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Vent damper

Hello experts,

Do I need to add a flue damper to my residential Weil McLain steam boiler to improve effieceincy and operation.

Comments

  • ChrisJ
    ChrisJ Member Posts: 15,457

    Hello experts,

    Do I need to add a flue damper to my residential Weil McLain steam boiler to improve effieceincy and operation.

    What kind?
    Oil? Gas?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • HVACNUT
    HVACNUT Member Posts: 5,750
    > @ChrisJ said:
    > (Quote)
    > What kind?
    > Oil? Gas?

    Barometric?
    Mechanical?
  • neurosteam
    neurosteam Member Posts: 34
    The boiler is fueled with gas.
  • neurosteam
    neurosteam Member Posts: 34
    I am not sure if I need a damper or not and what kind mechanical or not.
    It was recommended by local non steam contractor.
  • ChrisJ
    ChrisJ Member Posts: 15,457

    I am not sure if I need a damper or not and what kind mechanical or not.
    It was recommended by local non steam contractor.

    I assume the appliance has a drafthood? Or was it converted from oil to gas?

    Can you post some pictures?
    How's the chimney situation? Approx height, diameter, location etc.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • neurosteam
    neurosteam Member Posts: 34
    Chimney right behind the boiler. Picture attached.
  • neilc
    neilc Member Posts: 2,667
    it took me a moment to realize your picture was sideways,
    I got scared,

    if you're looking to eake out additional efficiency, then yes, a powered vent damper will stop some draw and cooling of the boiler, and the basement.
    don't let them sell you a barometric damper, not your application.

    Efficiency wise,
    your guy has tuned the burner already ?
    and you trust him / her ?
    known to beat dead horses
  • neurosteam
    neurosteam Member Posts: 34
    My guy is not an expert unfortunately. He tries and I try by increasing my knowledge through reading thanks to this forum. Tuning the burner? The burners get cleaned that’s it. He does not tune it.
  • HVACNUT
    HVACNUT Member Posts: 5,750
    You wouldn't save much by adding a mechanical flue damper. There is the large dilution air box at the back. Open underneath.
    kcopp
  • neilc
    neilc Member Posts: 2,667
    HVACNUT said:

    You wouldn't save much by adding a mechanical flue damper. There is the large dilution air box at the back. Open underneath.

    I almost hit the disagree button , , ,
    sure, there is a large dilution box there,
    and to close off that continuous draft, when the boiler isn't firing, does help keep the boiler that little bit warmer, along with not continuously drawing air out of the basement,
    the boiler heat sits in the basement.
    I'm a building envelope Nazi,
    close all the holes.
    I'm pretty sure any new boiler, or furnace, that is still atmospheric, come with the stack damper, to increase or provide this efficiency.

    and yeah, the gas burner needs to be tuned just like any other burner,
    OP, you should find a tech for this.

    known to beat dead horses
  • Where does the combustion air come from in the basement?—NBC
  • neurosteam
    neurosteam Member Posts: 34
    Basement combustion Air? Can you clarify more please.
  • mikeg2015
    mikeg2015 Member Posts: 1,194
    Only problem is the dampers aren’t cheap. Savings is probably 3% at most. And much of the saved heat goes into the basement which only indirectly heats the occupied parts of the house.

    That being said, even in summer I’ve witnessed a pretty strong draft when the sun hits the exposed part of the chimney. Which oddly would increase reverse stack effect where hot humid air leaks in from up high and cool conditioned air leaks out through the basement. It’s one of the reasons basement are so cool in summer. All the cool air is falling and leaks out the sill plate.

    As far as I’m aware, All atmospheric boilers have the flue damper after the draft hood so there some heat rolling out after shutdown.
  • ChrisJ
    ChrisJ Member Posts: 15,457
    mikeg2015 said:

    Only problem is the dampers aren’t cheap. Savings is probably 3% at most. And much of the saved heat goes into the basement which only indirectly heats the occupied parts of the house.



    That being said, even in summer I’ve witnessed a pretty strong draft when the sun hits the exposed part of the chimney. Which oddly would increase reverse stack effect where hot humid air leaks in from up high and cool conditioned air leaks out through the basement. It’s one of the reasons basement are so cool in summer. All the cool air is falling and leaks out the sill plate.



    As far as I’m aware, All atmospheric boilers have the flue damper after the draft hood so there some heat rolling out after shutdown.

    What about the fact the chimney stops sucking heat out of the basement in between cycles?

    I'm betting most of the heat lost into a basement ends up in the livingspace as well.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Motorapido
    Motorapido Member Posts: 307
    I have smart home temperature/humidity sensors throughout my house, including the main basement and boiler room. I saw a significant temperature increase in my basement and shorter time-to-produce-steam when I replaced my formerly broken automatic damper (meaning that the damper was always open before I replaced it) on my atmospheric draft gas fired steam boiler. Sure, it adds a control mechanism that will eventually fail, but it's keeping the rush of cold chimney air out of my basement and allowing my boiler to produce steam faster. I vote for you to add the damper. I fully insulated my wet returns, too, both to decrease the production of carbonic acid as the condensate cools and also to retain the condensate heat so the boiler can produce steam faster. Cheap investment in efficiency.
  • mikeg2015
    mikeg2015 Member Posts: 1,194
    My roughy math says it saves around $50 per year for natural gas. 40f average temp rise, 50cfm, $1/therm, 85% boiler duty cycle.
  • PMJ
    PMJ Member Posts: 1,265
    This one isn't sort of maybe or even close.

    Get the damper. Easily worth every penny.

    That wide open flue exhausts air you already paid to heat every minute your burner is off.

    Even if you supply outside combustion air that isn't the biggest thing. Time to steam from burner start is dramatically affected by this and as far as I can tell completely overlooked around here. The cooling effect on that boiler between cycles will add minutes to the time to steam on every firing. These minutes of burn time that don't need to be there add up. Outside combustion air without the damper will make this even worse as it would cool the boiler even faster without a damper.

    Think about it. These are all minutes you are firing the burner and not making steam. You are replacing heat that went up the flue in order to get the boiler back warm enough to make steam again. That is one loss that doesn't need to happen at all.

    Time to steam is a really big deal with regard to efficiency. Those who don't appreciate that won't appreciate what vacuum can do either which drops time to steam down a lot further yet.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
    ethicalpaul
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,849
    My boiler didn't have a vent damper, and it worked that way for years, but I added one, and my basement stays a lot warmer between cycles now.

    Originally, none of the piping in my basement had insulation, so the basement would get really hot when the boiler was on, but the hot air could go up the chimney with very little trouble, and the temperature swings were pretty extreme. Now, with the pipes insulated and the vent damper installed, it's warm all the time.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • Jamie Hall
    Jamie Hall Member Posts: 22,918
    Vent dampers probably aren't a bad idea. Will they save the cost of investment? Hard to say.

    One thought, though, which certainly doesn't apply to everyone: the mean time between failures on a vent damper has been, in my experience, much shorter than any other control or device, at least on the systems I've been exposed to -- and they fail closed. This not an issue when the structure is occupied and there is someone qualified to go and manually open the damper when it fails. When it is a structure where this isn't the case, however, it would be wise to have a remote alarm capability to tell the responsible person that the heat is off.

    Just based on experience -- and your mileage may vary -- I currently care for 3 historic properties, and have for a number of years. In that time I've had one total failure of a burner control (welded contacts on a relay) and no failures on any other device -- except an average of 3 failures per structure per year on vent dampers (which have all been removed for that reason).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • PMJ
    PMJ Member Posts: 1,265

    Vent dampers probably aren't a bad idea. Will they save the cost of investment? Hard to say.

    One thought, though, which certainly doesn't apply to everyone: the mean time between failures on a vent damper has been, in my experience, much shorter than any other control or device, at least on the systems I've been exposed to -- and they fail closed. This not an issue when the structure is occupied and there is someone qualified to go and manually open the damper when it fails. When it is a structure where this isn't the case, however, it would be wise to have a remote alarm capability to tell the responsible person that the heat is off.

    Just based on experience -- and your mileage may vary -- I currently care for 3 historic properties, and have for a number of years. In that time I've had one total failure of a burner control (welded contacts on a relay) and no failures on any other device -- except an average of 3 failures per structure per year on vent dampers (which have all been removed for that reason).

    Agreed, your mileage may vary.

    One tip - install them as far from the boiler as possible. I installed mine 23 years ago on a 10 inch flue. Still haven't had issue #1 with it and I run many more cycles than most.

    And as far as investment return the conventional wisdom will be that this is a marginal call. I think it is a clear winner on efficiency and mostly because of the time to steam issue. It is not just the already heated air leaving that you have to account for. It is the additional heat concentrated in the boiler that leaving air picked up on the way out. Straight up dead loss that is because it didn't need to happen at all. There will be additional minutes every burn to make up for it.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
    Hap_Hazzard
  • ChrisJ
    ChrisJ Member Posts: 15,457
    PMJ said:

    Vent dampers probably aren't a bad idea. Will they save the cost of investment? Hard to say.

    One thought, though, which certainly doesn't apply to everyone: the mean time between failures on a vent damper has been, in my experience, much shorter than any other control or device, at least on the systems I've been exposed to -- and they fail closed. This not an issue when the structure is occupied and there is someone qualified to go and manually open the damper when it fails. When it is a structure where this isn't the case, however, it would be wise to have a remote alarm capability to tell the responsible person that the heat is off.

    Just based on experience -- and your mileage may vary -- I currently care for 3 historic properties, and have for a number of years. In that time I've had one total failure of a burner control (welded contacts on a relay) and no failures on any other device -- except an average of 3 failures per structure per year on vent dampers (which have all been removed for that reason).

    Agreed, your mileage may vary.

    One tip - install them as far from the boiler as possible. I installed mine 23 years ago on a 10 inch flue. Still haven't had issue #1 with it and I run many more cycles than most.

    And as far as investment return the conventional wisdom will be that this is a marginal call. I think it is a clear winner on efficiency and mostly because of the time to steam issue. It is not just the already heated air leaving that you have to account for. It is the additional heat concentrated in the boiler that leaving air picked up on the way out. Straight up dead loss that is because it didn't need to happen at all. There will be additional minutes every burn to make up for it.
    The manufacturers like to set them up to slowly bake the motor/gear box directly over a drafthood for some reason.

    Mine is mounted up away from the boiler now but I had to modify and extend the cable.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,849
    PMJ said:

    One tip - install them as far from the boiler as possible.

    ChrisJ said:

    The manufacturers like to set them up to slowly bake the motor/gear box directly over a drafthood for some reason.

    DOH!

    I didn't even think of that. When I installed mine I just did it the way they showed in all the pictures, not even thinking that it could just as easily have been mounted at the top of the pipe as the bottom, or thinking about how heat might damage the motor. What a dork I am.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • PMJ
    PMJ Member Posts: 1,265

    PMJ said:

    One tip - install them as far from the boiler as possible.

    ChrisJ said:

    The manufacturers like to set them up to slowly bake the motor/gear box directly over a drafthood for some reason.

    DOH!

    I didn't even think of that. When I installed mine I just did it the way they showed in all the pictures, not even thinking that it could just as easily have been mounted at the top of the pipe as the bottom, or thinking about how heat might damage the motor. What a dork I am.
    I have nearly a 10 foot run to the chimney. Flue runs through a thin wall first so the damper is actually in different room than the boiler. Maybe why it has lasted so long.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,849
    I can't move mine that far away, but I can probably raise it a couple of feet--even more if I put it on the horizontal section. Is there any reason that wouldn't work? I've never seen one in that position, but I'm having a hard time convincing myself it wouldn't work.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • PMJ
    PMJ Member Posts: 1,265

    I can't move mine that far away, but I can probably raise it a couple of feet--even more if I put it on the horizontal section. Is there any reason that wouldn't work? I've never seen one in that position, but I'm having a hard time convincing myself it wouldn't work.

    Will be fine. Mine is in that long run which might be 15 degrees off horizontal.
    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
    Hap_Hazzard