General Construction Specifications
PART 1 - GENERAL
01 SECTION INCLUDES
A. Dry type two winding transformers.
1.02 REFERENCES
A. ANSI/NEMA ST 20 - Dry Type Transformers for General Applications.
B. ANSI/NEMA - ST 1 - Specialty Transformers.
C. ANSI/NFPA 70 - National Electrical Code (NEC).
03 SUBMITTALS
A. Submit product data under provisions of applicable Sections of Division 1.
1.03 DELIVERY, STORAGE, AND HANDLING
A. Store and protect products under provisions of applicable Sections of Division 1.
B. Store in a warm, dry location with uniform temperature. Cover ventilating openings to keep out dust.
C. Handle transformers using only lifting lugs and brackets provided for that purpose. Protect units against entrance of rain, sleet, or snow if handled in inclement weather.
PART 2 - PRODUCTS
03 ACCEPTABLE MANUFACTURERS - DRY TYPE TWO WINDING TRANSFORMERS
A. General Electric.
B. Square D - Sorgel.
C. Westinghouse.
2.02 DRY TYPE TWO WINDING TRANSFORMERS
A. Dry Type Transformers: ANSI/NEMA ST 20; factory-assembled, air cooled dry type transformers; ratings as shown on the Drawings.
B. Insulation system and average winding temperature rise for rated KVA as follows:
KVA Insulation Temperature
Rating Class Rise (degree C)
1-15 KVA 185 115
16-500 KVA 220 150
A. Case temperature shall not exceed 35 degrees C rise above ambient at its warmest point.
B. Winding Taps, Transformers Less than 15 KVA: Two 5 percent below rated voltage, full capacity taps on primary winding.
C. Winding Taps, Transformers 15 KVA and Larger: Six 2-1/2 percent, two above and four below rated voltage, full capacity taps on primary.
D. Sound Levels: ANSI/NEMA ST 20 Standard where installed in unoccupied rooms. Average 3 db below -ANSI/NEMA ST 20 Standard where installed in or above the ceiling of occupied spaces.
E. Basic Impulse Level: 10 KV for transformers less than 300 KVA.
F. Ground core and coil assembly to enclosure by means of a visible flexible copper grounding strap.
G. Mounting: Transformers 75 KVA and less shall be suitable for wall, floor, or trapeze mounting; transformers larger than 75 KVA shall be suitable for floor or trapeze mounting.
H. Coil Conductors: Continuous windings with terminations brazed or welded.
I. Enclosure: ANSI/NEMA ST 20; Type 1. Provide lifting lugs or brackets.
J. Isolate core and coil from enclosure using vibration-absorbing mounts.
K. Nameplate: Include transformer connection data.
PART 3 - EXECUTION
04 INSTALLATION
A. Set transformer plumb and level. Install on floor, wall, or trapeze as indicated on Drawings. Provide four inch thick concrete pad for floor mounted transformers. Provide clearances around transformer as required by NEC Articles 110-16(a) and 450-21.
B. Use liquid-tight flexible conduit, 2 ft minimum length, for connections to transformer case. Make conduit connections to side panel of enclosure.
C. Mount transformers on vibration isolating pads suitable for isolating the transformer noise from the building structure.
D. Provide seismic restraints.
05 FIELD QUALITY CONTROL
A. Field inspections and testing shall be in accordance with applicable Sections of Division 1.
B. Check for damage and tight connections prior to energizing transformer.
C. Measure primary and secondary voltages and make appropriate tap adjustments.
END OF SECTION
