You'll find there are a variety of options in how water pressure washing systems are made. If you know how and how often your unit will be used, you'll have an easier time determining if you need a light duty or heavy duty system. Units used less than five hours per week can usually be light duty, but those used more than five hours a week should be industrial or commercial grade, heavy duty systems.
Hot pressure washing systems have two power systems: the pump and motor system that creates high pressure water flow, and the water burner and coil system that heats the pressurized solution. Hot water burners require electricity to run the burner motor and fuel (kerosene, diesel, or propane) to heat the water in the heavy-duty heating coil. If the pressure washer system is electrically powered, you can use the same power source to power both the pump system and the hot water burner. But you'll still need fuel for heating the water. If the pump is gas powered, you will still need electricity to power the water burner.
Hot water pressure washer systems are heavier and more complex than cold water systems, and you'll need to maintain your system regularly and sometimes make repairs, so having a good source for burner repair parts is essential. Most gas units use a self-contained power source like a 12V battery or a 115V generator for electrical power to run the hot water burner.
Parts you may need to maintain or repair your water burner include igniters, fuel pumps, transformers, blower wheels, and burner motors. One common problem is finding there's not hot water. Usually this means there's not enough fuel, the thermostat is off, or the fuel filter is clogged. If the burner won't ignite, it may mean there's no fuel, the thermostat's set too low, the fuel filter or burner nozzle is clogged, or the pressure switch is defective. If your water burner produces smoke, it could mean the wrong fuel is being used, water is contaminating the fuel, there are air leaks in the fuel lines, or soot on the coils.
Hot pressure washer systems are more popular than ever as people discover just how much labor can be saved by using hot water systems. However, these systems do require an extra layer of knowledge about the hot water burners to keep the systems working properly. Learning to troubleshoot a hot water system isn't that different from trouble shooting your pressure washer pump system. There's no substitute for reading the manuals that come with hot systems, because these often include detailed troubleshooting guides that give you all sorts of things you can check for and try before taking your system to be repaired.