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tom baker said:
Why not use 12 or 14 THHN/W if you are going to the expense of using EMT?
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Once entering the house NM cable is fine and faster then fitting raceway to the destination. If you change over wiring method you need a junction box that does add some time/cost, and maybe isn't desired for appearance sake either. The use of UF cable would still work if not a dry location where the EMT is ran.
 
I think you are OK with your installation.

However, I do agree that NM cable is not allowed in wet location.

But your location does not seem to be wet. NM cable is allowed in locations that are "NORMALLY" dry and I think under the roof even though outside, it is "NORMALLY" dry.
 
edward said:
I think you are OK with your installation.

However, I do agree that NM cable is not allowed in wet location.

But your location does not seem to be wet. NM cable is allowed in locations that are "NORMALLY" dry and I think under the roof even though outside, it is "NORMALLY" dry.
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But is this location normally dry or is it damp?
 
kwired said:
But is this location normally dry or is it damp?
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IMO, it is normally dry.

If under the roof area it is normally damp, wouldn't that create mold issue? I don't know. Maybe the OP can chime in as to if that location is normally dry or normally damp
 
edward said:
IMO, it is normally dry.

If under the roof area it is normally damp, wouldn't that create mold issue? I don't know. Maybe the OP can chime in as to if that location is normally dry or normally damp
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I sort of agree with you, sleeving NM in a steel tube however is going to complicate things because there will be condensation issues inside that steel tube.
 
goldstar said:
Now that I think about it, if the EMT is terminated into a JB at one end and that JB is grounded then so is the EMT.
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The conduit is only considered to grounded if attached to the j Box with a connector listed as as grounding connector. I.E. pewter locknuts do not comply as a grounding locknut.


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kwired said:
I sort of agree with you, sleeving NM in a steel tube however is going to complicate things because there will be condensation issues inside that steel tube.
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I agree that there is a potential for condensation inside of this conduit and NM cable should not be used.


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ElectricMatt said:
I agree that there is a potential for condensation inside of this conduit and NM cable should not be used.


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If you are in southwestern US you have potential, if you are most anywhere else in the US you do have condensation at some point:happyyes:
 
ElectricMatt said:
The conduit is only considered to grounded if attached to the j Box with a connector listed as as grounding connector. I.E. pewter locknuts do not comply as a grounding locknut.
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Welcome to the forum. UL says they do, from the White-book,


GROUNDING
All metal fittings for metal cable, conduit and tubing are considered suitable
for grounding for use in circuits over and under 250 V and where
installed in accordance with the NEC, except as noted for flexible metal conduit
fittings and liquid-tight flexible metal conduit fittings.
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The term fittings includes locknuts

CONDUIT FITTINGS (DWTT)
USE
This category covers metallic and nonmetallic conduit fittings, such as
connectors, couplings, conduit bodies, short-radius conduit bodies, expansion
fittings, locknuts and sealing (liquid-tight) locknuts for use in the
assembly of nonmetallic and metallic wiring systems. Also covered are
fittings used to provide a transition between metallic and nonmetallic wiring
systems. All fittings are intended to be installed in accordance with
ANSI/NFPA 70, ‘‘National Electrical Code’’ (NEC), and are intended for
installation and use in accordance with the following information and the
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Roger
 
kwired said:
there will be condensation issues inside that steel tube.
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Honest questions here, not trying to imply you are wrong but asking for more information:

Why? Are there condensation issues on the underside of a porch roof? If not, what mechanism is going to cause the steel tube to be colder than the underside of the porch roof?

Thanks, Wayne
 
wwhitney said:
Honest questions here, not trying to imply you are wrong but asking for more information:

Why? Are there condensation issues on the underside of a porch roof? If not, what mechanism is going to cause the steel tube to be colder than the underside of the porch roof?

Thanks, Wayne
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Underside of roof will often be warmer then out in the open, but condensation occurs when temp drops below the dew point regardless of where it is at. That warmer air under the roof will hold more moisture, so if you manage to get it cooled off enough may actually have more condensation then some other areas. Metal tubing will have more condensation problems then a PVC tubing because of the higher rate it can transfer heat.
 
kwired said:
Underside of roof will often be warmer then out in the open, but condensation occurs when temp drops below the dew point regardless of where it is at. That warmer air under the roof will hold more moisture, so if you manage to get it cooled off enough may actually have more condensation then some other areas. Metal tubing will have more condensation problems then a PVC tubing because of the higher rate it can transfer heat.
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This happens a lot here in Texas where we swing from 80 degrees to 30 degrees. It happens so bad we put drains in frequently.


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I'm still trying to understand the physics here. My current understanding is that this is a competing rate effect: air gets exchanged slowly between ambient and the inside of a metal conduit system, while the temperature will change more quickly. So when the outside air cools off, the conduit cools off more quickly than the air inside can change to the new ambient cooler, less moist air, and you get condensation.

If so, then a sleeve on the underside of a porch roof is perhaps one of the least likely places for this to occur outdoors: one end is open, so the air exchange will be faster than a fully closed system. And the underside of a porch roof is a fairly protected location, so it will not see as quick temperature changes.

But maybe it still happens. Do you ever see condensation dripping out of a metal, ceiling mounted light fixture on a porch?

Thanks, Wayne
 
wwhitney said:
I'm still trying to understand the physics here. My current understanding is that this is a competing rate effect: air gets exchanged slowly between ambient and the inside of a metal conduit system, while the temperature will change more quickly. So when the outside air cools off, the conduit cools off more quickly than the air inside can change to the new ambient cooler, less moist air, and you get condensation.

If so, then a sleeve on the underside of a porch roof is perhaps one of the least likely places for this to occur outdoors: one end is open, so the air exchange will be faster than a fully closed system. And the underside of a porch roof is a fairly protected location, so it will not see as quick temperature changes.

But maybe it still happens. Do you ever see condensation dripping out of a metal, ceiling mounted light fixture on a porch?

Thanks, Wayne
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I tried to explain because it is protected it is less likely to condense in there. With winds we can get here I wouldn't say it will never condense in there as the air temp around that tube is not guaranteed to stay consistent like it might in still air. Now if OP has an enclosed porch, it may depend on circumstances but might not even considered to be a damp location.
 
kwired said:
I tried to explain because it is protected it is less likely to condense in there.
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Thanks. I didn't mean my last post to be argumentative, just trying to understand the physics here.

My last question was intended sincerely, not rhetorically: do conditions in some climates cause condensation inside, say, a ceiling mounted metal luminaire in an open porch? I totally agree condensation can occur inside conduit on the side of a building, I'm just wondering if it will actually occur in the more protected conditions of an open porch.

Cheers, Wayne
 
Anytime I have worked on lights under a patio or awning, mostly commercial, I have found moisture or evidence of. To me it is the same as installing receptacles in the soffit of a house; There is a very slight chance of moisture , but we install WP receptacles. Anything on the exterior of a building, in my experience, receives the classification of damp at minimum.


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