chimney liner

Jack_23

You have two atmospheric appliances. Therefore the dilution air from the diverters will add dry room air to the flue gases thereby changing the dew point temp. NFPA 54 has, since the 1992 edition when they first took a position on liners, consistently tighened up the requirements to support the use of liners. The problem is tht in most cases the masonry flues are quite a bit larger than necessary (when a gas expands it cools) and they love to absorb the heat from the flue gases. This causes a lazy draft situation and in many cases will lead to the flue gases reaching the dewpoint temp, condensing and causing problems. With masonry chimneys you are using 11th century technology to vent 21st century appliances. With a liner you will get a better light off, smoother operation of the boiler, likely better component life and all around better performance. Line it. It's easy! Well...some times it's easy!

stan_2

Could someone please give me the low down on chimney liners. When are they necessary. I noticed one boiler manufacturer recommends them when you install an atmospheric type boiler with a vent damper into an outside chimney. Does it make a difference if you are also venting a water heater into the same chimney? If a chimney runs up through a garage and out the roof, is this chimney considered an outside chimney? Any advice would be greatly appreciated.

Dale

Liners

Yes the garage example is an outside chimney. If you common vent make sure it's done before the liner. I have seen persons use the annular space. The 2 draft hoods make this a much better system as the depoint problem improves with more low humidity and warm basement air. Liners are so cheap now it pays to use them, size the common vent per liner manuf. or the 20 percent reduction in nfpa 54. There are approved flex connectors now if your labor rate warrants it.

bob young

chimney liner

i know zero on chimney liners . saw a job today 6" flue for gas boiler ,3" flue from h.w. heater connected to new stainless liner 5" no spillage is this possible?? IS it safe? is it legal? two storey residence

Earthfire

same question

Why does the local block supplier that stocks square 16x16 outside dimension chimney block and 6" clay tile determine the chimney size and not the flue requirements of the connected equipment? and then the local "chimney sweep" to make a quick sale throws in a 5" liner cause thats what will fit down the hole quickly?

Jack_23

Sizing guidlines on vents

> i know zero on chimney liners . saw a job today

> 6" flue for gas boiler ,3" flue from h.w. heater

> connected to new stainless liner 5" no spillage

> is this possible?? IS it safe? is it legal? two

> storey residence

Jack_23

Sizing guidlines on vents

Check out NFPA 31 and go to Appendix E. Several years ago. Brookhaven Labs was working on venting tables for the oil industry. Much good work wasdone by John Strasser and Rich Krajewski. The oil heat funding for Brookhaven was zeroed out and most of that work ended. With the research incomplete we were unable to put the much needed vent tables in the body of the code, Hence,Appendix E. You can reduce the size of a vent "with manufacturers recommendation"...in writing!If you look at the tables you can see how much heat you can put up te spout. Please check it out. It is pretty surprising.. In todays world, a masonry chimney is an excellent architectural device but a poor mechanical device. If you must build a masonry chimney do not line it with clay tile liners. Use stainless pipe. Will draw better and all around function better.