Section 5: Electrical ServicesAnchor: #i1002581
Item 628-Electrical Services
Item 628 contains specifications for furnishing and installing electrical services. This includes all components, including poles, service supports, foundations, anchor bolts, riprap, enclosures, breakers, service conduit (up to and including the elbow if below ground), and other associated materials that make up the electrical service equipment.
Electrical services that meet the material specifications are listed by type under Item 628 in the MPL for Roadway Illumination and Electrical Supplies.Anchor: #i1002594
Electrical services are designated in the ED standards with the codes shown in Figure 5-3.
Figure 5-3. Explanation of electrical service descriptive code.
- Anchor: #GLGOHHLP
- Schematic type refers to the wiring diagrams for electrical service Types A, C, D, or T from ED(6). Anchor: #UXKGTMKF
- Service voltage is typically either 120/240V or 240/480V single phase. Anchor: #DUVGNVVM
- Disconnect rating is the amp rating of the main breaker. Type T services have no main breaker and are designated with 000. Anchor: #MCFSVOEV
- SS is used if a safety switch ahead of the meter is required by the local electric provider. NS is used if a safety switch is not required. Anchor: #WPOLYPHG
- The service enclosure may be made of galvanized steel (GS), stainless steel (SS), or aluminum (AL). GS enclosures are only allowed as called for in DMS-11082 through DMS-11084. GS is not allowed for Type A services or for custom-built C or D enclosures. All Type T services are galvanized steel (GS). Anchor: #VUBYRKEP
- Enclosure mounted photocells (E) are mounted inside the service enclosure, positioned to receive light through a window. As an alternative, the photocell may be placed at the top of the service pole (T), or on each individual luminaire (L). Electrical services with no photocell are designated by (N). Anchor: #BGHUDTTC
- The service support types GC, OC, TP, SP, and SF are specified by DMS-11080 and the ED standards. Types OT, EX, and TS are existing or are specified elsewhere in the plans. Pedestal services PS are specified by DMS-11080, DMS-11085, and ED(9). Anchor: #QYRPQWGX
- Overhead services (OH) are fed from the electric utility to a weatherhead at the top of the pole. Underground services (UG) are fed from the electric utility through underground conduit into the bottom of the service equipment.
The ED standard sheets detail the different types of electrical services and their supports:
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- ED(5) contains general material and construction details that apply to all electrical service installations and should be included in all plan sets that have electrical services. It also contains the legend for electrical service descriptive codes. Anchor: #JSIOLGHX
- ED(6) contains schematics for electrical service Types A, C, D, and T and should be included in all plan sets that have electrical services. Anchor: #RELAWKCH
- ED(7) contains details for electrical services mounted on steel poles and steel frames. Anchor: #JAPCPBLJ
- ED(8) contains details for electrical services mounted on traffic signal poles. Anchor: #UMGOIBVD
- ED(9) contains details for pedestal electrical services Anchor: #GUDFCMNB
- ED(10) contains details for electrical services mounted on granite concrete, other concrete, and timber poles.
DMS-11080, "Electrical Services," contains the material specifications common to all electrical services specified by Item 628. This includes the circuit breakers, enclosures, labeling, control circuits, photocells, contactors, and service supports.
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- DMS-11081, "Electrical Services - Type A" Anchor: #YOPNAAEG
- DMS-11082, "Electrical Services - Type C" Anchor: #KMAYTSDF
- DMS-11083, "Electrical Services - Type D" Anchor: #SUKSPPCT
- DMS-11084, "Electrical Services - Type T" Anchor: #XFTPGTMT
- DMS-11085, "Electrical Services - Pedestal (PS)"
Type A Electrical Services
Type A electrical services are used to power lighting circuits only. All circuits are controlled by a lighting contactor and photo control. All circuits are automatically switched on during the night and off during the day. Line voltage for Type A services may be 120/240V or 240/480V.
Type A services use individual feed-through branch circuit breakers mounted to a back plate in the cabinet. Typically the maximum number of circuits in a Type A service is 4 or 5.Anchor: #i1021229
Type C Electrical Services
Type C electrical services are similar to Type A services in that they are used to power lighting circuits only. All circuits are controlled by a lighting contactor and photo control. All circuits are automatically switched on during the night and off during the day. Line voltage for Type C services may be 120/240V or 240/480V.
Type C services use a panelboard and plug-in breakers and can power more circuits than a Type A service. If more than 5 lighting circuits are needed at service, then a Type C should be used.Anchor: #i1021305
Type D Electrical Services
Type D electrical services are used to power both constant power circuits and lighting circuits. A Type D service contains a panelboard with a main breaker and several slots for plug-in type breakers. It contains a 2-pole lighting contactor and photocell that will switch one circuit on and off for lighting. Type D services are 120/240V only.
Type D services are typically used for traffic signals, where the controller requires constant power and the lights are only powered at night.Anchor: #i1021375
Type T Electrical Services
Type T electrical services are used for constant-power circuits only. It contains a load center with a maximum of 6 plug-in breaker spaces and has no main breaker and no lighting controls. Type T services are stock items from the manufacturer with galvanized steel enclosures only, and are not custom built like Types A, C, and D. Type T services are 120/240V only.
Type T services are used for signals and Intelligent Transportation Systems (ITS) locations with no lighting and a small number of circuits.Anchor: #i1021445
Pedestal services contain the electrical equipment in a pedestal enclosure rather than mounted on a pole. The pedestal is approximately 4 feet tall and may be made of aluminum or stainless steel. All conduits enter the pedestal from underground. A pedestal service may contain Type A, C, or D service equipment. Pedestal services are typically used in landscaped or pedestrian areas where a neat appearance is required.
The pedestal service contains the TxDOT service equipment in the front part of the pedestal, with the utility meter and connections in the back. The pedestal service is designed to use a standard utility kWh meter.
Electric utilities typically use a standard meter for 120/240V services, and some use a standard meter for 240/480V services. However, some utilities use a transocket to meter 480V services. A transocket has to be mounted in a separate cabinet and will not fit in the TxDOT pedestal.
If a 480V pedestal service is planned for a project, the designer should verify whether the electric utility requires a standard meter or a transocket. If a transocket will be used, it will need to be installed separately from the pedestal, or else a pole-mounted service could be used instead of a pedestal.