Committee... · Web viewThe heating and cooling coils shall be designed and sized to function at full load without the energy recovery system. Units with heat recovery systems shall

NIH Design Requirements Manual 2012 1Section 6.2

Section 6.2 Supply Air-Handling and Exhaust Systems6.2.0. General

6.2.1 Supply and Exhaust Air-Handling CapacityFor laboratories and animal research facilities, supply air handlers and exhaust fans shall be sized to provide 20% future requirement above design conditions to allow for changes in research and future growth. The requirement will apply to both for new or renovation projects The 20% shall apply to fans, motors, dampers, cooling coils, heating coils, humidifiers and filters.

For administrative and general use facilities, supply air handlers, return and exhaust fans shall be sized to provide at no more than 10% above design conditions for future growth.

Throughout this document, the term “capacity” shall be understood to be the total design capacity exclusive of this 20% future growth.

The 20% future requirement for administrative and general use facilities is to accommodate changes in research over the service life cycle of the unit

HVAC systems serving laboratories and animal research facilities shall further comply with the following:

1. 100% O.A. with no recirculation (single pass air).Provides protection against cross-contamination of airborne contaminants. Recirculating systems are not allowed due to potential for cross contamination, vapors and odors via HVAC system

2. Supply and exhaust systems using dedicated, pressure-independent air terminal devices shall be used.

3. Hot water reheat coils are required for the supply air terminals.

4. The four-pipe (with both reheat water valve and chilled water valve) active chilled beams terminal units shall be used in the laboratory spaces as an alternative to VAV-reheat systems Primary air flow will be introduced to the chilled beam via pressure independent air terminal. Chilled beams only provide sensible cooling to the space. The latent load is handled by a dedicated outside air system (DOAS). The chilled beam water temperature must be actively maintained above room air dew point to prevent condensation. Adequate number of chilled beams should be installed to avoid high flows. Chilled beams are impractical in cooling intensive rooms or in labs with high fume hood density. They also cannot be used in the spaces with high latent loads or where humidity control is critical.

Chilled beams (which decouple the air and cooling requirements) can significantly reduce the size of the air system when cooling loads drive the design air flow rates. Chilled beams adjust the flow of chilled water and hot water to match the changing loads and eliminate reheat energy and minimize outside air conditioning.

5. Make-up and exhaust air system capacity shall account for a minimum of one 1.2m (4 ft.) wide vertical sash fume hood (18” sash height) in every other laboratory module.

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6. Central systems may be supplemented by fan coil units, chilled beams, radiant panels, etc. (not allowed in tissue culture rooms and BSL-3 facilities).Fan coil units are not allowed in tissue culture rooms due to the presence of the condensate drain pans.

7. Unitary direct expansion HVAC equipment prohibited in laboratory and animal research facilities except where chilled water is not available in close proximity or where process requirements dictate the use of DX cooling (in lieu of chilled water) for precision temperature control. The A&E shall provide a detailed justification wherever DX equipment is proposed.

6.2.2 System RedundancyMultiple parallel supply air-handling units and exhaust fans shall be provided to operate simultaneously to meet full load conditions. Air handling units (AHU) shall be designed to provide N+1 reliability and maintain 100% capacity in the event of a lead component failure. Each AHU system 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.

Laboratory air handling systems and exhaust fans must operate continuously. N+1 redundancy provides inherent reliability to the system. N+1 fans housed within the single AHU cabinet cannot be interpreted as providing full redundancy requirements

6.2.3 Air Distribution Systems1. Ductwork may be single-wall or double-wall construction and may be round, flat oval, or

rectangular in shape.2. Duct lining is not permitted for use in air handling equipment and duct systems.

Duct lining is not permitted due to the possibility of releasing insulation fibers into the airstream. Also, any moisture in the system could harbor growth within the ductwork.

3. Flexible ductwork may be used for branch duct connections in low-pressure supply and air transfer duct systems. 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. w.g.) 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.

