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VTI UDS Series - Unitized Distribution Substation

Standalone Power Distribution Unit

• Features
• Options
• Photos
• Documents
• Specifications
• Ordering
• UDS Design Guide

The VTI Unitized Distribution Substation (UDS) is a versatile, proven and unique solution to electrical power distribution problems in industrial plants and buildings with requirements that cannot be met by the local power grid. The UDS is designed to provide electrical power distribution for industrial plants, commercial buildings, instrument loads, outdoor lighting or any other general purpose power distribution application. It is also used in typical Power Distribution Unit (PDU) applications such as communication facilities and data centers.

One unit provides all the components necessary for distribution of electrical power in an efficiently designed standalone enclosure, including a power distribution transformer, a current limiting disconnect device in the transformer secondary, and a panelboard for individual branch circuit breakers.

VTI's UDS's are engineered, fabricated, assembled, factory wired, quality controlled and tested on-site at VTI and shipped to the customer's site for easy installation. They are all UL or CUL labeled.

Limitless variations in power inputs and outputs are possible by selecting among the many available options for the UDS, which include primary disconnect devices, lighting contactors, weatherproof enclosures and K-rated transformers, among many others.

An integral part of the design criteria is to provide the appropriate ventilation for the transformer heat, in order for the transformer to be mounted internally in the UDS. This is accomplished by the rear chimney design which allows the transformer heat to bypass the distribution equipment and safely dissipate through the top of the cabinet.

All compartment doors are mechanically interlocked with the secondary disconnect switch handle so that the internal access is restricted until power is disconnected or "screwdriver override" is activated. The panelboard wiring compartment is especially spacious to allow easy top access for wire pulls and convenient connection of field wiring to the branch circuit breakers. The net result is an easy to order, easy to install, all in one, UL Labeled power distribution system meeting OSHA and NEC electrical standards.

UDS Advantages

The UDS offers the following advantages in electrical power distribution applications:

• Cabinet includes everything from one vendor
• Easy to install; connects to a 480V source
• Easy to wire; large spacious wire ways for load connections
• Completely factory wired and tested
• Interlocked compartment doors for safety
• Meets NEC requirements
• Field labor installation savings due to reduced installation time
• Additional savings acheived in reduced design, purchasing, and material handling
• Electrical and assembly drawings can be provided by electronic file

Please see our UDS Cost Comparison for a detailed cost/benefit analysis of a UDS installation.

Features

The UDS is designed with the following standard safety and convenience features:

• Free standing, totally enclosed, unitized structure
• Welded, heavy gauge steel construction
• Internally mounted transformer
• Separate compartmentalized secondary main breaker or fused disconnect switch with external lockable operator handle
• Rear chimney design allows the transformer heat to ventilate through the top of the cabinet, bypassing the distribution components
• 42 circuit, 3 or 4 wire, 225 Amp Panelboard for dead-front mounted plug-on or bolt-on circuit breakers
• 480 Volt primary wires isolated through factory installed internal conduit
• Separate power compartments isolated from one another (transformer, current limiting disconnects and circuit breaker panelboard)
• Extra large field wiring compartment
• Mechanically interlocked compartment doors with "bypass" mechanism to prevent entry by unauthorized personnel
• Key locked door for access to branch circuit breakers
• Recessed panelboard to allow individual circuit breaker lockout while remaining branch circuits are operating with panelboard door closed
• Cirrus grey enamel finish
• Lifting eyes for easy handling
• Factory wired, quality controlled and tested
• Meets all OSHA and NEC safety and electrical standards and is UL Listed and CUL (Canadian UL) Approved as a complete system.
  

Options

Units can be configured to meet specific customer requirements from the following options:

Transformer sizes:

1 Phase: 15, 25, 37.5 KVA
3 Phase: 15,30,45,75 KVA

Transformer Voltages:

1 Phase - 480 or 600V to 240/120
3 Phase - 480 or 600V Delta to 208V/120V Wye
3 Phase - 480 or 600V Delta to 480V/277V Wye
3 phase - 415/50Hz Delta to 415/240V Wye

Primary Disconnect:

Fused Disconnect Switch or
Main Breaker; Lockable Operator Handle

Secondary Disconnect:

Fused Disconnect Switch or
Main Breaker; Lockable Operator Handle

Panelboard:

Branch Circuit Breakers up to 42 positions,
selectable 1, 2, or 3 poles from 10 to 100A.

Enclosure: [NEMA Enclosure definitions]

NEMA 1 (General Purpose, Indoors) - 88.5"H x 27"W x 20"D
NEMA 12 (Dust tight) - 88.5"H x 27"W x 20"D
NEMA 3R (Weather tight) - 84"H x 27"W x 26"D
NEMA 4 (Water tight) * - 84"H x 27"W x 26"D

* The transformer compartment is vented for cooling

Single Phase Transformer Rating	Primary Protection Device Size	Secondary Protection Device Size	Contactor Rating ( * )
15KVA	40A - 480V 35A - 600V	80A - 240/120V	70A
37.5KVA	100A - 480V 80A - 600V	200A - 240/120V	175A

