26 22 00 Low Voltage Transformers.pdf

Parking Expansion at Joliet CBOC

Joliet, Illinois 4-9-2024

Project Number 578-371

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SECTION 26 22 00

LOW-VOLTAGE TRANSFORMERS

PART 1 – GENERAL

1.1 DESCRIPTION

A. This section specifies the furnishing, installation, connection, and testing of low-voltage dry-type general-purpose transformers, indicated as transformers in this section.

1.2 RELATED WORK

A. Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS: General electrical requirements that apply to all sections of Division 26.

B. Section 26 05 19, LOW-VOLTAGE ELECTRICAL POWER CONDUCTORS AND CABLES:

Low-voltage conductors.

C. Section 26 05 26, GROUNDING AND BONDING FOR ELECTRICAL SYSTEMS:

Requirements for personnel safety and to provide a low impedance path for possible ground fault currents.

D. Section 26 05 33, RACEWAY AND BOXES FOR ELECTRICAL SYSTEMS: Conduit.

1.3 QUALITY ASSURANCE

A. Quality assurance shall be in accordance with Paragraph, QUALIFICATIONS

(PRODUCTS AND SERVICES), in Section 26 05 11, REQUIREMENTS FOR

ELECTRICAL INSTALLATIONS.

1.4 SUBMITTALS

A. Submit in accordance with Paragraph, SUBMITTALS, in Section 26 05 11, REQUIREMENTS FOR ELECTRICAL INSTALLATIONS, and the following requirements:

1. Shop Drawings:

a. Submit sufficient information to demonstrate compliance with drawings and specifications.

b. Include electrical ratings, dimensions, mounting details, materials, required clearances, terminations, weight, temperature rise, wiring and connection diagrams, plan, front, side, and rear elevations, accessories, and device nameplate data.

2. Manuals:

a. Submit, simultaneously with the shop drawings, companion copies of complete maintenance and operating manuals including technical data sheets and wiring diagrams.

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1) Schematic signal and control diagrams, with all terminals identified, matching terminal identification in the transformers.

2) Include information for testing, repair, troubleshooting, assembly, disassembly, and factory recommended/required periodic maintenance procedures and frequency.

b. If changes have been made to the maintenance and operating manuals originally submitted, submit updated maintenance and operating manuals two weeks prior to the final inspection.

3. Certifications: Two weeks prior to final inspection, submit the following.

a. Certification by the manufacturer that the transformers conform to the requirements of the drawings and specifications.

b. Certification by the Contractor that the transformers have been properly installed, adjusted, and tested.

1.5 APPLICABLE PUBLICATIONS

A. Publications listed below (including amendments, addenda, revisions, supplements, and errata) form a part of this specification to the extent referenced. Publications are referenced in the text by designation only.

B. International Code Council (ICC):

IBC-21..................International Building Code

C. National Fire Protection Association (NFPA):

70-23...................National Electrical Code (NEC)

D. National Electrical Manufacturers Association (NEMA):

TR 1-13.................Transformers, Step Voltage Regulators and

Reactors

ST 20-14................Dry Type Transformers for General Applications

E. Underwriters Laboratories, Inc. (UL):

506-17..................Standard for Specialty Transformers

1561-11.................Dry-Type General Purpose and Power Transformers

F. United States Department of Energy

10 CFR Part 431.........Energy Efficiency Program for Certain

Commercial and Industrial Equipment

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PART 2 - PRODUCTS

2.1 TRANSFORMERS

A. Unless otherwise specified, transformers shall be in accordance with

NEMA, NEC, UL and as shown on the drawings.

B. Transformers shall have the following features:

1. Self-cooled by natural convection, isolating windings, //indoor//and outdoor// dry-type. Autotransformers will not be accepted, except as specifically allowed for buck-boost applications.

2. Rating and winding connections shall be as shown on the drawings.

3. Ratings shown on the drawings are for continuous duty without the use of cooling fans.

4. Copper windings.

5. Insulation systems:

a. Transformers 30 kVA and larger: UL rated 220 °C (428 °F) system with an average maximum rise by resistance of 150 °C (302 °F) in a maximum ambient of 40 °C (104 °F).

b. Transformers below 30 kVA: Same as for 30 kVA and larger or UL rated 185 °C (365 °F) system with an average maximum rise by resistance of 115 °C (239 °F) in a maximum ambient of 40 °C (104

°F).

6. Core and coil assemblies:

a. Rigidly braced to withstand the stresses caused by short-circuit currents and rough handling during shipment.

b. Cores shall be grain-oriented, non-aging, and silicon steel.

c. Coils shall be continuous windings without splices except for taps.

d. Coil loss and core loss shall be minimized for efficient operation.

e. Primary and secondary tap connections shall be brazed or pressure type.

f. Coil windings shall have end filters or tie-downs for maximum strength.

7. Average audible sound levels shall comply with NEMA.

8. If not shown on drawings, nominal impedance shall be as permitted by

NEMA.

9. Single phase transformers rated 15 kVA through 25 kVA shall have two

5% full capacity taps below normal rated primary voltage. All

26 22 00 - 4 transformers rated 30 kVA and larger shall have two 2.5% full capacity taps above, and four 2.5% full capacity taps below normal rated primary voltage.

10. Core assemblies shall be grounded to their enclosures with adequate flexible ground straps.

11. Enclosures:

a. Comprised of not less than code gauge steel.

b. Outdoor enclosures shall be NEMA 3R.

c. Temperature rise at hottest spot shall conform to NEMA Standards and shall not bake and peel off the enclosure paint after the transformer has been placed in service.

d. Ventilation openings shall prevent accidental access to live components.

e. The enclosure at the factory shall be thoroughly cleaned and painted with manufacturer's prime coat and standard finish.

12. Standard NEMA features and accessories, including ground pad, lifting provisions, and nameplate with the wiring diagram and sound level indicated.

13. Dimensions and configurations shall conform to the spaces designated for their installations.

14. Transformers shall meet the energy conservation standards for transformers per the United States Department of Energy’s 10 CFR Part

431.

PART 3 - EXECUTION

3.1 INSTALLATION

A. Installation shall be in accordance with the NEC, as shown on the drawings, and manufacturer’s instructions.

B. Anchor transformers with rustproof bolts, nuts, and washers, in accordance with manufacturer’s instructions, and as shown on drawings.

C. Install transformers with manufacturer's recommended clearance from wall and adjacent equipment for air circulation. Minimum clearance shall be 150 mm (6 inches).

D. Install transformers on vibration pads designed to suppress transformer noise and vibrations.

3.2 ACCEPTANCE CHECKS AND TESTS

A. Perform tests in accordance with the manufacturer's recommendations, and as required below:

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1. Visual Inspection and Tests:

a. Compare equipment nameplate data with specifications and approved shop drawings.

b. Inspect physical and mechanical condition.

c. Inspect all field-installed bolted electrical connections, using the calibrated torque-wrench method to verify tightness of accessible bolted electrical connections.

d. Perform specific inspections and mechanical tests as recommended by manufacturer.

e. Verify correct equipment grounding.

f. Verify proper secondary phase-to-phase and phase-to-neutral voltage after energization and prior to connection to loads.

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