approved contractor construction e-guide · single-phase transformer ... clark public utilities —...

Approved Contractor Construction e-Guide

Residential | Commercial

Clark Public Utilities PO Box 8900

Vancouver, WA 98668

TABLE OF CONTENTS

PAGE

Trenching 3

Wire 8

Single-Phase Transformer Set 13

Secondary Pedestal 36

Lighting 42

Metering 45

Three-Phase Transformer Set 55

Padmount Transformers 60

Single-Phase J-Box 62

Three-Phase J-Box 64

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Clark Public Utilities — Commercial Electric Service Handbook

Chapter 3: Commercial Underground Services / January 2011 � 17

Transformer location and access

Underground electrical facilities must be readily accessible by the utility duringconstruction and for future operation and maintenance. The area around padmounted electrical equipment must provide a clear and level working spaceand remain free from obstructions such as landscaping, poles, retaining walls,structures, fences, etc.

All transformers and padmounted equipment are to be located:

� Within 10 feet of a drivable surface but not closer than 5 feet (Figure 3).

� With the front of the equipment (door and lock side) facing toward the drivablesurface.

� With the transformer pad parallel to the edge of the drivable surface.

� Allowing 10 feet of clearance in front and 3 feet from the back and sides of theequipment (Figure 3).

� At least 2 feet from a sidewalk for pedestrian safety.

Figure 3 Commercial padmounted transformer location and access

drivable surface

VIEW FROM ABOVE

curb

transformer

3 ft. minimum of clear working spacefrom back and sides

5 ft. minimum to 10 ft. maximum of clear working space from drivable surface to front of transformer pad

edge of transformer pad

position transformer with door and lock facing the drivable surface

2 ft. minimum of clear working space from a sidewalk to front of transformer pad

sidewalk

door and lock

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18 � Chapter 3: Commercial Underground Services / January 2011

Transformer safety clearances

Clearances from padmounted transformers to structures are measured from the nearest metal portion of the transformer to the structure or any overhang. The clearance from a building is 10 feet if the building has combustible walls, and 3 feet if the building has non-combustible walls as shown in Figure 4. Table 4 provides additional safety clearances that apply to any oil-filled electricalequipment.

non-combustiblestructure and roof

combustiblestructure and roof

20 ft.

10 ft.

10 ft. minimum

operable windowor other opening

door or other opening

gas meter

transformer

transformer

transformer

hydrant

fuel dispensingfacilities

fireescape

10 ft.

10 ft.

10 ft.

10 ft.15 ft.

6 ft.

fuelstorage

3 ft.

min.

3 ft.

Figure 4 Commercial padmounted transformer minimum safety clearances

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20 � Chapter 3: Commercial Underground Services / January 2011

� If the distance between the corner posts exceeds 5 feet, a removable center post is required (Figure 5).

� If a removable center post is installed, the threaded joint requires treatment with an anti-seizing agent.

� Paint exposed section of post “traffic yellow.”

Figure 5 Guard post (bollard) installation for commercial transformers

FRONT VIEW

VIEW FROM ABOVE

3 ft.minimum

18 in.minimum

on 45°

removable center post,as required

2 ft.

domed concrete

FINAL GRADE

4 in. galvanized/steel pipe,

concrete filled

4 in. galvanized/steel pipe,

concrete filled

concrete fill

removable center post,as required

coupling

do not fillcenter post

with concrete

edge of transformer pad

commercial transformer

door and lock

edge of transformer

NOTE: Additional guard posts may be required at back and sides of transformer.

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Clark Public Utilities — Residential Electric Service Handbook

Chapter 3: Underground Secondary Services / February 2010 � 17

FRONT OF

TRANSFORMER####

use the utility providedwhite paint mark to position trench

(or use transformer lock if mark is not shown)

leave 8 ft. tail of triplexwire at transformer

NOTE: Clark Public Utilitiespersonnel will route wireinto energized facilities.

NOTE: Clark Public Utilitiespersonnel will route wireinto energized facilities.

2 ft.

secondary trench to secondary pedestal

secondarytrench topadmounttransformer

conduit aimed atcenter of pedestal

(leave 2 feet between end of conduit and pedestal)

transformer lock

transformer number

bushing required,do not permanently

attach to conduit

24 in.trench depth

18 in. minimum coverto top of conduit

8 ft. of makeup wire

2 ft.

6 in.

view from side

view from back

2 ft. to 2-1/2 ft. open

Figure 7 Typical secondary trenches to underground utility sources

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Clark Public Utilities — Residential Electric Service Handbook

Chapter 3: Underground Secondary Services / February 2010 � 13

CHAPTER3Underground Secondary Services

Preparing for the installation

Typically, an extension of secondary 120/240 volt electrical service is all that isrequired if less than 200 feet of secondary voltage wire is needed to connect the meter socket to a transformer. For homes with large motor loads such as multiple heat pumps or dryers, air conditioning units, etc., this distance may beless. All single-family residences not located within 200 feet of existing primaryrequire an underground primary line extension to place a transformer closer to the structure. See Chapter 4, Primary Line Extensions, for more information onthis type of installation.

