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Table of Contents:  

Section 6-2: Air-Handling Systems

Section 6-2: Air-Handling Systems

6-2-00 Design Requirements
       10 Design Guidance (Reserved)
       20 Design Information (Reserved)
       30 Design Document Requirements


6-2-00 Design Requirements

A. Air Handling Systems:
NIH facilities shall utilize air-handling systems to provide heating, ventilation, and air-conditioning.  Air-handling systems shall be fully automated and shall maintain the space temperature and humidity within the required range.  These air-handling systems shall comply with the following:
• Central air-handling units shall utilize 100% outdoor air for continuous, year-round operation.  Air recirculation is not permitted within research laboratory and animal facilities.
• All supply air to each laboratory and animal holding/support area shall be controlled by a dedicated, pressure independent air terminal device(s) equipped with hot water re-heat coil(s).
• Fan coil units may be used to supplement the cooling capacity where ventilation and make-up requirements are met by the central air-handling system.  Fan coil units shall not be located in tissue culture rooms.
• Laboratories that are provided with minimum required outdoor air ventilation and filtration from a central supply air system, supplemental terminal conditioning units shall be permitted to efficiently offset high cooling and heating loads without the use of single pass air from the central system using the guidance in the following references.

Reference;

1. Memarzadeh, “Energy Efficient Laboratory Design: A Novel Approach to Improve Indoor Air Quality and Thermal Comfort”; American Biological Safety Association (ABSA) Journal, Vol. 12, No. 3, 2007
 
2. Memarzadeh, “Controlling Laboratory IAQ and Energy Costs”; Heating, Piping, and Air-Conditioning Engineering (HPAC), October, 2007

• The use of unitary direct expansion equipment shall be restricted to serve unique ar-eas, such as computer rooms and support facilities, and only when chilled water is not available.
• Capacity and size of the make-up air system to serve fume hoods shall correspond to one 1.2 m (4 ft.) wide vertical sash fume hood in every other laboratory module.
• Capacity and size of the make-up air system for serve containment devices/equipment shall correspond to 120% of the programmed containment devices/equipment.
• Capacity of the cooling system shall include the program cooling demand plus an allowance for 20% future expansion of internal heat gain requirements.
• Minimum space ventilation rates (ACH) shall be as per requirements in Section 6-1.

A.1 System Redundancy:
Air-handling systems shall be provided with the following:
• Air-handling units (AHU) shall be designed to provide N 1 reliability and maintain 100% capacity in the event of a lead component failure.
• Multiple parallel air-handling units shall be provided to operate simultaneously to meet full load conditions.  Each AHU and its related components shall be capable of total isolation by the use of isolation dampers located upstream and downstream of each air-handling unit.
• Upon failure of any major component related to an AHU serving biomedical laboratories (non-containment such as BSL2), the remaining available air-handling equipment shall provide a minimum ventilation rate of 6 ACH in the affected area.
• Upon failure of any major component related to an AHU serving animal housing and support facilities (non-containment such as ABSL2), the remaining available HVAC air-handling equipment shall meet the entire HVAC load in the affected areas.
• Manifolding of AHUs to the same header shall be allowed for units operating at external static pressure differing not more than 0.19 kPa (0.75 in. wg) from each other.
• AHUs serving ABSL facilities shall be completely separate from other air handling systems.

B. Air distribution Systems
Air distribution system shall deliver heated and cooled air to all spaces to maintain the required space temperature range.  Supply air to each individual room shall be balanced for the actual airflow requirements (the highest cooling load or makeup air/ventilation airflow requirement).  The central supply and exhaust air systems shall be balanced for the total of the individual airflow requirements in each room plus the allowable duct leak based on the SMACNA duct construction manual.  Air temperature and air amount to each space shall automatically adjust as appropriate to accommodate variations in the space heating and cooling loads.  The duct system design for NIH buildings shall consider space configuration, space air diffusion, noise levels, duct leakage, duct heat gains and losses, balancing methods, fire and smoke control, initial investment cost, and system operating cost.

The ductwork systems shall be designed, fabricated and installed in accordance with ASHRAE and SMACNA standards.  Refer to Exhibit X6-2-A for a list acceptable air velocities to be used in the design and sizing of different HVAC components:

Ductwork may be single-wall or double-wall construction.  It may also be round, flat oval, or rectangular shape.  Duct fittings, joint methods, supports, and construction details shall be in accordance with SMACNA standards.  All fittings shall have documented pressure loss coefficients by either SMACNA or ASHRAE.  Irregular or makeshift fittings are not acceptable.  Factory-fabricated fittings by independent manufacturers may be utilized provided they have catalogued performance criteria.

Construction Documents shall specify the ductwork construction material, sealing and leakage class, and pressure classification construction as per SMACNA standards.  Refer to exhibit X6-2-B for a table showing the minimum ductwork construction to be used in NIH facilities.

Construction documents shall require the sheet metal contractor conduct pressure tests of the installed ductwork to quantify the leakage rate of the installed systems.  Duct leakage tests shall be conducted in accordance with SMACNA standards.  Ductwork shall be fabricated and installed to meet the sealing and leakage requirements in the following table:

Table 10 Duct Seal and Leakage Classes

 

 

 

 

 

Duct Pressure Classification (Rated Static Pressure) 

 

 

 

 500 Pa (2 in. wg)

 

 

 

and below

 

 

 

Duct Pressure Classification (Rated Static Pressure) 

 

 

 

750 Pa (3 in. wg)

 

 

 

Duct Pressure Classification (Rated Static Pressure) 

 

 

 

1000 Pa (4 in. wg)

 

 

 

and up

 

 

 

NIH Required Seal Class

 

 

 

A

 

 

 

A

 

 

 

A

 

 

 

NIH Required Sealing

 

 

 

Joints, Seams and All Wall Penetrations

 

 

 

Joints Seams and All Wall Penetrations

 

 

 

Joints Seams and All Wall Penetrations

 

 

 

NIH Required Leakage Class (1)

 

 

 

 - Rectangular Metal

 

 

 

6

 

 

 

6

 

 

 

6

 

 

 

NIH Required Leakage Class (1)

 

 

 

 - Round Metal

 

 

 

3

 

 

 

3

 

 

 

3

 

 

 

 

(1) See SMACNA “HVAC Air Duct Leakage Test Manual”, 1985 edition, Figure 4-1 for maximum allowable leakage for the each leakage class

 

Wet exhaust ducts or those duct systems that tend to carry moisture shall be pitched toward the source of moisture generation.  Drainage shall be provided in these systems.

