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I’m upgrading to a 200 amp panel and I’m using a surface mount on my stucco exterior. I tried reaching my inspector but due to the pandemic he’s been unavailable.

I will be applying urethane caulk around the top and sides of the box.

What is proper practice for running (nm-b) cable from the inside of the wall into the knockouts of my exterior main panel?

My electrician says to the caulk is enough, I just want a second opinion.

new panel

isherwood
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lemonpledge
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    If this is surface mounted to the outside of your house, you cannot use romex (NM-B) cable. This is considered a wet location. – PhilippNagel Aug 03 '21 at 17:28
  • If you wish to seek the blessing of a state official you will probably get better response from the building inspector rather than the electrical inspector. – NoSparksPlease Aug 03 '21 at 19:25
  • @NoSparksPlease I just want to know what would other electrician do in this situation and further educate myself – lemonpledge Aug 03 '21 at 19:42
  • @user3630509 correct, as soon as it exits the wall, you're outside/wet location. See for example https://diy.stackexchange.com/a/108301/65622 – PhilippNagel Aug 03 '21 at 21:48
  • NEC 334.12(B) Type NM cables shall not be used under the following conditions or in the following locations (4) In wet or damp locations, Article 100 Definitions, Location, Damp. Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. Examples of such locations include partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some cold storage warehouses. – NoSparksPlease Aug 03 '21 at 23:30
  • Determination of moderate degrees of moisture leaves much to the discretion of the local inspector. The interpretation I most got was if using NEMA 3R it must be at least damp. – NoSparksPlease Aug 03 '21 at 23:34
  • @NoSparksPlease I know I’m beating a dead horse here but I understand using conduit when an nm cable has to enter from the underside (or left/right side). My nm cable enters directly from the backside of the box which is mounted onto the exterior wall. (My inspector also emailed me back and said he wants the whole box sealed with caulk btw) – lemonpledge Aug 03 '21 at 23:36
  • In a conduit is still damp/wet location, in a 3R enclosure is still damp. – NoSparksPlease Aug 03 '21 at 23:44
  • @NoSparksPlease understood, I will rewrite my question in a different post – lemonpledge Aug 04 '21 at 07:13

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