Weil McLain 383 500 604 Fuses Flexible Adjustment: Allows for essential Flexible Adjustment: Allows for essential angular movement to prevent linkage binding during full motor stroke it is a standard requirement for maintaining the 82% AFUE and high thermal efficiency ratings of the Lochinvar Knight and Copper Fin series as these specific 12 amp components are frequently the primary point of failure when protecting the U Control module from external electrical faults Using a fast acting fuse in place of a slow blow fuse will lead to frequent failures because it cannot withstand the initial inrush current of the boiler’s internal components