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Joined: Feb 2001
Posts: 308
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A very good simple explanation!!!
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Joined: Feb 2001
Posts: 5
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thanks everyone. pauluk you answered my concern about having the lights and the recepticles fed from two different sides of the main pannel. I wasn't sure if that would create a problem but obviously it won't. I think i understand now if I ever wire a 240v circuit both breakers need to be on the same bus bar or you would have problems. Thanks again
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Joined: May 2001
Posts: 717
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HAH !!!!!!!!!! Obviously, you forgot about velocity factor.
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Joined: Feb 2001
Posts: 308
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No, you have it backwards. First off you have to have a handle tie on a two pole breaker so if there is a fault in one ungrounded conductor the power is killed to both. This means the two breakers will be on opposite busbars, not the same.
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Joined: Aug 2001
Posts: 7,520
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'73,
As Steve said, you got that last bit backwards.
If you wire a 240V circuit it has to be to a double-pole breaker which connects to both busbars.
Or are you confusing "busbar" with the left and right sides of the panel? It doesn't work one busbar for the left, one for the right. They are interleaved on each side (i.e A-B-A-B-A-B etc.), so any two adjacent positions will be on opposite hot lines.
Thus you could also get a 240V circuit from two adjacent single-pole breakers, with their handles tie together so that any overload disconnects both hot lines. (I think that's allowed by the NEC, but as I'm not in the U.S. I'll wait for the others to confirm or deny.)
*
George,
Velocity and differential phase shift is a big problem in wideband telecoms circuits. When I was working at Goonhilly we had all sorts of difficulties with this on mal-adjusted equipment.
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Joined: May 2001
Posts: 717
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Paul,
Of course, I was just 'raggin' on you. Understand, I'm a ham (Extra class, thank you THE OLD way) but most electricians have never heard of velocity factor, which of course is a major problem in telecom and rf circuits. Brief 'splanation for those reading this junk (junque ?). Electricity travels, ostensibly, at the speed of light.....IN A PERFECT MEDIUM... however, wire is not a perfect medium and the speed has to be adjusted for the path, hence, the velocity factor. Now that everyone is asleep, I'll tiptoe out.
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Joined: Aug 2001
Posts: 151
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Very well explained, Paul! I'll apologize (slightly) for my flippant remark to '73 about his brother-in-law (but what are brother-in-laws for then?), but I'm fairly sure we've all heard much the same thing from a customer that seems extraordinarily willing to accept such an opinion from someone with little or no experience, then question our explanation or repair because it didn't jibe with the "expert's".
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Joined: Aug 2001
Posts: 7,520
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Dallas,
No need to apologize for flippant remarks. My sarcasm has gotten me into trouble before now -- Some people have no sense of humor!
And yes, I've heard it before as well: "My brother has a friend whose aunt works in the billing dept. of Eastern Energy, so he must know what he's talking about."
George,
I've been interested in ham radio ever since I was young. I spent many happy hours in the 70s listening to the local top band net on a Saturday morning. I never got around to taking the "ticket," but I'm still an enthusiast.
The exam here went multiple choice some years ago. Not the same anymore (sigh).
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Joined: May 2001
Posts: 717
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Paul,
We killed the multi-choice test some months ago, our club never gave them anyway. The difference between an 'old' extra, and the 'new' extra is that in April 2000 the morse code requirement dropped to 5 wpm from 20 wpm. There is a lot of speculation that it will be done away with altogether in the near future, but I hope it is always a small part of the requirements.
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Joined: Aug 2001
Posts: 7,520
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Only 5 wpm for extra class?! Wasn't 5 wpm the old requirement for your novice and technician classes?
It was always 12 wpm here for a class A license; class B introduced in the 1960s was/still is no-code, but limits operation to VHF and above. We got a novice license some years ago.
There have been suggestions that the code should be scrapped here too, subject to conforming to international agreements for HF. I understand that the USCG no longer monitors the 500kHz CW distress frequency, so I can see it happening eventually. It'll be sad to see it go.
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