I had trouble installing a laser print at home that forced me to return to the shop and change it by a new one the next day.
Now, reflecting on the issue, I am in doubt over the cause of the problem.
At first I tried to plug it in the same UPS where the desktop computer is plugged (and where the old deskjet printer was plugged). The device (UPS) simply turned off after some noise and bips everytime I tried. I realized (looking on the internet) that the warm up of a laser printer need a lot of current in the first seconds. It is strange that there is no warning in the documentation of the printer, because I think that it is quite normal to put this type of equipment in a UPS.
When I plugged the (first) printer on a separated socket, it turned on initially, printed one test page, but suddenly starts to blink the LED's in a fashion that indicates, according to the supplier, a failure not possible to be solved by user action. Even after plug out and plug in again the printer was showing the same failure warning.
Before to turn on the replacement printer, I measured some sockets with a voltimeter. They have 3 holes, and most of them have 127 V between live and neutral, but not between live and earth. Except for that one where I plugged the first printer. I was afraid of another damage and plugged it on another socket. It is working normally.
Now: was the printer simply damaged from factory? Maybe the trials in the UPS can have damage it? Is that socket without a dummy earth responsible?