Romex outdoors and underground

[jr70895]

Hired an electrician to add 220 volt outlet for a/c window unit in mobile home. All the wiring is run outdoors in conduit except the last 4' will be underground in conduit.
I'm no electrician by any means but not sure it's done correctly.
1) The wire he used is 10/2 Romex NM-B wire for 20 amp a/c unit
2) Wire is In conduit from the outdoor panel, it runs on the ground along the side of the trailer. It then runs up the side a few feet to a disconnect box mounted on side the trailer.
3) Approx 4' is in conduit and will be buried about 12" or so to the power supply panel.

Here's the questions:
Can you run Romex in conduit outdoors? I've read no because it can trap heat and can cause issues. Was told since the wire required is 12 gauge using the 10 gauge will not allow it to get too warm.

Was told you can't use Romex underground because it's considered a wet environment even if in liquid-tite conduit.

What I've been reading is that it should be UF cable in conduit underground for protection and not in conduit in areas where the wire is protected against damage such as under the trailer.

Thanks

 

[Melensdad]

Romex brand is not rated for underground burial. There are some other brands that claim they are certified for direct burial.

 

[chowderman]

if it's under ground / buried it should be rated UF (UnderGround feeder)

sites say Romex is not suitable, and then ...

https://www.grainger.com/product/ROMEX-Underground-Feeder-Cable-12-4WZT7

thru the flower beds I ran UF in aluminum conduit (no rust away....) so people didn't dig into the wire and light themselves up . . .

 

[jr70895]

Electrician installed all new 10/2 UF wire from the outdoor electric pedestal to breaker box mounted on the outside of mobile home with a 20 amp breaker. The new window unit a/c says it draws 15.1 amps and is a 220v unit. Then 12/2 pigtail wiring was run thru the wall to the new added outlet.

The window unit is brand new and an a/c and heating unit.

After running about 30 minutes the a/c trips the stand alone outside 20 amp breaker. This has happened 3 times. Calling the electrician to return and see what the issue might be.

The first picture is the old a/c cable that's lying on the ground. 2nd picture is the new wiring hardwired into the 30 amp outlet on the right and in conduit.

The cable on the left in both pictures is the main cable coming into the trailer and has since been incased in protective conduit.

Does the pigtail need to be 10/2 also or is 12/2 acceptable? Also, just thinking forward I'm assuming installing a 30 amp breaker into the box would not be the answer. Just in case that his suggestion.