Aerial run to garage

Old 11-02-02, 09:09 PM
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Aerial run to garage


I am the proud owner of a 104 year old (can you say money pit?) victorian in Napa, CA. I need to temporarily replace an old aerial run between the house and the garage. The house will be going through some heavy renovations including a foundation replacement. After the foundation is complete, my plan is to run the power to the garage underground. However, I am in need of a short term solution...

Thanks, Larzo
Old 11-03-02, 01:35 PM
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Temporary power feeder and Grounding for your house and garage.

I am going to suggest that you run the temporary overhead to the garage as either open wiring on insulators or messenger supported wiring. You can buy the wire as thwn and run it as open wiring on insulators. Or you can buy it as type UF or USE conductors or cable and use a messenger to support it temporarily until you have a chance to bury it. In either case you must have enough wire or cable to traverse the distance to the garage by the route that the underground wiring will be run. If you use quadplex as the temporary supply the bare conductor will not be reusable in the conduit or directly buried because it is aluminum clad steel reinforced (ACSR) wire. ACSR is not suitable for use in underground conduit. If it were my home I would use a four conductor messenger supported feeder that is sized for the garage's future rather than it's present. If this wire is kept long enough to go in the conduit later than you will not have to buy new wire after the transition to underground wiring.

When you do dig the trench to your garage make it deep enough to separate the power and non power wiring by at least a foot. How I would do it is to dig the trench to at least three feet deep. Run a number two bare Grounding Electrode Conductor (GEC) in the bottom of the trench. Drive the two ground rods that are required for the garage at ten and thirty feet from the garage. Run the bare number two that is the GEC through the clamps on each rod. Connect the GEC to both buildings disconnecting means by terminating it to the bonded buss in the disconnecting means enclosure. Obtain inspection of your grounding electrode system. Back fill with three inches of sand. Run the feeder cable/s or conduit. Back fill with one foot of earth free of large stones or course gravel. Install conduit for low voltage communications wiring. Back fill to grade. during the inspectors first visit to inspect your grounding electrode installation find out if inspection is required on the feeder and/or the communications raceway prior to back filling the trench. By running the bare number two in the bottom of the trench you will improve the ground contact area of both buildings grounding electrode systems. If you run the feeder to the garage as individual single conductor UF or USE conductors you can use the bare number two as the Equipment Grounding Conductor (EGC) for the garage feeder circuit. If you use it that way the inspector may want you to run a separate GEC to the ground rods from the garage. The minimum size for both the GEC and the EGC is controlled by the size of the feeder Over Current Protective Device (OCPD) and depending on the size of the fuse or breaker protecting the garage feeder you can use a much smaller conductor for them. The draw back to using smaller wire is that it has to be run in raceway or cable to protect it from physical damage. If you run the larger number two bare copper it does not require protection from physical damage and it enlarges the earth contact area of the grounding electrode system.

Now about the grounding for your home. When you build the new foundation you will have an excellent opportunity to improve the safety and damage resistance of your entire homes electrical system. If you use 1/2" or larger reinforcing rods in the footer then work with your concrete crew to get that reinforcing steel double tied. Have a piece of rebar bent up to a 90 stub and have it tied to the top of the footer stirrups so that the stub will come up through the floor just inside the basement wall at the place were you are going to mount the service equipment. You can also stub up through the center of the wall to come out the top at the service equipment's location. Use galvanized rebar for the piece that gets stubbed up. If the reinforcing steel is smaller than 1/2" then you can run a bare number four copper conductor around the entire footer and tie it in position so it will end up encased in concrete at least two inches thick on all sides. Protect the conductor were it comes up out of the concrete with a PVC conduit stub. Make sure that the footer trenches do not get lined with plastic or a concrete encased electrode will be useless. If the footer trenches do get lined with plastic then you can run a bare number two copper conductor all the way around the outside of the footer after the forms are stripped but before the footer and basement walls are back filled. The code calls this a ground ring. Leave enough conductor so that it can be fastened to the basements outside wall and reach all the way to the bonded buss bar in the building's disconnecting means. If you take either of these approaches you will not have to mess around with driven rod electrodes. If there is a underground metal water pipe that has ten or more feet buried in the earth you will also have to run a grounding electrode conductor to it.

Do not miss this opportunity to improve the grounding of your homes wire carried utilities. The cost is very low compared to the amount of damage surges and spikes can do to your electrical systems and appliances over the life of your home.

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