How large a surge protection module should the distribution box be equipped with
Therefore, it is recommended practice that both the input circuit to the UPS and the associated UPS bypass circuits (including the manual maintenance bypass circuit) be equipped with effective Category "B" surge protective device, as specified in IEEE Std. SPD enclosures must be compatible with the target distribution box or panelboard layout, whether it's a surface-mounted load center or a flush-mounted industrial cabinet. For all other cases SPDs shall be fitted to protect against transient overvoltages, unless the owner of the installation declines such protection and wishes to accept the risk of damage to both wiring and equipment as tolerable. When installing a surge suppressor, it is important to mount it as close to the electrical equipment as possible in order to keep the wiring (lead length) between the electrical equipment and the suppressor as short as possible. At the incoming distribution box, if the main air circuit breaker is greater than 630 A or MCCB is between 315 A and 630 A, the upstream dedicated disconnector of SPD should use a 200 A circuit breaker or a 250~315 A fuse.
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