Can I use 400 amp AC breaker instead of class T 400 amp fuse

[Len Silva]

I would say that chances are 99 out of 100 that you will never blow that fuse and it is certainly much less expensive than a CB.  When a 400 amp fuse blows, you will know it and so will all the neighbors.

Len

[NJT5047]

Another reason for manufacturers recommending fuses over circuit breakers may be the speed at which they open.  A fuse is much faster. 
Large DC Circuit breakers are expensive in comparison too. 
JR

[Dallas]

Pat,
The Xantrex setup that I've read requires a T-fuse.

Mostly the reasoning behind it is that the T-fuse is nearly fast enough to possibly save the electronics in the inverter. Breakers aren't.

Do it your way, but if it's a new inverter under warrantee, I would put the fuse called for in it. It might make your case for replacement a little more tenable.

Just my way...

Dallas

[Sean]

Wow, lots of speculation on here from folks who, apparently, have not even read the documentation for your inverter before telling you why you can't do certain things.

So that I don't make the same mistake, perhaps you can tell us the model and voltage of your inverter?  After all, Xantrex makes the manuals for all their inverters available on-line.

FWIW, my own Xantrex inverter manual says nothing at all about preferring a fuse over a breaker.  It does, however, stipulate that the maximum allowable fuse is 400A, whereas the maximum allowable breaker is 250A.  While this may seem like a big difference, the fact is that the 250A breaker will provide better protection for your wiring, batteries, and inverter, and will only be a minor inconvenience if it ever trips, while the class-T fuse will likely be a real project to change.

Xantrex, BTW, will be happy to sell you their own branded 250A DC breaker for this purpose.  If you can get by with 200A, Square-D's QO-series breakers carry DC ratings, and there is a two-pole model available in that size, available at almost any home center for a reasonable price, with a two-pole enclosure commonly available for around $15.

I have a 400A class-T (actually, two of them, since I have separate 24volt and 12volt feeds off my battery bank).  I figure that if it ever blows, I have bigger problems than how hard it is to change the fuse.  Also, the fuse holder takes up less room than a circuit breaker and enclosure.  Lastly, my cables are four-ought, and getting cables that big into the panel and onto the lugs is a challenge. YMMV.

-Sean
http://ourodyssey.blogspot.com