| Capital Projects Home Page |
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| Division 15 Mechanical |
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| 15-7 | Air Handling And Air Distribution |
| A. | Fans |
| 1. | Centrifugal fans should be specified for most applications. Select size and type of fan based on life cycle cost and noise level considerations. Selected fans must be have performance characteristics capable of future flow increases of at least 10%. Due to their high noise levels axial fans should not be specified without prior consultation with CP. |
| 2. | Select fans which meet Air Moving and Conditioning Association (AMCA) construction and capacity rating standards. |
| 3. | Provide flexible connections between fans and ductwork. |
| 4. | Provide safety guards described in this division. |
| 5. | Provide bearings described in this division. |
| B. | Fan Drives |
| 1. | Provide V-belt drives with ratings of not less than 150% of motor horsepower. |
| 2. | Provide motors of five horsepower and smaller and not more than two drive belts with an adjustable pitch motor sheave. The midpoint of the adjustment range shall produce the specified fan revolutions per minute. |
| 3. | Provide motors larger than five horsepower and drives with more than two belts with a sheave which produces the specified fan revolutions per minute. |
| 4. | After testing the ventilating system, the contractor shall make, without additional cost, one change in the size of the non-adjustable sheave and belts to obtain the desired air quantities. |
| C. | Variable Frequency Drives |
| 1. | Specify only the following variable frequency drive (VFD) manufacturers to ensure compatibility with campus staff training and inventory: ABB, Saftronics or Toshiba. Discuss specification language with CP project manager to comply with campus requirements. |
| 2. | Warranty: All equipment and installation shall be warranted for a minimum period of 12 months from the date of start-up, This warranty shall include all costs of repair during the warranty period including transportation and shipping cost. |
| 3. | Standard Products: All materials and equipment furnished shall be new and of standard design and model. In addition they shall be the manufacturer's latest standard design that is current at the time of delivery, except for such modifications from manufacturer's standard product as may be required to conform to specification requirements. |
| 4. | VFD System: Provide a complete variable frequency drive system. Each system shall consist of: |
| a. | A power input circuit breaker. |
| b. | A drive power unit safety disconnect (service switch). |
| c. | A rectifier. |
| d. | Filter and inverter with regulator and controls (drive power unit). |
| e. | Inverter with regulator and contractors. |
| f. | Motor overload heaters. |
| g. | Transducers and instrumentation. |
| h. | User input/output terminals. |
| i. | A system control panel and system enclosure(s). |
| The output waveform of the drive power unit shall be sine-coded, pulse width modulated. | |
| The systems are to be installed as variable speed controllers for existing induction motor driven fans. | |
| 5. | Standards, Codes and References: Design, construction and fabrication shall be in accordance with good engineering practice and workmanship and in compliance with the following standards and codes as applicable. |
| a. | National Electrical Manufacturers Association (NEMA). |
| b. | Institute of Electrical and Electronic engineers (IEEE). |
| c. | Occupational Safety and Health Act (Cal/OSHA). |
| d. | NFPA National Electrical Code (NEC). |
| e. | Underwriters' Laboratory (UL) or Electrical Testing Laboratory (ETL). |
| f. | State of California and all Local Laws and regulations. |
| g. | Drawings: |
| 8844B-E1-0 | Typical control schematic for single motor variable frequency drive. |
| 8844B-E2-0 | Typical control schematic for dual motor variable frequency drive. |
| 8844B-E3-0 | Variable frequency drive control interface diagram. |
| Each variable frequency drive unit shall bear the approval sticker of a nationally recognized testing laboratory such as Underwriters' Laboratory (UL) or Electrical Testing Laboratory (ETL). | |
| 6. | Submittals to the University shall include three copies of following items for each different size or model system. |
| a. | Dimensional drawings showing all pertinent dimensions and total unit weights for the variable frequency drive system equipment. |
| b. | A complete set of drive power unit connection diagrams. |
| c. | A complete set of elementary and schematic drawings for all electric and electronic circuits. |
| d. | A complete set of wiring drawings showing schematics of each printed circuit board and all components both by circuit connection and position on board, and all component values. |