Duct lining is not permitted for use in air handling equipment and duct systems.  Duct lining is not permitted for either acoustical or insulation purposes; sound attenuators shall be used for controlling noise.  In addition, air streams shall not be in contact with any fibrous or porous materials.

Flexible ductwork may be utilized for supply air application to connect diffusers, grilles and registers to low-pressure duct mains.  Flexible duct runs shall be limited to 1.8 m (6 ft.).  Flexible ducts shall have a UL-rated velocity of at least 20.3 m/s (4,000 fpm) and a maximum UL-rated pressure of 2.5 kPa (10 in. wg) positive.  Flexible ducts shall be factory insulated and comply with the latest NFPA Standards 90A and 90B.  Flexible duct connections shall be made using stainless steel draw bands and manufacturer-approved tape.  Flexible ductwork shall not be used for laboratory exhaust.

All ductwork penetrating room wall (Above the ceiling) and all diffuser/register/grille penetrating hard ceilings shall be sealed.  See Exhibit X4-2-A “Sealant Table”.

C. Location of Outdoor Air Intakes and Exhaust Air Discharge:
Outdoor air intakes and exhaust discharges shall be located away from each other and to avoid re-entry of exhaust contaminants from any source.  Exhaust contaminants may be from any of the following sources:  all type of exhaust fans including animal room exhaust and lab exhaust, air-handling unit relief air, vehicle exhaust, loading docks, automobiles entrances, drive ways, passenger drop-offs, cooling towers, boiler or incinerator stacks, emergency generators exhaust, vacuum pumps exhaust, steam relief vents or other hot vents, plumbing vents, vents from steam condensate pumps units, kitchen hoods, refrigerant relief vents, mechanical/electrical room ventilation systems, etc.

Outdoor air intakes shall be, at least, 12 m (40 ft.) away from any of the exhaust contaminants sources listed above regardless of discharging upward, horizontally or deflected downward.  Other factors such as wind direction, wind velocity, stack effect, system size, height of building(s), and security concerns shall be evaluated, and location of intakes and outlets adjusted accordantly.

The bottom of all outdoor air intakes shall be located as high as practical, but not less than 3.6 m (12 ft.) above ground level and/or any adjacent building or site element within a horizontal distance of 4 m (13 ft.) from the air intake.

Construction documents shall include the design of exhaust stack height and discharge air velocity characteristics to overcome the building cavity boundary and avoid re-entrainment of exhaust.  Stacks shall be shown as part of the architectural design and the design rationale shall be described in the early design reports.  In general, exhaust stacks shall be designed to meet the following requirements:
• Discharge shall be a minimum of 3 m (10 ft.) above the roofline and any roof element within a horizontal distance of a 4 m (13 ft.) radius
• Upward velocity shall be a minimum of 15 m/s (3,000 fpm) at the point of discharge.  Reentry calculations may dictate higher discharge velocities.
• Safety concerns shall always take precedence over aesthetics.
• Manifolds for multiple exhaust fans shall have separate exhaust stacks for each fan to avoid having positive pressure ductwork on the discharge side of fans not operating.

See Appendix E.2 “Calculating Minimum Separation Distance Between Intakes And Exhausts” for a computational analysis in evaluating building external air flows as influenced by new and existing obstacles.

