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| 3. Insulation. All live parts should be sufficiently insulated so that there will be no danger of breakdown either from line to ground or from contact to contact after a fuse has blown. The cut-out or mounting should be able to withstand a dielectric test of two to three times the rated voltage or any tests specified by regulatory bodies. |

| 4. Durability. The mounting or cut-out should be able to withstand severe climatic conditions (both heat and cold, rain, ice, etc.) and should be protected against decay and insects, as well as from birds, squirrels, snakes, and other likely animals. Metal parts should either be non-corrosive or protected against corrosion (including salt-spray atmospheres) and rust. |

| 5. Contacts. Contacts should be sufficiently large to carry a normal rated current without heating. Radiating surfaces of the cut-out or mounting should be sufficient to dissipate heat generated by the melting fuse link and any arc that may form. |

| 6. Grounding. This is an added safety consideration. All nonenergized parts of the fuse mounting, including metallic parts, should be bonded together and connected to one or more grounds, or to a common ground mesh where one exists. Furthermore, the ground resistance should be sufficiently low to drain off high voltages should the mounting or cut-out fail as well as to operate other protective devices that will de-energize the portion of the circuit on which the failure takes place. Caution should be taken in using water pipes as grounds. Although they formerly provided excellent grounding sources, the use of nonmetallic pipes for water supplies make water systems questionable. Connecting wires should provide some disconnecting point at which ground resistance may be periodically checked. Such disconnecting points and the wire itself should be protected from possible tampering by the general public or any unauthorized personnel. |

| Maintenance |

| Little can be done about the maintenance of fuses and their mountings or cut-outs other than to inspect them visually. Since the life of practically all fuses is indeterminate (they do not weaken with age), no periodic replacement of them is usually undertaken. In a multipole or polyphase fuse installation containing two or three fuses, it is good practice to replace all fuses after one has blown. At some critical or sensitive installations, it is also good practice to keep a set of spare fuses for each different rating or type of fuse in service (see Table 11-2). |

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