4. Ductwork systems shall be designed, fabricated and installed in accordance with ASHRAE and SMACNA standards.

5. Refer to Exhibit X6-2-A for a list acceptable air velocities to be used in the design and sizing of different HVAC components. Refer to exhibit X6-2-B for a table showing the minimum ductwork construction to be used in NIH facilities.

6. 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:

Duct Seal and Leakage Classes

Duct Pressure Classification (Rated Static Pressure)

500 Pa (2 in. w.g.)and below

750 Pa (3 in. w.g.) 1000 Pa (4 in. w.g.)and up

NIH Required Seal Class A A ANIH Required Sealing Joints, Seams and Joints Seams and Joints Seams and

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Duct Seal and Leakage ClassesAll Wall Penetrations

All Wall Penetrations

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 latest edition of SMACNA “HVAC Air Duct Leakage Test Manual”, for maximum allowable leakage for the each leakage class.

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

8. Flexible ductwork shall not be used for exhaust and return system because it is easier for the ductwork to collapse under negative pressure.

9. Proper positioning of diffusers and grilles is vital for providing good distribution in the space.

Pressure testing of ductwork avoids unwanted leaks into surrounding areas, requiring more airflow from fans, avoids increased energy cost to operate the system, and avoids operating system at full capacity with no reserve capacity.Poor positioning of diffusers and grilles can result in either dead zones or zones with unwanted air turbulence.

6.2.4 Outdoor Air Intakes and Exhaust Air Discharge1. Outdoor air intakes shall be at least 12 m (40 ft.) away from any of the exhaust

contaminants sources (all types of exhaust fans including animal room exhaust and lab exhaust, 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.) regardless of discharging upward, horizontally or deflected downward. Other factors such as wind direction, wind velocity, stack effect, system size, height of building(s), snow drift and security concerns shall be evaluated, and location of intakes and outlets adjusted accordantly.

2. 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 any adjacent building or site element within a horizontal distance of 4 m (13 ft.) from the air intake.

3. Construction documents shall include the design of lab 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:

a. 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

b. 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.

c. Safety concerns shall always take precedence over aesthetics.

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d. Manifolded exhaust fans shall have separate exhaust stacks for each fan to avoid positively pressuring through a non-operating exhaust fan

Exception: Where 2 fans are required to operate simultaneously at 50% capacity, common discharge stack is permitted to minimize discharge pressure loss through each stack and reduce noise, while maintaining the minimum 3000 FPM stack velocity. Motorized discharge dampers are required in suction and discharge of each fan.

4. 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.

6.2.5 Air-Handling UnitsThe 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.

6.2.5.1. Air-Handling Systems for Administrative and General Use Facilities Air-handling systems for administrative, office, conference, and other general use facilities frequently employ variable air volume with terminal zone- or room-heating units. These systems are a recirculating type with ventilation rates designed to meet the latest ASHRAE Standards 62 and 90.1 or IMC. Air-side dry-bulb economizers provide free cooling when ambient conditions permit.

Air-handling systems for administrative buildings are best kept simple and zoned consistent with building use and occupancy schedules. Large conference or assembly areas with intermittent use should not be connected to units that supply routine office space. Air-handling systems found in these buildings may have the following features:

Single supply and return fans without redundant components. Night setback and morning warm-up control modes Mixing plenums with minimum and maximum outdoor air dampers to accommodate

minimum ventilation and economizer operations 30 percent efficient pre-filters and 60 percent efficient after-filters Preheat coils required to support morning warm-up functions Draw through chilled water coils Central AHU humidifiers only 750-1000 Pa pressure duct distribution to terminal control devices Fully ducted return air system with building pressure-controlled relief devices. Units shall be factory packaged and commercial-grade. Casing shall be double wall construction for all sections of the entire unit with a minimum

of 50 mm (2” in.) thick insulated panel for indoor units. Outdoor units shall be a minimum of 80 mm (3 in.) thick insulated panels. Outdoor units

shall have the exterior panels painted to pass a 1000 hour salt spray per ASTM B-117. Stainless steel drain pans shall be provided under cooling coil Design cooling coil velocity shall not exceed 500 FPM All unit sections shall have access doors to permit inspection and service of all

components. Units shall have offset coil pipe headers to allow individual coils to slide out of unit

casings.

