Quote
Garry Bartsch
So that 11A is the holding current? What amperage will it trip at?
Yes, 11A is the hold current. There isn't an absolute tripping current, it's all based on how much current for how long causing a temperature rise. The
datasheet for the polyfuses speced for RAMPS say at 25 degree C ambient, 55 amps should trip in a max of 7 seconds.
Quote
If your polyfuse didn't trip pulling 15A then mine shouldn't at 12-ish, granted polyfuses are all the same.
There is some variance just like with any other electronic components, but yes. I have a fan that blows on my RAMPS board keeping the drivers and mosfet cool, so that may help some. But 12 amps should be allowed to run for some time without too much of an issue. Once the bed reaches temperature and duty cycling kicks in, that will also help.
Quote
But say I did wire in a 15A car fuse. It would not trip till 15A but what would get hot before it did?
Presuming wiring was large enough gauge, I'd be most concerned with the heated bed screw terminals, as well as the traces. The screw terminals are already marginal at best.