Add a small furnace?

[jsnitzer]

Looking at adding an ex-mobile home furnace (oil fired forced hot air) to my attached garage/workshop for heat this winter. Can I just route the flue into the existig flue from the house furnace? [img]/forums/images/icons/confused.gif[/img]

[hazmat]

Check with local codes, but generally each appliance should have it's own flue to avoid backdraft & Carbon Monoxide problems.

[Pat]

Hazmat smacked that one on the head. Whether or not it will work well is one issue. Whether it would nulify your fire insurance is another issue. Insurance companies have been taking a lot of big hits in recent years and are getting real petty (some always were but most are now). For instance: your house burns down from a fire started by spontaneous combustion but in the rubble an insurance investigator finds some "not to code" wiring mods. If you think they won't use that to try to leave you out in the cold then you aren't tuned in to reality.

Depending on the bends, cross section, rise in the near horizontal runs, vertical runs, and so forth it MIGHT be OK from a purely engineering standpoint but still a BAD idea. A problem with heaters like this is that they usually are not "sealed combustion" type where air to support combustion comes ONLY from outside with NO WAY for stack gasses to get inside the heated space, even with severe back drafting. If both heating appliances were sealed combustion types then there wouldn't be an IAQ related safety issue, only a combustion efficiency issue.

If you can, with any amount of contortion, find a path from anywhere inside the heated home space to the burner on the appliance without going outside the heated space (like through a window) then it is sealed combustion. Otherwise it isnt. Odds are it is not sealed AND should have its own flue.

Pat

[jsnitzer]

Thanks Pat and Hazmat! I decided to pass on the furnace. Appreciate your advice. Also heard from Dave at furnace parts http://www.furnaceparts.com/oilfurnace.htm.

Dave reinforced what you both said - even if the flue is big enough, it unbalances the system - each furnace needs its own flue. Dave says that special stainless stovepipe for oil furnaces is available, but really, really expensive and may not meet code in my area.

Thanks all for saving me from a really bad idea! Now I still need a furnace, so maybe will look into those high efficiency propane jobs!