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Ice cold air blowing down chimney

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mow
mow Member Posts: 12
Boiler and water heater in basement of philly row home. Chimney is pictured. There was a cap but i removed it to look for obstruction. It's wide open. The boiler is 140k and the water heater 36k. I've lived in this house for 4 years and never noticed it before. Doesn't mean it wasn't happrning. Monoxide detecrs are new and not going off. When the boiler fires the room gets very humid and the spider webs blow everywhere.. The damper valve is opening and closing properly. If you put a match by the water heater it blows it out and the smoke comes into the room.

Pilot stays lit.

Two sides of chimney are on cold walls

Here's a video https://youtu.be/l42eXDYj_SM

Pics http://imgur.com/a/gK5Ze

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  • Jack
    Jack Member Posts: 1,047
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    You need to line your chimney. You say they are on a "cold wall". You may need an insulated chimney liner. You have that column of cold air that is heavier than warm pushing down. A masonry chimney has never seen a btu it did not want to absorb and they do it really well. The boiler fires and it just gets stuffed. The water heater probably doesn't draw at all unless the boiler has pre-heated the flue. As you note eventually, it will draw, and you may think it is ok. Now, let's look at the boiler sizing. If your boiler is oversized it will short cycle and your current situation is happening to one degree or another all the time. If the chimney is straight and there are no obstructions you could look at the venting tables and pick the correct size of liner. If you can get it in there use B-vent. Also, an insulated (b-vent) vent connector will help a great deal.
    This is the time to analyze your system. If the cost of the liner and the hassle warrant it, perhaps it is time to look at changing our the old system for a new high efficiency system that eliminates the need for the old chimney. In my own home, when we remodeled a couple years ago, I tore the whole chimney down and discovered a lot more space. Man. what a mess, BUT the end result was worth it. Keep us posted on your progress .
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    I wouldn't trust that CO detector. By the time it goes off, you will have too high of CO.
    The chimney may look clear, maybe it's blocked with ice.
    It's below design temp here in Philly today. And windy. And you have two exterior walls on the chimney. All working against you.
    Do you have anything (exhaust fans, etc.) that could pull air into the house?
    I would shut both appliances off, and get some heat at the base of the chimney. See if you can heat the base of the chimney with a blow dryer (maybe, probably not) to get it warmed and drafting.
    Or get some more heat going in the basement to warm it up.
    It's possible, but only testable by a technician with a combustion analyzer that you may need the boiler to fire a few minutes to warm the chimney and get your draft going. But you need to test for draft and CO with a combustion analyzer (so you don't die). I think by code it has to establish draft in 3 minutes.
    But whatever you do, don't fire those appliances on your own.

    There was an error rendering this rich post.

    Mike
  • neilc
    neilc Member Posts: 2,707
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    everything said above,
    plus,
    that CO detector, you can push the "Peak" button and it should read lower than alarm levels of CO down there.

    You should be sure to have another one(s) up in the house, by the sleeping spaces, and on every floor,

    Peak at the Peak button.
    known to beat dead horses
    j a_2
  • leonz
    leonz Member Posts: 1,159
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    Do you still have the old chimney cap?, If you do you need to put it back on the chimney.

    You also have to check the flue pipes for the boiler and the water heater to see if they are leaking you can do this with a lit cigarette while the boiler and water heater are running as the flue gasses can and will create vacuum at the flue pipe joints that are not sealed well if the leakage is small enough to allow a negative pressure gradient to occur.

    Your getting a down draft because the cap is no longer there to block the wind from coming down your chimney when there are high winds. Its a common problem and the cap reduces any wind that may blast through and around your city block.

    If you want a taller chimney cap like the one I have which is 3 foot tall with a spark arrestor screen and a rain cap all in one
    assembled chimney cap. All you need are tap con screws to anchor it in the chimneys concrete cap ring or the bricks if they are big enough. I purchased mine from Rockford chimney supply and had a local wood stove company install it for me.

    If you can reach the chimneys top without any issues you can install a chimney cap like mine with a helper as you need to install the chimney caps base that allows you to clean the chimney with a chimney brush if needed as the chimney cap is mounted with a hinge to allow it to just be lowered on one side to do an inspection or clean the chimney.

    With the chimney not insulated by the interior of the home it also makes the boiler and water heater work harder as cold air is denser than warm air and will weigh more and affect the gas appliances performance a bit-essentially all it is is that they are simply going uphill with a load, the load being the call for heat or hot water drawn from the hot water heater.

    Wind is like electricity and water their all lazy and will go where ever they can when they can.

    It would help also if you invested in a Dwyer Mark II manometer to keep track of the draft in your boiler. They come with well written instructions and all the parts you need except for the probe to make a permanent installation.

