base shall be complete with hold down bolts and wood blocking to maintain the spring base in a rigid position for shipping.
  3. On the discharge of the blower shall be a minimum of 6" flexible ducting, rigidly fastened to the blower and the blower discharge closure.
  4. Blower Shafts - Blower shafts shall be solid ground and polished. The shafts shall not pass through their first critical speed when the unit comes up to the rated RPM. Shaft shall be coated with a rust inhibitor.
  5. V-Belt Drives - All V-belt drives shall be standard capacity, furnished in matched sets with reinforced rubber belts. The sheaves shall be of a cast iron type and shall be complete with companion type driver sheave on drives with three belts or more. All drives shall be complete with a split taper bushing. Motors 7.5 horsepower and smaller shall have drive sheaves that are adjustable type with a plus or minus seven percent adjustability. The driver sheave shall be selected at the approximate mid-point of the adjustable range. Motors 10 horsepower and larger are to be fixed pitch type with another sheave available for final system balance. The overload shall be not less than 1.25.
  6. Motor Bases for V-Belt Drives - An adjustable motor base shall provide variation in center distance and shall be readily adjustable by means of screw adjustments. A locking nut, or similar device, shall be provided to secure the base in proper position.
  7. Lubrication - Mount all grease fittings directly on the bearings unless the latter are not readily accessible. Where equipment bearings are not visible or are inaccessible, provide easily accessible tubing extensions to the bearing lubrication fittings.
  8. Blowers shall have the capacity, class, and arrangement as indicated in the schedule.
  9. Belt guards are to meet OSHA guidelines with personnel safety as the highest design criteria. Guards shall, furthermore, be removable for belt and sheave maintenance, with insertion hole for tachometer.
  10. Motors shall be open dripproof (Optional - totally enclosed, fan cooled, explosion proof, or high efficiency), 1800 RPM, _____ volt, 3 phase, 60 Hz. Motor horsepower shall be as indicated on the schedule.


DIRECT MEDIA RECIRCULATING TYPE EVAPORATIVE COOLERS

  1. Evaporative cooling media is to be a crossfluted design and manufactured from cellulose paper impregnated with insoluble anti-rot salts and rigid saturates. The evaporative cooler shall be self-distributing and self-cleaning with an adjustable bleed-off rate of up to 15 percent. Media shall be non-combustible and U.L. 900, Class 2 listed. Media shall be removable by bolted closures for replacement. Media shall be sized for a minimum evaporative efficiency of 85 percent and a maximum air pressure drop of .5" W.G.
  2. Media over 6 feet in height will come with intermediate horizontal holding frames. Sump tank, frame and closures for air bypass shall be manufactured from a minimum of 16 gauge stainless steel. The drain pan shall be at least 4" deep and extend under the entire area of the evaporative cooler and extend downstream a sufficient distance as required to prevent water carry-over into the downstream section components. All piping shall be schedule 40 galvanized and will include recirculation pump, shut-off valves, water level valve, and system balancing valve. Distribution piping and cover pipe shall be removable and manufactured of schedule 80, PVC.

INDIRECT FIRED HEATER SECTION (Clamshell Type)

  1. Indirect gas fired furnace to be furnished for (indoor)(outdoor) application with gravity (induced draft) venting. Heat exchanger and burners are to constructed entirely from aluminized (409 stainless) steel. Heat exchanger is to incorporate venturi style tubes. Finger baffles are to be utilized to assure proper air distribution on the heat exchanger even at low air volumes.
  2. Burners are of aluminized (409 stainless) steel and include flared ports and a stainless steel insert. Burners are to be orificed for Natural (Propane) gas. All necessary safety and operating controls are to be included. These include, but are not necessarily limited to, high temperature limit cutout, combination gas valve, spark-ignited intermittent safety pilot with electronic flame supervision and timed lockout.
  3. Temperature controls shall be included and are to be (single stage) (two stage) (fully modulating) discharge temperature control.
  4. Casing of the gas fired furnace to be manufactured from zinc grip steel and have an baked enamel finish. Entire furnace to be contained within an indoor (outdoor) casing to provide a smooth rectangular silhouette. The casing is to be constructed of a minimum of 18 Gauge G-90 galvanized steel, and is to be provided with easy open access doors to provide for maintenance. The casing is to have screened (and filtered) air inlets to allow for proper amounts of incoming combustion air. The inlets are to have duct connections to allow for extension of ductwork for outdoor air if desired.
  5. The gas fired duct furnace is to carry a AGA label.