| e. | A complete manual including all necessary installation, operation, and maintenance instructions. |
| f. | A recommended spare parts list and a parts price list. |
| 7. | General VFD requirements: The drive power unit shall be of sufficient capacity and shall provide a quality of output waveform to achieve the full rated output of the driven motors listed in Part 3. In addition, the variable frequency drive system shall include the following ratings and parameters. |
| a. | Efficiency: Minimum drive unit efficiency shall be 94% at 100% speed and not less than 80% at 50% speed. |
| b. | Input Voltage: The input voltages shall be 3-phase, 240 or 480 volts + 10%, -5%, 60 HZ±5%, as required by location. |
| c. | Rating: The drive unit rating basis shall be 100% continuous with a service factor of 1.0. |
| d. | Input Circuit Protection (main circuit breaker): A properly rated thermal-magnetic molded case circuit breaker or a circuit breaker/current limiting fuse combination that provides the short circuit protection required below, shall be provided on the incoming power line. |
| i. | The circuit breaker shall be rated 200,000 amperes at 240 volts or 100,000 amperes at 480 volts interrupting capacity RMS for short circuit protection. |
| ii. | The circuit breaker shall be lockable in the off position and shall be interlocked with enclosure door, with provision for defeating the interlock. |
| e. | Drive Power Unit: The variable frequency drive power unit shall consist of converter, filter and in inverter sections. |
| i. | The converter section shall be a full wave, 3-phase diode bridge that shall provide a voltage source which output is regulated and limited. |
| ii. | The output of the converter shall feed a filter capacitor section. |
| iii. | The inverter section shall convert the DC output to an approximate sine wave current waveform at an adjustable frequency. |
| f. | Bypass Equipment: By-Pass capability shall require the following equipment to be supplied as part of the variable frequency drive package to ensure a coordinated system: |
| i. | Two AC motor contractors, with 115 volt coils, mechanically and electrically interlocked for inverter or bypass output. |
| ii. | Inverter and bypass contactor control relays for transferring output from the inverter to the bypass and vice versa. |
| iii. | Thermal motor overload devices with auxiliary contacts, wired into the output to provide motor overload protection in both inverter and bypass mode. |
| iv. | Auxiliary contacts on the inverter and bypass contactors and control relays as per the drawings. |
| v. | Where the variable frequency drive is required to drive two motors; two pairs of contactors (four total), each pair mechanically and electrically interlocked, and two thermal motor overload devices shall be provided. |
| g. | Control Power Transformer: A 120 volt control power transformer with primary and secondary protective fuses shall be provided for remote and local controls. |
| h. | Enclosure: |
| i. | The enclosure shall be a rigid wall-mounted or freestanding National Electrical Manufacturers Association (NEMA) 1 type. Operation, maintenance and parts replacement shall be from the front of the unit enclosure. No access from the sides or rear of the panel shall be required. Replacement type filters shall be used on all ventilation openings. Changing of filters shall be done without the opening of any enclosure doors. |
| ii. | The enclosure shall house all electrical and electronic components. |
| iii. | The equipment shall contain drive data nameplate mounted internal to unit with the following information: input voltage, full load current, drive horsepower rating, service factor, frequency range, maximum output voltage, model number, serial number, and shop order number. |
| i. | Controls, Control Relays, Pilot Lights and Indicators: |
| i. | Panel mounted controls and pilot lights shall be National Electrical Manufacturers Association (NEMA) type 13 oil tight. |
| ii. | Pilot lights shall be push-to-test transformer type with 6.3 volt lamps. |
| iii. | Control relays shall be industrial grade control type relays. |
| iv. | Indicators shall be industrial type panel meters, digital or analog as indicated. |
| v. | All wires shall be marked on both ends with the number shown on wiring diagrams. Output terminals shall be continually numbered with no repetition. Wire markers shall be heat shrinkable or interlocking sleeve type. |
| 8. | Technical Requirements: Design Criteria and Features: The drive power unit shall provide the following: |
| a. | Rated output voltage shall be 3-phase 208 or 480 volts, 60 Hz. |
| b. | Output frequency control variable over a 40 to 1 speed ratio range. |
| c. | Long term frequency stability shall be 1% or better for any given 24 hour period. |
| d. | Speed regulation at the motor shaft shall be 3% or better with standard National Electrical Manufacturers Association (NEMA) Design B induction motor, without special slip compensation. |