The following checklist will assist in preparing a project for the installation of secondary underground electric service. After these items have been completed,Clark Public Utilities will connect the service and set the meter (Figure 4).

dig out and expose back of

pedestal

conduit aimed atcenter of pedestal

bushing required,do not permanently

attach to conduit

24 in. radius,2 in. schedule 40,90 degree elbow

3 in. schedule 40 PVC

2 in.schedule

80 PVC

meter base(ground per NEC)

24 in.trench depth

8 ft. ofmakeup wire

secondarypedestal

6 ft. maximum5 ft. preferred5 ft. minimum

serviceentranceequipment

18 in. minimumicover to topiof conduit

2 ft. to 2-1/2 ft. open

6 in.

3 in. to 2 in.schedule 40reducer

Figure 4 Typical underground secondary service

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70'

70'

100'

140'

400'

200'

160'

200'

300'

150'#10 WIRE @ .009989 OHM PER 10'

75'

80'

100'

60'

200'

0.5374

0.3386

0.418

0.4974

0.458

0.4206

0.1808

0.2108

0.2208

0.2608

0.461

0.1708

0.1408

0.1808

0.2208

0.243

120'

250'

0.002

0.3786

0.17216

0.2198

0.28332

0.009

0.05

DISTANCE CHART

SOLID STATE METER

TOTAL WIRE DISTANCE

#12 WIRE @ .01588 OHM PER 10'

0.002 <MISC>

ADD ELECTRICAL MECHANICAL

150'

0.009 <TEST SW>

0.132

0.1798

100'

125'

35'

50'

0.01

CT TO METER DISTANCE

Meter Department Pre-Made Wire Bundles All are solid copper wire

1∅ Potentials #14 gauge Black, Green, W hite Currents #12 gauge Blue, Yellow, Brown 3∅ Potentials #14 gauge Black, Green, W hite, Orange Currents #12 gauge Blue, Yellow, Brown, Red Note: Maximum distance for #12 current wire is 35 feet one way to meet burden of 0.2 on rating factor 4 C.T.’s. For C.T. conduit run over 35 feet use #10 current wire to a maximum of 60 feet for a burden of 0.2. If a longer conduit run than 60 feet is unavoidable – see meter department for C.T. and burden chart’s and C.T. sizing.

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Clark Public Utilities Metering RequirementsCommercial Applications

Circle AW part numbers are for cross reference only. All Commercial current transformer cabinets shall have hinged doors.

CURRENT TRANSFORMER CABINET DIMENSIONS, CT MOUNTING BASE

See EUSERC Spec – 328B & 329B Over 800 Amps Switchgear Required Maximum wire size 600 MCM per lug or parallel per EUSERC SPEC. & UL label Rev 4: Changed blocks with a *.

Source Voltage

Ampacity Reference Circle AW Part Number

Meter Diagram Numbers

Number of Terminals

Bypass Provision Required

Test Switch Required

120 Volts 1∅ 2 Wire

0-100 Amps

U121314* MD01 4 Yes No

120/240Volt 1∅ 3Wire

0-200 Amps

U264 MD02 4 Yes No


0-400 Amps

324N, 324NF

MD03 4 Yes No


Over 200 Amps

12146 MD10 MD11

6 No Yes


0-200 Amps

124TB MD02 MD05 Dmd

4 Yes No


Over 200 Amps

12146 MD10 MD11

6 No Yes

120/208Volt 3Wire Network

0-200 Amps

125TB MD04 5 Yes No

120/208Volt 3Wire Network

Over 200 Amps

12148 MD12 8 No Yes

240Volt 3∅ 3Wire Delta

0-200 Amps

125TB MD06 5 Yes No

120/208Volt 3∅ 4Wire Wye

0-200 Amps

127TB MD07 7 Yes No


Over 200 Amps

121413 MD13 13 No Yes

240/120Volt 3∅ 4Wire Delta

0-200 Amps

127TB MD08 7 Yes No

240/120Volt 3∅ 4Wire Delta

Over 200 Amps

121413 MD14 13 No Yes


0-200 Amps

127TB MD07 7 Yes No


Over 200 Amps

121413 MD13 13 No Yes


0-200 Amps

125TB MD06 5 Yes No


Over 200 Amps

12148 MD12 8 No Yes

Amperes Dimensions Circle AW or Equivalent 200 Amps- 400 Amps 1∅ 24” X 30” X 11” 6019-HAL (LUG LUG) 401 Amps- 800 Amps 1∅ 30” X 36” X 11” 6019-HEL (LUG LUG) 200 Amps- 400 Amps 3∅ 30” X 36” X 11” 6019-HAL or 6067-HAL 401 Amps- 800 Amps 3∅ 36” X 48” X 11” 6019-HEL or 6067-HEEL

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Clark Public Utilities Metering Requirements Residential Applications

Circle AW part numbers are for cross reference only.

