Dry-Type Transformers 1000 Volts and Below – Instruction Bulletin PDF
43006–850–01

Section 4—Installation

Locating/Placing Ventilated and Non-ventilated Transformers

  1. Remove all packaging material. Keep the shipping pallet attached to the transformer to assist with moving the unit to its final installation location.

  2. Verify that the nameplate matches the description from the building layout drawings (kVA, primary and secondary voltages, etc.). See Sample Nameplate.

    Sample Nameplate

  3. Locate the unit per the building’s layout drawing.

  4. Verify the environment is suitable for the enclosure type.

  5. Ensure the location is readily accessible to qualified personnel (per NEC 450.13). Units located in the open can be mounted on walls, columns, or otherwise supported from structures.

  6. Ensure adequate ventilation since it is essential to properly cool ventilated transformers. Refer to National Electrical Code (NEC®) Article 450.

    • The minimum distance is marked on Nameplate NEC 450.9. See Minimum Distance Marked on Nameplate NEC 450.9.

    • Minimum distance varies by enclosure style. See the approval drawing from Schneider Electric for minimum distance.

    • Clean, dry air is desirable.

    • Filtered air may reduce maintenance if the location of the transformer presents a problem.

      Minimum Distance Marked on Nameplate NEC 450.9

  7. Mount any accessories prior to installing the transformer when using wall or ceiling (trapeze) mounting.

  8. Place the transformer in final position.

Mounting: Enclosure Styles
D, H, K, and E

Enclosure D, H, K, and E

Mounting Enclosure Style J: Ventilated

NOTE:

Units not for use on combustible floor (open bottom).

Floor Mounting Bracket: Enclosure Style K

Floor Mounting Bracket: Enclosure Style K

All Enclosure Styles (D, E, F, H, K and J)

Transformers Installed Indoors (Styles D, E, F, H, K and J):

  • Completely enclosed or completely enclosed with ventilated openings; complies with NEC 450.21 (A) Exception

  • Units greater than 112.5 k VA

  • Have 428°F (220°C) or 392°F (200°C) insulation systems; complies with 450.21 (B) Exception No. 2

See Transformers Installed Indoors: NEC 450.21 Exceptions A or B from Sample Nameplate.

Transformers Installed Indoors: NEC 450.21 Exceptions A or B from Sample Nameplate


Enclosure Clearances

Enclosure Style Front Clearance Side Clearance
(in. / mm)		 Rear Clearance
(in. / mm)
D Working Clearance for all styles vary substantially depending on voltage and specific application. Refer to NEC 110.26 0.50 / 12.7 Type EE – 3 / 76.2
All other styles – 6 / 152
H 3 / 76.2
E 3 / 76.2
K 0.50 / 12.7
J 0.50 / 12.7
F 12 / 305

Transformers can be converted from Floor to Wall mounted (See Converting from Floor to Wall Mounting (using factory kits) below and Wall Mounted Transformer) or Floor to Trapeze mounted (See Converting from Floor to Trapeze (Ceiling) Mounting
(using factory kits) and Trapeze (Ceiling) mounted transformer) using factory available kits. The kits are pre-punched to align with enclosure mounting holes; and, when the transformer is installed, holds the minimum clearance for the units. New Style K wall mounting bracket allows for 6 in. (152 mm) and 3 in. (76 mm) clearances, all other styles require a 6 in. (152 mm) clearance.

The factory kits do not include hardware, hardware must be supplied by the customer. Hardware includes the thread rod for trapeze mounting the transformers. The designer of record must size and choose the anchors and hardware because of the large variety of construction materials and techniques. Schneider Electric can not advise on the anchoring, the wall mounting, or sizing of rods for trapeze mounting.

Converting from Floor to Wall Mounting (using factory kits)

Enclosure Style Enclosure Number Maximum Weight (lb. / kg)
D 17 – 20 700 / 317
H 17 – 18 700 / 317
E 17 – 20 700 / 317
K 17 – 20 850 / 386

Wall Mounted Transformer

Converting from Floor to Trapeze (Ceiling) Mounting
(using factory kits)

Enclosure Style Enclosure Number Maximum Weight (lb. / kg)
D 17 – 24 1200 / 544
H 17 – 18 1200 / 544
E 17 – 22 1200 / 544
K 17 – 22 1200 / 544

Trapeze (Ceiling) mounted transformer

Enclosure D, E, H, K, J can be converted to Type 3R using field installed kits. See Type 3R Enclosure Kits.

