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Heating, Ventilation and Air Conditioning (HVAC)
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- The difficult part of evaluating heat exchangers is the fact that only 15–20% of a
standard heat exchanger is visible. The best way to determine if you have a failed heat
exchanger is to do the following
- Turn the unit on by raising the thermostat. This should cause the atmospheric burners
to come on. Look at the flame pattern before the fan comes on. There should be bluish
flames with a small amount of orange/yellow at the tips, and they should be erect or
vertical.
- Look at the burner flames again when the fan comes on. There should be no difference in
the flame pattern. If there is, then it suggests that the fan is forcing air from the
house side into the path of the flame, and forcing exhaust through a crack or hole in the
heat exchanger. This occurs because the fan will pressurize the heat exchanger from the
house air side.
- Although there are other methods to determine a failure, watching for a distorted flame
pattern, while not perfect, is a very dependable method.
- Learn more about heating.
How can you conclusively determine if a steam boiler is good or
bad? 
- You must first develop pressure in the system before
steam will be forced through a crack. Steam boilers do not develop pressure until air is
evacuated from all of the radiators and they are filled with steam. When the radiators are
filled, pressure builds up in the system. (From a cold start, this usually takes
40–70 minutes to develop, depending on the size of the system and size of the
burner).
- Residential units typically operate with 2–5 psi as the limit. Commercial steam
boilers may operate with 80–100 pounds or more, depending on the application.
- The limit control and the pressure gauge are usually located at the top of the boiler.
- Learn more about heating.
If you are a client and your question is not answered above,
click here to Ask the
Inspector
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