I can't speak for chests, but when I had an REC hooked up to a wooden pipe pulling out of a barrel it makes a lot of explosion noises (same as TNT going off) and visual effects when you forget to turn the REC power down to 1-2 MJ/t instead of 50 MJ/t when you power it. Also at 50 MJ/t it will empty a full barrel in about 5 seconds.

Strangely though, despite the explosion noises and effects it doesn't actually do any damage anywhere. If you are wearing good armour you can get near enough to disable the power without getting killed.