| e. | Overall rating shall be 150% of drive rating for one minute. |
| f. | Electronic start into running motor protection. |
| g. | Auxiliary outputs prewired to terminals for purchaser's use: |
| i. | A normally closed fault summary dry contact that opens on any variable frequency drive internal fault or AC power failure. |
| ii. | A 0 to 6 volt or 0 to 10 volt direct current output signal proportional to 0 to 150% speed. |
| iii. | A 0 to 6 volt or 0 to 10 volt direct current output signal proportional to 0 to 150% current output. |
| h. | The inverter regulator section shall include: |
| i. | Adjustable current limit (60-110%). |
| ii. | Adjustable volts per hertz for output power (+/- 10%). |
| iii. | Adjustable minimum and maximum speed or frequency (0-100% and 100-0%). |
| iv. | Torque limit adjustable from 50 to 100% of full drive rating. When torque limit is exceeded, output frequency shall decrease until load is within continuous torque rating limit at which point the speed shall stabilize. If minimum frequency is reached before the torque is reduced to a safe value, then the inverter output shall de-energize within 60 seconds. Operation with torque limit control engaged shall be visually indicated. |
| i. | The drive shall be capable of follower operation from a 0 to 10 volt direct current signal that may be either positive or negative and either grounded or ungrounded. |
| j. | Sealed contacts for all switched regulator and reference signals. |
| k. | The door of each variable frequency drive power unit shall include a control panel consisting of: |
| i. | Lockable input power disconnect handle (main circuit breaker). |
| ii. | Lockable drive power disconnect (service switch) that may be accessible only from inside the enclosure. |
| iii. | Off-hand-auto control select switch. |
| iv. | Bypass-inverter output selector switch. |
| v. | Start in auto (computer control) push-button. |
| vi. | Manual (Hand) speed adjusting potentiometer. |
| vii. | Power on indicating light. |
| viii. | Inverter fault indicating light. |
| ix. | Motor on inverter indicating light. |
| x. | Motor on bypass indicating light. |
| xi. | Speed or frequency meter (output, 3 digit LCD or LED digital, scaled 1 to 150%). |
| xii. | Ammeter (input current, analog only, scaled 0 to 150% of full load current). |
| xiii. | Normal-test switch. |
| xiv. | Voltmeter (input line voltage, analog only, scaled 0 to 150% of nominal). |
| l. | Independently adjustable acceleration and deceleration rates extendible up to 30 seconds, with torque limit override acceleration protection and regeneration protection during deceleration. |
| m. | Selectable coast-to-stop or ramp-to-stop control. |
| n. | "Normal-Test" switch that shall prevent closing of the bypass or inverter output contactors, to permit no-load on-line testing of variable frequency drive components. The normal-test switch shall be located inside the variable frequency drive cabinet, accessible to qualified maintenance personnel only. |
| 9. | System Protection: The following design, operation and maintenance features shall be incorporated in the drive power unit. |
| a. | A disconnecting device shall be supplied to disconnect all drive power unit internal wiring from the input power supply. The device shall be operated by a door-mounted handle that shall be lockable in the off position and shall be mechanically interlocked with the enclosure door. The locking safety mechanism shall be defeatable to allow for opening the enclosure without de-energizing the equipment. |
| b. | The current limit capability of the converter section shall react sufficiently fast to protect against a sudden random short circuit at the output terminals of the converter section. |
| c. | The converter shall be provided with high speed, current limiting input line fuses to protect against internal faults. |
| d. | Phase-to-phase and phase-to-ground short circuit protection. |
| e. | Additional protection shall be provided for: |
| i. | Input power failure. |
| ii. | Phase current imbalance. |
| iii. | Undervoltage |
| iv. | Incorrect phase rotation shall be provided. |
| Transient suppression for protection of internal components from line and load transients. | |
| vi. | Ground fault. |
| vii. | Electronic motor overload (IT) protection, adjustable from 60 to 100% of drive full load ampere rating. |
| f. | Heat sink temperature switches shall be supplied and an orderly shutdown shall occur on over temperature conditions. |
| g. | DC bus voltage clamp circuitry shall be provided to prevent damage due to AC line overvoltage. Excessive motor regenerative voltage shall not cause inverter to trip or damage components but shall decelerate motor to a safe operating mode. |
