Does the installation of elevator appliances need professional staff?

I have decided to install an elevator electric saver for my elevator, so when it is being installed, is it directly installed by its own staff, or is it necessary for professional staff to provide services at home?
In fact, we will find that when most elevator businesses use a lot of elevators, most of the enterprises will use more elevators. After a unified purchase, the unit will send a dedicated staff to the elevator to install the elevator. But there are also some units may lift number itself is very small, there may be only two or three, so in this situation, he was in the elevator Saver after the purchase, if you need a professional engineer door-to-door service, he will need to pay a service fee.
Maybe he would think this was not a special sum, and he wanted to install it through his own staff. Does this installation guarantee safety? We will find that when the elevator is installed, it has a special installation process. And we need to check the elevator first, no problem after the installation, after the installation, the need for trial operation. Our ordinary staff don't know enough about elevator, so we have to find professional staff to install to ensure safety.