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Grounding an old electrical system

The majority of my home has an ungrounded electrical system (at least, there's no green line in the boxes). However, the addition in the back of the house IS grounded. Can I ground the original wiring simply by tying the cases to the ground line in the addition, or would I be better off calling a licensed electrician for the task. Also, if I need to call someone, roughly what would the job cost, assuming I've provided adequate info for an estimate?

Re: Grounding an old electrical system

Do not connect a ground bond wire between the ungrounded plug receptacles unless the ground wire is connected back to the service panel. If you connect the receptacles together without a ground connection to the service panel and you had a short circuit to the metal of the box, it would not trip the breaker, but it would make all the bonded boxes live and a very real risk of shock.
An easier and safe way would be to install a gfic breaker on the affected circuits and forget about the ground wire.

Please consult with a certified electrician in your area before doing anything

Re: Grounding an old electrical system

lots of older electrical wiring is contained in rigid or flexible metalic conduit or cable (like greenfield or bx) and uses bonded metalic outlet boxes, which the outlet controls self-bond to the metalic outlet box when mounted.

you may well have a equipment ground via the cable sheath (or a bonding ribbon within) or conduit if it exists in the older part of your home.

consult with a licensed electrical contractor to determine this for you if you are unfamiliar or uncomfortable determining this yourself. your local building office can advise you what rules are in effect regarding modification (if necessary) of the older portions of your electrical system.

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