D. Air-Handling Units:
The Basis of Design report shall define the type and quality of air-handling equipment proposed for use in NIH facilities.  In addition, the report shall provide justification for the equipment selection.  The following requirements apply to all air-handling units to be used in NIH facilities:
• Casings shall be double wall construction for all sections of the entire air-handling unit.  Wall construction shall be a minimum of 50 mm (2 in.) thick insulated panel with 48 kg/m3 (3 lb/ft3) density insulation in accordance with ASTM E84.  Exterior panel shall be 1.316 mm (18 gauge) solid G90 galvanized steel.  All interior panels shall be 1.621 mm (16 gauge) solid G90 galvanized steel.  Interior panel shall be the panel that with-stands the unit’s internal air pressure.  Unit floor shall be a minimum of 4.7 mm (3/16 in.) aluminum plate with diamond tread, all welded construction.  Panel construction shall allow the replacement of individual panel sections without disturbing adjacent panels.  Outdoor units shall be a minimum of 80 mm (3 in.) thick panels.  Outdoor units shall have the exterior panels painted with a minimum of a three step paint process to pass a 1000 hour salt spray per ASTM B-117.
• Casing construction shall include thermal breaks between exterior panels and interior panels.
• Casing construction shall be water and air tight.  The manufacturer’s standard cabinet construction shall comply with the latest ASHRAE/ANSI Standard 111 leakage class of less than 9 for demount units as measured in accordance with AMCA Standard Z10-85.  The fully assembled unit shall have a maximum air leakage rate of 1% of the supply air volume.
• All factory and field penetrations shall be completely seal and not reduce the leakage rating of the casing.  This includes all casing penetrations within the unit and between unit’s components.  All penetrations for components such as electrical lighting, controls, etc. shall be sleeved and sealed to prevent leakage and condensation damage.  This shall also apply to heat recovery units.
• Access doors shall be provided on both sides of each equipment section.  Doors shall be a minimum of 600 mm (24 in.) wide.  Each door shall be provided with a vision panel no less than 300 mm (12 in.) by 300 mm (12 in.).  Door swing shall help seal the access door with the unit’s internal air pressure.
• Lights shall be waterproof, marine type, and provided in all sections of the unit, which are more than 1.4 m (54 in.) high.  Lights shall be controlled from a single pilot switch located adjacent to one of the access doors.
• Air filters may consist of cartridge-type elements; roll filters are not acceptable.  The design face velocity shall not exceed 2.5 m/s (500 fpm) nor shall manufacturers’ standard nominal ratings be exceeded.  The preferred filter face section dimensions are 600 mm (24 in.) x 600 mm (24 in.).  Pre-filters shall be utilized.  All filter banks shall have intermediate supports to prevent bank deflection at maximum design pressure differentials.  Minimum 30% efficient filters shall be installed upstream of any heat recovery device.
• A pressure gauge shall be provided, on the unit’s exterior, at each filter section.  One gauge shall be provided for each filter bank.
• Coils shall have copper tubes with aluminum fins.  Galvanized coil frame shall be provided for heating coils and stainless steel frame for cooling coils. The use of Turbulators is not acceptable.
• Cooling coil’s air face velocity shall sized for a nominal air face velocity not to exceed 2.0 m/s (400 fpm) for the present design conditions and 2.5 m/s (480 fpm) for the future growth capacity.
• Maximum size for individual coils shall be 3.0 m (10 ft.) long by 0.91 m (3 ft.) high.  If larger coils are required then multiple coils shall be provided.
• Multiple coils shall be valved separately so that, if any individual coil fails, it can be isolated and drained while the remaining coils stay in operation.  Coils shall be installed to allow the removal of individual coils without disturbing pipe headers or anything else that would prevent the remaining coils from operating.  Coils shall be removable without major rigging.
• Integral face by-pass dampers/coils are preferred over standard coils with separate by-pass dampers.
• Return header for multiple-stacked coils shall be piped in a reverse return configuration to assist with the balancing of the water flow. Strainers shall be provided on the feed line for each coil bank.  Control and balancing valves shall be installed on the return line.  Each coil shall be provided with a balancing valve with integral memory stop.  Combination balancing, shutoff, and flow meter devices are not acceptable.
• Each AHU section shall be provided with drains that permit the internal wash down of the unit in the event of a coil failure.
• Drain pans shall be provided for each cooling coil.  Intermediate stainless steel drain pans shall be provided for each coil bank, which is more than one coil high.  The drain pan shall be stainless steel with a positive slope to a bottom drain connection.  Pan drains shall be properly trapped.  Static pressure conditions accounting for dirty filter(s) shall be used to calculate the trap height. Drain pans shall extend a minimum of 12-1n. downstream of the cooling coils.
• Moisture eliminators may be considered where carryover presents a problem.  However, eliminators shall not impede service access for cleaning of the coil face surface.
• Fans may be vane-axial, airfoil centrifugal (single or double width), or plenum as justified by life-cycle cost analysis.  All fans shall be of a minimum construction class II as per the Air Movement and Control Association (AMCA).  Fans shall be totally isolated from the unit by the use of inertia bases and spring isolation.  Fan volume control shall be achieved by using controllable pitch vanes on axial fans and VFDs on centrifugal and plenum fans.  Fans shall be arranged in the draw-through position.  Blow-through configurations are not allowed.
• Fans shall be vibration isolated from the remaining parts of the unit and the connecting ductwork system.
• Fan shafts shall be solid
• When space limitations dictate that fans be placed in close proximity of heating or cooling coils, the distance between the fan inlet and the coil shall be a minimum of a wheel diameter for single width fans and 1.5 wheel diameter for double width fans
• Sound attenuators may be necessary to meet the room sound criteria.  When feasible, they shall be integrated as a part of the AHU.  Sound attenuators shall be pack-less type.  The silencer rating shall be certified in accordance with ASTM E-477.
• Control dampers shall be low leakage opposite blade for modulation control and parallel blade for open-closed operation.  Ultra-low leakage, industrial-quality isolation dampers shall be installed at the discharge of manifolded systems.
• Unit louvers shall be AMCA rated and selected for low-pressure drop with less than 0.003 kg/m2 (0.001 lb/ft2) penetration at 3.8 m/s (750 fpm) free-area velocity.
• Heat recovery may be considered as demonstrate by the life cycle analysis.  The heating and cooling coils shall be designed to function at full load with or without the energy recovery system.  Units with heat recovery systems shall be designed such that devices could be out of commission without any interruption to AHU system operation.

D.1 Air-Handling Units Type:
Air-handling unit’s type and configuration would depend on the unit size and the particular type of project:
• Factory-package air-handling units are generally small in capacity, less than 9,440 L/s (20,000 cfm), and do not serve critical program functions.
• Factory-fabricated, custom-designed, central AHUs are generally large, greater than 9,440 L/s (20,000 cfm) that use 100% outdoor air. 
• Field erected, custom designed, central AHUs are generally large and are designed for installation in existing buildings where access is restricted, or designed for new buildings where the construction phasing does not permit the installation of large factory-fabricated sections.

D.1.a Factory-Package Air-Handling Units:
Factory-packaged air-handling units shall comply with the additional following requirements:
• All units shall be institutional-grade.
• All unit sections shall have full-height access doors to permit inspection and service of all components
• External fan motors are preferred, and in all cases, fan bearing lubrication piping shall be extended to the exterior to the casing wall.
• Units shall be in a draw-through arrangement.
• Factory-packaged units shall have offset coil pipe headers to allow individual coils to slide out of unit casings.
• Units shall be fully tested at the factory before shipping.  Testing shall verify capacity and leakage rate. Unit casings shall be pressure rated for the total system design operating pressure plus 25%.

