----- Original Message ----- From: "Robert E. Griffith" To: Sent: Monday, July 16, 2001 10:51 PM Subject: Re: [EE]: Bulb Life -- Burned out bulb resurected > Why couldn't you have the two circuits in the kitchen on the same phase as > long as they each have a 15-amp breaker back at the box? Surely the single > phase could handle the combined 30-amp load, so what's the advantage of > having them on different phases? I would think that any 240v appliance in > the kitchen would need it's own circuit, so its not for the combined 240v. > > The book I used when wiring my kitchen showed alternating the circuits of > the 3 wire BX so that each box had only one circuit. > > Wait a minute; maybe I just figured it out. When there is load on both > circuits, if the circuits are 180 degrees out of phase then the current on > the common neutral would tend to cancel - creating a smaller current load on > the neutral wire. If they were in phase, the current on the neutral would > be the sum of the two circuits so it would have to be rated for the sum of > the two circuits (30-amps). Is that it? Yep, that's it. > Here's a somewhat related question. In my basement, I have a chop saw on a > 15-amp circuit that blows occasionally when the saw starts. If the wire on > this circuit is thick enough, can I replace the 15-amp breaker with a 20-amp > breaker? What gauge is rated for 20-amp? It is a short run to the box and > it runs through conduit - not bx, so maybe I could just pull the heavier > wire if I need to. 14 guage wire --> 15 AMPS 12 guage wire --> 20 AMPS 10 guage wire --> 30 AMPS > There was originally a 240v circuit in this conduit. Along the conduit are > 120v receptacles and a single 240v receptacle. I do not know whether they > shared any wires. Could they - legally? Can you put 120v receptacles on a > circuit that is also used as half of a 240v circuit? In the box, a 240v > breaker is just two 120v breakers with a bar connecting them so that if one > trips, they both trip. I believe that this is legal. However, if you have any 240V loads, then you MUST have a ganged breaker. Actually, interally most 240V breakers are not just two 120V's with a bar between them. In the olden days this was more likely true. Now the bar is generally just cosmetic. Bob Ammerman RAm Systems (contract development of high performance, high function, low-level software) -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics