Go Power F-400 Class-T 400 Amp Slow Blow Inverter Fuse

The Go Power F-400 is the 400 amp Class T slow blow fuse that guards the main DC feed between your battery bank and a Go Power inverter. It's the single most important piece of protection in a high-current inverter install, and it's the one people skip until they've seen what a shorted 4/0 cable can do. This is the replacement fuse Go Power builds for its own inverter fuse blocks, so it drops in clean and carries the interrupt rating those big DC circuits actually need.

Why Class T? Because an inverter running 2000 to 3000 watts pulls serious amperage off a 12V bank, and a dead short at the battery can dump thousands of amps before anything reacts. A Class T fuse is built for exactly that. It's a DC-rated semiconductor fuse with a very high interrupt capacity, so when something goes wrong it clears the fault fast and terminates power for good instead of arcing across the gap. That's the whole job. Protect the cable, protect the boat, protect you.

The slow blow part matters too. Inverters don't sip power, they surge. Fire up a 3000 watt unit and the soft-start inrush can spike well past the steady-state draw for a moment. A slow blow characteristic rides through that startup surge without nuisance-tripping, then still opens hard on a real fault. So you get a fuse that leaves you alone during normal operation and drops the hammer when it counts.

This 400 amp rating is the top of Go Power's Class T line, which runs from 110 up to 400 amps. It's sized for the bigger inverters, the 3000 watt class and similar high-draw setups. The fuse works across 12, 24, 32, and 48 volt battery systems, so it fits everything from a simple 12V house bank to a larger 48V setup, as long as you've sized your cable to the load.

Speaking of cable, this is where installs go wrong. A 400 amp fuse belongs on a 400 amp circuit. Pair it with heavy cable, 4/0 AWG is the common call on the battery-to-inverter run, and keep the run as short as you reasonably can. Undersized wire on a long run heats up, and that heat migrates into the fuse body and the lugs. Do it right and the fuse runs cool and boring, which is exactly what you want from a fuse.

Mounting is simple but not casual. Put the fuse as close to the battery positive as you can, within a few inches, so it's protecting the whole cable run and not just the far end. Use a proper marine-rated fuse block or holder, torque the lugs to spec, and check them again after the first few weeks. Loose connections are the number one cause of melted terminals on high-current DC. Pick a dry, accessible spot, keep it up out of the bilge, and mount it so you can actually get a wrench on it if you ever need to swap the fuse.

Who's this for? Anyone running a Go Power inverter big enough to need 400 amp protection, on a boat or an RV. If you're building out a 12V house bank to run AC loads underway or at anchor, this is the fuse that sits between a good day and a very bad one. It's a spare worth keeping aboard, too. A blown main fuse with no replacement on the shelf means no inverter until the next chandlery, so a lot of owners keep one in the spares kit.

One honest note: this is the fuse only. If you don't already have a Go Power fuse block to seat it in, you'll want the matching block as well. And if a fuse blows, don't just drop another one in and walk away. A Class T fuse doesn't nuisance-trip. If it opened, something caused it, and it's worth finding the short or the overload before you power back up.