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weatherhead
A weatherhead, also called a weathercap, service head or service entrance cap, is a weatherproof service drop entry point where overhead power or telephone wires enter a building, or where wires transition between overhead and underground cables. At a building the wires enter a conduit, a protective metal pipe, and the weatherhead is a waterproof cap on the end of the conduit that allows the wires to enter without letting in water. It is shaped like a hood, with the surface where the wires enter facing down at an angle of at least 45°, to shield it from precipitation. A rubberized gasket makes for a tight seal against the wires. Before they enter the weatherhead, a ''drip loop'' is left in the overhead wires, which permits rain water that collects on the wires to drip off before reaching the weatherhead.
A weatherhead termination is only used at low voltages (up to 600 volts), since higher distribution voltages require more insulation between conductors and metal enclosures. Higher voltage connections are made through a pothead. 〔Anthony J. Pansini ''Guide to Electrical Power Distribution Systems'',The Fairmont Press, Inc., 2005 088173506X, page 138 〕
Weatherheads are required by electrical codes or building codes. They are also used on utility poles where overhead power lines enter a conduit to pass underground.
==References==
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抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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