Look up the maximum Zs earth fault loop impedance values for circuit breakers, MCB's, MCCB's and fuses. MCB's. MCCB's. Rewire-able fuse wire HBC Fuses. HRC BS 88 Fuses. 100% and 80% temperature adjusted values. Includes disconnection times for 0. 2s, 0. 4s and 5 seconds. Various manufacturer specific MCCB Zs charts.