i have a poppery roasting set-up using a 10A powerstat variac to control the heater coil. The variac is a model that I have seen used and recommended on numerous home roasting sites, but i am blowing fuses consistently, about 4 or 5 minutes into the roast.

as i think about it, this makes sense: 1500 watts / 120V = more than 10A. So how are other people using a 10A variac with success? I have heard that people use fuses with a higher rating, which is ok because it would take more than a <15 minute coffee roast to overheat the variac. I'm a little wary of this because it's just generally an electronics no-no, but i could be convinced...i don't want to spend money on a beefier variac. anything i should keep a close eye on if i decide to use a higher rated fuse? or does anyone have this same experience and other thoughts?

thanks,
matt

I was also blowing fuses for a while on my variac, even though I was seldom using the full power. Turned out that there was a bad contact inside the variac. After tear down and repair the fuse stopped blowing.

If you are starting the roast at full power (130 Vac) with a resistance of 12.5 Ohm (1500W/120Vac), the current will be 10.5 A. It would not take very long for the fuse to burn.

I usually start the roast at 80% then increase gradually until 1st crack than reduce a bit to slow the end of the roast.