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New Flue

FWDixon Member Posts: 78
New Lower Flue

I pulled my flue off the other day to clean it and it practically fell apart. The bottom of the chimney was 80% blocked with dirt and debris, and coupled with the low return water temps in my boiler (which is causing the flue gas to condense) the galvanised pipe was at its end. I currently have it carefully patched with hi-heat, acid and fire-resistant tape (not ideal, but it's still in the 30's here) and while I am waiting for the chimney folks to come out and "inspect" my flue to tell me it needs replaced, I am wanting to educate myself a small bit.

So....The boiler is an old Burham RS-112 Oil unit that was Converted to NG with a Wayne P250AF burner. The Wayne manual specifies a 6" flue pipe and at least a 1/4" rise in the pipe run from boiler to chimney (I have about 8"). The current flue is run straight up out of the top of the boiler then turns to run up at about 30 degrees to the point where it enters the chimney. About halfway along the horizontal-ish run is the draft control (which is opening a lot farther now that I've cleared the bottom of the chimney, yay). One thing I didn't see in the wayne manual was the minimum gauge for the flue pipe nor the ideal location of the draft control (the instructions all were based off using a draft hood). Also, should the horizontal run be flat or continued to be run at the slight up angle? (Was reading on a draft control manufacturers site and gave my current set up for oil burners by a flat run for gas burners with the draft control at the end of a bull tee directly above the attachment point to the boiler).

Thanks in advance.


  • FWDixon
    FWDixon Member Posts: 78
    Vent Type

    I was considering buy B-vent for the flue pipe but am not sure that it is warranted. What I have currently looks to be 22 or 24 gauge single wall galvanized duct.
  • Bob Harper
    Bob Harper Member Posts: 882
    Level II inspection

    I would ask the chimney contractor to perform a Level II inspection, which is a comprehensive top to bottom inspection. That will determine if the chimney is suitable for continued use and what repairs if any are warranted. Since there was material at the base of the chimney that means that material is no longer where it started up in the flue, hence your flue can no longer perform its intended function. You will need a liner. The liner must be suitable for the class of service. Since this chimney once served oil, any liner must be 316 alloy of stainless steel or better. Most liners are 316Ti these days with a pinch of titanium thrown in. Get one with a transferrable lifetime warranty btw.

    The liner must be at least the size of the appliance collar. In addition, corrugated liners must be de-rated for corrugation (20%) plus an additional 20% for any offsets.

    The vent connector galvanized steel pipe gauge thickness is determined by NFPA 211, which calls for 26 ga. below 6", 24 ga. 6-10", 22 ga. for 10-16" then 16 ga.above 16". You can drop one ga. size smaller if using stainless steel. In other words, for a 6" flue, you can use a 24 ga. galv. or 26 ga. ss connector. Follow 211 for pitch, connections, support, etc. No flat runs--min. 1/4" per foot slope upwards to the chimney.

    You can not use B-vent inside a chimney that once burned oil--it will eat it up.

    The barometric damper should be located close to the appliance but leave at least 2 duct diameters from the appliance collar and any ells to you can drill your test hole for combustion analysis. I try to locate them on the vertical rise if possible. If you must install it on the horizontal leg, you have to reposition the adjusting weight to the left side of on Field RC dampers. Bull head tees for baros. are not recommended for oil. See the diagram from Field Controls for damper placment.
  • heatpro02920
    heatpro02920 Member Posts: 991
    Keep an eye on this

    I would install co detectors throughout, I had a service call about 4 days ago with a similar problem, the chimney deteriorated and blocked the flue way. I ended up installing a temporary power venter in a basement window so they can run the unit until the chimney is repaired.

    Not an easy task and will not work in all basements, had to remove the window build a plate to hold the venter run the cables and control, I was there for 3 hours, and after he gets his chimney straightened out I have to go back and undo it all....

    good luck and be safe..
  • icesailor
    icesailor Member Posts: 7,265
    All tiled up:

    If you see sand in the bottom of the flue and it is up to the vent termination, the chimney and flue are shot. It needs to be re-lined or replaced.

    If the chimney is old (50+), the old dead mud slingers hated flue tiles and didn't like to use them because they cracked or were difficult to cut if you had to offset. Plus, the mudslingers weren't much concerned about draft. As long as the smoke went up the chimney, it was OK with them.

    When tiles were really pushed, mudslingers resorted to "Parging" where they took mortar and covered the whole inside of the chimney flues to make them tight. Some might be fussy and use a wet water brush to make them smooth. Most just left it like it came off the trowel. Rough to create more turbulence in the flue.