    It may be time to think about a boiler without a standing pilot with a domestic hot water coil in the steam chest as standard equipment so you can use one gas appliance for both needs.

    Just be sure to test the CO2 alarm once a month as a matter of normal practice.
  • unclejohn
    unclejohn Member Posts: 1,833
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    Try locking the boiler damper in the open position to keep the chimney warm and drafting. There should be a switch on the damper motor marked hold open or some thing like that. You only get hi CO2 readings if the equipment is not burning properly. But you should for sure get chimney lined.
    j a_2
  • mow
    mow Member Posts: 12
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    I rigged up a an electric infrared heater pointing at the chimney and I removed the chimney cap and put a fan on it to suck.

    Boiler damper is set to open

    Peak co 12ppm


    I have draft!!!!

    I realize this is not Ideal


    My boiler is oversized but im in no position to replace it atm.

    The chimney is 25'. Would 6" double wall b vent suffice as an insulated liner?
  • unclejohn
    unclejohn Member Posts: 1,833
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    I would remove the fan. Once you establish draft you should ok until you can get a chimney guy.
  • neilc
    neilc Member Posts: 2,707
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    that's 12 ppm more than you want,
    both buttons together reset to zero,
    what do you read upstairs?
    known to beat dead horses
  • NY_Rob
    NY_Rob Member Posts: 1,370
    edited January 2018
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    Don't use setback tonight... keep the house at 70f all night long that will keep your boiler active or frequent cycling and will serve to warm the chimney which will keep your draft going.



  • Jack
    Jack Member Posts: 1,047
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    B-vent is double wall and therefore insulated as it comes. I do not have a vent sizing guide perhaps someone here can size it based upon info all ready provided. You may be able to reduce the vent pipe size which will make it much easier to drop rigid pipe down the flue. Is it a straight shot? If not, then you will need to use flex.
  • mow
    mow Member Posts: 12
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    All three zones are at 72.

    Chimney is a straight shot. 7x6 3/4" terracotta lined

    Would six inch single wall pipe work?

    Any other options here?

    Six inch flex duct? Haha.
  • Gordy
    Gordy Member Posts: 9,546
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    Funny how these draft issues rear their ugly head with the cold snaps below design. Seems probably the water heater was enough to keep the flue warm. Cold snap put a stop to that.
  • j a_2
    j a_2 Member Posts: 1,801
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    What ya got for make up air?
  • mow
    mow Member Posts: 12
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    Nothing in particular for make up air. The basement is open to the rest of the house. No closed doors. I pulled the space heater and replaced the vent cap last night. Still drafting this morning. The biggest change is the basement is now really cold.

    Does the liner need to be insulated? Im thinking of running 6" aluminum flex. The insulation costs an arm and a leg!!


  • j a_2
    j a_2 Member Posts: 1,801
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    If we’re my house and it was working now,I’d let it rip...if I were working for you I’d go exactly by the book, post some info on horizontal and vertical heights and total load,someone may have a sizing book handy....Go to chimney liner web sights. And the code used in your area...
  • Jack
    Jack Member Posts: 1,047
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    I just dug up a '12 copy of NFPA 54. B-vent capacity of two Natural draft appliances at 25' is 172k btu for 5". The Od on 5" is slightly less than 6". If you use flex, you will need at least 6" which I can assure you will not go down that flue in one piece. Seal off the water heater connection to the chimney and tie the water heater into the vent connector for the boiler close to the chimney. Get rid of the single wall vent connector and do that in B-vent as well. Seal off the top of the masonry flue once the system is installed. Make sure you use a B-vent that has a smooth wall locking system. A twist lock in other words. Selkirk or Dura-vent would be my choices. Once the joints are locked together, do put a couple screw in the joint. DO NOT penetrate the inner liner. This kind of work is, or can be, maddening. You will need help on the roof as well as in the basement. Get the B-vent in the hole and the system performance will improve.
  • bob eck
    bob eck Member Posts: 930
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    Is your local gas utility company offering any type of rebate for installing a high efficiency condensing gas boiler? If so look at putting in a combi boiler and side wall vent it if possible or you can use the old chimney as a chase and run a plastic polypropylene flexiable chimney liner kit up the chimney. Innoflue has them. If doing this you can not vent any other appliances in that chimney.
  • mow
    mow Member Posts: 12
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    Thank you Jack and everyone else for your input. 24 hours and it's still drafting nicely. I suspect it lost its draft when we went away for a week over the holidays. I lowered the temp to 64°.

    I will figure out a b vent setup as you described and install it when I can do without heat for a day.

    Thank you!