Traffic Signal Design Guidelines _draft for review_

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Traffic Signal Design Guidelines _draft for review_ Powered By Docstoc
					City of Fort Worth Transportation & Public Works TRAFFIC SIGNAL DESIGN GUIDELINES November 2008 The following guidelines shall be used for the engineering design of traffic signal installations within the City of Fort Worth. These guidelines shall be secondary to the Texas Manual on Uniform Traffic Control Devices (MUTCD), the National Electric Code (NEC), and the National Electric Safety Code (NESC). This document is intended to be a general design guideline and shall not substitute for engineering analysis and engineering design recommendations. Variations from these guidelines should be documented in the signal file. The “Traffic Signal Plan Microstation Guidelines”, symbol libraries, and sample border layouts shall supplement the “Traffic Signal Design Guidelines”. Example plan sets, specifications, and contract documents shall also be used to illustrate desired format.

I. A.

BASIC DESIGN Signal heads

Traffic signal heads should be arranged in accordance with MUTCD. Generally, two heads are used for major approach movements. A third signal head should be provided if a left-turn lane exists, and it will need a future left-turn phase. Signal heads should be mounted on mast arms unless otherwise needed for exclusive lane movements, e.g.: right turn lanes or a protected / permitted left turn where the median width is greater than 30 feet and motorist may pull outside the 20° cone of vision, then the designer should consider mounting a signal head on a signal pole up-right. Heads should be vertically aligned. Horizontally mounted alignment should only be used to accommodate visibility or utility restrictions. All signal heads should be federal yellow in color. 12-inch signal lenses shall be used in all instances for traffic signals and warning devices such as school flashers and advanced warning flashers. Light emitting diodes (LED) lamps will be used for all indications and pedestrian indications. Protected plus Permitted Left-turns: The 5-section "cluster", or “house head,” lens arrangement should be used for protected/permitted left turn movements for mast arm mountings. If a mast arm can not be provided due to the geometry of the intersection, then vertically arranged 5section heads should be mounted on pedestal poles or signal pole up-rights. A LEFT TURN YIELD ON GREEN (symbolic ball) ,R10-12, sign a or LEFT TURN SIGNAL YIELD ON GREEN (symbolic ball), R 10-21, sign shall accompany all protected plus permitted left turn signal head installations. The LEFT TURN SIGNAL YIELD ON GREEN (symbolic ball) 01/22/10 Page1 of 19

should be used when a left turn bay is provided. The LEFT TURN YIELD ON GREEN (symbolic ball) should be used for all other conditions. Protected Left Turns: One 3-section turn head should be provided for protected left turn movements. This display is composed of a red ball, a yellow arrow, and a green arrow. LEFT TURN SIGNAL (R 10-10) signs should be placed adjacent to the left turn head. Louvers are not used unless required to restrict visibility from conflicting movements. Dual Left Turns: Where engineering analysis deems it necessary to provide dual left turn movements, then a left turn head shall be provided for each left turn lane. Split Phasing: Where engineering analysis deems it necessary to split approach movements, then the left most signal head shall be a four section head. This display is composed of a solid red, a solid yellow, a solid green, and a green arrow. Pedestrian Accommodations: Pedestrian heads and push buttons should be used to permit the safe crossing of all intersection approach legs. All new signals should have ADA push buttons and signing as shown on the CFW signal standards sheets. If an approach does not have pedestrian heads, then the symbol “no crossing” (R9-3A) sign should be provided. ADA accessible wheelchair ramps should be included on all traffic signal projects where none currently exists. For new signals constructed in the CBD, the signals may have ADA push buttons. For the CBD, the typical standard is to install poles without push buttons and to place the pedestrian phases on recall. However, depending on the area development, ADA push buttons may be considered. Back plates: Generally back plates should only be used and maintained in the following cases:  At all CBD intersections;  On State maintained intersections where traffic signal plans specifically call for back plates;  Where needed as determined by the Engineer to provide good visual contrast. B. Cabinet Placement