    If you look into the chimney through the open flue opening, and you see brick, there's no liner. If you see just bricks, it isn't parged. If you look up the flue with a mirror or something like a Ryobi Tek-4 Inspection Scope ($100,00 at Orange, Brown & Grey) and see only bricks, the mortar is dissolving. Brick/block mortar is Portland cement, lime and screened sand. The really old dead mudslingers got it in barrels. They mixed their own mortar mix to what they learned. Concrete is just Portland Cement, sand and gravel. Lime was added to the Portland Cement to make "mortar" and to make it more plastic and sticky. But the more lime, the stickier and weaker the mix became. But some old Brickies used to add extra lime to their pre-mixed mortar that came in bags. That makes the mortar more susceptible to deterioration from acids in flue gasses. Another problem with old field mixed mortar is that if the lime ratio is higher than it should be, the mortar stays sticky but has less adhesion. Bricks in chimney's are laid as "Stretchers". The mortar laid down as the bed is well compressed. It is the amount buttered on the ends where problems begin. There are various ways to butter the ends with a trowel. But if you get too much on it, it squeezes out and falls away. Wasteful. Or, not enough to compress to get a good seal. And there is where the problems start. Because although the helper/tender is supposed to strike the joints with a striker, if the chimney is inside and against a wall, you can't joint the places you can't get to. Leaks. If you're driving down the road, look UP. See that nice brick chimney with all the black stains on the sides? That's the flue gasses escaping through the vertical joints on an oil boiler. You won't see it on a gas system. No soot or smoke. Draft occurs because flowing air has less pressure than static air that is in the building. High pressure flows to low pressure. Heat flows to cold. When you have all those vertical leaks in the bricks, you're going to have leaks and bad draft. Tight house, tight basement, drafty unfinished attic, equal bad draft. There will be far less draft at the top of the chimney than at the flue base.

    If you see sand in the bottom of the flue, it needs to be lined. If you look up the chimney and see only the edge of bricks, it needs to be lined. Sometimes, when mudslingers go to replace old chimneys, they only go to the attic floor. You can pull the bricks off with your hand or a light tap with a brick hammer to take it apart.

    Line the flue.
  • FWDixon
    FWDixon Member Posts: 78
    Chimney folks came out

    and gave the chimney the all clear. The debris build up in the chimney is from 75 years of no chimney cap. He said that even though the chimney is unlined, there were no signs the mortar was degraded or safety was compromised. So at some point I may still do a liner, but at least it's not a must.

    The pipe in the boiler room is shot (obviously) and they are going to give me a quote to replace it all. Also, I asked them about installing a cleanout at the base of the chimney and a cap.
  • icesailor
    icesailor Member Posts: 7,265
    edited March 2014
    Buffalo Chips:

    The "Chimney Folk(s)" is full of Buffalo Chips. Where did the sand come from? Dropped off by The Nam in the Moon? 

    Have children been living in the house in the past and The Sandman dropped sand in the chimney while he came down the chimney like Santa Claus? Did he put a camera down the flue?

    Does the flue run through a attic space where you can see it?

    If you can, I'll bet that if you had a quality draft gauge, and you capped the chimney top, and opened the windows in the attic, you'd still have draft in the chimney.

    Many "Chimney Specialists" haven't a clue where draft comes from or how it works. If you had spent over 60 years, trying to make small sailboats go through the water or across the ice with wind speeds from none to a little more, you get to understand what makes it work.

    What kind of draft gauge did he use of have?

    One like this one or better. The big one. It doesn't fit in your pocket.
  • FWDixon
    FWDixon Member Posts: 78
    The chimney is external to the house

    and only enters next to the boiler. As I live near the coast, blown sand is very common due to the frequency of hurricanes and nor'easters. And, as the chimney does not have any type of cap, it is quite likely that this airborne sand and debris could have ended up inside the chimney. He did scope the chimney, not sure on the draft gauge as I was doing work elsewhere in the house while he was here.
  • Bob Harper
    Bob Harper Member Posts: 882

    Chimneys have been required to be lined since 1927. Whenever you replace equipment you must inspect the chimney and repair it as necessary so its is suitable for the class of service. You got ripped off by this company. Even if the chimney looks ok, the material in the base tells us it is not. Reline it. Do not use this company again and I'd request a refund. Every standard in the industry disagrees with their assessment. including most IOM manuals. 
  • icesailor
    icesailor Member Posts: 7,265
    3 sided chimney's:

    If you live in Massachusetts, and have a 3 sided outside chimney, you probably can't use the chimney even if it is relined because it will never get warm enough to draught/draw properly.

