I have come across a question that I can't seem to get an answer to. I am AMAZED that I can't. Can you address with me the issues surrounding deliberately shorting a circuit in order to rapidly locate a circuit breaker?
Christopher.
This is an excellent question, and no, I haven't been asked this before so it is a good issue to address. I have never in my entire career as a professional electrician, purposely shorted out a circuit to trace the breaker location. However, I have seen others do it and use this practise on a somewhat regular basis. I do not support this practise.
A circuit breaker is designed to trip upon short circuit or fault conditions, and will open the circuit before damage can occur from the condition. Breakers are sized to protect the smallest wire size in the circuit, and the rated full load current of that wire. A properly functioning breaker will also trip under continuous over-load conditions at or near the rating of the breaker. Take for example, a circuit wired with #14 AWG wire, protected by a 15 amp breaker. I will give you 2 examples of why this is not a good idea. Some manufacturers of distribution equipment have lost their approvals for making breakers for household distribution because after tripping under a short circuit condition, once reset, they will resist tripping again under the same condition. No manufacturer names mentioned here, but one of them continues to maintain a large market share in the industry. I can't comment as to whether the problems have been corrected, but I will trust they have.
Example #1: I was using a reciprocating saw to cut off a wood ceiling truss in a porch, and failed to see a #14/2 wire stapled to the back of the truss that was covered in dust and dirt, and thus very hard to see. After completing the cut, with dust flying and debris falling, I looked at the blade of the saw and it looked as if someone had taken a human sized bite out of the blade. The live wire had arced and sparked it's way through the blade, blowing the metal away like a welding torch, all out of my view as I was on the other side cutting over my head. I couldn't believe that a 15 amp breaker would not have tripped under this condition. Just curious, I pulled out my meter and checked to see if the wire was still live, and to my amazement, it was! The breaker feeding that circuit was just a standard, 15 amp, single pole breaker (manufacturer name withheld).
Example #2: In older homes, where renovations to the system have been performed by well meaning homeowners, or helpful handy-friends, I have seen situations where an extra outlet or entire circuit has been added by splicing in to another circuit, like the 40A range circuit, using #14/2 wire spliced in a junction box tucked up in the floor joists. Imagine the extra pop that shorting out the 40A breaker will make! To sum it up, not a good practice. Imagine molten copper jumping from your intentional short circuit, leaping behind your safety glasses and melting through your eyelid in to the squishy part your eye!
On a personal note, we are still in Vernon B.C., and plan on moving on to Vancouver on Thursday of next week. Happy Thanksgiving to our fellow Canadians, and have a good weekend to the rest of the word!
Thank-you to my cousin Karen, and her husband Lloyd Knox for allowing us to stay on their R.V. lot here in Swan Lake Rec. Resort for the past couple of weeks.
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