| h. | Instantaneous electronic overcurrent trip circuitry shall be provided for protection of inverter section power electronic devices independent of protective fusing. This circuitry shall include visual indication, in the regulator section, of any instantaneous overcurrent trip. |
| i. | The filter capacitors shall have automatic discharge circuitry that will cause discharge within approximately three minutes after the drive system is de-energized. |
| j. | The inverter section shall be provided with high speed current limiting fuses to protect against internal faults. |
| k. | Inverter overload protection shall provide shutdown on an inverse time basis dependent on the extent of the overload. |
| l. | Two second power outage ride-through capability: The inverter shall maintain constant volts per hertz at motor terminals during outage. Rundown time is determined by system inertia and losses only. |
| m. | The inverter shall not trip due to supply system AC transient spikes when the bypass run mode or when OFF. The drive manufacturer shall provide electronic circuitry that prevents such a trip, or an electrically operated isolation contractor on the supply side of the inverter. |
| 10. | System Test and Troubleshooting: |
| a. | The variable frequency drive system equipment shall include a display for system malfunction identification and troubleshooting. As a minimum the following indicators shall be provided: |
| i. | Overcurrent trip. |
| ii. | Overvoltage trip. |
| iii. | Torque limit. |
| b. | A diagnostic fault microprocessor may be utilized to perform all diagnostic testing. |
| 11. | Mode of Operation: The system shall provide for operation as follows: |
| a. | Off-Hand-Auto control selector and Bypass-Inverter output selector switches: |
| i. | In off position there shall be no output from the variable frequency drive system. The inverter cannot be started and the bypass contactor cannot be closed. |
| A. | When moved to off from hand position, variable frequency drive system output shall cease, subject to the following: If the output selector switch is on bypass, the inverter output will be disconnected and power to the fan motor shall derive from the bypass contactor and circuit. |
| B. | If the output selector switch is on inverter, the inverter shall immediately open. |
| ii. | In hand position the fan motors shall run from bypass or inverter output, according to the setting of the output selector switch. |
| A. | If the output selector switch is on bypass, the inverter output will be disconnected and power to the fan motor shall derive from the bypass contactor and circuit. |
| B. | If the output selector switch is on inverter, the inverter shall operate and power to the fan motor shall derive from the inverter. Speed shall be controlled by the front door-mounted speed control. |
| iii. | In auto position the fan motors shall be controlled by remotely sourced computer-controlled inputs. variable frequency drive system output shall be inverter or bypass, according to the setting of the output selector switch. The on signal will be provided by momentary closure of a remote dry contact. The off signal will be provided by momentary opening of a remote dry contact. Speed control will be provided by a 0 - 10 volt analog signal. |
| A. | If the output selector switch is in bypass, the inverter will be disconnected and power to the fan motor shall derive from the bypass contactor and circuit. Start-stop functions will be remotely controlled. |
| B. | If the output selector switch is in inverter, the drive shall operate and power to the fan motor shall derive from the inverter. Both start-stop functions and speed setpoint will be remotely controlled. |
| C. | The inverter output frequency shall increase or decrease at the preselected rate when on or off signals are received or when changes in speed control are made while in both auto and inverter modes. When an off signal is received, the inverter contactor shall not open until the speed has ramped to near zero. When an on signal is received, the inverter contactor shall close before the speed is ramped up to the preset or input speed. |
| iv. | When switching from hand to auto and vice-versa, when in inverter output, the control system shall be so configured that the drive shall not go through complete shut down while making any speed adjustments. |
| b. | Start in Auto, Push-button Switch: This momentary contact switch shall functionally parallel the computer controlled on signal when the control selector switch is in auto. It shall provide for restarting the fan motor whether in bypass or inverter output mode. |
| c. | Normal-Test Switch: This maintained contact switch shall disconnect the bypass and inverter contactor coils from control power when in test position to permit no-load testing and adjustment of variable frequency drive components. |
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