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Here we explain the inspection and adjustment of draft regulators or barometric dampers on oil fired heating equipment: A Guide to Barometric Dampers on Oil Fired Boilers, Furnaces, Water Heaters: inspection, adjustment, cleaning, troubleshooting. InspectAPedia offers impartial, unbiased advice without conflicts of interest. We will block advertisements which we discover or readers inform us are associated with bad business practices, false-advertising, or junk science. Our contact info is at InspectAPedia.com/Contact.htm.This website answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect residential heating systems to inform home owners, buyers, and home inspectors of common heating system defects. The articles at this website describe the basic components of a home heating system, how to find the rated heating capacity of an heating system by examining various data tags and components, how to recognize common heating system operating or safety defects, and how to save money on home heating costs. We include product safety recall and other heating system hazards. © Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Guide to Inspecting Barometric Dampers or Draft Regulators on Oil Fired Heaters, Furnaces, Boilers, Water HeatersDetails about draft control on oil fired heating systems (such as the oil fired heater shown in the photo above), including furnaces or boilers, are discussed right here at Draft Regulators barometric dampers on oil fired equipment. (Details about draft control for gas fired heating systems, including furnaces or boilers, are discussed at Furnace Draft Hood on gas fired equipment. Readers should also see CHIMNEY INSPECTION & REPAIR GUIDE and Flue Vent Connectors - Boilers, Furnaces for inspection, defect identification, and repair suggestions for chimneys and flues. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Why we need the Barometric Damper or Draft Regulator on a Boiler or Furnace
The force with which this air or combustion gas moves is the "draft" inside of the heating appliance. Too much draft increases heating appliance operating cost by venting heat out through the chimney instead of transferring the heat into the building where it was wanted. Too much draft can also increase chimney temperatures to an unsafe level. Too little draft can result in incomplete combustion, soot-clogging of heating equipment (dangerous), and more dangerous heating appliance malfunctions such as oil burner puffbacks and in some cases dangerous production of carbon monoxide gas that leaks into the building (a potentially fatal problem). So virtually all fossil-fuel-fired heating appliances provide some sort of draft control or draft regulator to keep the draft at required levels both in the combustion chamber and out through the chimney. Details of Why is a draft regulator is needed ?
For example wind blowing over a chimney top can increase draft, as can a second appliance using the same chimney as the heater. Since the force of draft is not normally constant, and since we want the draft to be constant for optimum oil burner operation, the barometric damper is installed. If the oil burner sees flue draft that is too low the combustion gases will not vent safely out of the building and the heating equipment may suffer from backpressure in the combustion chamber, causing overheating or other malfunctions. Also see OIL BURNERS and OIL BURNER NOISE SMOKE ODORS Our photo (above left) shows a chimney that extends less than two feet above a flat roof on a one story home, resulting in inadequate draft and sooty burner operation. The home suffered recurrent oil burner sooting, puffbacks, high and repeated heating service repair bills, and ineffective attempts by heating service techs to "fix" the problem by running the oil burner at high temperatures - a trick that mostly served to increase the heating bills for the home. If you have this problem see Chimney Too Short and Chimney Height Extensions as well as Draft Inducer Fans. At DRAFT MEASUREMENT, CHIMNEYS & FLUES we illustrate how this particular short chimney and inadequate draft problem were finally fixed. If the oil burner sees flue draft that is too high combustion gases will vent out of the building just fine, but we're sending too much heat up the chimney by moving combustion gases too fast through the heater, thus we're sending our oil dollars up the chimney as heat rather than into the building as heat. The service technician adjusts the barometric damper to maintain a continuous draft in the range we described above. Then if local conditions change, the barometric damper can open or close to let in more or less additional air into the flue and chimney, keeping the draft constant. Are Barometric Draft Controls Used on Gas-Fired Equipment?Incidentally, draft controls might be found on gas-fired heating equipment too, but the specifications are quite different. Gas fired heaters such as domestic gas fired furnaces are usually designed to operate at very low over-fire drafts - which means almost zero draft will be measured at the flue vent connections. That's why you usually don't see a hinged-door barometric draft regulator on gas fired equipment. Take a look at DRAFT HOODS - gas fired for details. Field Corporation [1], and Tjernlund [2] draft regulator producers, provides different model draft controls for gas fired equipment, such as the Field Type MG1 and MG + MG2 regulators which use double swinging gates that open inward under normal up-draft conditions and outward in case of blocked flues, thus relieving internal pressures. Since improper venting of gas fired appliances easily produces very dangerous, potentially fatal Carbon Monoxide (CO), it is critical that these appliances are vented properly. Do not ever install an oil-fired appliance draft regulator such as the Field Type AF shown here onto gas-fired equipment. Where Should the Draft Regulator (Barometric Damper) be Installed?