Type F enclosure – must be factory order if installed outdoors.

Type 3R Enclosure Kits

Grounding

  1. Permanently and adequately ground the enclosure and core assembly of dry-type transformers in accordance with NEC requirements.

    • Windings may be grounded with consideration given to local conditions and in accordance with the NEC.

    • The ground terminal bar must be UL listed for this purpose.

    • In accordance with NEC 450.10, the terminal bar shall be bonded to the enclosure in accordance with NEC 250.12 and shall not be installed on or over any ventilated openings.

  2. Connect the transformer, related accessories and components to ground in accordance with NFPA 70 (NEC).

  3. Terminate all grounding and bonding conductors at a common equipment ground point on the enclosure.

  4. Remove paint from around the area where the ground terminal bar is mounted to increase contact with enclosure parts.

    • Enclosure Styles D, E and H: An area is available in the transformer’s base to drill and mount the ground terminal bar.

    • Enclosure Style K: Three pre-drilled holes are stamped ground to mount the ground terminal bar.

    • Enclosure Style J: Two pre-drilled holes are stamped ground to mount the ground terminal bar.

Square D brand secondary lug kits include a four-conductor ground terminal bar. The bar can also be obtained as a separate device from Schneider Electric. Refer to Square D Lug Kits for Dry-type Transformers and see Four-conductor Ground Terminal Bar.

Four-conductor Ground Terminal Bar

Seismic Qualifications

Seismic limits for dry-type low voltage transformers are obtained from tri-axle shake table test results that are conducted in accordance with the AC156 test protocol. Certifications are based on the location where units are installed and building codes governing the installation.

Building codes results are available for CBC 2001, CBC 2007, CBC 2010, IBC 2000, IBS 2003, IBC 2006, IBC 2009, NBC 2005, NBCC 2005, NBCC 2010, NFPA 5000, UBC 94, CBC 95, UBC97 and UFC 3-310-04.

Contact your local Schneider Electric distributor, or call 1-888-Square D

(1-888-778-2733) to obtain the specific level of Sds, z/h and Ip for each enclosure style.

The levels supplied are based on the units being mounted and the notes on the approval drawings of each part number. Drawings are available that include mounting dimensions, mounting hole dimensions, overall dimensions, unit weight and approximate center of gravity location to assist in a seismic qualification. Contact your local Schneider Electric distributor, or call 1-888-Square D (1-888-778-2733) to obtain these drawings.

Other parties are responsible for detailing the equipment connection and anchorage requirements (including the lateral restraint system, if appropriate) for the given transformer installation. The installer and manufacturers of the anchorage and lateral restraint system are responsible for ensuring that the mounting requirements are met.

Sound/Vibration Control

The transformer has been designed to minimize the amount of audible sound produced. Sound isolation pads are secured between the transformer mounting bracket and the enclosure using bolts and nuts. The mounting hardware is tightened prior to shipment to prevent damage.

Loosen the nut one full turn to float the transformer on the isolation pads, thereby isolating the transformer from the enclosure. This will reduce audible sound levels even further. See Loosening the Nut One Full Turn (Four Places) Label and Floating the Transformer on the Isolation Pads/Sound Damper.

Loosening the Nut One Full Turn (Four Places) Label

Floating the Transformer on the Isolation Pads/Sound Damper

In addition, the area where the transformer is located can affect the sound level:

  • Try to avoid installing the transformer in a corner, narrow hall or in an area with smooth surfaces. Doing so can result in the sound being reflected and amplified.

  • Securely fasten all the enclosure panels. Loose panels can result in rattling, thereby increasing the sound produced.

  • Use flexible conduit, if possible.

  • Ensure that the type of structure on which the transformer is mounted is strong enough to support the weight of the transformer.

Making Electrical Connections

  1. Use flexible raceways, conduits and connectors, when possible, as attachments to transformer enclosures. This will help to reduce audible noise generation.

  2. Adhere to NFPA 70 (NEC) and minimum wire bending space requirements for the transformer enclosure. As an industry standard, bundle associated phase, neutral and equipment grounding conductors together within the transformer enclosure.

  3. Always use a calibrated torque wrench to tighten electrical connectors and terminals. For additional guidance, refer to Standard UL468A.

  4. Ensure that raceways, conduits and connectors enter the enclosure only in an area shown on the drawings. Access points for each enclosure style are listed below:

  5. Keep all access points below the top terminal board to prevent heat from exiting through the raceways, conduits and connectors. The sticker will show this top location on all enclosure styles (also shown on drawings). See Label to Show Top Location on Enclosures (Access Points Below the Top Terminal Board).

