When Did Switching With Breakers Become Common Place?

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Phys Guru Join Date: Feb 2006 Location: middle of nowhere, Pennsylvania Posts: 2603 Good Answers: 63	When Did Switching With Breakers Become Common Place? 01/31/2013 1:14 PM
	I am quite dismayed with the responses on this site to my post "Double Pole Breaker - The Sequel", as a very wromg answer received a 2 rating. One response receiving a 2 rating said neutrals must never be switched. WRONG! You all better read NEC 240.22 and NEC 430.105. Yes - they may - particularly in the case I was describing. In an industrial panel, which I was describing, no-one would use the branch circuirt breakers in one of these as a switch. To begin with, such a panel requires shutting off all power to the panel before the door can be opened to access the breakers. Then what? - repower by defeating the door interlock and procede to turn motors on and off with the breakers as a means of control - of course not. They are manually switched only as an aid to maintence. They are over current devices covered by the 240.22 mentioned and as long as the "heat" is disconnected with the neutral, everything is fine. The thing that really concerns me is that this site is promoting the idea that a circuit breaker should routinely be used as a switch. A 489 rated breaker for an industrial panel simply is not made for repeated manual tripping. The manufacturer of the breakers in question never mentions using them as switches, but certainly indicates how many fault trip cycles they can handle. __________________ Remember when reading my post: (-1)^½ m (2)^½
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#2 "Re: When Did Switching With Breakers Become Common Place?" by JRaef on 01/31/2013 7:11 PM (score 3)

