My guess: kitchen was originally fed from a shared-neutral circuit, something else (the outlet in question) fed off that, he got some wires crossed and gave your carpet machinery 240.

We would really need a much, MUCH better description than "there are wires everywhere" to give any useful advice beyond: "call an electrician". There are definitely some major problems by the sound. (one being that you now have a 240-volt 120-volt outlet, the 'flying splices' [wires without junction boxes] being another)

As I'm sure you can figure, every house is different, so there is no generic "this is why your vacuum cleaner blew up just move this wire here and press that button" answer. More detail is necessary.

Further, there are two groups of people I consider qualified to work on electrical wiring. One is properly- trained electricians, the second is people who know when they're in over their heads and it's time to ask the advice of someone with more knowledge. Since YOU are in here asking about YOUR HUSBAND's work, he's not exactly scoring points in the second category, so I have to strongly encourage seeking out someone who fits the first!

Put a meter on the receptacle in question. What's the voltage? If he doesn't have one, that is just another indicator that he's in over his head and needs to get some professional help.

I don't want to sound like I'm piling on here, but I think you have two problems: 1) possibly bad wiring done by the previous owners, and 2) possibly bad wiring done by your husband (I'm guessing he did not get a permit for this work). The situation you described suggests a house fire waiting to happen. Please do yourself a favor and get a qualified electrician in to assess the situation before you have an even bigger problem.