    Label to Show Top Location on Enclosures (Access Points Below the Top Terminal Board)

  6. Ensure that the side access complies with NEC 312.6 (A): Minimum Wire-Bending at Terminals. Bottom access must comply with NEC 312.6 (B): Minimum Wire-Bending Space at Terminals.

  7. Follow UL 1561 which requires that all lugs be suitable for 194°F (90°C). In addition, the conductors' temperature rating table must be 167°F (75°C) for the size to meet the current requirements of the overcurrent protection device and nameplate currents. Refer to VERSAtile™ Compression Lugs and Mechanical Set-Screw Types—UL Listed Lugs AL9CU, Square D Lug Kits for Dry-type Transformers and Terminal Sizes, Mechanical and Compression Lugs and Wire Ranges for a list of Square D lug kits, wire ranges by kVA and US voltage systems.

  8. Make sure that the contact surface is clean. This will minimize the possibility of a high resistance contact which could cause localized heating and possible premature failure. Refer to Connections and Contact Surfaces for instructions to apply an approved electrical compound.

  9. Connect phases to proper terminals for proper motor-rotation. The phase diagram is shown on nameplate. The nameplate also shows the taps locations and voltage rating for each tap. See Phase Diagram, Tap Locations and Voltage Rating Marked on Nameplate.

    Phase Diagram, Tap Locations and Voltage Rating Marked on Nameplate

  10. Connecting the source of supply to the transformer secondary is permitted by NE C450.11 where the installation conforms to the manufacturer’s instructions.

    When the source of supply is connected to the transformer secondary, the inrush current will increase. The overcurrent device should be selected based on NEC 450.3(B) using the 250% allowance in order to reduce the potential for nuisance tripping during energization. Secondary overcurrent protection will be required.

    Do not make any connections to the supply side HO or XO terminals on a WYE configured transformer winding. See Caution Label for Delta Wye or Wye Delta Connected Transformers.

    Caution Label for Delta Wye or Wye Delta Connected Transformers

Pre-commissioning/Pre-energizing Checks and Testing

Cleaning

  1. Ensure that all of the packing material, including any packing material used inside the enclosure of the transformer used to support and protect the unit during shipping, have been removed.

  2. Vacuum away as much dust as possible. Dust will act as a thermal insulating material which will increase the temperature of the unit and could possibly decrease operational life. Refer to Cleaning.

Visual and Mechanical Checks

Perform the following visual and mechanical checks below. In addition, refer to Performing Visual and Mechanical Checks for a detailed listing of instructions.

  1. Visually inspect the transformer for physical damage. Repair any physical damage, if possible, and provide suitable protective barriers to prevent future damage.

  2. Compare the transformer nameplate information with the drawings and/or specifications for the installation.

  3. Verify proper connection of the taps in accordance with the nameplate information.

  4. Check the clearance of all electrical connections. Verify all connections for tightness with a calibrated torque wrench.

  5. Visually check the core, frame, enclosure, conduits, raceways and conductors for proper ground bonding. In addition, refer to Grounding and Bonding.

Electrical Testing

DANGER
hazard of electric shock, explosion, or arc flash
  • Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E. NOM-029-STPS-2011, or CSA Z462.
  • This equipment must be installed and serviced only by qualified electrical personnel.
  • Perform such work only after reading and understanding all of the instructions contained in this bulletin.
  • Turn off all power supplying this equipment before working on or inside equipment.
  • Always use a properly rated voltage sensing device to confirm power is off.
  • Always practice lock-out/tag-out procedures according to OSHA requirements.
  • Carefully inspect your work area, and remove any tools and objects left inside the equipment.
  • Replace all devices, doors, and covers before turning on power to this equipment.
  • All instructions in this manual are written with the assumption that the customer has taken these measures before performing maintenance or testing.
Failure to follow these instructions will result in death or serious injury.

Refer to Section 6—Maintenance to perform the following pre-commissioning electrical testing:

  1. Measure contact resistance using a low resistance ohmmeter. Refer to Contact Resistance.

  2. Perform insulation resistance tests with an appropriate device. Refer to Insulation Resistance.

  3. Perform a turns ratio test on all taps and on the full winding voltages for each phase. Refer to Turns Ratio.

  4. Measure and record the winding resistances on larger transformers (>500 kVA). Refer to Winding Resistance.

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