My brother keeps messing with me

My brother has been working towards being a licensed HVAC technician. In order to get his certification, he has to log in a certain amount of hours in the HVAC industry. He needs to go on HVAC repair jobs with an actual licensed contractor. Kind of like student teaching or an internship in the HVAC world. After that, my brother will need to take a lot of tests to prove he has the heating and cooling knowledge to be in the field. Right now though, he has only logged in a few in field hours. My brother however feels he knows a lot about HVAC repairs. Everytime I have him over to my house I cringe inside. I am praying every time that he does not touch my heater or AC unit. I am sure that by the time he is done with the program, he will know a lot. Right now though, he has a big ego and no knowledge. My brother has messed up my HVAC epically quite a few times. He has taken apart my whole furnace and then put it back wrong. He has damaged the fan blades on my cooling system. He also tried to clean my ductwork and ended up making a hole in it. I hate to tell him to stay away from my HVAC equipment. But, my brother is just not good enough to handle it yet. He does need practice, but I don’t want to pay for all the mistakes that he makes in my house. The sad part is that he actually thinks he does a good job.

HVAC installation