So a discussion came up today on transformer protection. And it seems everyone has a different opinion on what is proper/code.

I have always tried to fuse the primary to 150% of rated VA, with current limiting time delay fuses. And not worry about fusing the secondary. If I couldn't fuse the primary, then I would 150% fuse the secondary.

Well I got talking to few fellow techs today about this. And the opions are all over the place. From the secondary should be fused and not the primary. From you should fuse both. From fast blow fuses and not time delay. To fuses rated at 100% of VA, with no extra current for inrush.

Is there a NEC code that addresses this?