![]() ![]() I have seen homes where one of these breakers has apparently been sitting This means that the whole kitchen will now have only one circuit's load capacity, instead of two. This actually leaves all the outlets still working because the circuit that didn't trip now feeds its hotness through the unremoved metal tab to the other half of all the outlets. More often, the breakers are quite separate and the first one to trip thereby prevents the second from tripping. If the breaker handles of the two circuits are tied together, as would be required by now, they will both trip, and someone will have to figure out what was done wrong. When homeowners or handymen now replace even just one of these worn or unfashionable receptacles without breaking away the metal tab that connects top and bottom halves of the hot side, the two circuits, which were purposely fed from opposite main busbars to let them share one neutral without overloading it, will pass a 240-volt short between them. Anyway, by now this well-meaning idea has even backfired: The fact that homeowners and home-dwellers were unaware of this made the idea almost useless, in my opinion. The idea was to distribute heavy loads more easily between the two required circuits. homes wired in the 1960s (and a little before and after also some family rooms during that time) often had two distinct 20-amp "appliance" circuits reaching each normal (duplex) receptacle by way of two-circuit cable. ![]() The other possibility is a similar situation occurring to the home's whole system when the If you notice a sustained weird dimming of lights in one part of the home and lights burning brighter than normal in another part, this is one possible cause. Damage can occur, especially to sensitive electronic equipment. And since their lights and appliances were not designed with such a voltage and connection scheme in mind, the result is that the items served by one former circuit will tend to run brighter than usual and those of the other dimmer. If the neutral connection at the panel's neutral bar or at a box the cable is run to goes bad, the two circuits will become entirely one 240-volt circuit, with one (former) circuit's set of loads arranged in series with the other's. There is a disturbing malfunction that can occur with a multi-circuit cable at the panel or a box it goes to. The whole system for the home is doing this all the time because the two hot main power company wires share one neutral from the panel back to the transformer. A's 5 amps and 5 of B's 6 amps are the same thing - they are essentially a 240-volt circuit at that point, flowing from breaker to breaker and ultimately out to the two ends of the power company transformer's coil. Even wire B is sending 5 of its amps along wire A, with the 1 amp difference - the imbalance - going on the neutral. Where is A's 5 amps of current "coming from" or "going to" at that instant? It is not connecting to the panel by way of the neutral it is by way of wire B, driven by the 240 volts between them. Instead, 1 amp would be flowing on the neutral, and at a given instant (remember this is alternating current) it would be flowing in the direction that would seem to complete the motion of current in wire B, and against the direction that would seem needed to complete wire A's circuit. If 5 amps is flowing on hot wire A and 6 amps on hot wire B, the neutral path they share will not be found to be carrying 11 amps (as it would if the hots were, against code, fed from the same main wire through the same busbar). But if you were to trace the flow of two-circuit current from the panel to that first box at a time when each part of the multicircuit was using different amounts of electricity, here is what you would find: The two parts of this multi-circuit usually split apart from each other at that point and then behave like most other 120-volt circuits. This sort of arrangement saves a little wire and labor at installation time by using a cable containing black, red, and white wires between the panel and (usually just) the first outlet or switch box it is run to. The hot wires are 240 volts apart from each other and each is 120 volts from the neutral. It involves two hot wires sharing one neutral as their "return" path. It is called a multiwire branch circuit but for our purposes it would be clearer to call it a two-circuit cable. and Canadian homes mirrors the main wiring feeding the home from the power company. A particular kind of circuitry often found in U.S. ![]()
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