D.1.b Factory –Fabricated Air-Handling Units:
Factory-fabricated air-handling units shall be fabricated as per details in the contract documents.  Contract documents shall fully detail the size, dimensions, and specific component configuration of each factory-fabricated air-handling unit, including: all components, capacity of all components, all controls components, all sequences of operation, access areas, access doors, casing openings, service clearances, and overall dimensions.  Layouts shall include sections to define the overall height and vertical location of duct connections, dampers, louvers, etc.  These units shall comply with the additional following requirements:
• All units shall be custom-designed and of institutional grade.
• Units shall be preassembled fully tested at the factory before shipping.  Testing shall verify capacity and leakage rate. Unit casings shall be pressure rated for the total system design operating pressure plus 25%.  After installation at the field, these units shall be field-tested.
• Units shall be preassembled on a structural steel base. The units shall be shipped as one piece if possible, or in as few sections as possible. The number of field-casing joints shall be reduced as much as feasible.
• Casing shall be double wall and factory fabricated with structural, acoustical, and thermal performance certified by testing data.  Casings shall have a solid interior and exterior shell and true thermal breaks.
• Casing access doors are required on both sides of each unit component including: heating and cooling coils, fans, filters, dampers, sound attenuators, heat recovery devices, humidifiers, and any other components requiring routine service.  Access doors shall be man sized, 0.6 m (2 ft.) wide x 1.8 m (6 ft.) high

D.1.c Field Erected Air-handling Units:
Field erected units shall be fabricated as per details in the contract documents.  Contract documents shall fully detail the size, dimensions, and specific component configuration of each field erected air-handling unit, including: all components, capacity of all components, all controls components and all sequences of operation, access areas, access doors, casing openings, service clearances, and overall dimensions.  Layouts shall include sections to de-fine the overall height and vertical location of duct connections, dampers, louvers, etc.  These units shall comply with the additional following requirements:
• All units shall be custom-designed and of institutional grade.
• Unit casing shall be pressure rated for the total system design operating pressure plus 25%.  After the field installation is complete, these units shall be field-tested as a complete unit to verify capacity and leakage rate
• Casings shall be double wall and factory fabricated with structural, acoustical, and thermal performance certified by testing data.  Casings shall have a solid interior and exterior shell and true thermal breaks.
• Casing access doors are required on both sides of each unit component including: heating and cooling coils, fans, filters, dampers, sound attenuators, heat recovery devices, humidifiers, and any other components requiring routine service.  Access doors shall be man sized, 0.6 m (2 ft.) wide x 1.8 m (6 ft.) high
• Contractor-shop-fabricated casings or filter frames for air-handling units are prohibited.
• These units shall be fully field tested.

E. Air Filtration Systems:
Air Filtration shall be provided to all supply air used to provide heating and air-conditioning.  As a minimum, supply air shall pass through a pre-filter and filter on the upstream side of heating and cooling coils.  Filter average efficiencies shall be MERV-8 (30%) and MERV-14 (95%) respectively, based on ASHRAE Standard 52.2, Minimum Efficiency Reporting Value (MERV).  HVAC air systems shall automatically adjust fan speed to compensate for the additional system static pressure produced by filter loading.  In addition, the following shall be provided:
• Final filtration shall be provided downstream of supply air fans serving ABSL facilities to protect against particulate and other containments possibly generated by the air handling equipment.  Average efficiency of the final filters shall be  MERV-14 (95%), based on ASHRAE Standard 52.2, Minimum Efficiency Reporting Value.
• The A/E shall review the project’s program requirements to establish specific filtration criteria.

F. Humidification Systems:
Winter humidification shall be provided where required to maintain space humidity requirements.  In the Bethesda campus steam from the central plant shall be utilized for this purpose.  In other NIH locations, the A/E shall verify suitability of using plant steam with the Project Officer during the design stage.  Written record of this verification shall be included in the Basis of Design Report.

Humidification systems shall comply with the following:
• Clean steam shall be used for humidification in special areas such as: transgenic animal housing and barrier housing.  Clean steam shall also be used for autoclaves, sterilizers, and rack washers when required by program and/or manufacturer.
• The A/E shall consult with the Project Officer to establish a list of additional areas requiring the use of clean steam.
• Clean steam shall be produced by a steam-to-steam generator by vaporizing either: RO water, double distilled water or softened water.

Humidifiers shall be steam separator type with jacketed steam injection, which do not require a drain from the steam manifold.  They may be located within air-handling units or installed in the supply air ductwork.  Duct mounted steam distribution manifold shall be installed within a fully welded stainless steel ductwork section.  The stainless steel section shall extend 0.6 m (2 ft.) upstream the manifold and at least 2 m (6 ft.) down stream the manifold.  The down stream length may need to be extended depending on the absorption distance for the particular system design.  Stainless steel ductwork shall be pitch and connected to a drain.  Steam piping to the humidifier shall include a manual isolation valve for equipment isolation during service.  Humidifier controls shall include an automatic isolation valve to remain close during cooling mode.  Humidifier controls shall also include a high limit humidistat located downstream of the humidifier manifold.

G. Fans:
Variable and constant air volume centrifugal and plenum fans serving multiple zones shall be equipped with variable frequency drives (VFDs) for control of volumetric flow rate and duct static pressure.

All fans on a manifold or in parallel configuration shall be identical and have identical isolation dampers and volume/pressure controls.

All fans shall be constructed to meet a Class II rating.  They shall be fully accessible for inspection, service and routine maintenance.  Fan bearings, where possible, shall be serviceable from outside hazardous or contaminated exhaust airstreams.  Inline fans with motors or drive exposed to exhaust airstreams are not permitted.

Fans shall have a certified sound and air rating based on tests performed in accordance with AMCA Bulletins 210, 211A, and 300.  See AMCA Standard 99, Standard Handbook, for definitions of fan terminology. The arrangement, size, class, and capacity of all fans shall be scheduled on the contract drawings.

Certified fan curves including power curves as well as acoustical data shall be submitted for each fan. All data shall be from factory test(s) performed in accordance with applicable AMCA standards. Data shall include published sound power levels based on actual factory tests on the fan sizes being furnished and shall define sound power levels (PWL) (10-12 W for each of the eight frequency bands).

Fan curves shall show: volumetric flow rate of the fan as a function of total pressure, brake horsepower and fan efficiency.  System curves shall include estimated losses for field installation conditions, system effect, and actual installed drive components.  All losses shall be defined on the fan curves.  Data may also be submitted in tabular form, but tables are not a substitute for actual performance curves.

All fans shall be statically and dynamically balanced by the manufacturer and shall be provided with vibration isolation.  All fans 18.6 kW (25 HP) and larger shall also be dynamically balanced in the field by the manufacturer upon installation completion.  All fan’s parts shall be protected against corrosion prior to operation.

Belt driven fans shall be provided with drives with multiple V-belts.  Belts shall be cogged type and shall be constructed of endless reinforced cords of long staple cotton, nylon, rayon, or other suitable textile fibers imbedded in rubber.

