Pittsburghsasha Posted October 5, 2014 Report Share Posted October 5, 2014 I have an 80% furnace. The furnace exhaust vent sits on the gas line.....is this safe? Thanks. Click to Enlarge 62.86 KB Quote Link to comment Share on other sites More sharing options...
Scottpat Posted October 5, 2014 Report Share Posted October 5, 2014 Nothing should be in contact with the flue pipe. As for being safe, unless that pipe gets hot enough to ignite the gas inside the pipe you have nothing to worry about. The chance for that happening are about as good as getting hit by a meteorite. Quote Link to comment Share on other sites More sharing options...
Marc Posted October 5, 2014 Report Share Posted October 5, 2014 It goes against common sense, shouldn't be installed that way but if it's a rigid steel gas line, I don't see a problem with it. I'm not aware of any manufacturer prohibition against it. Marc Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 5, 2014 Report Share Posted October 5, 2014 I have an 80% furnace. The furnace exhaust vent sits on the gas line.....is this safe? Thanks. If it's a rigid steel gas pipe, then it's fine. Quote Link to comment Share on other sites More sharing options...
plummen Posted October 5, 2014 Report Share Posted October 5, 2014 Did they atleast use B vent pipe?Ok,now I see the picture![:-slaphap Quote Link to comment Share on other sites More sharing options...
resqman Posted October 5, 2014 Report Share Posted October 5, 2014 Nothing should be in contact with the flue pipe. As for being safe, unless that pipe gets hot enough to ignite the gas inside the pipe you have nothing to worry about. The chance for that happening are about as good as getting hit by a meteorite. Fuel only ignites in the presence of the proper concentration of oxygen. Too much or too little and it will not ignite. A sealed gas pipe should have no oxygen. Regardless of how hot it gets, it should not combust... unless oxygen at the proper concentration is available inside the pipe. Quote Link to comment Share on other sites More sharing options...
Pittsburghsasha Posted October 5, 2014 Author Report Share Posted October 5, 2014 Thanks everyone. I think most of it is B vent...can't see one of them...the vertical part of the vent is actually touching the dry wall..... Quote Link to comment Share on other sites More sharing options...
kurt Posted October 5, 2014 Report Share Posted October 5, 2014 B vent needs 1" minimum clearance to combustibles. Quote Link to comment Share on other sites More sharing options...
Chad Fabry Posted October 5, 2014 Report Share Posted October 5, 2014 B vent needs 1" minimum clearance to combustibles. What Kurt said and gypsum wall board is considered combustible. Quote Link to comment Share on other sites More sharing options...
Scottpat Posted October 6, 2014 Report Share Posted October 6, 2014 The clearance requirements are embossed on the pipe right above the paper barcode sticker..... Quote Link to comment Share on other sites More sharing options...
caryseidner Posted October 8, 2014 Report Share Posted October 8, 2014 B vent needs 1" minimum clearance to combustibles. What Kurt said and gypsum wall board is considered combustible. I see B vents contacting drywall all the time and always call it out, but I've never seen any burn marks on the drywall. Has anyone? Does this really happen? Quote Link to comment Share on other sites More sharing options...
kurt Posted October 8, 2014 Report Share Posted October 8, 2014 Nope. I've had folks whose opinions I respect insist they get really hot, but I've not seen it. Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 8, 2014 Report Share Posted October 8, 2014 Nope. I've had folks whose opinions I respect insist they get really hot, but I've not seen it. As long as the furnace is working properly, the outside of the B-vent is never going to get very hot. But when things go wrong, the temperature can really take off. Quote Link to comment Share on other sites More sharing options...
