Thread: HVAC Return Vent Less Than 10 Feet From Wood Burning Insert

I looked at a house yesterday where the return HVAC vent in the living room was less than 10 feet from the fireplace. But the fireplace now has a wood burning insert with doors that latch shut. I guess this is no longer an open combustion source and the 10 foot rule would not be applicable (or maybe it still is).

Thoughts?

For those who don't know what I'm talking about, return air vent openings should be located no less than 10 feet from open combustion sources for safety purposes (ie - mid efficient furnaces and water heaters and open fireplaces).

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Direct vent would be exempted from this rule----atmospherically vented would not.
HTH,


BTW, is this a factory built fireplace or masonry?

Originally Posted by Bob Harper

Direct vent would be exempted from this rule----atmospherically vented would not.
HTH,


BTW, is this a factory built fireplace or masonry?

Is there a direct vented wood burning insert?

Masonry fireplace. No direct venting. It vents into terra cotta flue lined three story masonry chimney. I assume this what you mean by atmospherically vented Bob?

Was the return a part of a heating system, cooling system or both? High return? Floor return? Are the combustion are vents in the firplace? I have to assume there are supply vents in the room also so a negative pressure is probably not present.

Nick, if this is a woodstove insert then it is susceptible to the 10ft rule because those doors open for loading and it is Not a sealed combustion direct vent. If it has a direct connection to the first flue tile, it may be a problem due to flue sizing and condition.

The return vent aside. Shouldn't a wood burning insert in a masonry fireplace have a listed stainless steel flue pipe that goes all the way out the chimney with a proper cap? It sounds like it is an insert that is utilizing the original clay tile flue the way he described it. I thought that a flue pipe had to be listed for the insert installed in this manner.

Its a good way to heat the home with the fan unit in the furnace, when the fireplace is going strong the thermostat will be over-ridden by the fireplace heat, and then can cirulate the heat using the fan control

Gotcha Bob. Thanks.

To Frank B.- yes, you are correct. The chimney must be suitable for the class of service. That means it would have to pass a level II inspection to NFPA 211 stds., which few can. It would also have to meet the flue sizing requirements, which often force a liner down otherwise pretty good chimneys. The liner must be listed to UL 1777 for a high temp. or 2,100F rating. This is a function of the level II inspection to determine the requisite amount of insulation to meet the listing. Most will require the maximum insulation because they have combustibles touching the chimney.

A full length liner makes sweeping a breeze and vastly improves performance.