Signal cabinets should be located for convenient access by signal maintenance staff. The cabinet location should have reasonable access by signal technician vehicles with minimal blocking of travel lanes. If possible, the cabinet should be located near the power source, off-street parking, or on the departure side of the intersection. Location should also be sensitive to vehicular movements that could hit the cabinet. The cabinet should be placed to allow personnel a view of the controller face and the detector amplifiers, and also provide a good view of vehicles at the intersection and the traffic signal indications. Cabinets should not be located in center medians or right turn islands. C. Ground Boxes


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Two sizes of ground boxes are used, small (approximately 11” x 18” opening) and large (approximately 19” x 31” opening). A large ground box is typically placed near the controller cabinet to accommodate multiple conduits. Ground boxes shall be constructed of polymer concrete in accordance with Texas Department of Transportation‟s (TxDOT) Specifications. A concrete apron should be provided around ground boxes not located in sidewalks. The apron should be 1-foot wide, 3-1/2 inches thick and have #10 concrete mesh wire or two #3 steel bars for reinforcement. D. Conduit

Three-inch conduit shall cross all legs of the intersection, leaving one spare conduit leg (having one bare # 8 ground wire ), unless otherwise approved by Traffic Services Engineer. No conduit shall be filled greater than 40% of its capacity in accordance with the NEC (a worksheet is provided in Appendix „C‟). All underground conduits shall be Schedule 40 PVC. Rigid metal shall be used for all conduits above the ground. Two (2) inch conduit should be used for electric service conductors and vehicle detector lead-ins for set back loops. E. Cable

A 20-conductor, 14-guage stranded cable should be provided from the controller cabinet to each pole foundation. A bare 8-gauge bonding conductor shall bond all the intersection‟s grounding rods together and lead back to the cabinet grounding bus. Luminaires shall be wired in a parallel circuit from the power service point around the intersection. Two #8 AWG stranded cables (one black and one white) shall run to each pole with luminaire heads by-passing the controller cabinet. At signalized intersections, luminaires are metered. F. Poles and Mast Arms

Poles should be kept out of median areas to reduce the chance of knockdowns. Poles should be located as far away from the back-of-curb as possible given the available right-of-way and existing utility conflicts. Where possible, poles should be located near the intersection of sidewalks to provide easy access to the pedestrian push buttons. Mast arms shall be long enough to extend over the center of the left most approach lane. Street light heads are typically used at all four-corners to provide a high level of illumination. All signal design plans shall include street light installations and removals if the project requires modification to the existing street light system. Caution should be taken to ensure that NESC spacing requirements to overhead electric lines are not violated. A mast arm stabilizer (harmonic dampening device) is required on all arms greater than 36 ft in length.


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All poles and mast arms shall be supplied by the City for City projects that include traffic signals. This includes developer driven projects. However, in these cases, the contractor or developer must purchase these items from the City. Surface Treatments: Typically, poles are left with the natural galvanized surface. Older nongalvanized steel poles are painted aluminum color. In certain locations, a special paint color may be required on all signal pole hardware as noted below:  Cultural District area: Cultural District Green;  CBD and the Fossil Creek area: Urbanscape Brown;  Stockyards area: Brick Red. G. Controllers and Cabinets The Type 170 controller shall be used at all intersections. Two types of 170 cabinets are used: tall cabinets (332) and short cabinets (336). The 332 cabinet is used as the primary type of signal cabinet. Both cabinets can perform 8-phase fully actuated control. The 332 cabinet can accept more loop detectors and has more internal room. The 332A cabinet with the auxiliary load bay is typically reserved for diamond interchange locations, intersections with more than five approach legs, or intersections with other special phasing considerations. A 332 cabinet should be used for all locations using video detection. The 336 cabinet is used at locations that require a pole mounted cabinet, “T” intersections, or intersections with unique geometric conditions where a limited number loops or phases are required. All controller and cabinet assemblies shall be supplied by the City for City projects that include traffic signals. This includes developer driven projects and TxDOT traffic signal projects within Fort Worth. However, in these cases, the contractor or developer must purchase these items from the City.

H. Electric Service If overhead electric service is present, then wood pole mounted service should be used, and a #6 triplex cable should be installed. If underground service is present, then pedestal service should be used, and three # 6 wires should be installed from the transformer to the pedestal service. A minimum two # 8 wires shall be used from the service meter to the controller cabinet. The service meter should be located on the same corner as the existing power source and the signal cabinet. The City will furnish all pedestal services, and the contractor or developer will purchase this item from the City for all developer driven projects in Fort Worth. I. Detection Systems

Detector design should accomplish a signal operation with minimal delay, offer safe operation, and minimize maintenance of the detection system. Types of detection systems in use currently include the following:  Inductive loop detection; 01/22/10 Page 4 of 19

 

Microloop ™; and Video detection.

