Water takes too long to heat up

Issue description:

Why does the boiler heat up the water for a long time, what are the reasons, which master to call?

There can be several variants of the problem:

There are 2 heating elements in the boiler, one is covered. Therefore, only one works and, accordingly, the heating time has increased. The solution is to disassemble and replace the burned out heating element.

The heating element is covered with a layer of scale, heat transfer decreases, heating time increases. It is treated by disassembling and cleaning the heating element.

If the heating element has burst, then in silence you can hear a hissing inside when the boiler is on. Also, water flowing from the tank can pinch with current. If there is an RCD (a small box with a button on the network cable), then the boiler will turn off automatically when the heating is turned on, because the water is in contact with the open coil of the heating element.