On Wednesday, March 9, 2016 at 11:20:45 PM UTC-5, wrote:
On Wed, 09 Mar 2016 20:03:19 -0500, wrote:

On Wed, 09 Mar 2016 14:38:32 -0500, wrote:

On Wed, 09 Mar 2016 14:08:58 -0500, wrote:

On Wed, 09 Mar 2016 10:17:25 -0500, wrote:

On Wed, 9 Mar 2016 03:14:37 -0700, rick wrote:

OK, so let's say I ignore code and install romex in conduit in a wet location. And over time water condenses in the conduit so the romex becomes and stays wet.

What's the big effin deal?

The first thing you see is nuisance trips of the GFCI

Does the insulation break down and allow electricity to flow between L1 and neutral?

Eventually the water can "wick" down the paper packing in the NM and
drip into other boxes.

If you want the question I have not heard answered is why the
manufacturers still use the paper in the first place.
There is a listing for NM without paper, using plastic filler, called
NM-c that tolerates more water than NM-b and less than UF but when you
poke around, that comes back as UF cable in their catalogs so I assume
they don't want to catabolize the UF business by upgrading NM-b to
NM-c.

It must be available somewhere because it has a name, "barn cable".

NM-b (Romex) dry only
NM-c (Barn cable) damp and dry
UF (underground feeder) dry, damp or wet
There is no paper in Canadian NMD-90 cable. I checked 4 different
samples I have here, 14, 12, and 10 guage.

Perhaps that's why an associate who thought he could beat the system
had to tear out ALL of the American NM cable he had used to wire his
house - the inspector took one look - no CSA stamp on the sheath and
he condemned the whole job. All of a sudden saving over 50% on his
cabling costs wasn't such a great deal any more!!!

Like I said on a previous post (or more) on another thread - Canadian
codes when it comes to safety tend to be much stricter than american
requirements. Many things that pass UL don't come close to passing
UL-c or CSA.

I did some reading on NMD90. It appears there is no internal wrapper.
Maybe that is why they give up 300v in the ratings. NM-b is 600v
rated, NMD90 is 300.
Which is still well over the required rating for a center tapped
single phase 120/240 volt electrical supply.

Well over? 250v (the max in the 240v standard) is more than 80% of the
rating

Actually peak voltage in a 240V AC circuit is 340V.