Ruud furnace keeps blowing 24 VAC 2 Amp fuse within 12 hours

I had a similar problem but it was because I had two furnaces and a damper control on the fresh air intake. Because the two furnaces were wired with independent transformers, and the transformers were wired opposite, the transformers would basically fight each other through the damper control and pop the fuse. It would only occur when both furnaces called for heat simultaneously, which wasn't very often as we usually have only one or the other turned on at a time. Fixed by removing the damper control.

A short to ground might cause the fuse to blow, also.

It's more likely a short than some device using too much current. I would start by inspecting all of the wires to look for breaks, burns, or worn insulation. Pay particular attention to where wires are joined together, and where wires go through a bracket or housing.

Next, get the system to run, even if just in fan mode. Then give the various wires a good wiggle. This could help narrow down our search area.

If that doesn't work, get a second fuse holder and couple of fuses, plus a larger fuse (i.e., 5 AMP). Put the larger fuse in to the existing fuse holder. Then wire the second fuse holder in to various areas and test. For example, put a fuse in line with the R wire to the thermostat. If the new fuse blows, then the problem is with the thermostat wiring.