Since mid 2005 most residential water heaters sold in the US have been equipped with a safety device to keep flash back fires from leaving the burner chamber.

The technology prevents such fires by trapping and burning dangerous gas vapors inside the heater while preventing ignition of the vapors in the room.  The new water heaters incorporate new technology that helps accomplish the requirements of the new ANSI Standard.

This technology consists of:

  • A device to prevent ignited vapors from passing out of the combustion chamber
  • A one way intake system to control the movement of makeup air into the combustion chamber
  • An inner door and burner assembly to create a sealed junction with the combustion chamber, preventing combustion air and flammable vapors from entering the chamber through the front of the water heater

Each manufacturer accomplishes these tasks by incorporating slightly different technology, but in most cases a screen of some sort is generally used. Also each unit generally has a device that will shut the gas off to the unit if the combustion chamber becomes over heated called a thermal cutoff switch.

This newer technology on the surface can be a very advantages safety feature, but it also can create additional service issues that many home owners are not prepared to deal with.

The most common issue is the intake that controls the movement of makeup air into the burner chamber can become clogged with lint, dust or pet hair. As this happens it can affect the combustion process in the burner chamber, causing the flame to burn dirty creating soot build up and eventually shutting the burner down all together. Cleaning or keeping the intake screen from clogging can be one of the most important maintenance task, check with your manufacturer for recommendations as to how to accomplish this, generally if not described in the owners literature you can find a phone number and or web site that will describe the process specific to your brand and model.

Another issue we have run into is the venting process itself. Many older homes still use a brick chimney of some sort to vent the combustion gases out of the home. This is a simple process based on the fact heat rises, but if the chimney on cold days becomes too cold it can resist the flow of the flue gases out the chimney until the chimney can warm up enough to vent properly.  With the old technology some flue gas role out would occur, which is not a good thing, carbon monoxide concentrations around the unit and in the home often occurred during times of initial start-up. With the new technology and the sealed nature of the burner chamber more times than not the cutoff switch will register an over temperature issue and shut the gas valve off, requiring that the pilot be re-lit.

Another service issue can be caused by inadequate ventilation. Newer homes and often older homes are being better sealed to make the home more energy efficient; this however, can cause ventilation issues with atmospherically vented appliances like your water heater. As homes are sealed up to prevent the loss of heated indoor air, combustion air vents must be provided to gas burning appliances like your water heater.

In the end, what used to be a relatively simple system of heating water for your families use has now become quite complex with a lot of maintenance and service requirements to keep things running smoothly.  We recommend at least annual inspections and cleaning but in some dustier locations this maintenance could be required more often.  If you feel like this is beyond your capability or desire give Patterson Plumbing & Heating a call and we can put you on a routine schedule to keep things heating the way they were designed.

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