Gas Furnace Venting Into Chimney

This undermines the entire purpose of venting the furnace in the first place.

Gas furnace venting into chimney.

For instance a 100 000 btu furnace venting into an interior chimney with a 38 square inch liner would not be allowed regardless of chimney height. However using an interior chimney is extremely limited. To ensure proper venting however a liner must first be installed in the chimney. This structure generally uses the furnace vent pipe through roofbecause the b venting pipe is designed in vertical manner.

The height of the chimney the area of the liner and the input of the appliance all play a role in the use of the chimney. This chimney rule can be applied to wood burning fireplaces heating stoves and any oil fueled appliances but remember that manufacturer requirements have to be incorporated into it. The vent pipe must be firmly attached and sealed where it enters the chimney in order to prevent it from falling out to prevent air leaks into the chimney reducing the effective draft and to prevent flue gas leaks out of the chimney. A gas stove can be vented through an existing chimney whether it is a manufactured or masonry chimney.

Taking care of the vent on your gas furnace is extremely important but working improperly and damaging your vent can have catastrophic results. If any gaps remain and the vent isn t airtight the toxic gases will leak back into your home. They can t all rise to the top of the chimney so some of them backdraft through the vent pipe itself and enter the home s crawlspace. A conventional natural gas furnace will vent the dangerous combustion gases through a simple vertical exhaust system that is attached to the furnace.

When venting two appliances separately into a common chimney always install the smaller flue pipe appliance with lowest gph input at a higher point into the chimney than the larger flue pipe for the appliance with the largest gph input. The vent pipe or flue is a vital component of the furnace that transmits emissions from the combustion process out of the building. The exhaust system typically uses metal venting often routed into a chimney stack to exhaust the combustion gases created in the furnace fire chamber. For gas venting appliances the chimney flue venting rules are more complex simply because of the variety of products on the market.

The area around the flue piping should be sealed where it enters the chimney. When the vent is withdrawing air from the house it expels the gas outside through the vent. When the furnace exhausts into the chimney the gases quickly cool off before exiting to the outdoors. Refer to figure 2.

To aid in removing the vent pipe a thimble or slip joint may be used.