CURRENT TRANSFORMER CABINET DIMENSIONS, CT MOUNTING BASE

* Optional Notes: 1. CT Metering for 200- 400 Amp panels required pre-approval from Clark Public Utilities 2. All CT cans shall be mounted outside. Rev 2: Add optional CT cabinet dimensions and notes.

Source Voltage

Ampacity Reference Circle AW Part Number

Meter Diagram Numbers

Number of Terminals

Bypass Provision Required

Test Switch Required

120 Volts 1∅ 2 Wire

0-100 Amps

011 MD01 4 No No


0-200 Amps

204, U204 MD02 4 No No


0-400 Amps

324N, 324NF

MD03 4 Yes No


Over 400 Amps

UO11, 011, 925 or 926

MD09 MD11A

5 or 6 No No

Amperes Dimensions Circle AW or Equivalent 200 Amps- 400 Amps 1∅ Window 24”h X 32”w X 9”d PED *401 Amps- 800 Amps 1∅ Buss Mt. 24”h X 30”w X 11”d hinged door 6019-HAL (LUG LUG) 200 Amps- 400 Amps 3∅ Window 30”h X 36”w X 11”d PED *401 Amps- 800 Amps 3∅ Buss Mt. 36”h X 48”w X 11”d hinged door 6019-HEL (LUG-LUG)

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Chapter 4: Commercial Metering / January 2011 � 33

1 in. electrical conduit

FINAL GRADE


30 in. wideconduit35 ft.

maximum

11 in. deep

36 in.tall

18 in. minimum

hinged door required,hinges on opposite

side of CT enclosurefrom meter socket

permanent load andline identifying labels

corresponding toappropriate connections

groundper NEC

groundper NEC

Load

Line

Test Switch

CT mounting base

Installation requirements for current transformer mounting bases are as follows(Figure 9):

� Mounting base is rated for a minimum of 50k amps fault current.

� Line and load side terminations require two bolts per connector and two bolts on the neutral bus.

� The customer furnishes all lugs and terminates both load and line side conductors to the bus.

� A 4-wire delta service requires orange marking of the high leg.

Switchboard metering

Switchboard metering is required for three-phase services over 800 amps. At the customer’s option, this type of metering may be installed for services sized 201 to 800 amps. The customer-installed equipment must be EUSERC-approved.

Figure 8 Typical 401–800 amp single-phase current transformer (CT) metering

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34 � Chapter 4: Commercial Metering / January 2011

N

CT

7 in. minimum 7 in. minimum

two CT mounting bolts,6 places typical

bus marking “CT”typical 3 locations

10–32 machinescrew and washerdrilled and tapped

into bus

insulating support

insulating barrier

5 in. minimum

1-1/2 in.

7/8 in.

3/4 in.

1-3/8 in.

1-3/8 in.

1/4 in.

8-1/8 in.

3-5/16 in.

CTCT

All customer-installed switchboards require a:

� Current transformer (CT) mounting base.

� Service section.

� Set of bus bars/links.

� Panel(s).

� Meter base with provisions for a test switch.

� Means for locking the meter enclosure with independent 24-hour access to utility personnel.

� Concrete mounting pad.

� Case ground as required per the NEC.

NOTE: Customers requiring more than 480 volts of service will have primarymetering. Ownership and maintenance agreements for primary metered serviceswill be mutually agreed upon with Clark Public Utilities.

Figure 9 Commercial three-phase CT mounting base

NOTE: For additional information see EUSERC drawing 329B.

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Chapter 4: Commercial Metering / January 2011 � 35


Multiple metered services

Commercial tenant spaces

Non-residential multiple meter installations such as ganged, modular and switch-board metering have the following requirements:

� Spacing to socket centers a minimum of 3 feet and a maximum of 6 feet abovethe finished grade or the floor of an approved equipment room (factory-builtmeter packs require meters installed at least 3 feet above the ground).

� Meter packs with more than six meters require a main disconnect per the NEC(Figure 10).

� All self-contained meter bases require a safety socket or a manual link bypass.

� Each metered service is permanently labeled. (See Multiple meter labeling section for additional information.)

� Panel covers must be secured prior to connection of the service.

Figure 10 Multiple meter socket detail

Maindisconnect

serviceentrance

disconnectrequired ifmore thansix meters

addresslabel withminimum

1 in. letters

floor or finished grade

3 ft. min.

6 ft. max.

8-1/2in.

min.

7-1/2 in.min.


hard plastic, metal or phenolic block labels with raised

or engraved lettersmeter and corresponding disconnect

labeled with unit number using minimum 1/2 in. letters

buildingmeter labeled

“HOUSE”with minimum1/2 in. letters

Bldg B

123 Clark St

100

100

200

200 300 400 500 600

300

400

500

600HOUSE

NOTE: See page 31 for meter base bypass requirements.

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