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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%.

6.2.5.2. Air-Handling Systems for Laboratory and Animal Research Facilities

The design requirements for air handling systems for laboratories and animal research facilities are described in Section 6.1 and in other areas of this section. The following requirements apply to all air-handling units to be used in NIH laboratory and animal research facilities:

1. Casings shall be double wall construction for all sections of the entire air-handling unit. Wall construction shall provide a minimum of R-17 insulation Exterior and interior wall panel shall be solid G90 galvanized steel or aluminum. All exterior and interior wall r panels shall be 1.316mm (18 gauge) solid G90 galvanized steel minimum, or 0.05 inch thick Aluminum minimum. Cooling coil and humidifier sections shall be constructed of stainless steel interior panels for galvanized units. Unit roof and floor gauge (or thickness) shall be one gauge (or thickness) higher than wall to handle weight of personal. 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.

2. Outdoor units shall be double wall construction with minimum of R-19 insulation. 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.

3. Units shall be custom factory fabricated and custom field erected. Units shall be preassembled and fully tested at the factory before shipping. Units can be shipped as one piece if possible, or in as few sections as possible to limit the number of field –casing joints.

4. Unit casings shall be pressure rated at maximum operating pressure +50% or 10” w.g., whichever is less. After installation at the field, these units shall be field-tested.

5. Field erected AHUs are generally large in capacity 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-packaged or fabricated sections

6. Casing construction shall include full thermal breaks between exterior panels and interior panels.

7. Casing construction shall be water and air tight. The fully assembled unit shall have a maximum air leakage rate of 0.5% of the supply air volume at the prescribed test pressure indicated in Item 4 above. The unit deflection shall be L/240 at the prescribed test pressure. All factory and field penetrations shall be completely sealed and shall 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 caulked to prevent leakage and condensation damage. This shall also apply to heat recovery units.

8. Access doors shall be provided on both sides of each equipment section. Doors shall be man sized and 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.

9. 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.

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10. 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.

11. A manual magnehelic pressure gauge shall be provided, on the unit’s exterior, at each filter section. One gauge shall be provided for each filter bank. BAS shall also monitor the differential pressure cross the filter.

12. Air handler coil tubing shall be of nominal 0.035 inch copper tubes with aluminum fins of at least 0.0095 inch thickness. Cooling coils shall be no more than 8 rows deep and 12 fins/inch to enhance cleaning and heat transfer. Galvanized coil frame and casings shall be provided for heating coils and stainless steel frame and casings for cooling coils. The use of Turbulators is not acceptable.

13. Cooling coil’s air face velocity shall be 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.

14. 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.

15. 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.

16. Integral face by-pass dampers steam coils are preferred over standard coils with separate by-pass dampers.

17. 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.

18. Each AHU section shall be provided with drains that permit the internal wash down of the unit in the event of a coil failure.

19. 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. Drain pans shall extend a minimum of 12-in downstream of the cooling coils. 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) at fully loaded (100%) condition shall be used to calculate the trap height.

20. Moisture eliminators may be considered where carryover presents a problem. However, eliminators shall not impede service access for cleaning of the coil face surface.

21. 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 VFDs on centrifugal and plenum fans. Fans shall be arranged in the draw-through position. Blow-through configurations are not allowed.

