This is another achievement that will happen with chance, but this is also one where it's not that hard to set things up. A Chain Reaction is caused when the dials fall into place and immediately create a new path without you moving anything. This will happen often on its own, but stacking 3 will happen much quicker with planning. The U-dials are key for making this happen, as is leaving one or two collectors with a long but unconnected path when you let another path disappear. Doing this, you drastically reduce the number of dials that have to fall into the correct placement for a Chain Reaction to occur. Using U-Dials, your chances are better since you can create a path from one on top of an existing path and watch it fall into place by your own planning, taking reliance on chance out of the equation. There is a small moment when the old dials disappear and the new ones have yet to fall where you can manipulate dials and still continue a chain.