Mike Lamb Posted October 8, 2014 Report Share Posted October 8, 2014 I have never seen a B vent causing any signs of overheating a surface no matter what it is touching. Does someone have a picture? Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 8, 2014 Report Share Posted October 8, 2014 I have never seen a B vent causing any signs of overheating a surface no matter what it is touching. Does someone have a picture? I've posted some in the past. They show burned vinyl on insulation near the B-vent just above the furnace. Right now, I'm in Connecticut and I don't have access to my archive. If I remember, I'll post them when I get back next week. I've never seen or heard of heat from a B-vent damaging the paper on drywall, charring wood, or anything like that. Quote Link to comment Share on other sites More sharing options...
Marc Posted October 8, 2014 Report Share Posted October 8, 2014 I've seen it blacken fiberglass insulation. Got several pictures but they're buried in 11 years of reports. Marc Quote Link to comment Share on other sites More sharing options...
Brandon Whitmore Posted October 9, 2014 Report Share Posted October 9, 2014 I've seen plenty of scorched plastic/vinyl on plenum insulation as well. About the only time I've seen house fires or signs of major scorching @ venting areas are when people place combustible items atop natural draft water heaters. Quote Link to comment Share on other sites More sharing options...
John Kogel Posted October 10, 2014 Report Share Posted October 10, 2014 I have never seen a B vent causing any signs of overheating a surface no matter what it is touching. Does someone have a picture? I happened to snap this pic today, a note from the authority to the flunky? Click to Enlarge 44.36 KB No, it is not what you asked for, but it has relevance, I thought. [] Quote Link to comment Share on other sites More sharing options...
caryseidner Posted October 10, 2014 Report Share Posted October 10, 2014 I have never seen a B vent causing any signs of overheating a surface no matter what it is touching. Does someone have a picture? I happened to snap this pic today, a note from the authority to the flunky? Click to Enlarge 44.36 KB No, it is not what you asked for, but it has relevance, I thought. [] Jeeez, that's nothing! My morning breath can melt plastic [:-yuck] Quote Link to comment Share on other sites More sharing options...
Hearthman Posted October 11, 2014 Report Share Posted October 11, 2014 The wall firestop in the pic appears to be laid over plastic. Therefore, one cannot ascertain if it is encroaching on stated clearances or not. A firestop must be framed in on four sides with an inner and outer listed firestop. If this is scrap sheetmetal, it would fail but I think I see the rivets for the spacers. Still, I'd call for a pro to remove and inspect it. Often well meaning people will pack insulation into firestops which is a major fire hazard. Yes, the surface temps. on much B-vent run so cool it won't char ordinary combustibles or even melt plastic. The 1" clearance factors in for an abnormal overfire condition to provide for some margin for error. Note that most FVIR water heaters exhaust temps exceed 600F, which exceeds the design limit of B-vent at 540F. All vent and vent connectors must be properly supported. This means support in two intersecting planes at all offsets plus a vertical support for any sections going through the roof or every 10 vertical feet. You must use the listed base support too. HTH Quote Link to comment Share on other sites More sharing options...
Marc Posted October 11, 2014 Report Share Posted October 11, 2014 What should be used for FVIR water heaters in place of B vent? Marc Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 12, 2014 Report Share Posted October 12, 2014 I have never seen a B vent causing any signs of overheating a surface no matter what it is touching. Does someone have a picture? I've posted some in the past. They show burned vinyl on insulation near the B-vent just above the furnace. Right now, I'm in Connecticut and I don't have access to my archive. If I remember, I'll post them when I get back next week. I've never seen or heard of heat from a B-vent damaging the paper on drywall, charring wood, or anything like that. I've posted these before, but here they are again. Click to Enlarge 28.13 KB Click to Enlarge 25.33 KB Click to Enlarge 24.72 KB Quote Link to comment Share on other sites More sharing options...
kurt Posted October 12, 2014 Report Share Posted October 12, 2014 That looks like single wall transitioning to B vent @ the elbow, duct tape "connectors". Is that right? Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted October 12, 2014 Report Share Posted October 12, 2014 That looks like single wall transitioning to B vent @ the elbow, duct tape "connectors". Is that right? Nope. All B-vent. Quote Link to comment Share on other sites More sharing options...
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