    If you came up with that scenario about the blowing sand on your own, fine. Its wrong. But if a "Chimney Expert" told you that, he is an ignorant fool. Unless your house faces the NW and has a sand dune in front of it built up by the beach in front of it, It can't happen. And the fact that the outside pressure from the wind is lower than the pressure inside the house, makes the chimney always drawing and the sand will NOT come down the chimney flue.

    During the "No Name Storm" that The Perfect Storm was made from, where I lived it blew 100 MPH from the East. On an east facing shore, there are 100' cliffs. The sand blew up and over the cliffs and over the houses on the other side of the street. Some lawns looked like it snowed on them. But there was no sand in the fireplace hearths. The chimney draft kept the sand from coming down the chimney.

    If you live in Massachusetts near the shore, I strongly suggest you consider a direct vented Mod/Con gas boiler. You can jam oil exhaust up a 3 sided outside cold chimney and it will be fine. Oil is forgiving. Just don't try it with gas. If you do, and it has a draft hood, the spill over switch will be shutting off constantly. If it has a Field MC double acting draft control, the gate will be like a little kid on a swing. Back and forth.  
  • FWDixon
    FWDixon Member Posts: 78
    Flue Liner

    Got the quote today and it includes a flue liner (seems the person at the shop noticed the lack of a liner and had the same reaction you all did). I don't have even a fraction of what they are asking for the whole enchilada, but can afford the self-install variety (316ti Flex-pipe) and to have them do the boiler connection part.

    So, what I am thinking is getting them to replace the flue pipe from the boiler to the chimney and installing a cleanout door and vertical liner myself. That said, to size the flue pipe they are going off of what is currently there, which is the connector size of the boiler but larger than what is spec'd in the conversion burner manual (7" connector, 6" for 125MBTU burner (installed but not working) or 5" for 75MBTU burner, which is what I need). I have a new HVAC company coming out to do a combustion analysis on the current Wayne P250AF conversion burner and either set it to 75MBTU or replace it (was told the Carlin EZ burner was better due to a shorter flame which is better for my RS-112). Should I wait til the burner work is done then have the chimney guys size the new pipe for the boiler or proceed with the replacement and the 7" diameter?

    Also, I'm assuming the chimney liner needs to be the same size as the flue pipe, but with the liner being flexible was thinking maybe it needs to be slightly larger to account for the increased resistance?
  • icesailor
    icesailor Member Posts: 7,265
    Alone at last:

    You see a lot of plumbers and heaters that work alone. They develop all kinds of schemes to do their job alone. One thing I always remember about moving stuff is to "Keep one end on the ground". A wheeled dolly qualifies as keeping one end on the ground.

    You seldom see an electrician that works alone and doesn't have a helper. That's because it is extremely difficult to "fish" wires. You often need someone to push while you pull, pull while you push or feed, or keep the wire from developing a$$hats. What my good electrician friend calls wire twists. That said, I've done a lot of stupid things in my past. Unless you can find someone to help you fish that liner in, and one of you need to be on the roof feeding it down while the other pulls it down with a chain. you might find that it is stupid money to have a professional do the flue. Its something that even I wouldn't do alone. Especially the roof part.
  • FWDixon
    FWDixon Member Posts: 78

    I am a small boat electrician and have half a garage full of clever devices to fish wires by myself, and a couple of neat ones saved to speed dial as well :D
  • icesailor
    icesailor Member Posts: 7,265
    Cleaver devices:

    I'm sure that you are and I don't doubt your ability.

    I'm just thinking about myself. How it will be if, after dropping a chain down the chimney, connected to the flue liner, I can hold it up (while standing on the roof to feed it down, while pulling it through from the bottom. Or, while pulling from the bottom, it gets stuck and needs a push down from the top. While pulling the chain from the bottom. I was only suggesting that for me, it would be a 2 man job. I could scamper up a roof with the best of them. Better than many. I always put vent terminals through roofs by myself, no help and no leaks. But in the back of my mind was always, if I fall and get hurt, and can't work, is this really worth it?

    That's not a one man job. Not even for me.
  • FWDixon
    FWDixon Member Posts: 78
    I spend a lot of time

    Climbing from bilge to fly bridge, figured I would use one of the devices saved in my phone that runs on beer so I'm not climbing from boiler room to rooftop :D