Direct Vent to garage - foolish or outright dangerous?

gforrest2November 22, 2007

I want to install my Majestic DV fireplace against a wall common with our garage. Rather then spend $800+ on their proprietery 7" vent piping to run about 20'+ over and up, what would be the problem with connecting the inner 4" hot pipe to my furnace exhaust via tee or wye? And to protect this hot pipe, I would go ahead and run the 7" outer pipe up to the furnace pipe, about 6' away (i.e., none of the 4" pipe would be exposed). Is this a fire hazard or some other dangerous situation? Does my 25,000 BTU fireplace put out more exhaust heat than my 80,000 BTU furnace? They generally would not run at the same time. And if this is feasible, can I just use galvanzied steel stove pipe? Maybe I'm just an idiot, but I don't see what the problem is. I think it meets the intent - the combustion chamber is sealed, hot air is exhausted out of the house via the furnance exhaust system, and combustion air is drawn in from the garage. Would the fact that the exhaust and intake pipes will be different lengths affect how the fireplace burns? And if this is just an outright bad idea, anyone know where I can get 4" x 7" direct vent piping at a discount? Sorry for the long post. Happy Holidays. PS. This is not the first DV fireplace I've installed.

Thank you for reporting this comment. Undo

If you are not sure, don't even think about doing a project like this until you check with a qualified installer. Saving a few bucks could cost you your house or worse. Its been my assumption that you should never tie into existing venting. I would install this unit by itself and leave the furnace out of the equation. Just my opinion. Good Luck.

    Bookmark   November 22, 2007 at 7:20PM
Thank you for reporting this comment. Undo

A)Direct vent appliances may only be installed according to the manufacturer's instructions, using the pipe recommended by or made by the manufacturer, in fact this to applies to all non-b-vent boxes.

B) your furnace is most likely a forced vent(draft inducer) which would push the exhaust back into your firebox which would not work. If this is not the case the pipe still has to be sized to carry exhaust correctly, but either way "A" overrides anything else.

You are a very thoughtful person and your idea makes perfect sense, but in this case it will not be acceptable. I bet you have created some pretty cool stuff in your time with such a creative mind.

    Bookmark   November 23, 2007 at 7:02PM
Thank you for reporting this comment. Undo

Where do we send the flowers? Seriously what is your families lives worth? This is not a good idea.

    Bookmark   November 25, 2007 at 11:31PM
Thank you for reporting this comment. Undo

At our last house, the POs had tied the gas water heater exhaust and the gas furnace exhast together into one flue. We had continual problems with gases backing up into the basement - when the furnace was running, it created so much force that the water heater exhaust could not push it's way up the chimney and backed up into the basement. We were forced to vent them separately.

My guess is that your situation is very similar - your furnace probably creates a much stronger draft than your gas fireplace and will force exhaust gases back down into your living space via the fireplace. I wouldn't risk it...

    Bookmark   November 30, 2007 at 8:43AM
Thank you for reporting this comment. Undo

Direct Vent to garage -
"foolish or outright dangerous?"


lkplatow is right, I wouldn't risk it either..........

    Bookmark   November 30, 2007 at 3:12PM
Thank you for reporting this comment. Undo

Thank you all for your responses. I somewhat came to my senses. I forced a Napoleon 4"x7" adapter on to my fireplace that allows me to use Simpson 4"x 6 5/8" piping. After seeing a sample of the Duravent piping, I thought about building my own piping (not much to it, a small pipe inside a large pipe held in the center with 3 standoffs riveted in place) but Winter is coming and I need the fireplace operational soon. FYI, my dealer quoted me $921 for about 18' of pipe, 3 elbows and a termination kit for the Majestic pipe I was supposed to use. The same amount of Duravent pipe was $339.

    Bookmark   December 5, 2007 at 12:43AM
Sign Up to comment
More Discussions
Help me decide on a fireplace unit for new build
We are doing a gas Heatilator unit. Is there much difference...
Couple of questions about installing stone veneer
Little background - original lava rock fireplace was...
Vermont stove
I have a resolute acclaim stove and the sealer around...
Converting wood fireplace to gas fireplace
Help, I'm overwhelmed. Any link to a good site that...
replacing wood burning stove with wb fireplace, will it work?
Living room had a wood burning stove. There's a 6"...
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™