Measure Chimney & Flue Draft when adjusting the barometric damper / draft regulatorDetails are at DRAFT MEASUREMENT, CHIMNEYS & FLUES. Excerpts are just below.
How Does a Barometric Draft Control or Draft Regulator Work?
It's easy to understand how a draft regulator work: as Carson Dunlop's sketch above shows. The service technician measures draft over the fire and in the breech, and she moves a little weight on the hinged barometric damper door to cause the door to open wider or less wide to let more or less room air into the chimney as needed. As long as the gas pressure inside of the flue and chimney is less than room air (that is, it's "negative" as we explained below), air from the room wants to enter the chimney through the barometric damper opening. Like the porridge in Goldilocks and the Three Bears, there are three possibilities: The draft as sensed at the barometric damper is too strong (maybe a wind is blowing over the chimney top, increasing the draft): in this case the draft inside the flue, at the breech at the draft regulator is more negative - maybe -1.2 " w.c.. Since the air in the room is at normal pressure it will be stronger than the pressure inside the flue, so air in the room will push the draft regulator door "in" and make it open, letting room air flow into the chimney until, balanced by the setting of the weight on the moving draft regulator's door, the incoming room air enters the flue in enough volume to drop the draft pressure back to its desired setting, maybe to -0.04" w.c. The draft as sensed at the barometric damper is too weak (maybe a wind is blowing down the chimney flue because we left off our chimney cap): in this case the draft inside the flue, at the breech and thus at the draft regulator is less negative, maybe -0.01" w.c. than we wanted - we're having trouble sending those flue gases up the chimney. The little weight on the draft regulator door causes the door to close, reducing the inflow of room air into the flue, and thus increasing the draft in the flue back to the desired number, maybe to -0.04" w.c. once again. The draft as sensed at the barometric damper is just right: it's hovering where we set it at -0.04" w.c. In this case the barometric draft regulator is probably showing its little door a little bit open, with a little room air flowing into the flue. (Otherwise we wouldn't have any room to close the door to increase the draft when we need to do so.) And the draft in the flue is staying at the desired number, maybe -0.04" w.c. How is the Barometric Draft Control Adjusted? What are the recommended draft settings?
Weight location & adjustment on barometric draft controls
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Weight location & adjustment on barometric draft controls: the weight that is adjusted to regulate the operation of the draft control needs to be properly located as well as adjusted. T |
Field controls also points out that
It is essential that CO2 readings be taken to determine proper [draft regulator] adjustments. (This test and others should be conducted by a qualified fuel oil dealer or appliance installer for your safety). [1]
While we and the draft regulator manufacturers give typical draft measurement numbers for draft over the fire and at the damper itself, some oil burner manufacturers may require specific draft settings other than those standard ones. In addition, variations in chimney and building details from one installation to another may affect how the oil burner, heating appliance itself, flue vent connector, chimney, chimney cap, and site wind conditions all interact. Ultimately we need to know these effects on combustion. We want not only proper draft and [usually] no backpressure in the combustion chamber, we also want efficient combustion - that's where the CO2 measurement comes in.
For a detailed guide to inspecting draft regulators and barometric dampers please see How to Inspect a Barometric Damper.
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Soot production or soot blow-back stains at the combustion chamber inspection port or burner mounting tube (or soot in general).
Regardless of whether the draft regulator is serving an oil fired heating boiler or an oil fired water heater, soot coming out of the barometric damper or out of the flue vent pipe, or the presence of soot and burn marks on the heater, or even noises: stumbling, rumbling, noisy oil burners, as well as odors, are examples of improper oil burner operation that need prompt service.
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Our photo at above left shows an example of improper oil burner operation on an oil fired water heater: both systems show soot blow-out at the water heater's combustion chamber inspection port.
At above right, a different heating system appliance shows soot beginning to blow back out of the draft regulator itself. And notice the sloppy installation? The draft regulator was not installed level. The weight system does not work properly when the damper door is out of level.
Often these soot marks are a symptom of excessive pressure or "back pressure" inside the combustion chamber. Since this water heater is connected so closely to the chimney in a pretty new house, our first guess was that the water heater itself needed cleaning.
Oil fired appliance sooting problems can be caused by an oil fired water heater or heating boiler that is way past due for cleaning (soot blocks the exhaust flue), by a blocked chimney, by improper draft regulator adjustment, or other defects.
I am fascinated by and appreciative for your publication "Guide to Barometric Dampers..." Many thanks for the complete explanations.
I am getting the run-a-round from the 'service' people from the service company; I'm not sure they know much more than I.
I have one question which I hope you will answer: when the oil burner is not operating, should the damper door be closed? Logic would suggest to me that it should be closed but I am terribly uninformed. - R.D.B.
A competent onsite heating or chimney and flue inspection by an expert usually finds additional clues that help accurately diagnose a problem with the heating appliance or the flue and chimney that vent its combustion products.
That warning made, yes, in general, a properly adjusted and balanced barometric "flapper" door is in the vertical or closed position when the heating flue to which it is connected is not in use. If the door is open you may be wasting warm air and heat from the area around the heating boiler or water heater that the damper is serving. Field Controls puts it this way:
Always set the [barometric damper draft] control to maintain as low a draft as will give good combustion and meet the requirements for heat. [1]
Why? Because if you set the draft higher than necessary, you are wasting money, sending heat up the chimney instead of into the building (or if it's a water heater, into the hot water tank). We need enough draft that the oil burner does not blow soot back into the building, and so that combustion is efficient, but we do not want excessive draft.
Below we list reasons that your draft regulator door is staying open. If you check all of these out and find that the installation is correct, the equipment is all operating normally, but that chimney and wind conditions are keeping the draft regulator open (and heat is thus wasted from your home), a solution could be the installation of an automatic flue vent damper that opens before the oil burner turns on and closes automatically when the oil burner has turned off. [See our photo at left]. Watch out: Installing an automatic flue damper can reduce building heat loss through the flue but we do not want to see this "solution" installed before you have an accurate diagnosis of just why your flue damper door is hanging open. We discuss automatic vent dampers in detail at Automatic Vent Dampers where we explain how they work, how they save money, and what they look like. |
The heater is cooling down: If you are looking at the damper right after the oil burner has shut down, the heater is still hot and a mix of hot air and combustion gases are still zooming up the flue and chimney. If the draft effect of those rising gases is creating an updraft that is more than proper for optimum heater adjustment, the damper door will open to admit room air, thus reducing the draft seen in the flue.
The draft regulator is not properly adjusted. One of the basic tune-up steps performed on oil fired heating equipment, usually right after the system is serviced and cleaned, is to check for proper draft over the fire and in the flue. The in-flue measurement is usually made through a hole drilled in the space between the top of the heater and the under-side of the draft regulator. See What is the Right Draft Measurement at Oil Fired Heaters?.
The draft regulator hinges or pivot pins are sticking. On occasion, especially if someone was trying to "adjust" a draft regulator or damper by bending or banging on it, we find that the regulator's door hinge sticks. The door may stick in the open or shut position, interfering with proper operation.
It's easy to check for this sticky hinge problem: just gently push the door open and shut with one finger - it should move freely. When the oil burner is off and the system is cool, if you can push the regulator flapper door into a position in which the door sticks and does not return to the "closed" position on its own, the hinge is binding or the damper is not properly installed. Sometimes a little cleaning and a dab of oil on a hinge (I used pencil lead) is needed. If parts are badly rusted or smashed, just replace the unit.
The damper is installed on a shared flue or shared chimney: while it is not a recommended practice, if the damper is installed on a flue vent connector ("flue pipe" or "stack pipe" - the metal pipe connecting the heater to the chimney) that is shared with other heating appliances, then heat in the other appliance that is running or that has just shut down and is also "hot" can cause enough up-draft to cause the damper door to open.
In addition to the fire safety and code issues that severely limit any sharing of actual chimneys, the reason that manufacturers recommend that each heating appliance have its own flue damper is exactly this: you cannot adjust the barometric damper or draft regulator to optimize the performance of more than one heating appliance on a shared flue. Details are at Shared Chimney & Shared Flue Hazards.
The draft regulator is not properly installed - out of level or in the wrong location. A key reason that the manufacturers of draft regulators want the regulator face or "door" to be in the vertical position and the hinge axis of the door to be horizontal, is that the weight and calibration of the draft regulator adjustment and the response of the draft regulator to changing draft conditions depends on being in that position.
Even if the heating service technician adjusted the regulator for proper draft when the oil burner was up to temperature and running, if the damper is not properly installed it may not respond just right to changes in draft conditions such as wind over the chimney top.
In addition to out of level or wrong location, Field Controls also notes that the opening of the draft regulator should be pointing away from nearby walls or obstructions as these will interfere with its proper operation. Even if the installer placed the draft control properly plumb and level on the flue tee, if s/he forgot to set the locking screw (found at the bottom of the draft control assembly), the regulator may have rotated in its mount and may now be improperly positioned. [1]
Outdoor conditions are causing excessive chimney draft. For example at some building sites and depending on variables such as wind direction, nearby hills, chimney height, roof shape, height of chimney top above roof, chimney cap design, nearby trees or other obstructions (yep there are a lot of variables), wind blowing over the top of a chimney can actually increase the chimney draft to a too-high level, causing the barometric damper to open even if the oil burner is not running.
Hi there -- My home has both heat pump and oil heat and I prefer to use the oil. I have a ? - several years ago our elec co came and installed a programmable thermostat as well as doing something to our furnace.
