<font color="blue"> Q. Is it alright to share one neutral and ground between two separate circuits?
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Are the breakers on the same line(120 line to neutral), or are they on each line (220 line to line)?
If they are on the same line the neutral current is the sum of the line currents and you can over rate the neutral line. If they are on each line the neutral current is the difference of the line currents and the neutral line is within rating.
No these are two separate 110v circuits. You're right 12-2 romex is cheap, but right now it means a drive into Des Moines (35 miles). I have the 12-3 already and could use it up and complete the job without leaving town.
If I did go after hardware again, I could also buy 20a rated switches and stay with 20a circuit breakers. This would allow me to use higher wattage bulbs and stay at the recommended 80%.
Right now I'm in no great hurry b\c it's so cold. I'm not out there for extended amts of time and I don't like working with 12g wire in the cold. This has become a good learning project for me and I appreciate the advice of those more knowledgeable.
Inspector 507 would know more about this than me, but,I believe that running 300w bulbs in 500w fixtures to get the amperage within spec would be a "listing" violation if you had it inspected. The reason is that the next guy to come along wouldn't have a clue of why you had de- rated the bulbs and could replace them with 500w bulbs, thereby overloading the circuit.
If you have lots of 12-3 just use it as if it were 12-2 and ignore the red wire. I don't know if this would follow code or pass inspection, but it would get your neutral loads correct.
If you've got the 12/3 and want to use it.....by all means do so. You can run the 2 hots and share a neutral without any problems as long as you put the breakers in the right spots in the panel. Breaker 1 on leg A and breaker 2 on leg B. 2 breakers on leg A or B will overload the neutral.
If the 300 watt bulbs fit, use them. You won't have a problem with the listing of the fixtures.
[img]/forums/images/icons/smile.gif[/img] This has been one heck of an informative thread. [img]/forums/images/icons/smile.gif[/img] I've seen overloaded neutrals with INFRARED on many occasions and was never quite clear as to just what the problem was, other than too much current coming back on one wire. That business of using leg A and leg B on the red and the black is new to me. Makes sense now that I think about it, but still new. [img]/forums/images/icons/crazy.gif[/img] It has been real handy having the in-spec-tor available to post answers to all of this electrical stuff. [img]/forums/images/icons/smile.gif[/img] Thanks Inspector 507!!! [img]/forums/images/icons/smile.gif[/img]
Maybe I did not explain it well. I was not advocating using a larger breaker than is called for, say for example using a 30 amp breaker to run loads on a 15 amp circuit. This is clearly unsafe.
What I am talking about is running multiple loads off of one 15 amp breaker. You are allowed to do this to some degree but many times in new home construction a contractor will string one outlet off another, etc.... Net effect is you have half the outlets in a small kitchen on one 15 amp breaker. Code allows some of this to a point since the idea is if you have three outlets you will not draw 15 amps from all three at one time.
I was pointing out that if you daisy chain fewer outlets than the code allows the inspector will not complain. To many is another story.
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