Combined boilers can work on two or three different types of fuel, but there are those that can work on all these: solid, liquid, gases and have a built -in heating heating heating element. The price of combined boilers is quite high, and it is advisable to use them only with regular interruptions in the supply of fuel. The design of the boiler for several types of fuel as a whole reduces its utility coefficient by 10-20%
On combined gas-liquid boilers to switch to another type of fuel, it is only necessary to replace the burner, it takes 15-20 minutes.
Combined boilers with electric heating and heating are usually supplied to the heater in the case of interruptions with the supply of the main fuel (in the presence of active automation), or are turned on manually.
Solid fuel combined with others are usually used if necessary manual supply, with the possibility of turning on the automatic mode in a different type of fuel.