Forgive for not knowing the correct terminology:

For one of our 2 outside Carrier units, the copper refridgerant line exits the wall and will run about 25 feet to where the Carrier unit sits on its pad. As is typical, this line is wrapped in a thick foam sleeve.

The HVAC guy wants to bury it in a shallow trench so it does not just sit there on the ground along the exterior wall. Is this acceptable? If so, should the foam sleeve be wrapped in something additional??