Iron, Golden and Diamond chests have two recipes(three, if counting upgrades). For instance, you can craft iron chest using 8 iron ingotsand a chest, or using 4 iron ingots, 4 glass and a copper chest(which, in turn, is crafted from 8 copper ingots and a chest).
However, recycling said chests returns the contents of the first crafting recipe, which leads to a duping mechanic. Well, you get less items overall(if you crafted the chest using the second recipe), BUT you still get more, say, iron, than you used in crafting.

Decided to block the chest recipes to avoid the dupe loop. Fixed for v0.3.5.2ALPHA: https://github.com/OreCruncher/ThermalRecycling/releases/tag/v0.3.5.2ALPHA

v0.3.5.4 has been released and includes these changes. Closing.