Variable-pitch sheaves shall be used to accommodate initial balancing and shall be replaced with fixed pitch when balancing is complete.  Sheaves shall be constructed of cast iron or steel, bored to fit properly on the shafts, and secured with keyways of proper size (no setscrews) except that for sheaves having 13 mm (1/2 in.) or smaller, bores setscrews may be used.

Fans shall be furnished complete as a package with electric motors, motor drives, fan bases, and inlet and outlet ductwork connections.

H. Motor and Variable Frequency Drives:
Refer to section 10 “Electrical” for additional requirements

H.1 Motors:
Motors utilized on NIH projects shall be premium high efficiency and selected to optimize the efficiency of mechanical and building systems.  Motors shall always be of adequate size to drive the equipment without exceeding the nameplate rating at the specified speed or at the load that may be delivered by the drive.

Motors shall be rated for continuous duty at 115% of rated capacity and base temperature rise on an ambient temperature of 40°C (105°F).  Motors 560 W (3/4 HP) and larger shall be three-phase, Class B, general-purpose, squirrel cage, open-type, premium-efficiency in-duction motors in accordance with National Electrical Manufacturers Association (NEMA) Design B standards, wound for voltage specific to the project, 60 Hz AC, unless otherwise required by the design.  Motors 373 W (1/2 HP) shall be either single or three-phase.  Motors smaller than 373 W (1/2 HP) shall be single-phase, open-capacitor type in accordance with NEMA standards for 115 V, 60 Hz, AC. Motors 124 W (1/6 HP) and smaller may be the split-phase type.

All motors 0.75 kW (1 HP) and larger shall have a composite power factor rating of 90% to 100% when the driven equipment is operating at the design duty.  Devices such as capacitors, or equipment such as solid-state power factor controllers, shall be provided as part of the motor or motor-driven equipment when required for power factor correction.

Motors specified to be controlled by variable speed drives shall be rated for such use.  Per CEE Premium Efficiency Criteria, minimum efficiencies for TEFC motors shall be equal or greater than those shown in the minimum efficiency table included in Exhibit X6-2-C “Mini-mum Motor Efficiency”.

H.2 Variable Frequency Drives:
Variable Frequency Drives (VFD) to be used in NIH facilities shall include consideration to the following:
• Harmonic distortion on both the supply and motor side of the VFD.
• Equipment de-rating due to harmonic distortion produced by VFDs.
• Audible noise caused by high-frequency (several kHz) components in the current and voltage.

The design of system utilizing VFDs shall incorporate the following provisions:
• An independent and dedicated VFD shall be provided for each prime motor and each standby motor in equipment requiring the use of VFDs.
• Equipment motors shall be matched to the drive so that low speeds can be achieved.
• VFDs shall have a manual bypass independent of the drive.  For motor 37.3 kW (50HP) and larger, a reduced voltage starter shall be provided in the by- pass circuit.  Motors shall operate at full speed while in the bypass position when-ever the speed drive is de-energized and/or open for service.
• VFDs shall be located in environments that are within manufacturer’s specifications.
• VFDs that serve fans shall be able to maintain operation during short power fluctuations.  That is the VFD shall be able to maintain the operation of the motor during short interruptions of the building electrical power system with out the need to shutdown the equipment and without damaging the motor.
• 18 pulse VFDs shall be provided for all motors 56 kW (75 HP) and above.
• 6 or 12 pulse VFDs shall be provided for all motors less than 56 kW (75 HP).
• VFDs shall be provided with integral passive or active harmonic filters, phase multiplication devices and any other components required to mitigate harmonic voltage total distortion (THD) to 5%, current THD to 5% at any load level, and no individual harmonic greater than 3% distortion.
• Compliance measurement shall be based on actual THD measurement at the VFD circuit breaker terminals during full load VFD operation.  Designs which employ shunt tuned filters shall be designed to prevent the importation of outside harmonics, which could cause system resonance or filter failure.  Calculations supporting the design, including a system harmonic flow analysis, shall be provided as part of the submittal process for shunt tuned filters.  Any filter designs, which cause voltage rise at the VFD terminals, shall include documentation in compliance with the total system voltage variation of plus or minus 10%.  Documentation of Power Quality compliance shall be part of the commissioning required by the VFD supplier.
• Actual job site measurement testing shall be conducted at full load condition and a copy of the report shall be included in the operation and maintenance manuals.  Harmonic measuring equipment utilized for certification shall carry a current calibration certificate.  The final test report shall be reviewed for compliance by a manufacturer’s certified representative.  Text and graphical data shall be supplied showing voltage and current waveforms, THD and individual harmonic spectrum analysis in compliance with the above standards.
• VFD locations shall be as close as practical to motor to minimize motor circuit conductor length issues.  VFD incoming power wiring, wiring from VFD to motor, and motor control wiring shall be installed in separate, dedicated conduits.

Refer to Appendix E.4 “Harmonic Control in Electric Power Systems” for additional information regarding harmonic distortion concerns.  Refer to Appendix E.6 “Selecting and Specify Variable Frequency Drives for HVAC Systems” for additional information regarding variable frequency drives concerns.

I. Emergency Electrical Power Generators:
Emergency electrical power generators shall comply with the following requirements:
• Generator set shall be located in such way to facilitate service and future replacement.
• Provide at least 1.2 m (4 ft.) of clearance space around the generator set.  There shall be access for replacing the engine and/or the electric generator without moving the generator set or accessories, such as the day tank.
• Generator set shall be installed to avoid producing structure-borne vibration.
• Generator set shall be located where it will be acceptable to have the noise generated from engine, radiator fan, and exhaust system.
• Generator set shall be located away from areas of high ambient temperatures.
• Generator set shall be located to provide protection from the weather and from vandalism.
• Location of the engine exhaust discharge shall be determined by a wind wave analysis.
• See Chapter 10, Electrical, for additional requirements.

Engine exhaust system shall not create excessive back pressure on the engine and shall not be connected to any other exhaust system serving other equipment.  Soot, corrosive condensate, and high exhaust-gas temperatures will damage idle equipment served by a common exhaust system.