INDIRECT GAS FIRED HEAT EXCHANGER

  1. Indirect gas fired furnace to be furnished for indoor application with induced draft venting. Heat exchanger drum and front header is to be made entirely from 409 stainless steel. The secondary heat exchange surfaces shall be made from carbon steel.
  2. Heat exchanger is to incorporate primary surface drum and secondary surface tubes in a four pass design. Baffles are to be utilized to assure proper air distribution on the heat exchanger at low air volumes. The primary surface is to be no less than 14 gauge, the secondary tubes are to be no greater than 3" in diameter and no less than .055" wall thickness. The front and rear headers, as well as the intermediate headers are to be a minimum of 12 gauge. The front and rear collector boxes shall be a minimum of 8" deep. The front and rear collector boxes shall overhang the drum and include an integral directional baffle to direct air to cover the entire box as well as the box to tube joint.
  3. No more than 20,000 btuh/ft cubed of primary drum volume shall be allowed. No more than 35,000 btuh per 5 ft. sq. of the combined drum and tubes surfaces, (excluding the headers and such), shall be allowed.

POWER GAS BURNER

  1. Furnish and install one gas burners having a rated capacity to burn XXXX MBH of 1000 BTU per cu. ft. of natural gas at a pressure of xxxx in at inlet of the burner gas control train.
  2. The burner shall burn the specified quantity of fuel without objectionable vibration, noise or pulsation with not more than 20% excess air and no CO in the products of combustion. In addition, when firing gas, the burner shall be guaranteed to produce less than 90 PPM NOx emissions and further shall be designed for future field conversion to operate at 40 PPM NOx emissions or less without replacing the complete burner assembly.
  3. The burner shall incorporate a stainless steel flame retention type combustion head for long life and efficient operation. Combustion head shall be symmetrically round with internal gas pilot.
  4. Primary-Secondary air control shall be a design function of the combustion head. Combustion heads requiring an internal adjustment will not be accepted.
  5. The burners are to be equipped with a cast blower housing with integral fan scroll. Sheet metal fabricated housings will not be acceptable.
  6. A permanent observation port shall be provided in the burner to allow observation of both the pilot and main flame.

GAS VALVE TRAIN FOR EACH BURNER

  1. The gas train piping shall include a 1/4" NPT pressure tapping with 1/4" pipe plug upstream and downstream of each valve and regulator in the gas train.
  2. Provide a pressure gauge to indicate the gas burner manifold pressure.
  3. Furnish and install one manually operated ball valve upstream of all valves.
  4. Provide one main gas pressure regulator of tight shut off type with vent to outside atmosphere, in accordance with local codes.
  5. One safety shutoff valve shall be proven closed during pre-ignition by proof of valve closure interlock switch on valve.
  6. Provide a second automatically motor operated gas safety shutoff valve to operate simultaneously with the above gas valve.
  7. A normally open, fully ported, electrically operated valve shall be provided in a vent line connected between the two safety shutoff valves. The vent pipe shall be run outside to atmosphere and provided with union check vent valve operation.
  8. A manually operated lubricated gas valve shall be located downstream of both automatic gas valves to permit leakage testing of the valves. A leak test gauge and gauge cock shall be provided.
  9. Gas pressure supervision shall be provided by approved pressure switches interlocked to accomplish a non-recycling safety shutdown in the event of either nigh or low gas pressure.

BURNER CONTROLS

  1. The off-low fire-high fire operation of the burner shall be controlled by means of a temperature control.
  2. An additional high limit safety of the manual reset type shall be provided to control the burner.
  3. Pre-purge operation of the burner fan shall be provided.
  4. A manual restart of the burner shall be necessary in the event of shutdown due to flame failure.
  5. All three-phase motors shall be controlled and protected by an automatic starter with thermal overload protection. Starter shall be interlocked to prevent burner operation when overload relays are tripped out.
  6. Supply a burner mounted diaphragm air flow switch to prevent the energization of the main fuel valves in the event of insufficient comb