There seems to be some confusion regarding terminology and the location of the overcurrent protective devices being discussed.
In the US and Canada, if a circuit breaker is located in the panelboard, John is generally correct that the neutral will not be controlled by the circuit breaker. On the other hand, if the circuit breaker is located in utilization equipment, there are no particular rules, regulations or standards that I am aware of preventing one pole of a circuit breaker from also controlling the neutral, except that, when the neutral is so controlled, all phases must be disconnected by common a control mechanism. The common vernacular applied to supplementary overcurrent devices that resemble branch circuit breakers is to also call them circuit breakers. Even the manufacturers and distributors of such devices call them circuit breakers. While incorrect in installation code terms, this is very likely what most respondents are referring to. Regards, Peter L. Tarver, PE ptar...@nortelnetworks.com -----Original Message----- From: Wagner, John P (John) [mailto:johnwag...@avaya.com] Sent: Monday, October 09, 2000 3:28 PM To: 'brian_kunde'; emc-pstc; 'Russell, Ray' Subject: RE: Overcurrent Protection: One or Both Sides? I take some exception to the response below. Single phase connections between phases either on a delta or wye system do not have a neutral connection. There are two grounded delta systems -- corner ground where one phase is grounded, or center tapped ground on one of the phases (commonly called high leg). There are also variations of the grounding scheme to allow for impedance grounded systems where appropriate. A standard two pole breaker os not designed, nor can it be used to interrupt neutral. For that, a special shunt trip braker is needed. John P. Wagner AVAYA Communication 11900 N. Pecos St, Room 2F58 Denver CO 80234 email: johnwag...@avaya.com phone: 303 538-4241 fax: 303 538-5211 > ---------- > From: Russell, Ray[SMTP:ray_russ...@gastmfg.com] > Reply To: Russell, Ray > Sent: Monday, October 09, 2000 5:15 AM > To: 'brian_kunde'; emc-pstc > Subject: RE: Overcurrent Protection: One or Both Sides? > > > Hi Brian, > > I see most of the return postings have focused on the UK, which has a > terminated neutral system. There are several installations especially in > the > US, where the power could be derived from a delta, or unterminated neutral > system. I believe in this case, overcurrent protection is required on both > lines. In addition, the 2 pole circuit breaker method provides a suitable > 2 > pole disconnect. > > Good Luck, > > Ray Russell > ray_russ...@gastmfg.com > > -----Original Message----- > From: brian_kunde [mailto:brian_ku...@leco.com] > Sent: Friday, October 06, 2000 12:32 PM > To: emc-pstc > Subject: Overcurrent Protection: One or Both Sides? > > > > > The issue of designing in Overcurrent Protection on one side or both sides > of > the AC mains keeps coming up. We deal in Laboratory Equipment so the EN > 61010-1 > is the standard we use. I'm not sure what EN60950 would say on the > subject. > > The only area I have found that deals with this question is a NOTE in > section > 9.6 of EN61010-1 which says, "Overcurrent protection devices (e.g. fuses) > should > preferably be fitted in all supply conductors." > > This seems "GRAY" to me and I get beat up on it all the time. I feel that > overcurrent protection should be on all current carrying conductors. With > a > 230V~ product you never know where in the world the product will be > shipped, > if > the AC Main has a grounded neutral, or if the receptacle is polarized. > So, > I > feel you never know for sure which line or if both lines will be "HOT" in > reference to Earth ground. > > If my thinking is correct, shouldn't ALL 230V~ products have overcurrent > protection on both sides of the line? I would think so, but I see > products > everyday that only have ONE side of the line fused. My superiors feel > that > if > others can get away with it, why can't we. Why add the extra cost of > double > pole breakers or double fuse holders if it is not necessary? > > Am I being too cautious or do I have a point? > > Thank you for your support and advice. > > Brian Kunde > LECO Corp. > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson: pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
