ME-300F and ME-400F Instruction Sheet
© 2011 Magnum Energy, Inc.
Magnum Energy, Inc.
2211 West Casino Rd.
Everett, WA USA 98204
425-353-8833
www.magnumenergy.com
Introduction
The Magnum Energy Class-T Fuse/Fuse Block is designed to provide code 
compliant overcurrent protection. It protects the battery bank, inverter, 
and cables from damage caused by short circuits and overloads. A fast 
acting, current-limiting Class-T fuse cartridge delivers instantaneous 
protection in the event of a short circuit, as well as a time delay to allow 
the momentary current surges that are common in inverter applications. 
Magnum large fuse blocks are available in 300 and 400 amp models. 
A rugged injection-molded polycarbonate base and thermoformed ABS 
cover provide durability, easy installation, and good looks in a compact, 
cost effective package.
Fuse selection is based upon the size of the conductor between the 
battery and the load. Keep in mind that the conductor’s current carrying 
capability is affected by: the length of the cable between the battery 
and the load, and the conductor’s wire type and temperature rating. 
Refer to Table 1 for assistance in selecting a fuse.
Installation
The battery, fuse block, and inverter should be located as close together 
as possible – without being in the same enclosure. Batteries can produce 
explosive gasses that may be ignited by the fuse. For code compliance, locate the fuse within 18” (45 cm) of the battery, and with at least 6” (15 cm) 
clearance from other equipment on each end. When changing the fuse, it 
may be energized by the battery; allow additional clearance if grounded 
metal surfaces (such as the inverter’s chassis) are nearby.
Attach the fuse block base to a secure surface using the appropriate 
hardware (refer to Figure 1). Make the connections to the fuse block 
fi rst (see Figure 2 for proper hardware stacking), then to the battery, 
and fi nally to the inverter.
NOTE: Do not install the fuse in the grounded conductor.
Torque the Hex nuts to ~244 inch-pounds (27.6 N-m). The lock washers 
provided must be installed to ensure a quality and long lasting connection.
Check the cables for correct polarity with a voltmeter before making the 
fi nal connections to the inverter. Replace the fuse block’s cover to prevent 
accidental contact with the fuse’s live terminals.
WARNING: Failure to comply with torque specifi cations 
may result in damage and premature failure of the product. 
Failures caused by not adhering to the proper torque specifi cations are not covered by warranty.
WARNING: Before replacing a fuse, ensure all AC/DC power 
sources are de-energized (i.e., breakers opened, fuses removed) to prevent accidental shock.