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? 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. 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. --BobG -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Dwayne Reid Sent: Monday, July 16, 2001 7:04 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Bulb Life -- Burned out bulb resurected At 05:23 PM 7/16/01 -0400, Paul Hutchinson wrote: >IIRC, The National Electric Code specifically prohibits using a common >neutral between the two phases. Not correct! Specifically, kitchen receptacles in homes are wired with 2 phases and a neutral: this allows 2 breakers (ganged) to feed a single duplex receptacle so that plugging a toaster and an electric frying pan into the top and bottom of a single receptacle does not trip a breaker. The local inspectors test for this by measuring the voltage between the 2 hot terminals on each kitchen receptacle: if they do NOT measure 230Vac, it fails the test. Industrial wiring shares the neutral between the 3 phases for most 120V outlets and for area lighting. You tend to find dedicated neutrals only on special outlets such as those dedicated for computers and such. dwayne Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 17 years of Engineering Innovation (1984 - 2001) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads