To assemble the wall connection to artefacts there is no problem with the nut and the corresponding ferrule.It is allowed because in case of problem you should be able to close the path and ready. The regulation in some cities speaks of the tramno of the copper pipe ... which cannot exceed 50 cm
Thank you, there are no losses so I suppose everything is correct, if there is a leak I suppose it will be minimal and gradually and thus close the passage and renew the sealing work. I do not do it because there are several heaters and the cost is not within my reach now, besides there is no leakage problem, of course.