22. Direct drive small plug fans (commonly called “fan wall”) arranged is an array may be used to replace a traditional single large fan where there are space constraints. Each fan

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shall be provided with isolation damper so air does not the short circuit through the non-working fan. Direct fans motors operating with VFD’s shall not operate at higher than 90Hz frequency and motor size shall be based on the operating frequency. Units operating with direct drive fans should be carefully selected so the operating speed during VFD bypass mode does not exceed the maximum allowed fan rpm.

23. Fans shall be vibration isolated from the remaining parts of the unit and the connecting ductwork system.

24. Fan shafts shall be solid and precision ground and polished.25. Fan bearings shall be selected for minimum average life of L10 200,000 hours 26. 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.

27. Sound attenuators may be necessary to meet the room sound criteria for the room served by the AHU. 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.

28. Control dampers shall be low leakage opposite blade for modulation control and parallel blade for open-closed operation or for mixing. Ultra-low leakage, industrial-quality isolation dampers shall be installed at the discharge of manifolded systems. Sufficient space should be provided to remove and install actuators without the need for removal of dampers or other equipment.

29. Fan airflow measurement in or near the fan inlet should not impede airflow 30. Unit louvers are typically used for outdoor air intakes. Louver 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. Louvers shall be drainable and be constructed of anodized aluminum or stainless steel with 304 SS hardware and bird screen.

31. Heat recovery may be considered as demonstrated by the life cycle analysis. The heating and cooling coils shall be designed and sized to function at full load 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.

32. 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.

33. The NIH Project Officer shall determine if NIH representative will witness the factory-testing for the mission critical AHUs.

Air handling unit requirements are predicated upon AHUs having a service life much longer than traditional commercial units.

6.2.5.3. Air-Handling Systems for Clinical Facilities Air-handling units designed for clinical facilities shall be similar to air handers used in NIH laboratory and animal research facilities: except these units are typically provided with return fans with economizer system. The air handlers are provided with second filter bank downstream of fan. Consideration should be given to ensure the final filter is not too close to the fan resulting in uneven air distribution across the filter and potential wetting of the filter from upstream cooling or humidifier.

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6.2.6 Air Filtration Systems1. Air filtration shall be provided to all supply air used to provide heating and air-

conditioning for laboratories and animal research facilities. As a minimum, supply air shall pass through a pre-filter and final filter on the upstream side of heating and cooling coils. Filter average efficiencies shall be MERV-8 (30%) for pre filter and MERV-14 (95%) for final filter, 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.

2. Final filtration shall be provided downstream of supply air fans serving animal research 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.

3. Supply air for clinical facilities shall pass through a prefilters and final filters at the air handling unit. Filter average efficiencies shall be MERV-8 (30%) for pre filter and MERV-14-15 (95%) for final filter based on ASHRAE Standard 52.2, Minimum Efficiency Reporting Value (MERV). HEPA filtration (MERV 17 and above) may be required for patients vulnerable to infections. If HEPA filters are used they should be designed for maximum of 300 FPM. The A&E shall consult with NIH Safety and NIH DTR prior to the designing HEPA filters in the system.

4. Fan filter modules (FFU) are self-contained filter assembly with fan, prefilters, shallow HEPA filter and speed controls. FFU’s are not recommended unless the duct system is incapable of providing the pressure drop or an addition of a HEPA filter would create an imbalance in the system. FFU’s are costly, require service and can generate room noise when multiple units are installed in the room.

6.2.7 Humidification Systems1. 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.

The chemicals such as amines introduced in steam typically remain at below exposure level recommendations by OSHA, ACGIH or FDA 2. 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 When located in the air handling unit the humidifier section shall be located upstream of the cooling coil section (which should be off in summer) to ensure efficient distribution and absorption of vapor into the air stream. Connections should be piped to exterior of the unit casing. 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 of the manifold and at least 2 m (6 ft.) downstream from the manifold. The downstream length may need to be extended depending on the absorption distance for the particular system design. Stainless steel ductwork shall be pitched and connected to a drain. Steam piping to the humidifier shall be low pressure and include a manual isolation valve for equipment isolation during service. Humidifier controls shall include an automatic isolation valve to remain closed during cooling mode. Humidifier controls shall also include a high limit humidistat located downstream of the humidifier manifold.