Engine exhaust piping shall comply with the following:
• Refer to Exhibit X6-3-A for requirements of the engine exhaust pipes:
• Exhaust pipes shall be freestanding, not supported by the engine or muffler.
• Exhaust pipes shall use vibration-proof flexible connector.
• Exhaust pipes shall be guarded to prevent contact with personnel, and avoid person-nel injuries and burns.
• Exhaust pipes shall be routed to avoid fire detection devices and automatic sprinkler heads.
• Exhaust pipes shall be vented to the atmosphere away from building doors, windows, and ventilation intake vents.  Insulated thimble pipe fittings shall be used at the point where the exhaust pipe penetrates the exterior wall or roof.  A hinged rain cap shall be provided on the vertical discharge.
• Horizontal exhaust pipes shall be pitched downward and away from the generator set.  At the end of the horizontal run, a condensate drain trap with hose connection shall be provided.  A drain valve shall be provided at the bottom of each vertical section of the exhaust piping.

Sound reducing mufflers shall be included in the engine exhaust system muffler.  It shall be either inside or outside the generator set enclosure.  Construction documents shall include the selection of the proper muffler to reduce the exhaust noise to an acceptable level.
• Residential Muffler: suitable where some low background noise is always present, 18 to 25 dB (A) sound reduction.
• Critical Muffler: suitable for hospitals, residential dwellings or where background noise is minimal, 25 to 35 dB (A) sound reduction.
• The muffler shall be installed as close as possible to the engine.

Generator sets that are installed outside a building, with integral weather protective housing, shall have critical-grade type mufflers.  The generator set shall be located so engine exhaust will disperse away from buildings, building air intakes, and will not cover walls and windows with soot.

I.1 Emergency Generator Room Ventilation:
The space where the emergency generator is located shall include a ventilation system to remove heat and fumes dissipated by the engine, electrical generator, accessories, and other equipment located in the room.  A maximum 11°C (20°F) room temperature rise above ambient shall be utilized in designing the ventilation air system.

Air intake louvers to ventilate the generator room shall be sized to accommodate the amount of combustion air needed by the engine, the amount of cooling air that flows to the radiator and any other amount of air needed to ventilate the room.  Control air dampers on the air intake louver shall be fast acting to meet code requirements.

I.2 Engine’s fuel oil system:
The emergency generator shall be provided with a safe an uninterrupted source of fuel oil #2.  The fuel oil system shall be engineered and installed to industry standards.  The design of the fuel supply and storage system shall comply with the following requirements:
• The fuel oil supply tank shall be located as close as possible to the emergency generators.  Emergency generator(s) fuel oil shall not be used for any other purpose and shall not be shared with any other equipment.
• The fuel oil supply tank shall hold enough fuel oil to run the generator(s) at full load for a minimum of 24 hours without refueling.  Tank-sizing calculations shall be based on the full load hourly fuel consumption.  Other considerations for tank sizing shall include the duration of expected power outages versus the availability of fuel deliveries and the shelf life of the fuel oil.  The shelf life of #2 fuel oil is 1.5 to 2 years.
• The design of the fuel oil system shall specify all tank specialties such as fuel level alarms, filling accessories, control devices and all monitoring and testing devices.
• Underground fuel oil supply tanks shall be double wall fiberglass and shall be provided with a leak detection and monitoring system.
• Day tanks shall be as close as practical to the generator’s engine and shall be at an elevation where the highest fuel level in the day tank is lower than the diesel fuel injectors.  Day tanks shall be vented to the outside when installed indoors.
• Underground fuel oil piping shall be double wall fiberglass and shall be provided with a leak detection and monitoring system.  Above ground fuel oil lines shall be black steel.  Compatible metal fuel oil pipes and fittings shall be used to avoid electrolysis.
• A flexible section, of code-approved tubing, shall be used between the engine and the fuel supply line to isolate vibration from the generator’s engine.
• Fuel oil supply pipes and pumps shall be sized to handle a fuel oil flow rate three times greater than the full-load fuel oil consumption rate specified by the generator manufacturer.  In multiple day tanks applications, the main fuel oil pump system shall be sized for three times the total fuel oil flow with all generators at full load simultaneously.  Fuel oil return pipes may be sized for twice the total fuel oil flow.  Engine return-fuel oil shall be piped to the fuel oil supply tank.
• The fuel oil supply line to each generator shall be provided with an electric solenoid shutoff valve.  The solenoid valve shall be connected to the engine starter circuit to open the valve prior to energizing the generator.

I.3 Equipment connected to the Emergency Electrical Power System:
Emergency electrical power shall be provided to all critical mechanical and laboratory equipment.  At a minimum the following mechanical equipment shall be connected to the emergency electrical power system.
• Exhaust air fans.  This includes: all lab exhaust, all animal room exhaust, all fume hoods exhaust, and critical exhaust air systems
• Supply air fans, exhaust air fans, and all associated devices and equipment which serve animal room environments.
• Supply air fans associated with exhaust fans, which are connected to the emergency power.  These supply air fans shall provide a comparable amount of supply air to maintain pressure differential between rooms, air to serve fume hoods, and to prevent cross contamination and the building from becoming negative.
• Air handling systems associated with the active smoke purge/evacuation systems.
• Computer room air handling units.
• Air-conditioning system serving the main telecommunications room.
• Air-handling system serving elevator machine rooms, when elevators are on emergency power.
• Water chillers, cooling towers, pumps, and associated systems, which serve critical areas.
• Heating systems including: boilers, heating water pumps and associated fuel oil system.
• Steam condensate pumps.
• Pumps and all devices and components associated with the fuel oil system serving the emergency electrical power generator.
• Entire automatic temperature control system including: control panels, control devices, air compressors, etc.
• Electrical heat tracing for hydronic piping.
• Domestic water pumps.
• Sewage ejector pumps.
• Sump pumps.
• Medical gas systems including: compressors, pumps, controls and associated alarms.
• Hands free toilet flushers and lavatory faucets.
• Critical scientific equipment identified by program requirements.