Left turn lanes: A single 6‟ x 40‟ quadripole loop should be used. Right turn lanes: Detection zones may be required in right turn only lanes. Major street and minor street through lanes: Presence loops are used if vehicle speeds are less than 35 mph. Presence loops at stop bars are 6‟ x 40‟ quadripole loops with leading edge set 10 feet behind the curb line of the major cross street. (The designer should be cognizant of the loop lead-in possibly crossing a pavement expansion joint and call attention to the standard detail sheet for lop installation.) Set back loops are used for approaches of 35 mph through 45 mph. This design places the loop at the back of the dilemma zone. Setback loops are 6‟ x 6‟. Table 1 Set Back Loop Placement (Assuming a 5 second travel time) Approach Speed: Detector Set Back from (mph) (fps) Stop Bar (feet) 35 51 260 40 59 300 45 66 330 For speeds 50 mph or greater, a multi-loop design is used. This design places a 6‟ x 6‟ loop in each lane. Table 2 Multi-Loop Placement* Detector Set Back for Stop Bar (feet) 220 225 275 320 350 350 320 375 430 475 N/A 415 475 540 600

Approach Speeds (mph) 50 55 60 65 70 (fps) 74 81 89 96 103

Extension (sec) 2.0 1.2 1.4 1.2 1.2

* From Applications Manual / Detector Chapter; TxDOT- Traffic Operations Division- Traffic Management Section-Austin, Texas

Additional loop placement considerations: Check intersection or roadway for any expansion joints or change in pavement types that will affect loop detector or lead-in installation. If either of these pavement conditions exist, the loop may be split on either side of the joint. Lead-ins shall not cross expansion joints. One loop detector should be used for each lane. One loop leadin cable should be used per loop detector. If brick treatments are planned for the roadway, efforts 01/22/10 Page 5 of 19

should be made to place loop detectors in concrete base before bricks are installed, or use alternate detection systems. Loops lead-ins shall be 18 gauge, four-conductor cable that is twisted and shielded. Loop leads should be numbered according to Section 2 F. Video Detection Areas: Video detection areas should be graphically illustrated as dashed lines. In addition to the dashed lines, video detectors and loops should be labeled using a lower case “v”. Stop bar detection areas should be shown as 6‟ x 40‟ dashed rectangles, while set back loops should be shown as narrow dashed rectangles crossing all approach lanes. Both areas should be labeled. For setback detection areas, the distance from the stop bar should be given, as well as a distance to any roadside object that may assist with loop placement through the video monitor. The City shall furnish all VIVDS for City signal projects, and the contractor or developer shall purchase this item from the City for all developer driven projects in Fort Worth. J. Phasing

All phasing should be according to the City‟s Traffic Signal Operations Guidelines as summarized below:  Each intersection approach should be phased individually for greater operation flexibility. Concurrent movements should be accomplished through controller functionality rather than field wiring.  The engineer should strive to use the minimum cycle time phasing. Left turn phasing should be used if justified by engineering analysis.  Protected/permitted left turn phasing should be used unless sight restrictions are present, or a combination of opposing travel speeds and intersection width require the use of protected only phasing.  Protected only left turn phasing should be used when there is poor visibility of oncoming traffic. The poor visibility may be caused by extra wide medians or vegetation. It should also be used at intersections with dual left turns or when left turning vehicles are opposing three or more lanes of traffic traveling at least 40 mph.  Lagging left turn phasing may be used for dual left turns operating in actuateduncoordinated mode. If an intersection has two opposing movements with dual left turns, then the approach with the larger volume should lag.  Phasing should be designed to match traffic movements at the intersection. The use of phasing schemes that vary by time-of-day is acceptable.  Right Turn Overlap phasing may be used for exclusive right turn lanes.  For CBD locations, one-way pairs shall be two-phase operations with the east/west street designated as the primary street and the north/south street being the cross street. K. Signal Operation

Coordination: Coordination is implemented if a coupling analysis shows benefit based on traffic volumes and intersection spacing. Coordination groups may vary by time of day and day of week based on link volumes.