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3. Adiabatic humidifiers shall not be used for humidification in laboratories, animal facilities at NIH. Adiabatic humidifiers are not allowed in clinical facilities per ASHRAE 170. Steam is sterile and therefore eliminates risk of introducing viable microorganisms in the air stream. Ultrasonic humidifiers shall not be used at NIH because of risk of aerosolized fine particles that could deposit in the lungs.

4. Humidification systems shall also comply with the following:a. 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.

b. The A/E shall consult with the NIH Safety and DTR to establish a list of areas requiring the use of clean steam.

c. Clean steam shall be produced by a steam-to-steam generator by vaporizing either: RO water or distilled water or deionized water.

d. Clean steam to steam generators may be provided with medium pressure steam to reduce the size of the generators.

6.2.8 FansVariable 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.

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

2. All fans shall be constructed to meet a minimum of 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 drives exposed to exhaust airstreams serving laboratories and animal research facilities are not permitted.

3. 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.

4. 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).

5. 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.

6. 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.

7. 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.

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8. 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.

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

6.2.9 Motor and Variable Frequency Drives

6.2.9.1 MotorsMotors 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.

1. 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 induction 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.

2. 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.

3. 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 “Minimum Motor Efficiency”. Motors used on VFD’s shall be provided with Class F insulation. Motors used on VFD’s shall be provided with shaft ground ring to mitigate effects of bearing currents and protect bearings from premature failure.

6.2.10 Variable Frequency DrivesVariable Frequency Drives (VFD) to be used in NIH facilities shall include consideration to the following:

1. Harmonic distortion on both the supply and motor side of the VFD.2. Equipment de-rating due to harmonic distortion produced by VFDs.3. Audible noise caused by high-frequency (several kHz) components in the current

and voltage.

6.2.10.1 The design of system utilizing VFDs shall incorporate the following provisions1. An independent and dedicated VFD shall be provided for each prime motor and

each standby motor in equipment requiring the use of VFDs.2. Equipment motors shall be matched to the drive so that low speeds can be

achieved.

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3. VFDs shall have a manual bypass independent of the drive. For motors 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 whenever the speed drive is de-energized and/or open for service.

4. VFDs shall be located in environments that are within manufacturer’s specifications.

5. 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 without the need to shut down the equipment and without damaging the motor.

6. 18 pulse VFDs shall be provided for all motors 56 kW (75 HP) and above.7. 6 or 12 pulse VFDs shall be provided for all motors less than 56 kW (75 HP.8. 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.

9. 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.

10. 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.

11. 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.

6.2.10.2 Additional Variable Frequency Drive InformationRefer 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.

Refer to section 10 “Electrical” for additional requirements.

6.2.11 Emergency Electrical Power GeneratorsEmergency electrical power generators shall comply with the following requirements:

1. Engine exhaust system shall not create excessive back pressure on the engine and shall not be connected to any other exhaust system serving other

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equipment. Engine exhaust back pressure should be calculated before exhaust system layout is finalized Soot, corrosive condensate, and high exhaust-gas temperatures will damage idle equipment served by a common exhaust system. Excessive exhaust back reduces engine power and engine life

2. Engine exhaust piping shall comply with the following:a. Refer to Exhibit X6-3-A for requirements of the engine exhaust pipes.b. Exhaust pipes shall be freestanding, not supported by the engine or muffler.c. Exhaust pipes shall use vibration-proof flexible connector.d. Exhaust pipes and mufflers shall be guarded to prevent contact with

personnel, and avoid personnel injuries and burns.e. Exhaust pipes shall be routed to avoid fire detection devices and automatic

sprinkler heads.f. Exhaust pipes shall be vented to the atmosphere away from building doors,

windows, and ventilation intake vents. It is recommended that exhaust system be carried up as high as practical to maximize dispersal. Dispersion analysis may be required to determine effect of exhaust fumes at various intakes.

