Q.The electrical system of my Victorian Queen Anne-style home (circa 1900) consists of a mixture of knob and tube, cotton-covered braid, nonmetallic, and plastic sheathed cables. The prior owner put in new wire and left the system a mess. When switched off individually, the three circuit breakers do not open the circuit. However, when all three breakers are switched off, the circuit is deenergized. Under normal use, the amperage on the three circuits is about 6A. I have discussed this with other engineers/electrical contractors, and all were unable to come up with an effective troubleshooting methodology.
My question is threefold: 1. How dangerous is this situation? 2. What could be the cause? 3. Short of rewiring the house, is there a methodology to troubleshoot this problem and separate the three circuits?—T.K.
A. This is an electrician’s nightmare. Often, the most practical way of determining the condition of a particular wiring system is to pull it out.
First, this is an extremely dangerous situation. You have described an obsolete wiring system that has exceeded it’s useful life (being connected in such a way that it would require a huge overload to clear a fault). If the three circuit breakers are rated at 15A each, the tripping current will be in excess of 45A. Most lamp cords, light-duty extension cords, and small appliance cords cannot withstand such a severe overload. A short in a table lamp would most likely cause the lamp cord to ignite. The house wiring would overheat, possibly starting a fire.
Second, unqualified individuals may have caused this situation, making bad connections. The insulation could also be deteriorating, allowing adjacent branch circuit conductors to contact each other.
Third, you could troubleshoot by checking all recently made connections for errors. If this doesn’t solve the problem, check all points where the branch circuits intersect (i.e. common gang boxes) for damaged insulation, allowing adjacent conductor contact.—G.B.
A. Because all three breakers must be off simultaneously to de-energize the home’s wiring, the load side of all three breakers is probably tied together—possibly at three or more different splice points in the house. No wire sizes or breaker amperage ratings are given, but this cannot be a good situation, load-wise. This probably means a meltdown and fire before the circuit breakers would trip.
This situation must be corrected for the home to be safe. All wiring must be traced, and circuits separated. It’s ridiculous to have only three circuits for an entire house. An electrician, who is familiar with the NEC, should trace out all wiring, separate circuits, and ensure wire sizes are protected properly and circuits are not overloaded. Though this may be cheaper, rewiring would be best to ensure adequate capacity for the electrical loads of a modern home.—J.R.D.
A. The wiring T.K. describes is a complete mess. I’ve had experience with buildings like this. By the time T.K.’s patched up all the illegal wiring and deteriorated knob-and-tube, he’ll have rewired the house anyway—but in a disorganized, halfway fashion. Three circuits aren’t enough. Bite the bullet, and fix it right. Take out the old wire and all the illegal stuff. Sell it for scrap if you can. Install a sensible service entrance, correct what can be reasonably brought into conformance, and complete a wiring system that has the proper methods, materials, and capacities. If walls need opened for plumbing or heating repair, take advantage of the opportunity and coordinate everything. T.K. needs a qualified electrician.—E.P.M.