Regarding Question #1, Bundled Conductor derating using the 75 oC or 90 oC column, one caveat:

Even if the wire is rated at 90 oC, like THHN, if either end terminates to lugs of a device rated for a maximum of 75 oC, then the 75 oC ampacities must be used. This is often the case with motor control equipment (combination motor starters) and some breaker panels on the main lugs.

Your answer to Q2 contradicts your answer for Q10. If it is installed in a raceway (raintight conduit or plastic vapor barrier) is not a wet location. Why would NM cable not be allowed if temp derated for the overprotection of having a raceway that protects it from the elements?

Q2. Can Type NM cable be installed in a raceway in a ground floor slab?

A2. Maybe. Type NM cable is not permitted to be installed in a wet location [334.12(B)(4)] and a raceway in a concrete slab in direct contact with the earth is considered a wet location [Article 100]. If however, there is a plastic vapor barrier between the earth and the concrete slab, then the raceway would not be located in a wet location. Q10. Can I run Type NM cable in a raceway outdoors on the building?

A10. No. Cables installed in raceways in above ground wet locations must be listed for use in wet locations [300.9], and Type NM cable is not listed for use in a wet location [334.12(B)(4)].

Hi Mike

Can you tell me the ampacity of the type nm cable installed in a raceway, I was giged on this before because the raceway was from box to box it was not concidered a sleve for protection. thanks

Q9. Can I use 14 AWG conductor pigtails from 12 AWG, 20A circuit so that I can back-stab the wires to the receptacle? A9. No. Branch circuit tap conductors are not permitted for receptacle outlets [210.19(A)(4) Ex No.1 (c)].

Pigtailing is so common and required for ground and Neutral(removal of a device cannot interrupt neutral or ground lines) so this is conflicting. Now down sizing is a different story.

So what gives?

Regarding question 3. The answer is essentially correct but their are foot notes so to speak. The wild leg of an open delta 3 phase is coded orange and isolation transformer legs also per NEC are color coded (Health Care Facilities 517). The open delta wild leg ID may be otherwise identified but if color is used I believe it must be orange. However, all 3 phase conductors must be somehow identified for voltage-though color is an alternative for this identification. I'm writing this from memory but I'll try to find exact references if they're needed. To be truthful, I haven't checked the 2008 NEC on the open delta high or wild leg rule.

ENJOY YOUR CODE QUESTION, FOR US OLD ELECTRICIAN`S,

Regarding color coding. Notice that the traditional coding follows the spectrum left to right. Phase A is black or brown, Then phase B would be red, Phase C would be toward the blue end of the spectrum. If you come across a color code that you're not familiar with, think of the resistor color code which also follows the color spectrum-left to right. This rule is not written in stone but it will help getting motor rotation right the first time.

FOR QUESTION 2 NM, I WOULD NOT USE IT, ONLY IN DRY LOCATION'S

In regards to Question #3 - Did the 1975 NEC have a "required" color code, including "required" colors for even switch legs? I have been told this is where these colors originated at by a couple of "old timers". Just wanted to know if this is fact or not.

On Q2, I understand your reference to the definition Art 100, but I don't think the vapor barrier makes a difference. I think the reason that conduit in a slab is a wet location needs to be uncovered. I have always understood it is the temperature differential that causes the condensation in the conduit resulting in the conduit filling up with water. I don't think the vapor barrier would make a difference.

Mike:

IIn the 1950s my father needed power to an enclosure 30 feet away from the house. Not knowing that it was a code violation rans four runs of #12 with #14 ground ROMEX underground to the building. These conductors lasted until 2004 when a gas line developed a leak and the ROMEX was damagfed by a backhoe putting in a new gas line. We replaced the old ROMEX, that looked like new, with type UF cable. Location: Missoula Montana.

That old NM was tough stuff.

Thanks , Mike, I always appreciate the extra you do to enhance this industry!

On Q7. I don"t think we Know enough about this installation. If this were just supplying a single circuit it seems to me 230.31(B) exception would apply giving us a min. of 12awg. Also 230.18 (A) If this were a two circuit installation, 230.18 (B) would apply giving us a 10 awg wire.

ON Q10. I believe it would depend on where the conduit is run outside the building. A conduit under the eaves or below the sofit would be in a damp location and therefore acceptable.

On Q4. I don,t see anything that prohibits the cleaning of the componants in this case. I believe the key words in 112.12(C) are "damaged or contaminated" and "internal parts", so I don't believe we are talking about the can. Granted it would depend on how encrusted things were and how you would clean them. Acoustical spray is readily water soluable and aesily remofed by a damp cloth. I would remove the bus assembly and clean it with nothing but a cloth dampened with water, (no solvents allowed) let it dry thoroughly and replace. of course if really encrusted, this could take more time than it is worth. Usually overspray is no harder to remove with a damp cloth than dust.

On Q6. Depends on what kind of closet it is. if it is a utility closet, requirements of110.26, 230.211, 312.3 would apply.

On Q9 I agree that according to210.19(A)4(c) this is disallowed but I can't figure out why this would be disallowed on an individual type recept. Can you shed any light on this?

can romex wires in a residential home have paint on the outer insulation,