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SECTION 16461 - DRY-TYPE TRANSFORMERS (600 V AND LESS) PART 1 GENERAL 1.1 RELATED DOCUMENTS A.
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SECTION 16461 - DRY-TYPE TRANSFORMERS (600 V AND LESS)

PART 1 GENERAL

1.1

RELATED DOCUMENTS
A.

Drawings and general provisions of the Contract, including General and Supplementary
Conditions and Division 1 Specification Sections, apply to this Section.
1.2

SUMMARY
A.

This Section includes the following types of dry-type transformers rated 600 V and less, with
capacities up to 1000 kVA:
1.

Distribution transformers.
2.

Control and signal transformers.
1.3

SUBMITTALS
A.

Product Data Include rated nameplate data, capacities, weights, dimensions, minimum
clearances, installed devices and features, and performance for each type and size of
transformer indicated.
B.

Shop Drawings: Wiring and connection diagrams.
C.

Source quality-control test reports.
D.

Output Settings Reports: Record of tap adjustments specified in Part 3.
1.4

QUALITY CONTROL
A.

Electrical Components, Devices, and Accessories: Listed and labeled as defined in NFPA 70,
Article 100, by a testing agency acceptable to authorities having jurisdiction, and marked for
intended use.
B.

Comply with IEEE C 57.12.91.
C.

Energy-Efficient Transformers Rated 15 kVA and Larger: Certified as meeting NEMA TP 1,
Class 1 efficiency levels when tested according to NEMA TP 2.
1.5

DELIVERY, STORAGE, AND HANDLING
A.

Temporary Heating: Apply temporary heat according to manufacturer's written instructions
within the enclosure of each ventilated-type unit, throughout periods during which equipment
is not energized and when transformer is not in a space that is continuously under normal
control of temperature and humidity.
1.6

COORDINATION
A.

Coordinate size and location of concrete bases. Cast anchor-bolt inserts into bases. Concrete,
reinforcement, and formwork requirements are specified in Division 3.
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B.

Coordinate installation of wall-mounting and structure-hanging supports.
PART 2 PRODUCTS

2.1

MANUFACTURERS
A.

Manufacturers: Subject to compliance with requirements, provide products by one of the
following:
1.

Square D/Groupe Schneider NA.
2.

Eaton/Cutler-Hammer.
3.

GE Electrical Distribution & Control.
4.

Siemens Energy & Automation, Inc.
5.

Acme Electric Corporation; Power Distribution Products Division.
2.2

MATERIALS
A.

Description: Factory-assembled and -tested, air-cooled units for 60-Hz service.
B.

Cores: Grain-oriented, non-aging silicon steel.
C.

Coils: Continuous windings without splices, except for taps.
1.

Internal Coil Connections: Brazed or pressure type.
2.

Coil Material: Copper.
2.3

DISTRIBUTION TRANSFORMERS
A.

Comply with NEMA ST 20, and list and label as complying with UL 1561.
B.

Cores: One leg per phase.
C.

Enclosure: Ventilated, NEMA 250, Type 2.
D.

Indoor Transformer Enclosure Finish: Comply with NEMA 250 for "Indoor Corrosion
Protection."
1.

Finish Color: Gray.
E.

Outdoor Transformer Enclosure Finish: Comply with NEMA 250 for "Outdoor Corrosion
Protection."
1.

Finish Color: Gray.
F.

Insulation Class: 220 deg C, UL-component-recognized insulation system with a maximum of
150 deg C rise above 40 deg C ambient temperature.
G.

Taps for Transformers Smaller Than 3 kVA: None.
H.

Taps for Transformers 7.5 to 24 kVA: Two 5 percent taps below rated voltage.
I.

Taps for Transformers 25 kVA and Larger: Two 2.5 percent taps above and four 2.5 percent
taps below normal full capacity.
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J.

Wall Brackets: Manufacturer's standard brackets.
K.

Fungus Proofing: Permanent fungicidal treatment for coil and core.
L.

Low-Sound-Level Requirements: Maximum sound levels, when factory tested according to
IEEE C57.12.91, as follows:
2.4

CONTROL AND SIGNAL TRANSFORMERS
A.

Description: Self-cooled, two-winding dry type, rated for continuous duty, complying with
NEMA ST 1, and listed and labeled as complying with UL 506.
B.

Ratings: Continuous duty. If rating is not indicated, provide at least 50 percent spare capacity
above connected peak load.
2.5

SOURCE QUALITY CONTROL
A.

Test and inspect transformers according to IEEE C57.12.91.
B.

Factory Sound-Level Tests: Conduct sound-level tests on equipment for this Project.


PART 3 EXECUTION

3.1

EXAMINATION
A.

Examine conditions for compliance with enclosure- and ambient-temperature requirements for
each transformer.
B.

Verify that field measurements are as needed to maintain working clearances required by
NFPA 70 and manufacturer's written instructions.
C.

Examine walls and floors for suitable mounting conditions where transformers will be
installed.
D.

Proceed with installation only after unsatisfactory conditions have been corrected.
3.2

INSTALLATION
A.

Install wall-mounting transformers level and plumb with wall brackets fabricated by
transformer manufacturer.
B.

Install floor-mounting transformers level on concrete bases. Construct concrete bases of
dimensions indicated, but not less than
4 inches
(100 mm)
larger in both directions than
supported unit and
4 inches
(100 mm)
high.
1.

Anchor transformers to concrete bases according to manufacturer's written instructions,
seismic codes at Project.
3.3

CONNECTIONS
A.

Ground equipment according to Division 16 Section "Grounding and Bonding."
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B.

Connect wiring according to Division 16 Section "Conductors and Cables."
C.

Tighten electrical connectors and terminals according to manufacturer's published torque-
tightening values. If manufacturer's torque values are not indicated, use those specified in
UL 486A and UL 486B.
3.4

ADJUSTING
A.

Record transformer secondary voltage at each unit for at least 48 hours of typical occupancy
period. Adjust transformer taps to provide optimum voltage conditions at secondary
terminals. Optimum is defined as not exceeding nameplate voltage plus 10 percent and not
being lower than nameplate voltage minus 5 percent. Submit recording and tap settings as test
results.
B.

Output Settings Report: Prepare a written report recording output voltages and tap settings.


END OF SECTION 16461