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Diamond Operation: All diamond intersections should use 3-phase (Figure 3) and/or 4-phase (Figure 4) operating schemes. Phasing schemes with NEMA phasing and overlaps, or split ring operation may also be used if warranted using computer models, such as Synchro or PASSER. Connection to Traffic Signal System: All new and reconstructed traffic signals should be connected to the QuicNet traffic signal system. Interconnect by the use of CATV drops shall be part of any new or rebuilt installation outside the CDB area. Within the CBD area, dedicated cable should be installed. L. Pavement Markings

All signalized intersections will have parallel bar crosswalks. Crosswalk markings are 12” wide solid white lines that are a total width of 10‟, although the crosswalks can be a minimum of 6‟ wide if field conditions warrant it. Stop bars are 18” wide solid white lines. Other markings may be necessary. M. Emergency Vehicle Preemption (EVP) OpticomTM equipment should be used as the standard for EVP. All new and major reconstructed signals will include OpticomTM equipment on all approaches. N. Reconstructed Signals All reconstructed signals, shall include the removal and salvage of existing signal equipment which shall be removed after the proposed signal has been activated. All foundations shall be removed 2‟ below grade. The replacement surface should match the adjacent material. Ground boxes shall be removed and disposed of by the contractors, who will backfill the excavated area to a grade that shall match the surrounding area. The existing conduit runs and inductive loops shall be abandoned, and the cable shall be removed and disposed by the contractor.

II. A.

DESIGN PLANS Plan Preparation

Prior to the submission of any reports or plan sets, the engineer must attend an on-site field meeting with the City’s traffic signal design staff. All pertinent utility locates should be contacted by consultant and visibly marked. Each traffic signal design set will include a short report, which includes the traffic signal warrant study, the existing/proposed conditions descriptions, a photo-log of intersection approaches, the recommendations for signal design, including illumination, an existing conditions layout that may include removal items, and the preliminary layout that includes cabinet, pole, mast arm, and service placements. This report will be completed prior to the submission of the traffic signal construction plan sets and is considered the 30% submittal.


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The traffic signal construction plan set should consist of at least 4 sheets (existing conditions layout, traffic signal design layout, signs & markings, and sidewalk ramps) per location showing the maximum amount of roadway geometry allowed by an 11” X 17” sheet or a half size plan set for both major and minor approaches. The sheet must use a landscape orientation and the major approach must be on the long side of the 11” X 17” sheet. The scale to be used for all sheets will be 1” = 50‟ unless otherwise approved by the City‟s Signal Design Staff.   Existing Conditions Layout showing existing conditions, including traffic signal or flasher equipment, and utilities. Traffic Signal Design Layout (per intersection) showing existing utilities (utility poles, street lights, storm drains, fire hydrants, etc.), permanent traffic signal poles and mast arms, pedestrian signal poles, pedestrian signals, push buttons, controller cabinet assemblies, signal heads, street lights, detector loops or other detectors, conduit, ground boxes, power sources with distribution to signal service, communications connections, wiring diagrams, pavement markings, signal phasing plan, Opticom equipment, conduit and cable chart, pole summary chart, phasing sequence, pole details, pole locations diagram, and all other items required for the complete construction of the signals. Signs and Markings Layout (per intersection) showing all existing and proposed signs, and showing all existing and proposed pavement markings. This sheet shall include estimates of the materials required, including a sign quantities table and a markings quantities table, to complete the work proposed on the sheet. If significant signs and markings changes are proposed, then a signs and markings removal sheet should also be included. Sidewalk Ramp Layout (per intersection) showing existing and proposed sidewalks, 4‟ x 4 (minimum) landing pads, ramps, and any concrete removals. The sheet shall include a table summarizing the estimated yards of concrete required to complete the proposed work.



Three additional sheets may be required based on the existing intersection conditions and engineering recommendations:    Geometric Modifications Layout showing intersection improvements and demolition items such as roadway and/or driveway modifications. Minor improvements such as cutting back a median nose may be included on the Sidewalk Ramp Layout sheet. Signal Removal Layout showing signal, flasher, or street light equipment that is to be removed from the intersection. Interconnect and Service Layout showing existing and proposed interconnect and service

All plans shall be produced in MicroStation format. These plans must be compatible with the CAD software version used by the City‟s Signal Design staff. Do not use any reference files for electronic plan submissions. In addition, the plan sheet checklist included in Appendix A must be included with every plan submission.