g. Insulated thimble pipe fittings shall be used at the point where the exhaust pipe penetrates the exterior wall or roof. A hinged rain cap or fabricated rain shield shall be provided on the vertical discharge.

h. 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.

i. Locate muffler as close to the engine to reduce corrosion due to condensation

j. Expansion joints shall be provided in long straight tums of pipe and where exhaust changes direction

6.2.11.1 Emergency Generator Room Ventilation1. 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. The maximum room temperature shall be determined on the operating limits of other equipment in the room as well as fire detection specifications.

2. 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. The intake damper shall be in a fail-safe position.

3. Inlet and outlet should not be located on the same wall and airflow shall allow to flow across the entire generator set from alternator end to radiator end.

4. Radiator discharge ducts shall be self-supporting.

6.2.11.2 Engine’s fuel oil system

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The emergency generator shall be provided with a safe and uninterrupted source of #2 fuel oil. The fuel oil system shall be engineered and installed to industry standards. The advantage of sub-base tank fuel tanks is that the fuel system can be factory designed and assembled however fuel capacity requirements and inability to refill and access the tank may make them impractical.The design of the fuel supply and storage system shall comply with the following requirements when using remote fuel oil tank:

1. 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. Secondary containment with leak detection and alarm is required to prevent leaking fuel from entering the soil or the sewer system. 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, (Diesel generator sets consume approximately 0.07 gallons/hour per rated KW of fuel at full load) 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 fuel tanks must be adequately vented to prevent pressurization

2. The design of the fuel oil system shall specify all tank specialties such as fuel level alarms, duplex pumps, filling accessories, control devices and all monitoring and testing devices.

3. Underground fuel oil supply tanks shall be double wall fiberglass and shall be provided with a leak detection and monitoring system.

4. 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. Day tanks are typically sized for 2 hours of operation for the generator set at full load

5. 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.

6. 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.

7. 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 return line shall not include a shut-off device

8. 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.

9. Provisions shall be provided for manually filling the tanks should it be necessary

6.2.11.3 Generator Set Noise 1. The emergency generator noise levels at the property line shall follow the local county

noise ordinances and requirements. For properties located in Montgomery County

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(including Bethesda, MD), the maximum allowed noise level is 55 dBA during daytime and 5 5dBA during night time for residential receiving properties.

2 The A&E shall assess noise performance requirements early in the design cycle and design appropriate sound attenuation measures based on the site conditions.

3 Generators sets located outdoors shall be provided with integral sound attenuators enclosures.

4 “Residential” or” Critical" grade silencers are typically effective in reducing exhaust noise and should be evaluated as part of the noise performance assessment.

6.2.11.4 Generator Space Requirements The emergency generator sets shall be provided with adequate access on both sides of the engine for service, to allow removal of the largest component, for fuel and electrical distribution system components.

6.2.11.5 Generator Fire Protection Requirements The fire protection system must comply with the authority having jurisdiction (AHJ) which is the Fire Marshal on NIH’s Bethesda’s campus. Some of the requirements include:1. Provide adequate ventilation in the room to prevent buildup of exhaust gases2. Provide adequate fire resistant construction for room construction3. Provide appropriate fire detection devices 4. Provide appropriate number of fire extinguishers in the room5. Provide manual emergency stop outside the generator to facilitate shutting down the

generator in the event of fire.6. Follow AHJ’s requirement on the amount of liquid fuel stored inside the building. Typical

maximum allowed by code is 660 Gallons.

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Documents

Committee... · Web viewThe heating and cooling coils shall be designed and sized to function at full load without the energy recovery system. Units with heat recovery systems shall