Use the right cable: NM-B (“Romex”) is not for direct burial. Plan transitions: protect the point where wiring emerges from the ground (for example, with conduit risers . The use of unarmoured cables, such as HO7RN-F rubber flexible cables or unarmoured XLPE cables buried in the ground, is becoming more popular, especially for DC string wiring of photovoltaic (PV) systems and for certain interconnections in electric vehicle (EV) charging installations. For such. Underground wire sizing is very different from indoor runs, as underground circuits tend to run much longer, which makes voltage drop a major concern. Since voltage drop is an issue, the solution is to. This document is published in accordance with the requirements of Chapter 5 of the National Electricity Rules (NER). It is a functional requirement document only and is not intended to contain any comprehensive or project specific designs, specifications or other information. Other cable types can be buried, but may need a little extra protection to ensure they remain as free as possible from damage.
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