Originally Posted By: jtedesco
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Joe Tedesco, NEC Consultant
www.nachi.org/tedescobook.htm
Originally Posted By: ekartal
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Combination clamp on meter - PDA.
Erol Kartal
ProInspect
Originally Posted By: jpeck
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Looks like he is thinking real hard before cutting that wire.
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Jerry Peck
South Florida
Originally Posted By: dvalley
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Lets see…Which one can I splice into?
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David Valley
MAB Member
Massachusetts Certified Home Inspections
http://www.masscertified.com
"Some cause happiness wherever they go; others, whenever they go."
Originally Posted By: jmyers
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Hmm…I know one of these has got to be a hot wire!
Joe Myers
Originally Posted By: tallen
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Gone
–
I have put the past behind me,
where , however, it now sits, making rude remarks.
www.whiteglovehomeinspections.net
30 Oct 2003-- 29 Nov2005
Originally Posted By: dbroad
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He must be Italian, and he is playing with his spaghetti. What bad manners.
Originally Posted By: Kevin McMahon
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What am I missing? Looks like a pic of a breaker box…no wires showing??? Was the picture changed???
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ABC Home Inspection, LLC
Originally Posted By: jtedesco
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Yes, the subject and the picture were changed because of an inappropriate comment made in a reply.
Have you encountered these types of breakers used with multiwire branch circuits and do you understand the issue?
--
Joe Tedesco, NEC Consultant
www.nachi.org/tedescobook.htm
Originally Posted By: jmyers
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Joe T.
I don't recognize those brand of breakers.
I would have to say if they are multiwire, the twins can not serve a 240 volt outlet, since the neutral would be using the same phase. Each breaker would need a seperate neutral wire for each hot wire. Most likely they are not common trip for 240 volt outlets, but are common disconnect, making running a 240 volt outlet on them a no no.
That is a good point, most inspectors don't know that the twin breakers handles can not be tied together in order to achieve a 240 volt outlet, at least I believe that was the point you were trying to make.
Please share with me, the point you were trying to convey, now that you have my curiousity! 
Joe Myers
Originally Posted By: Kevin McMahon
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No, I’m not familiar with the issue regarding these breakers…please fill me in!
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ABC Home Inspection, LLC
Originally Posted By: jtedesco
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Joe:
You have the point, and if the set of any two "twin" breakers that are on the same phase were to be connected to a black and red wire of a 3 wire 120/240 volt (multiwire branch circuit) the neutral would carry the full load of each circuit, which is one of the reasons why the neutral wire burns up.
Originally Posted By: Kevin McMahon
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Ok…maybe this is a dumb question, but what would the purpose be for a twin breaker, if they cannot be used for 240v circuit? Is this a design flaw on this system, or is it something else entirely? I’m by far not an expert on electrical systems, but I will learn more the more I see and read about.
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ABC Home Inspection, LLC
Originally Posted By: tallen
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Gone
–
I have put the past behind me,
where , however, it now sits, making rude remarks.
www.whiteglovehomeinspections.net
30 Oct 2003-- 29 Nov2005
Originally Posted By: jmyers
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Kevin,
Twin breakers can be used for separate individual circuits, so you can in fact get two circuits from a space where you normally would only get one.
If you were to run out of room for breakers in a panel, you would have to resort to installing a new panel, or the more cost effective solution of replacing those single breakers with twin breakers thereby increasing the number of circuits the panel will allow.
The next time you look at a double pole breaker, take note that each pole on that breaker is running on a separate phase of the service, meaning the 240 volt circuit can utilize the same neutral wire.
Think of the service as a circle, phase A is 1/2 of that circle, or 180 degrees. Phase B is the other half of that circle for another 180 degrees for a total of 360 degrees. The same neutral wire can be used when the 240 volt circuit is using different sides of the phase, or the full circle, each running on different parts of the circle.
Take this example, if you take a #14-2 wire which is capable of 15 amps one hot, one neutral you have a single pole(120 volt) 15 amp circuit. Now it would stand to reason that if you needed a two (double, 240 volt) pole 15 amp circuit you would need 4 wires 2 hots and 2 neutrals. Since each pole is running off a different phase (remember the two different parts of the circle, you only need one neutral or a 14-3 wire which is 2 hots and 1 neutral.
Just a note, so you don't end up being more confused than when we started, electricity is measured in waves, not circles. I used the circle because it is much easier to imagine a circle cut into parts than to imagine a wave cut into parts. Each wave represents a different phase of the service. The waves intersect at different points, but never overlap each other. With a three phase, you are simply adding a third wave to the picture, versus the two waves of the single phase.
To add ever more confusion to you, it is ok to place a 240 volt outlet on the same phase of the service, however, the neutral must be sized accordingly, meaning it is capable of handling both loads. So for a 15 amp, 240 volt circuit the hots would be #14 wire (15 amps) and the single neutral would be a #10 wire (30 amps).
I hope I explained that well enough that you have at least a basic understanding. I have this thing, I think the only stupid question is the one that you did not ask. Home inspectors are probably the worst at swallowing their pride and asking what many perceive as stupid questions. On the other hand you have people like you and me that ask when we don't know or don't understand which will just make us all that much better than them. 
Joe Myers
Originally Posted By: jtedesco
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Look here and download information about circuit breakers from UL:
http://www.ul.com/regulators/circuit600.pdf
Originally Posted By: jmyers
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Joe T.
I give up. Why should we pay careful attention to those breakers?
Joe Myers
Originally Posted By: jpeck
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Not just THOSE breakers, but all half size breakers (am I correct, Joe?).
This is because, in Joe T.s reference to multi-wire circuits, multi-wire circuits may only be used off full size breakers, so one breaker is on one bus bar and the other breaker is on the other bus bar, making 240 volts between the breakers, thus making the shared grounded conductor a true "neutral".
If these (half size breakers) are used for multi-wire circuits, then there is -0- volts between the multi-wire circuit conductors, meaning the shared grounded conductor is not a "neutral", but a twice loaded grounded conductor (carries the full current of each circuit, thus could easily overload the grounded conductor for its size).
Also, on multi-wire circuits, there can be no 240 volt loads, only 120 volt loads.
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Jerry Peck
South Florida
Originally Posted By: jtedesco
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For the reasons this discussion has identified where related to the loads. Paying careful attention to this would better be described as “make sure that they are installed properly”, get it yet Joe?
–
Joe Tedesco, NEC Consultant
www.nachi.org/tedescobook.htm
Originally Posted By: jmyers
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| Quote: |
| Also, on multi-wire circuits, there can be no 240 volt loads, only 120 volt loads. |
If I remember correctly twin breakers are also made in a double pole configuration with common trips for 240 volt circuits. Look them up in the Siemens catalog, I think that I seen them in there at some point in my life. I believe they make them in a variety of configurations, from 2 single poles with a double pole, 2 double poles and 4 single poles. 
Did they quit making them?
Joe Myers