*
At the end of the thread:
http://webx.taunton.com/WebX?128@@.2cbf22fb
Bob Walker posts:
> Often, an older inefficient furnace/boiler is replaced with a higher efficiency unit which puts much less heat into the flue, so that the flue is quite a bit cooler and thus the water vapor in the flue gases condense beforew they’re outta there.
> This can lead to major deterioration of the flue because of the acids in the flue gases/vapor/condensate.
> If the condensed mositure is making into the walls, you have to be concerned with what;s going on in there.
> Have this possibility checked by a chimney sweep who uses a video camera run up the flue.
After a sweep confirms the problem, how do you solve it?
Rich Beckman
Replies
*
Flue liner ?
*New B vent inside the flue.The other sudden surprise on some of these units is that the basement (which used to be reasonably warm due to 'inefficiency') is now quite a bit colder. We can't count on heating units to heat their own space any more.Jeff
*Boss has it: a flue liner - generally doesn't need to be B-vent, although I suppose there might be situations where that's appropriate
*Thanks.Flue liner was the only thing I could think of, but I couldn't help but wonder since the other thread was left without that discussion.What's a B-vent?Rich Beckman
*i What's a B-vent? Standard metal chimney for a boiler or furnace. As opposed to direct vent (PVC piped exhaust for furnace). With direct vent you have a lot of condensate due to low exhaust temp. and therefore fittings for piped or pumped condensate. Jeff
*I thought B-vent was that twin walled, gotta use the special caulk to join it, costs me a hundred dollars a section, vent pipe.I thought flue liner was just the thin, single walled, easy to use stuff.
*The flue liner I installed was a coil of stainless flex. You measure from the top of the flue to the thimble and cut it a little short. Then stretch it out and put it through the thimble. Can't remember the brand name but it came with the furnace.
*How about a power vent instead of using the flue?cc
*B-vent is a double wall flue, typical required clearance to combustibles is 1" -- Single wall galvanized needs 6".It's hard to describe the visual difference; stop in a building supply and it'll take about 10 seconds to figure out. (B vent will usually have the clearances printed on a lable on the vent)To me, "standard" is single wall galvanized venting intro a masonry chimney, B-vent is used mainly on 80+ (mid) efficiency appliances (furnaces and boilers (?)) and direct vent is 90+ which uses the PVC. If there's an "open box" at the bottom of the vent flue and single or double wall, it's standard efficiency; if there's a draft inducer (little blower motor) on the metal vent (usually double wall B-vent_) it's 80+ mid-efficiency (and you need to consider whether the furnace and water heater have been properly vented especxially if it's a pre-1975 house); if there's PVC it's probabaly a 90+ dierct vent. (If the plastic vent is gray, call an HVAC contractor today, that stuff has been recalled for safety concerns.)Usually you can see the burners for standard and 80+ and can't see them for 90+ except usually thru a little round glass viewing port, but sometimes you don't have a sealed combustion chamber for the 90+ and can see the burners.This stuff can get tricky and for most people it pays to hire an expert; OTOH if you want to spend the time it's not rocket science.
*Inside another chimney ? Easy one. Go with the stainless flex. (single wall)
*Cultured marble window sills! Has annyone ever used them? What are the pros and cons?
*
At the end of the thread:
http://webx.taunton.com/WebX?128@@.2cbf22fb
Bob Walker posts:
> Often, an older inefficient furnace/boiler is replaced with a higher efficiency unit which puts much less heat into the flue, so that the flue is quite a bit cooler and thus the water vapor in the flue gases condense beforew they're outta there.
> This can lead to major deterioration of the flue because of the acids in the flue gases/vapor/condensate.
> If the condensed mositure is making into the walls, you have to be concerned with what;s going on in there.
> Have this possibility checked by a chimney sweep who uses a video camera run up the flue.
After a sweep confirms the problem, how do you solve it?
Rich Beckman