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About Bruce Grant
Expertise
I can answer any questions about residential electrical wiring and most questions about commercial wiring. In my own business, I insist on using best practices in all work we do (which to me means "to Code" or BETTER, using the most recommended ways to do things).
Experience
I'm 65, but learned wiring basics as a teenager. I only used this knowledge for myself, friends and family until early 2002, when economic downturns suddenly made my 30 years in IT irrelevant. Through the Internet, I bought many books on wiring and electrical code and switched careers, becoming an unlicensed electrical contractor, carpenter, and handyman. I now know, after 7 years in the industry, everything I need to get a California C-10 License except some of the Industrial wiring stuff (which I'll probably never use, but need to pass the test). The main reason I haven't yet obtained the License is lack of funds to pay for it and the required insurance. Eventually, I'll get it.
Education/Credentials
* BS in Physics and Mathematics from Oregon State University, 1967
* Primarily self-taught from books written for electrical and construction pros, but also informal training from more experienced pros
Past/Present Clients
homeowners and small businesses in the San Francisco Bay Area, mainly on the S.F. Peninsula
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You are here: Experts > Home/Garden > Home Improvement/Repair > Electrical Wiring in the Home > Tripping breaker
Expert: Bruce Grant - 11/4/2009
Question
Hello I had a hot tub in my yard that I got rid of. I dug a trebch to the garage and just routed the cables underground to the garage. Installed a breaker box in the garage . The wire size is #10 for 50 amp. My problem is that the breaker for the original spa is a ground fault unit and trips after the lights in the garage have been on for no more than 10 minutes. It trips in the house not in the breaker box installed in the garage. ANy suggestions or start with replacing the spa breaker????
Answer
Bill,
First, you should know that #10 wire is rated for no more than 30 Amps, not 50. Therefore you should be using a breaker no larger than 30A on that circuit. For a 50A circuit, you would need #6 wire or larger. If you really have #10 wire on a 50A breaker, then be sure to correct that for safety's sake.
You mentioned that you dug a trench and routed the wiring underground to the garage.
If so, was the wiring UF (Underground Feeder) cable designed for direct burial?
** If so, did you bury it deeply enough (at least 12 to 18 inches, depending on the situation) and/or protect it otherwise to prevent mechanical damage from gardening, vehicles, etc.?
** If not, was the wiring encased in the proper type of watertight conduit? [NOTE: EMT is NOT acceptable.]
** If neither, then moisture may be causing a partial short to ground which would cause a GFCI breaker to trip. The cable/wiring should be replaced or properly enclosed in watertight conduit according to the National Electrical Code and whatever your local Codes are.
The basic principal of a GFCI is that it compares the current from the source (Hot) to the current returning via the Neutral wire. If these differ by a certain amount or more, then some of the current is leaking to ground (such as through a person or an electrical fault), and the GFCI trips (as a safety measure). Current Electrical Codes require all receptacles in a garage to be GFCI or protected by a GFCI. If the buried cable meets the criteria in the previous paragraph, then double-check all of the connections (which should all be inside junction or breaker or fixture boxes).
Since the breaker does not trip immediately, look for a "small" error such as an incomplete splice inside a wire nut or a loose wire strand touching or being very close to something it shouldn't. Don't overlook the possibilities of a similar problem in the lighting fixtures in the garage.
I hope I've given you enough information to solve your problem. If not, don't hesitate to send a follow-up with whatever else you've found out. Good luck to you.
Bruce
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