Electrical Service Entrance
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Electrical Service Entrance
This article series discusses procedures for safe and effective visual inspection of residential electrical systems including electrical panels and other components, when the inspection is conducted by trained buildinginspection professionals, home inspectors, electrical inspectors, and electricians.
A study by the author showed that very common sources of water leaks into and damaging electrical panels include frayed SEC, leaksat the top of the meter, and leaks at the building wall where the SEC passes from the bottom of a meter pan intothe building electrical panel.
TomYou'll want to take a look at the SEC wire cable sizing tables above on this page, and you'll need to specify one more detail: the panel ampacity or service ampacity of the home. You need a bigger wire for 200A or 150A than for a 100A service.
JoshThere may indeed be safety problems with your electrical panel but I cannot reliably assess them from your brief e-text. Perhaps a licensed electrician or even a home inspector (see page top EXPERTS DIRECTORY) can take a look for you, on-site, and give more useful advice.Also see ALUMINUM WIRING IDENTIFICATION _Wire_Identification.php
Jim If I understand correctly we have a 60 Amp service entry cable feeding an electrical panel that has a 100A main switch. Indeed that's improper. If all of the circuits in the panel below the main draw more than 60A the service entry cable is overloaded, could overheat, and could be a fire risk; We often see this problem when someone adds a higher capacity electrical panel (called "heavying-up" by some of my friends) without making sure that the incoming service entry cable wiring has been updated as well.Under-fusing is "safe" but inconvenient. Over-fusing is dangerous. You are describing over-fusing.
So if a tree does fall on a mast or service drop, the chart above will give you an idea who is responsible for what, but it ultimately depends on where you live and which utility company services you.
The overhead service drop conductors are spliced to the service-entrance conductors at the home. This connection is called the drip loop. The drip loop is required to keep water from traveling along the length of the service-entrance conductors and entering the service-entrance conduit at the weatherhead. Overhead service-entrance conductors are attached to service masts with clamp-on porcelain or similar nonmetallic insulators. Overhead service-entrance conductors that terminate at the side of a house, under a roof eave, or on the roof fascia board are attached to screw-in porcelain or similar nonmetallic insulators.
Electrical service masts that penetrate the roof must have a roofing boot properly secured at the roof line to prevent water leaks. The roofing boot must be properly sealed, glued and screwed flush with the roof membrane. If nails are used, they must be sealed properly. Nails can corrode over time and the membrane can split so be sure to use the right tools for the job and take the time to be sure it is properly sealed. Mast bracing must also be sealed with flashing at the roof line intersection.
The service mast must be plumb (not leaning) and properly attached to the frame of the home by installing securely fastened metal conduit straps every 3-feet. Malleable pipe straps and 4-inch lag screws in studs may sometimes be substituted. There will be a raintight threaded conduit hub where the service mast enters the top of the meter socket enclosure.
Utility companies install electrical distribution either below ground or above ground, and they make the decision on which one will be used in your installation. The long-term overall cost is less for overhead electrical distribution compared to underground distribution, but sometimes the utility will install underground distribution, but it comes with an additional installation and maintenance cost to the property owner. The location of the electric meter will be determined by the electric utility based on the size of the service, the type of service and the type of distribution equipment, such as a transformer or distribution pedestal.
Utility companies are very strict when it comes to breaking seals or removing meters. In addition to the obvious safety hazards, liability and theft of electricity are major concerns for utility companies. Always consult with the utility company before accessing the interior of the meter socket enclosure or attempt repairs to a service mast.
For those who regularly install single-family residential electrical services, the work can often seem repetitive. Resulting in a step-by-step process that leaves many with the impression that they can do the work in their sleep. And many likely could. Then there are those who do not have much experience with residential electrical services and are trying to navigate the basics of what goes into a typical installation.Whatever side of the coin you fall on, this blog has something for you.While some of the items mentioned here are long standing NFPA 70, National Electrical Code (NEC) codes and processes, there are a couple changes within the 2020 NEC that will modify how residential electrical services will be installed moving forward.
The grounding electrode system in electrical services creates a common connection between electrical equipment, grounding electrodes that are present and/or required, and the earth so as they are at the same relative potential. This helps to stabilize voltage on the system and limit the voltage that can be imposed on the system by lightning strikes and other potential surges. NEC section 250.50 states that all grounding electrodes listed in 250.52(A)(1) through 250.52(A)(7) that are present in the building or structure must be bonded together to form the grounding electrode system. The following are grounding electrodes, some with specific requirements, that are permitted by the NEC for grounding:
In conclusion, there are many consistent ways in which residential electrical services continue to be installed. Based on the ever-changing need to continually make the world a safer place, there are also changes that happen within the NEC to incorporate those needs. This blog intends to give you the most up-to-date information based on the 2020 NEC, however, it is not intended to serve as a consultation or installation instructions for any given scenario. Electrical work should always be done by professional electricians who know the local code requirements. Those same electricians also have established relationships with the Authority Having Jurisdiction (AHJ) in that area where they can reach out and get clarification if needed. It takes all stakeholders working together to keep this electrified world a safer place for all people and property.
Topaz Service Entrance electrical products provide easy access when electrical service is being established or requires maintenance. Service entrance caps are available in threaded, PVC, clamp on with split insulator and set screw type to protect service entrance cables. Meter hubs and flashings are also available so secure and protect conduit and ventilation pipes.
Looking at Fig. 230.1 in the NEC, we can see that the second and third major areas of Art. 230 provide requirements for service entrance conductors (Part IV) and service equipment (Parts V, VI, and VII).
Before you begin a service installation, determine which conductors are actually part of the service (line side of the service equipment) rather than feeders and branch circuits (load side of the service equipment).
Before applying any adjustment or correction factors, size the service entrance conductors at least 125% of the continuous loads, plus 100% of the noncontinuous loads. Base your calculations on the terminal temperature rating ampacities listed in Table 310.16 [110.14(C)].
Locate service heads and goosenecks above the point of attachment, per 230.26. Where it's impractical to locate the service head above the point of attachment, locate within 2 ft of the point of attachment [230.54(C)].
Service heads must provide a bushed opening, and ungrounded conductors must be in separate openings. Drip loop conductors must be below the service head or below the termination of the service entrance cable sheath. Arrange service drops and service entrance conductors to prevent water from entering service equipment.
The service disconnecting means must consist of either a manually operated switch or a power-operated switch or circuit breaker also capable of being operated manually [230.76]. It must open all service entrance conductors from the premises wiring of the structure [230.70].
Install the service disconnecting means at a readily accessible location nearest the point of service conductor entry (either inside or outside the structure) [230.70(A)(1)]. In a multiple-occupancy building, each occupant must have access to the service disconnecting means [230.72(C)]. However, if electrical maintenance is provided by continuous building management, the service disconnecting means can be accessible only to building management personnel.
Because service entrance conductors don't have short circuit or ground-fault protection, they must be limited in length when installed inside a building. Some local jurisdictions have specific length requirements (Fig. 2).
You can have a maximum of six service disconnects for each service permitted by 230.2, or each set of service entrance conductors permitted by 230.40 Ex 1, 3, 4, or 5 [230.71]. This is per service, not per building. Make sure these are grouped per 230.72.