6-2-10 Design Guidance (Reserved)


6-2-20 Design Information (Reserved)


6-2-30 Design Document Requirements

A. Testing and Balancing:
The design of HVAC systems for NIH buildings shall include a complete and comprehensive testing, adjusting, and balancing of environmental and mechanical systems to produce the design objectives.  The testing and balancing shall be done in coordination with the commissioning process as required by the NIH Model Commissioning Guide.

The testing and balancing (TAB) process shall be specified to meet one or both of the following standards (latest edition):
• National Standards for Total System Balance as defined by the Associated Air Balance Council (AABC)
• Procedural Standards for Testing, Adjusting and Balancing of Environmental Systems as published by the National Environmental Balancing Bureau (NEBB)
All TAB work shall be performed by an independent TAB contractor who is certified by either AABC or NEBB.

The TAB report shall be certified for accuracy by an independent professional engineer familiar with the testing and balancing of the project but not affiliated with the TAB contractor’s organization. The TAB contractor shall provide all required pre-construction plan checks and reviews; shall test, adjust, and balance the air and water system; and shall submit completed reports, floor plans indicating TAB points, analysis, and verification data showing proper system performance that meets the intent of design.

NIH buildings often are constructed and occupied in multiple phases.  The TAB process specified shall address the requirements of interim balancing to support occupancy of buildings during completion of multiple construction phases.

The A/E, Project Officer, DOHS, commissioning agent, and research staff shall develop an occupancy/move plan and operation strategy that shall be specified in the contract documents.  The A/E shall define a TAB procedures/specifications that fully supports the phasing of the mechanical work, where phasing is required, and assures that the installed mechanical systems adhere to the design objectives during all phases of construction and upon completion of entire project.

Table 11 Typical Design Air Velocity in HVAC Systems

  Element / System Ductwork

 Maximum Face Velocity

 

 

 

 

 

 

 

m/s (fpm)

 

 

 

  -  Up to 500 Pa (2 in. wg) pressure class in mechanical shafts

 

 

 

      -  Ductwork above occupied areas

 

 

 

      -  Air outlets devices

 

 

 

7.6 (1,500)

 

 

 

 

 

 

 

 

6.1 (1,200)

 

 

 

3.8 (750)

 

 

 

  -  750 Pa (3 in. wg) to 1,000 Pa (4 in. wg) pressure class in mechanical shafts

 

 

 

      -  Ductwork above occupied areas

 

 

 

12.7 (2,500)

 

 

 

 

 

 

 

 

10.2 (2,000)

 

 

 

  -  Outdoor/relief air

 

 

 

7.6 (1,500)

 

 

 

  -  Animal research facility exhaust ductwork

 

 

 

7.6 (1,500)

 

 

 

Coils

 

 

 

 

 

 

 

 

  -  Cooling/dehumidifying coils

 

 

 

2.3 (450)

 

 

 

  -  Heating Coils - Hot water

 

 

 

2.5 (500) - 3.8 (750)

 

 

 

Filters

 

 

 

 

 

 

 

 

  -  Viscous impingement

 

 

 

1.0 (200) - 4.0 (800)

 

 

 

  -  Dry-type, extended-surface & Flat (low efficiency)

 

 

 

Duct velocity

 

 

 

  -  Pleated media

 

 

 

2.5 (500)

 

 

 

  -  HEPA

 

 

 

1.3 (250)

 

 

 

Louvers

 

 

 

 

 

 

 

 

  -  Intake (1)

 

 

 

  -  Exhaust

 

 

 

2.5 (500)

 

 

 

3.8 (750)

 

 

 

 

Note:
(1) Air Intake louvers shall be sized to not exceed the rating of the louver and avoid water penetration


Table 12 Minimum Duct Construction Standards

Application

 

 

 

SMACNA Pressure Class (Note 1)
 Pa (in. wg)
Ductwork Materials 

All ductwork, unless noted otherwise

 

 

 

500 (2)

G90 galv.

Outdoor air intake, relief, return, and general exhaust air plenums (notes 2, 9, and 10)

 

 

 

500 (2)

G90 galv.

 

 

 

Low-pressure supply air and return air ductwork, constant volume (note 9, and 10)

 

 

 

500 (2)

 

 

 

G90 galv.

 

 

 

Low-pressure supply air ductwork downstream of air terminal units (note 4, 9, and 10)

500 (2)

G90 galv.

Low-pressure return air ductwork upstream of air terminal units (note 4, 9, and 10)

500 (2)

 

 

 

G90 galv.

 

 

 

Low-pressure general exhaust air ductwork (note 9, and 10)

500 (2)

 

 

 

G90 galv.

 

 

 

Low-pressure wet exhaust air ductwork

 

 

 

500 (11)

 

 

 

Alum or ss

 

 

 

Low-pressure hazardous exhaust air ductwork upstream of air terminal units (note 7)

 

 

 

500 (2)

 

 

 

(note 6)

 

 

 

Medium-pressure supply air ductwork upstream of air terminal units, vav or cv air terminal units (note 3)

 

 

 

1000 (4)

 

 

 

G90 galv.

 

 

 

Medium-pressure general exhaust air ductwork downstream of air terminal units, vav or cv air terminal units (note 3)

 

 

 

1000 (4)

 

 

 

G90 galv.

 

 

 

Medium-pressure hazardous exhaust air ductwork downstream of air terminal units, vav or cv, duct operating pressure up to 750 Pa (3 in. wg) (note 3 & 7)

 

 

 

1000 (4)

 

 

 

(note 6)

 

 

 

High pressure hazardous exhaust air ductwork downstream of air terminal units, vav or cv air terminal units, duct operating pressure above 750 Pa (3 in. wg) to 1250 Pa (5 in. wg) operating pressures (note 5 and 7)

 

 

 

Class I/industrial

 

 

 

1500 (6)

 

 

 

(note 6)

 

 

 

Hazardous exhaust air, positive pressure segment up to 1250 Pa (5 in. wg) operating pressure (note 7)

 

 

 

Class I/industrial

 

 

 

1500 (6)

 

 

 

(note 6)

 

 

 

Special hazard exhaust air ductwork (note 3 and 8)

 

 

 

1000 (4)

 

 

 

ss

 

 

 

