Prior to filling the system, it is good practice to pneumatically test the piping for leaks. After filling the system, the fluid should be cold circulated through all possible flow paths and the pump strainer cleaned to remove all debris. After cold circulation, the system must be “boiled out,” or brought up to operating temperature in a controlled manner to remove residual water and steam. When boiling out the system, all possible flow paths should be open. The system should be brought up to a temperature approximately 50°F (28°C) higher than the maximum anticipated operating temperature - but within the limits of the thermal fluid.
After the system has been boiled out, combustion settings, pressure switches and temperature limit settings can be finalized and recorded. It is important to use a commissioning agent who understands both the combustion and system operation. Some heater manufacturers furnish commissioning services.