Three Phase Transformer Rating	Primary Protection Device Size	Secondary Protection Device Size	Contactor Rating ( * )
15KVA	25A - 480V 20A - 600V	50A (208Y/120V) 25A (480Y/277V)	50A 20A
30KVA	45A - 480V 40A - 600V	100A (208Y/120V) 45A (480Y/277V)	110A 40A
45KVA	70A - 480V 60A - 600V	150A (208Y/120V) 75A (480Y/277V)	175A 60A
75KVA	125A - 480V 100A - 600V	250A (208Y/120V) 125A (480Y/277V) (Main Breaker only)	225A 100A

Other Options

Many additional options are available to meet electrical engineering specifications and customer requirements:

• A current limiting disconnect device (circuit breaker or fused disconnect switch) on the transformer primary side.
• An electrostatically shielded transformer for instrument loads.
• 80°C rise transformer
• Transient Suppression Network
• A NEMA 12, Modified 3R or 4X enclosure
• A Circuit Breaker Lockout Kit for padlocking Branch Circuit breakers in the "off" position.
• A lighting contactor with HOA switch for photocell or timer-controlled night lights.
• Isolated Copper or Aluminum Ground Bar
• All-copper lugs, neurtal and ground bus
• GFI or EPD style circuit breakers
• Flush mounting trim
• Bottom entry for customer load connections
• Dual 42 position panelboards, providing potential for up to 84 circuits per unit.
• IEC Panelboard with branch circuit breakers

Transformer Options include:

• Copper or Aluminum Windings
• K-rating
• 80°C and 115°C rise

VTI can accomodate many more options than are listed here. See the Ordering Information below, or contact us for inquiries or more information about UDS options.

Specifications

Power Dissipation

The following power dissipation rates are based on a UDS with the following configuration:

• Standard (non K-rated) HEVI-DUTY NEMA Type TP-1 Energy Star compliant 3-phase transformer rated for 480V Primary and 208/120V Secondary with a 150°C Rise, fully loaded
• SquareD NQOD Panelboard populated with 42 1-pole, 20A Type QO circuit breakers

KVA Rating	Phase	Power Dissipation (Watts)
15 KVA	3	606
30 KVA	3	921
45 KVA	3	1203
75 KVA	3	1647

Photos

Documents

The following materials are available:

• UDS Operations Manual  (15K)
• Sample Panel Schedule Format  (30K)
• UDS Dimensional Drawing  (35K)
• Typical Sample UDS Specification  (272K)
• Section 16000 Specification for UDS  (52K)

Ordering Information

VTI can modify the UDS in many ways according to a customer's needs. We recommend our online UDS Design Guide, which will allow you to configure UDS units to your own specifications, and will automatically generate a written quote, including pricing. Registration for this service is easy and free, and includes access to Design Guides for our other products as well.

You are also welcome to contact VTI directly for questions or to discuss ordering if you prefer.

UDS Model Number Construction Guide

VTI uses a systematic method to construct descriptive Model Numbers for the UDS. These model numbers include complete specifications on any unit and are suitable for inclusion in your Request for Quote, Project Plan or other documents. To build a model number for a UDS, please use the following guide:

where the components of the model number include:

disconnect	FD (Fused Disconnect) MB (Main Breaker)
KVA	1Ø : 15, 25 or 37 KVA 3Ø : 15, 30, 45 or 75 KVA
CU	enter CU if copper transformer only.
phase	1 Phase or 3 Phase
voltage	1Ø : 240 or 480 Volt 3Ø : 480, 600 or 480/277 Volt
option list	enter comma-separated list of option codes (see below)

add multiple suffixes as required to the end of the Model Number:

Option Suffixes
PD	Primary Non-Fused Disconnect	K4	K4 Transformer for Typical Non-Linear Load
PB	Primary Breaker	K13	K13 Transformer for more severe Non-Linear Load
PFD	Primary Fused Disconnect	80C	80°C rise transformer
CBL	VTI Circuit Breaker Lockout Kit	IGBCU	Isolated Ground Bar, Copper
ST	Shielded Transformer	IGB	Isolated Ground Bar
LCT	Lighting Contactor (must specify Amps and # of poles)	ACU	All Copper Lugs, Neutral and Panelboard Bus
HOA	Hand-off Auto switch for Contactor	4X	Modified NEMA 4 Enclosure (must specify corrosion type: SST, AL or Corrosion Resistive paint)
CP	Copper Panelboard bus only	3R	NEMA Type 1 NEMA 3R Constructed Enclosure
BE	Bottom Entry	GBCU	Ground Bar, Copper
FMT	Flush-Mounting Trim panel	GB	Ground Bar (aluminum)
2X42	Dual 42 Circuit Panelboards (34" Enclosure Only)	RF	Rejection Fuses

Example:
a 3 phase UDS with a Main Breaker (MB), 30KVA Transformer (30), a 480V secondary (480), the Circuit Breaker Lockout kit (CBL), an Isolated Ground Bar (IGB), and an enclosure conforming to NEMA 3R (3R) would have the model number:

Note: all UDS's come with a 42-circuit panelboard. Please specify the quantity and size of branch circuit breakers required when placing an order. You may download a sample Panel Schedule format from this site.

Please note that our online UDS Design Guide will automatically generate these model numbers for you, as well as provide a written Quotation for any number of UDS units, including pricing. You are welcome to Register for VTI Technical Services now to use this service. You will then have access to the UDS Design Guide as well as Design Guides for other products.