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Preliminary plan submittals: The short report is considered the preliminary plan set and should be submitted as follows: 2 reports which include 11” x 17” sheets showing the existing conditions layout and the proposed traffic signal layout at a scale of 1” = 50. Pre-final plan submittals: The pre-final (90%, 95 %, or 99%) plans should be submitted as follows: 2 sets of 11” x 17” plan sheets at a scale of 1” = 50‟ For joint projects with other City Departments, the scale, sheet size, and border may vary according to project type. Final submittals: The final (100%) plans should be submitted as follows: 1 set of 11” x 17” Mylar reproducible; 3 sets of 11” x 17” plan sheets on bond paper; and MicroStation files on compact disk. B. Site Specific Information

The following items should be evaluated during the initial design stage & shown on plans: Street names and block numbers Street widths and dimensions Lane widths and dimensions Lane lines and dimensions from curb face Existing conduit and ground boxes Street lights and conduit Sewer lines and manholes Storm drain lines and sewer inlets Water lines and fire hydrants Other utilities overhead or Underground Telephone CATV Electric Gas Fiber Optics Other Existing signage and pavement markings Electric power source, including proposed connection C. Area Specific Information On street parking Driveways Curb & gutter Pavement edge if no curb & gutter Sidewalks Sidewalk Ramps Land use each corner Trees or other vegetation Building lines within 15‟ of curb face ROW lines dimensioned to face-of-curb Utility Poles by Owner TUX AT&T Street Lights Other Proposed electric service location Speed Limit

The engineer should note the following facilities and evaluate incorporating them into the signal design where possible:  Fire stations  Hospitals  Schools and school routes or crossings  School zones or flashers  Adjacent signalized intersections  Railroad crossings 01/22/10 Page 9 of 19


Signal Information

The engineer should make special note of, and include specific facilities for railroad interconnect to railroad cabinets. Appendix „A‟ is a check list of items that the engineer should be certain to include on the plan sheets and are clearly labeled. E. As-Built Plans

City Staff or the Design Engineer, as designated by the scope of work, may update electronic copies of the plan sheets after installation is complete. The sheets will note field changes recorded by the Inspector. Copies will be printed and labeled As-Built. Copies will be distributed to signal maintenance personnel for future reference.


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Standard NEMA phasing

The standard phase numbering scheme is shown below.

Major Street Minor Street

Ø6 Ø1 Ø8 Ø3

Ø4 Ø5

Ø7 Ø6 Ø1

Major Street

Ø7 Ø4 Ø5 Ø2

Ø2 Ø3 Ø8

Minor Street

Major Street Runs North-South

Major Street Runs East-West


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APPENDIX A: Plan Sheet Checklist

Traffic Signal Checklist
Note: Use for new, modified, or reconstructed signals Site Specific Information: Street names and block numbers Major street orientation Street widths and dimensions Lane widths and dimensions Lane lines Existing conduit and ground boxes Street lights and conduit Water lines and fire hydrants Sewer line and manholes Storm drain lines and sewer inlets Other overhead or underground utilities: telephone, CATV, electric, gas, fiber optics, other Existing signage and pavement markings On street parking Driveways Curb & gutter Pavement edge if no curb & gutter Sidewalks Sidewalk ramps Land use at each corner Trees or other vegetation Building lines within 15' of curb face ROW lines dimensioned to face-of-curb & Labeled Easements dimensioned to R.O.W. & Labeled Proposed electric service location Speed Limit Area Specific Information: Fire Stations Hospitals Schools and school routes or crossings School zones or flashers Done Comments


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Adjacent signalized intersections Railroad crossings

Geometric Design Layout: Intersection layout showing intersection improvements or demolition items Traffic Signal Design Layout:

Estimate summary Existing intersection layout, including existing signal, flasher, street light, signs, or markings that are to be removed. Poles: Specify pole type, including non-City poles utilized for signal hardware Mast arm lengths International pedestrian heads and ADA pushbutton & sign assemblies Street lights on poles Dimension locations from curb Heads: Numbers Signal faces Placement Louvers or 3M programmable lens Pedestrian heads Head size Distance between heads (show dimensions) Detectors: Phase & detector number Dimensions Distance back from stop for setback detectors Detection system type : loop, video, or others Detector Type: presence, setback, split-loop, calling, queue Other Notations: OpticomTM Service location Interconnect notes


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CATV cable drop North arrow Scale bar Title block Existing and proposed traffic signal legend Location number Drawing number Tables & Diagrams Summary of Conduit and Cables Table Summary Pole Table Signal Pole Locations Diagram NEMA Phasing Diagram Close-up details for each signal pole Signs & Markings Design Layout: Stop bars Lane buttons Left turn signs and arrows (no pavement markings except dual left turns) Right turn signs and arrows Other signs and markings as necessary Sign Quantities Table Markings Quantities Table Sidewalk Ramp Design Layout: Proposed sidewalk ramp locations Proposed sidewalk (infill) locations Existing sidewalk ramps to be removed Concrete quantities summary table Traffic Signal Detail Sheets: Miscellaneous Traffic Signal Details Ground Box And Detector Details Type 170 Cabinet Installation Details Electrical Service Details Electrical Service Details: Pedestal Service Wiring Connections Details Traffic Signal Pole Foundation Details Sidewalk Ramp Details Traffic Control Plan Details Typical Street Construction Details


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Typical Pavement Markings Detail Sheets Typical Pavement Markings Detail Sheet 1 of 3 Typical Pavement Markings Detail Sheet 2 of 3 Typical Pavement Markings Detail Sheet 3 of 3


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LEVEL Note: Curb=





1 1 2 2 2 2 2 2 2 2 2

0 0 51 51 51 51 51 51 15 15 114

0 0 0 0 0 0 0 0 0 0 0

0 0 1 1 1 1 2 1 1 0 2 0-1 0 1 0 0 0 1

N/A " " " " " " " " " " "

2 2 0 Note: use gray scale for utilities & label @ 3"oc 3 3 GAS (0) 3 37 1 3 80 TEL (0) 3 3 4 4 5 6 6 6 7 8 80 80 96 80 6 112 0 37 1 0 phantom 0 0 0 0 0 0 E (0) 0

(cell) NA


1 1 1 0 0 1

7 (cell) (cell) (cell)


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Import Aerial font from Micro Soft to Micro Station 9 80 0




2 0R 3

12 12 12

0 1 0

0 0 0

1 1 1

(cell) (cell) (cell)

12 12 12 12

0 2 0 0

0 0 0 0

1 1 1 1

(cell) (cell) (cell) (cell)


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Cable Type

Size Diameter AWG # 10 # 10 #8 #8 #8 # 20 RG11 RG6 # 22 # 18 # 14 # 14 # 14 # 14 # 14 # 14 # 14 # 14 0.335 0.360 0.565 0.633 0.690 0.770 0.895 0.975 Total Diameter 1.000 1.250 2.000 3.000 4.000 Total


Total Area 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Total Area 0.000 0.000 0.000 0.000 0.000 0.000

Number of Cables 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Number of Conduit 0 0 0 0 0 0.000

single conductor White single conductor Black single conductor White single conductor Black Bare Opticom Cable (3 cond. Shielded) CCTV Coax CCTV Coax 4 cond. Shld. Loop Lead-in Cable 4 cond. Shld. Loop Lead-in Cable 2 cond. Shld. Loop Lead-in Cable 4 conductor 8 conductor 12 conductor 16 conductor 20 conductor 24 conductor 32 conductor

0.160 0.160 0.270 0.270 0.129 0.270 0.405 0.225

0.080 0.080 0.229 0.229 0.052 0.229 0.515 0.000 0.159 0.000 0.353 0.407 1.003 1.259 1.496 1.863 2.516 2.986

Conduit 1" 1 1/4" 2" 3" 4" If positive number, then conduit is large enough to 60% void: Notes: (1) If service is less than 400 feet use # 8 for service wire. (2) If service is between 400 and 800 feet use # 6 service wire. 01/22/10

Area 3.142 4.909 12.566 28.274 50.265

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