Notes:
(1) This is the minimum SMACNA pressure classification to be used for the construction of ductwork and associated components in the listed application.  Duct construction shall be as listed but no less than 250kPa (1 in. wg) higher than the calculated operating static pressure, including future capacity, for the given section of ductwork, which ever is greater.
(2) Plenums need to be constructed of minimum 1.316 mm (18-gauge) G90 galv. steel.  These panels need to be insulated
(3) Air risers serving multiple floors need to be constructed to meet at least SMACNA 1500 Pa (6 in. wg) duct construction
(4) This type of ductwork construction requires compliance with SMACNA class A for duct sealing and leakage.
(5) Air risers serving multiple floors need to be constructed to meet at least SMACNA 2500 Pa (10 in. wg) duct construction
(6) Epoxy-coated, G90 galvanized steel, or stainless steel (ss)
(7) The term “hazard exhaust” generally applies to common exhaust systems serving non-containment laboratories such BSL-2 and ABSL-2, fume hoods, animal research facilities, biosafety cabinets, etc., which, by their relatively light hazard rating, may be exhausted by a common exhaust system serving non-containment areas.
(8) The term “special hazard exhaust” generally applies to exhaust air systems serving containment areas such as BSL3 laboratories, radioactive hoods, etc., which, by their critical nature or extreme hazard, shall be exhausted individually and typically require special filtration.  Ductwork serving containment areas such as BSL-3 shall be welded stainless steel.
(9) Ductwork leak testing for this application is not required.
(10) This particular ductwork system does not require leak test during construction.
(11) Wet exhaust air ductwork serving sterilizers, autoclaves, and cage washers shall be stainless steel.


Table 13 Minimum Full-Load Nominal Efficiency of Electric Motors (1)

 

kW (HP)

 

 

 

Open Motors

 

 

2 POLE

 

 

 

377 rad/s

 

 

 

(3600 RPM)

 

 

 

Open Motors

 

 

4 POLE

 

 

 

188 rad/s

 

 

 

(1800 RPM)

 

 

 

Open Motors

 

 

6 POLE

 

 

 

125 rad/s

 

 

 

(1200 RPM)

 

 

 

Enclosed Motors

 

 

2 POLE

 

 

 

377 rad/s

 

 

 

(3600 RPM)

 

 

 

Enclosed Motors

 

 

4 POLE

 

 

 

188 rad/s

 

 

 

(1800 RPM)

 

 

 

Enclosed Motors

 

 

6 POLE

 

 

 

125 rad/s

 

 

 

(1200 RPM)

 

 

 

0.75 (1)

 

 

 

77.0

 

 

 

85.5

 

 

 

82.5

 

 

 

77.0

 

 

 

85.5

 

 

 

82.5

 

 

 

1.1 (1.5)

 

 

 

84.0

 

 

 

86.5

 

 

 

86.5

 

 

 

84.0

 

 

 

86.5

 

 

 

87.5

 

 

 

1.5 (2)

 

 

 

85.5

 

 

 

86.5

 

 

 

87.5

 

 

 

85.5

 

 

 

86.5

 

 

 

88.5

 

 

 

2.2 (3)

 

 

 

85.5

 

 

 

89.5

 

 

 

88.5

 

 

 

86.5

 

 

 

89.5

 

 

 

89.5

 

 

 

3.7 (5)

 

 

 

86.5

 

 

 

89.5

 

 

 

89.5

 

 

 

88.5

 

 

 

89.5

 

 

 

89.5

 

 

 

5.6 (7.5)

 

 

 

88.5

 

 

 

91.0

 

 

 

90.2

 

 

 

89.5

 

 

 

91.7

 

 

 

91.0

 

 

 

7.5 (10)

 

 

 

89.5

 

 

 

91.7

 

 

 

91.7

 

 

 

90.2

 

 

 

91.7

 

 

 

91.0

 

 

 

11.2 (15)

 

 

 

90.2

 

 

 

93.0

 

 

 

91.7

 

 

 

91.0

 

 

 

92.4

 

 

 

91.7

 

 

 

14.9 (20)

 

 

 

91.0

 

 

 

93.0

 

 

 

92.4

 

 

 

91.0

 

 

 

93.0

 

 

 

91.7

 

 

 

18.6 (25)

 

 

 

91.7

 

 

 

93.6

 

 

 

93.0

 

 

 

91.7

 

 

 

93.6

 

 

 

93.0

 

 

 

22.4 (30)

 

 

 

91.7

 

 

 

94.1

 

 

 

93.6

 

 

 

91.7

 

 

 

93.6

 

 

 

93.0

 

 

 

29.8 (40)

 

 

 

92.4

 

 

 

94.1

 

 

 

94.1

 

 

 

92.4

 

 

 

94.1

 

 

 

94.1

 

 

 

37.3 (50)

 

 

 

93.0

 

 

 

94.5

 

 

 

94.1

 

 

 

93.0

 

 

 

94.5

 

 

 

94.1

 

 

 

44.7 (60)

 

 

 

93.6

 

 

 

95.0

 

 

 

94.5

 

 

 

93.6

 

 

 

95.0

 

 

 

94.5

 

 

 

55.9 (75)

 

 

 

93.6

 

 

 

95.0

 

 

 

94.5

 

 

 

93.6

 

 

 

95.4

 

 

 

94.5

 

 

 

74.6 (100)

 

 

 

93.6

 

 

 

95.4

 

 

 

95.0

 

 

 

94.1

 

 

 

95.4

 

 

 

95.0

 

 

 

93.2 (125)

 

 

 

94.1

 

 

 

95.4

 

 

 

95.0

 

 

 

95.0

 

 

 

95.4

 

 

 

95.0

 

 

 

111.9 (150)

 

 

 

94.1

 

 

 

95.8

 

 

 

95.4

 

 

 

95.0

 

 

 

95.8

 

 

 

95.8

 

 

 

149.2 (200)

 

 

 

95.0

 

 

 

95.8

 

 

 

95.4

 

 

 

95.4

 

 

 

96.2

 

 

 

95.8

 

 

 

 

(1) As per efficiency values in the NEMA MG 1-1998, table 12-12 for NEMA Premium Efficiency Electric motors

 

 
This page was last updated on May 23, 2013