don't do that. get a proper fuse, for safety sake
fuses are complicated well engineered parts that require some thought for specifying. if you are gonna whack some random shit in there, at least try to get it half right.
littlefuse has fusing guidelines for transformers.
http://www.ttiinc.com/attach/2257144.html?type=support&primitive=0This will at least get you in the ballpark.
To properly select a fuse, you must
1) select select a mean time between failure you are happy with (lets say 10,000 on/off cycles).
2) measure inrush currents, operating currents, overload currents, and use fuse manufacturer tables to select a proper fuse.
The more cycles you have, the less protection it offers. The less cycles you have, the more protection it offers.
![Evil >:D](https://www.eevblog.com/forum/Smileys/default/evil.gif)
. It's not so bad as it looks though, if you really do some engineering this might not hold true.
Luckily, for transformers, you often don't need to do all the measuring, so long you have the transformers specs. Simply google fusing transformers and there will be plenty of informative material.
As for your inrush current, since you are building your own device, i recommend a time delay relay, it is a much more robust circuit then a NTC.