A. Provide variable frequency drives to operate variable torque loads as shown on the Drawings and as specified herein.

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1 DIVISION 23 HEATING, VENTILATING, AND AIR CONDITIONING (HVAC) SECTION PART 1 GENERAL 1.01 DESCRIPTION A. Provide variable frequency drives to operate variable torque loads as shown on the Drawings and as specified herein. B. All variable frequency drives on the project shall be by the same manufacturer QUALITY ASSURANCE A. All equipment shall be UL listed and labeled and in accordance with applicable NEMA and ANSI Standards. B. The variable frequency drive(s) shall be provided with a three (3) year full parts and labor warranty, commencing at Project Completion. Warranty periods that begin at startup or on a ship date are not sufficient. C. NEMA ICS Safety Standards for Construction and Guide for Selection, Installation and Operation of Variable Frequency Drive Systems. D. NEMA - Enclosure for Electrical Equipment. E. IEEE Standard 444 (ANSI-C343). F. IEEE Standard 519. G. IEC 146A. H. IEC 16800, Parts 1 and MANUFACTURERS A. Square D, ABB, Toshiba, Eaton/Cutler-Hammer, and Yaskawa RELATED WORK SPECIFIED ELSEWHERE A. Conformance with all sections of the specifications is required. Additional requirements for the equipment specified within this section are included in, but not limited to the following Sections: , "TEMPERATURE CONTROL" 13-HC

2 PART 2 PRODUCTS 2.01 VARIABLE FREQUENCY DRIVE UNIT WITH BYPASS (ALL VFD'S EXCEPT THOSE FOR AIR HANDLING UNITS) A. The drive unit shall be microprocessor based using insulated gate bipolar transistors (IGBT). The unit shall put out variable frequency and voltage at a constant volts-per-hertz ratio for controlling standard AC induction motors using pulse width modulated technology. B. The drive unit and all components shall be mounted in a single NEMA 1 enclosure with a front accessibility only requirement. Enclosure shall contain a disconnect switch and semiconductor type current limiting fuses or circuit breaker giving the unit a 65,000 AIC rating. The disconnect switch shall extend through the enclosure front and be pad-lockable. All system components shall be mounted in a common steel enclosure. C. The enclosure shall contain separate fuses or circuit breaker for the drive unit and fuse or circuit breaker in the bypass circuit. There shall be a manually operated integrated bypass contactor interlocked and electrically with a drive output contactor allowing removal of the drive unit while permitting motor operation. Units serving 50 Hp motors or larger shall be provided with soft start on the bypass circuit. D. A minimum of 3% impedance by line reactors and/or input DC bus reactor shall be provided to limit the total harmonic voltage distortion to 5%. E. Motor thermal overloads shall be on the load side of the contactors. F. Output 3 - phase current sensing overload relay to provide motor protection in either VFD or bypass mode. G. Switching Frequency: To minimize electrical and acoustical noise the switching frequency shall be adjustable from 2 khz to 10 khz (minimum range). The anticipated full-speed carrier frequency settings are as follows: volt up to 30 Hp: 8-10 khz volt, 40 Hp and above: 4 khz volt up to 50 Hp: 10 khz volt, 60 to 100 Hp: 8 khz volt, 100 Hp and above: 4 khz. H. Adaptive electronic motor overload protection shall be provided which shall protect both motor and VFD at all frequencies. Electronic circuits protecting the motor at full speed are not acceptable. The circuits shall sense load and speed and shall reset the thermal trip curve for low speed motor protection. The initial trip point shall be adjustable from 40% of VFD continuous rating RATINGS A. Efficiency: 96% at 100% speed 80% at 50% speed B. Displacement Power Factor: 0.98 minimum HC1-033

