Atmospheric Combustion Appliances in Pioneer Valley

An Atmospheric Combustion Appliance is typically a Natural Gas or Propane fueled appliance, commonly a warm air furnace, a hot water or steam boiler, or a water heater that utilizes a chimney. Because some people get confused between chimneys and flues, click here for an easy to understand explanation.

Because Atmospheric Combustion Appliance is such a mouthful, we often times call the appliance chimney vented. It means the same thing, just less techno jargon. Chimney vented appliances have been popular for well over a 100 years; thousands if you want to include the conventional fireplace.

Chimney vented appliances rely on Mother Nature to work properly. A chimney is simply a vertical shaft that relies on two elements for proper operation: Height and Temperature Difference (us technical people call this Delta T, or ΔT). The greater the two elements, the greater the draft. Draft is simply the suction, or negative pressure that is being applied to the appliance creating the heat. Too much or too little draft isnt good; it can actually be very dangerous.

This chimney vented water heater has endured thousands of light-offs with inadequate draft due to poor chimney performance, negative pressure in the basement, or both.

Many of us have seen fires being lit in a cold fireplace. We understand that there will be a little smoke that will spill out of the fireplace in the beginning. This is simply because one of the two elements has not been established yet you guessed it, the temperature of course. Once we get the flue heated, then draft is established and the chimney works as it should.

Chimney vented appliances have to endure the exact same process. It is expected that a small amount of flue gas will spill out of the draft hood when the appliance first lights. Within moments, draft is established and the unit is venting safely and properly.

The danger comes when the chimneys natural ability (again, its Mother Nature or physics, your choice) to draft is compromised by the other forces that may be present in the building, either natural or mechanical. An example of a non mechanical occurrence would be what we call in the industry chimney affect. An example of a mechanical occurrence would be a motorized ventilation product such as bathroom fans, kitchen exhaust hoods, or even attic fans.

Some combustion appliances that utilize a chimney are not quite as vulnerable as what was described above, although the last thing this web site should do is numb your senses to the potential dangers (essentially, no draft spells extreme danger). Power Burners, such as oil burners that rely on a motor to force the combustion process (if the motor fails, you have no combustion), or even gas conversion burners (like the ones the gas companies sold and installed thousands of in the 1970s) also rely on a motor to inject the flue/gas mixture into the combustion chamber. These burners still require proper chimney operation to be safe.