passingtongreen Guru Join Date: Aug 2009 Location: Glen Mills, PA. Posts: 2385 Good Answers: 114	#1 Re: When Did Switching With Breakers Become Common Place? 01/31/2013 5:37 PM
	I have only a slight idea of the technicals in your OP, but I point out that the site provides a forum. It is moderated for PCness, not for the accuracy of the information and opinions in the posts __________________ In a time of universal deceit, telling the truth is a revolutionary act. George Orwell
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JRaef Guru Join Date: Sep 2006 Location: California, USA, where the Godless live next door to God. Posts: 4665 Good Answers: 804	#2 Re: When Did Switching With Breakers Become Common Place? 01/31/2013 7:11 PM
	Hmmm... don't know where to start. In the other thread, there are indeed several erroneous statements but none that, at first glance, lead to the creation of a dangerous situation in my opinion. Yes, you are correct in that the NEC does allow for switching a neutral under that specific set of circumstances. But in trade schools, they don't really want "electricians" taking responsibility for deciding when it is and is not appropriate, so a lot of people have learned it as "no switching a grounded conductor" period, safer that way. As to breakers being used as switches, that changed a long time ago. It used to be that if you wanted a breaker that is rated to be used as a switch, you had to order it as "SWD" (SWitching Duty) rated. But years and years ago, the breaker mfrs decided it was too expensive to make parallel product lines, some of which didn't sell as well, so they abandon the practice and now all breakers are SWD rated whether they say it or not. So yes, it is perfectly acceptable from a mechanical and duty cycle standpoint to use breakers as switches, and it is done all the time. Falt trip cycles are completely different in terms of the duty, we are talking about using it in NORMAL switching. Now, that does not invalidate your point about the fallacy of having to shut down the power to open a box in order to shut off a breaker, you are correct in that being asinine. But remember, people here cannot see how your panel is built. A lot of panels I have built have what is called a "dead front" where the breaker handles stick through the plate, allowing them to be operated without completely opening the panel and exposing the user to the live terminals. Case in point: Not mine actually, but I have built similarly. __________________ All I every really wanted to be, was... A LUMBERJACK!.
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Phys Guru Join Date: Feb 2006 Location: middle of nowhere, Pennsylvania Posts: 2603 Good Answers: 63	#8 In reply to #2 Re: When Did Switching With Breakers Become Common Place? 02/01/2013 8:58 AM
	Sorry - I know - makes an assume - a** of... I assumed that since I mentioned this was an industrial control on process equipment, an industrial control panel would be in the minds of those responding - not common lighting panels, which is apparently what many assumed. I know they use those as switches all the time. However a double pole breaker in one of those with the neutral cut simultaneously with the 120V would not be a code violation. Yes - I admit you are right that they can be used as switches now - I use what AB calls a manual starter all the time, and it is just a MPCB. Even has a nice rotary handle. I have yet to come up with a situation to use that manual starting ability. Who wants the worker on the floor of the plant deciding when that 50 HP pump is going to run? Let the PLC decide that. Looks like your example shows one that does let the worker on the floor decide when to start a motor. (did this go to Asia? - they are still big on manual running of plant equipment) Is it time for me to retire? __________________ Remember when reading my post: (-1)^½ m (2)^½
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ronseto Guru Join Date: Sep 2008 Location: Vancleave, Ms about 30 miles inland from Biloxi and the coast Posts: 3197 Good Answers: 106	#3 Re: When Did Switching With Breakers Become Common Place? 01/31/2013 7:12 PM
	I agree that circuit breakers should not be used as circuit interrupters; it can only lead to premature failure. An on/off switch is a lot cheaper to replace than a circuit breaker. __________________ Mr.Ron from South Ms.
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pnaban Guru Join Date: Jun 2010 Location: srilanka Posts: 2725 Good Answers: 5	#5 In reply to #3 Re: When Did Switching With Breakers Become Common Place? 02/01/2013 12:35 AM
	In domestic consumer units(UK)and in load centres(USA) in final circuits single pole MCB used to isolate the circuit without switching off the neutral. Is there no danger of shock from neutral backfeed from another circuit which is energised? __________________ pnaban
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#6 In reply to #5 Re: When Did Switching With Breakers Become Common Place? 02/01/2013 3:39 AM
	Slight, then the neutral will be close to earth potential as it is connected to earth at the distribution transformer, in the case of a TT system, and elsewhere as well with the various TN-[x] systems. Most, if not all, domestic electricians will work with isolated live and connected neutral without fear. If there is a shock-making voltage on the neutral, then it indicates a serious supply problem and needs to be addressed by the utility service provider without delay. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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oilytinman Participant Join Date: Nov 2010 Posts: 4	#9 In reply to #6 Re: When Did Switching With Breakers Become Common Place? 02/01/2013 8:40 PM
	Neutrals can carry a shock potential when used with two or more phases having a common neutral. If only one of the phases is interrupted then the remaining phases will use the common neutral as a return path for the phase that is still energized. This means that disconnecting a neutral wire at any point in the circuit will have high potential that is still load connected and near earth potential on the side that still has a path to the panel. I replaced a service panel in a house several years ago and I was surprised that the electrical inspector did not verify that when I transferred original circuits in the old power panel I made certain that I assigned different phases of circuits using a common neutral to the new panel. If I had not paid attention to phase assignments it would have meant that I was feeding two fifteen amp breakers to one common neutral and overloaded the existing three conductor wiring.
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tcmtech Guru Join Date: Jun 2009 Location: South of Minot North Dakota Posts: 8376 Good Answers: 775	#4 Re: When Did Switching With Breakers Become Common Place? 01/31/2013 8:27 PM
	Around here its common place to have the main breaker panels as the primary lighting switching devices and the like as well in many commercial applications. I have seen many business show rooms, shops, and school gymnasiums that are over 40 - 50 years old that have used the primary breaker panels as their main switching centers for everything that gets turned on and off in a daily or more frequent use. Never thought otherwise about it really.
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silverfox Power-User Join Date: Nov 2011 Posts: 286 Good Answers: 15	#7 Re: When Did Switching With Breakers Become Common Place? 02/01/2013 7:21 AM
	There is no problem using an MCB to switch a circuit instead of a lets say a light switch. It not normally done because the MCB is in a DB rather being in a room. Obviously this argument can be expanded to your circumstance. Years ago neutrals were not switched. You would certain never fuse a neutral. Loosing the star point would cause the phase voltages to move around - some high some low. With modern day circuits there is a lot of noise on the neutral - imbalances and harmonics and the neutral can carry a voltage. From a point of safety you would isolate the neutral. There are switches that ensure the neutral is a slow break and a fast make. There is a huge difference between switching a load off with an MCB and an MCB coming out in anger due to a massive short.
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IanR Guru Join Date: Jul 2007 Location: FL Space Coast Posts: 536 Good Answers: 14	#10 Re: When Did Switching With Breakers Become Common Place? 02/04/2013 10:00 AM
	Where I work, we build systems for the government and the military. Every unit we build, or have built for us, uses the circuit breaker as the main switch. Granted these are industrial circuit breakers (Airpax, etc..) that are probably designed for this purpose. I cannot say if it applies to panel breakers in the facility distro or not, but we have never had issues with switching those breakers, either.
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Phys Guru Join Date: Feb 2006 Location: middle of nowhere, Pennsylvania Posts: 2603 Good Answers: 63	#11 In reply to #10 Re: When Did Switching With Breakers Become Common Place? 02/04/2013 10:29 AM
	Yeah - a main breaker is switched, but how often is one switched? Power up the panel and usually it is on for days or even weeks. I was assuming (there's that word again) that the switching in my original post that others were referring to was like on lighting panels, where switching is a daily or even several times per day, or in my case in the original post where I was discussing an industrial control panel, the breakers were on motors on pumps and would be switched as often as a process was run, possibly ten times per shift. That's a lot of switching for what is really overcurrent protection. __________________ Remember when reading my post: (-1)^½ m (2)^½
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#2 "Re: When Did Switching With Breakers Become Common Place?" by JRaef on 01/31/2013 7:11 PM (score 3)

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Users who posted comments:

IanR (1); JRaef (1); oilytinman (1); passingtongreen (1); Phys (2); pnaban (1); PWSlack (1); ronseto (1); silverfox (1); tcmtech (1)

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