3 C. Input Voltage: 460 or 208 (as shown on plans) volt +15%. D. Input Voltage Frequency: 48 to 63 Hz. E. Ambient Temperature Tolerance for Continuous Operation: 0-40 degrees C. F. Relative Humidity Tolerance for Continuous Operation: 0-95% at 40 degrees C. G. Maximum Non-Derated Altitude for Continuous Operation: 1000 meters. H. Speed Range: 2.5 Hz to 72 Hz. I. Minimum Powerloss Ride Thru: 2.0 seconds for units 5 Hp and larger. J. Adjustable Ramp Time Range: 0.1 to 999 seconds. K. Speed Regulation: 3%. L. Skip Frequencies: Two (2) or more. M. Maximum Corrected Harmonic Voltage Distortion Reflected into Supply: 5%. N. Operating Capacity: Provide variable frequency drives sized for continuous operation at 110% of the driven motor's full load rated current. Base sizing on the ambient environmental conditions listed above. O. Input surge protection using metal oxide varistors CONTROL FUNCTIONS A. All programmable parameters shall be adjustable from a digital operator keypad located on the front door of the VFD. Parameters shall include: 1. Programmable frequency command (keypad, remote). 2. Programmable start command (keypad, remote). 3. Forward start, stop, and digital speed control via digital operator keypad. 4. Programmable maximum and minimum frequency limits. 5. Programmable acceleration and deceleration times. 6. Programmable carrier frequencies, V/Hz, and critical frequency avoidance lockout zones. 7. Programmable electronic overload and torque limits. 8. Programmable multiple attempt restart. 9. Programmable preset speeds. 10. Programmable dwell time at start to maximize motor starting torque. 11. Programmable "Speed Search Transfer" function. (The VFD shall be capable of start from bypass or fault trip into a spinning load from 100% forward to 100% reverse rotation without stopping the motor or creating a fault condition. 13-HC

4 B. The VFD shall have the following system interfaces: 1. Inputs a. Process control speed reference interface to receive a 0-10 volt DC signal or 4-20 milliamp signal. b. Remote mode start contact. c. Remote preset speed contacts. d. Remote reset contact. 2. Outputs a. Run relay with an isolated set of Form C contacts. b. Dry contact output to indicate protective function trip. c. Analog output signal proportional to output frequency. d. Provide serial communications link via RS-485 connection. e. Provide BACNet Communication Protocol connection in accordance with the requirements of the Building Automation System (BAS). C. Monitoring and Displays 1. The VFD shall have an alpha-numeric display indicating monitored functions as described in the following: a. Output current b. Output frequency c. Motor rpm percent d. Trip cause (up to four sequential faults. All system information shall be stored for the three (3) seconds previous to the last fault) e. Output voltage f. DC bus voltage g. Output power 2. External Pilot Devices or Functions: a. Hand-Off-Auto Switch (for speed control) b. Speed potentiometer c. Fault Pilot Light (LED) d. Drive on Pilot Light (LED) D. Protection Functions 1. The VFD shall include the following protective features: a. AC input line current limiting fuses rated 200,000 AIC b. Overcurrent protection c. Overvoltage protection d. Undervoltage protection e. Overfrequency protection f. Phase loss protection g. Overtemperature protection h. Ground fault protection i. Adjustable current limit j. Line-to-line and line-to-ground short circuit protection k. Input line reactors HC1-033

5 E. Other Functions 1. Auxiliary drive status relay with two Form C relay pairs, rated 2 amps resistive at 120- volt AC for indication of running condition. 2. VFD shall include dv/dt filtering or line reactors on all 460 volt motors 15 Hp and less if the wiring between the VFD and the motor exceeds 120 feet (wire path) and on all 460 volt motors 20 Hp and greater if the wiring between the VFD and motor exceeds 200 feet /460 volt motors operating at volts and 460 volt inverter duty motors in full compliance with NEMA MG-Part 31, are not required to have output filtering. Adjust the distances per manufacturer's recommendation and submit chart for review VARIABLE FREQUENCY DRIVE UNIT WITHOUT BYPASS (ONLY FOR AIR HANDLING UNIT VFD'S) A. The drive unit shall be microprocessor based using insulated gate bipolar transistors (IGBT). The unit shall put out variable frequency and voltage at a constant volts-per-hertz ratio for controlling standard AC induction motors using pulse width modulated technology. B. The drive unit and all components shall be mounted in a single NEMA 1 enclosure with a front accessibility only requirement. Enclosure shall contain a disconnect switch and semiconductor type current limiting fuses or circuit breaker giving the unit a 65,000 AIC rating. The disconnect switch shall extend through the enclosure front and be pad-lockable. All system components shall be mounted in a common steel enclosure. C. A minimum of 3% impedance by line reactors and/or input DC bus reactor shall be provided to limit the total harmonic voltage distortion to 5%. D. Motor thermal overloads shall be on the load side of the contactors. E. Output 3 - phase current sensing overload relay to provide motor protection. F. Switching Frequency: To minimize electrical and acoustical noise the switching frequency shall be adjustable from 2 khz to 10 khz (minimum range). The anticipated full-speed carrier frequency settings are as follows: volt up to 30 Hp: 8-10 khz volt, 40 Hp and above: 4 khz volt up to 50 Hp: 10 khz volt, 60 to 100 Hp: 8 khz volt, 100 Hp and above: 4 khz. G. Adaptive electronic motor overload protection shall be provided which shall protect both motor and VFD at all frequencies. Electronic circuits protecting the motor at full speed are not acceptable. The circuits shall sense load and speed and shall reset the thermal trip curve for low speed motor protection. The initial trip point shall be adjustable from 40% of VFD continuous rating. 13-HC

6 H. Adaptive electronic motor overload protection shall be provided which shall protect both motor and VFD at all frequencies. Electronic circuits protecting the motor at full speed are not acceptable. The circuits shall sense load and speed and shall reset the thermal trip curve for low speed motor protection. The initial trip point shall be adjustable from 40% of VFD continuous rating RATINGS A. Efficiency: 96% at 100% speed 80% at 50% speed B. Displacement Power Factor: 0.98 minimum. C. Input Voltage: 460 or 208 (as shown on plans) volt +15%. D. Input Voltage Frequency: 48 to 63 Hz. E. Ambient Temperature Tolerance for Continuous Operation: 0-40 degrees C. F. Relative Humidity Tolerance for Continuous Operation: 0-95% at 40 degrees C. G. Maximum Non-Derated Altitude for Continuous Operation: 1000 meters. H. Speed Range: 2.5 Hz to 72 Hz. I. Minimum Powerloss Ride Thru: 2.0 seconds for units 5 Hp and larger. J. Adjustable Ramp Time Range: 0.1 to 999 seconds. K. Speed Regulation: 3%. L. Skip Frequencies: Two (2) or more. M. Maximum Corrected Harmonic Voltage Distortion Reflected into Supply: 5%. N. Operating Capacity: Provide variable frequency drives sized for continuous operation at 110% of the driven motor's full load rated current. Base sizing on the ambient environmental conditions listed above. O. Input surge protection using metal oxide varistors CONTROL FUNCTIONS A. All programmable parameters shall be adjustable from a digital operator keypad located on the front door of the VFD. Parameters shall include: 1. Programmable frequency command (keypad, remote). 2. Programmable start command (keypad, remote). 3. Forward start, stop, and digital speed control via digital operator keypad. 4. Programmable maximum and minimum frequency limits. 5. Programmable acceleration and deceleration times HC1-033

7 6. Programmable carrier frequencies, V/Hz, and critical frequency avoidance lockout zones. 7. Programmable electronic overload and torque limits. 8. Programmable multiple attempt restart. 9. Programmable preset speeds. 10. Programmable dwell time at start to maximize motor starting torque. 11. Programmable "Speed Search Transfer" function. (The VFD shall be capable of start from bypass or fault trip into a spinning load from 100% forward to 100% reverse rotation without stopping the motor or creating a fault condition. B. The VFD shall have the following system interfaces: 1. Inputs a. Process control speed reference interface to receive a 0-10 volt DC signal or 4-20 milliamp signal. b. Remote mode start contact. c. Remote preset speed contacts. d. Remote reset contact. 2. Outputs a. Run relay with an isolated set of Form C contacts. b. Dry contact output to indicate protective function trip. c. Analog output signal proportional to output frequency. d. Provide serial communications link via RS-485 connection. e. Provide BACNet Communication Protocol connection in accordance with the requirements of the Building Automation System (BAS). C. Monitoring and Displays 1. The VFD shall have an alpha-numeric display indicating monitored functions as described in the following: a. Output current b. Output frequency c. Motor rpm percent d. Trip cause (up to four sequential faults. All system information shall be stored for the three (3) seconds previous to the last fault) e. Output voltage f. DC bus voltage g. Output power 2. External Pilot Devices or Functions: a. Hand-Off-Auto Switch (for speed control) b. Speed potentiometer c. Fault Pilot Light (LED) d. Drive on Pilot Light (LED) D. Protection Functions 1. The VFD shall include the following protective features: a. AC input line current limiting fuses rated 200,000 AIC b. Overcurrent protection c. Overvoltage protection d. Undervoltage protection e. Overfrequency protection f. Phase loss protection g. Overtemperature protection 13-HC

8 h. Ground fault protection i. Adjustable current limit j. Line-to-line and line-to-ground short circuit protection k. Input line reactors E. Other Functions 1. Auxiliary drive status relay with two Form C relay pairs, rated 2 amps resistive at 120- volt AC for indication of running condition. 2. VFD shall include dv/dt filtering or line reactors on all 460 volt motors 15 Hp and less if the wiring between the VFD and the motor exceeds 120 feet (wire path) and on all 460 volt motors 20 Hp and greater if the wiring between the VFD and motor exceeds 200 feet /460 volt motors operating at volts and 460 volt inverter duty motors in full compliance with NEMA MG-Part 31, are not required to have output filtering. Adjust the distances per manufacturer's recommendation and submit chart for review. PART 3 EXECUTION 3.01 INSTALLATION A. Install fabricated steel floor stands for mounting drives where loads are in the center of a room or mounting the drive to a wall as required. Floor stands shall be an appropriatelysized galvanized metal framing system or 2 inch steel angle with galvanized finish. Provide the complete installation of all accessories provided with the variable frequency drive (including but not limited to the line reactor and the output filter). This contractor shall provide fuses (as furnished by the variable frequency drive manufacturer) in all fuse holders. Final connections to equipment shall be by the Electrical Contractor and shall be made using liquid-tight flexible steel conduit. B. Provide nameplates in accordance with all other provisions of these specifications. C. Drives shall be protected from dirt and moisture at all times. D. The line reactors and output filters shall be integral to package STARTUP AND TESTING A. Start up and testing shall be conducted by manufacturer's authorized field technical representative. B. Provide a full functional test of all components and operation of variable frequency drives in accordance with manufacturer's recommended procedure. C. Operate system for a minimum period of seven (7) consecutive days with no problems before final acceptance by Owner. END OF SECTION HC1-033

DENVER PUBLIC SCHOOLS DESIGN AND CONSTRUCTION STANDARDS This Standard is for guidance only. SECTION MOTORS, STARTERS & DRIVES

DENVER PUBLIC SCHOOLS DESIGN AND CONSTRUCTION STANDARDS This Standard is for guidance only. SECTION MOTORS, STARTERS & DRIVES PART 0 DESIGN STANDARDS 0.01 GENERAL DESIGN GUIDELINES A. Coordinate starter needs for mechanical equipment prior to 50% CD and confirm again for 100% CD submittal. B. Coordinate temperature controls requirements