Since that time there have been several incidents that the damper door gets stuck and then "bursts" open with a loud explosion noise -- scary. A local HVAC co replaced the door but the problem with the damper door still exists. T
he hubby has adjusted some weight on the thing but ... You would have thought the folks that replaced the door would know what to do. I'm afraid to have to use it and the heat pump is worthless. Any advice would be greatly appreciated. I reside in MD.
Mary get someone you know who knows heating systems, if he arrives with out his test equipment do not let him try to set up the burner or adjust the draft regulator as its job is to maintain the fuel air ratio when the outside conditions try to change it. It can not be done accurately by eye.
Mary: a bent pin or even out of round opening can cause a barometric damper (draft regulator) door to "stick" closed. It's a simple mechanical repair that is easily performed by an attentive heating service technician. Or if the device is badly damaged or missing parts, it's not costly to replace the whole assembly.
Hubby changing the weight setting on the draft regulator door is not a good idea, though freeing up the door to move is just fine. The weight setting is a draft adjustment. Incorrect draft means incorrect burner operation.
Watch out: a stuck-shut draft regulator results in increased draft over the fire - something that increases heating system operating cost, but not something that would easily explain that loud "explosion noise" when the regulator opens. Rather, I suspect that your oil burner is not properly adjusted, is dirty, or is otherwise malfunctioning.
For example, an oil burner that does not shut down crisply at the end of a burn cycle can dribble unburned oil into the combustion chamber. At the next startup operating cycle that unburned oil is ignited to cause an explosion in the combustion chamber - referred to in the trade as a "puffback". Puffbacks can be dangerous, damaging the equipment and risking blowing soot all over the place, and in extreme cases the whole heating appliance can be badly damaged.
In conclusion I agree with Mr. Scott's advice: you need a service call from a trained, competent heating service technician, ASAP.
HI, I have a oil fired boiler that provides hot water base board heating and domestic hot water. I have just had the boiler serviced which includes cleaning and checking of draft etc. The serviceman is very competent. He has been servicing it for years. The flue is an 8" flue inside of a 10" insulated pipe because the pipe goes up a boxed in chimney of plywood and the plywood is stucco outside. I have a gas fire place also which is direct vented to the outside.
The flue pipe comes up the side of the box and then once it gets past the fireplace vent is offset to the center of the box. I believe the pipe is then reduced at the top to a 6" pipe and cap. It has been this way for 15 years, but suddenly I am smelling exhaust fumes after the burner runs and sometimes after it shuts off. The service man has been back several times and have tried different things and made sure the setting for draft are correct. He said the pipe is very clean and the furnace runs very efficiently
. I only seem to smell the fumes at the first level floor and not in the basement.
The next step would be to remove the outside surface of the box to see if we can see any separations where the pipes lengths connect, but I want to make that the last resort, because of the expense. Is there any other steps I can try to see where the smell is coming from. - Steve Henninger
Steve Henninger,
If your heating appliance was designed for an 8" flue, that is, the diameter at the top or back of the heater is 8" in diameter, then any reduction to 6" is asking for a draft problem. It's true that a heater might appear to work "fine" with a constricted draft, especially if it were set up to give priority to the draft (perhaps at the expense of most economical operation). By that I mean it's possible to set an oil fired appliance to run "hot" to get better draft, and even to run cleaner, but setting hotter than normal wastes fuel, sending more of each heating dollar up the chimney rather than into the building.
Now later, maybe years later, fussy technician shows up, cleans and services the system, and sets it up at what s/he views as optimal for economy as well as safe operation. But now the constriction at chimney top begins to make more trouble.
Or alternatively, the chimney itself has changed - a leak or hole, combustion air supply to the appliance has changed -someone closed a door or window, or site conditions have changed - someone cut down a tree, wind direction changed or increased, etc. Something that just pushes draft problems over the edge of recognition.
I just had my chimney clean and they put the vacuum into the damper instead of going into the sealed opening in chimney . I found my damper damaged the counter weight was on the floor . Is this standard practice in the chimney cleaning business practices. I will be making a complaint to consumer affairs and suing them for exposing me to carbon monoxide poisoning. Neil
Neil, in my OPINION, it sounds as if your service tech may have taken a bit of a shortcut. Certainly if there is an easy direct view into a "dead end chimney flue" through the damper I can understand the temptation to just reach the vacuum in through the damper to vacuum out the debris - an important safety step to avoid a blocked flue.
But if you were having the heating system serviced and cleaned (that is your boiler or furnace was supposed to have been cleaned), on most systems it is necessary to remove the flue vent connector, damper assembly, and flue connection to the chimney as well as the top of the boiler or furnace in order to vacuum out the heater itself.
And if all that disassembly were performed, it would be easier then to vacuum the chimney base directly.
Further, what you describe is not a complete chimney cleaning - just removal of debris from the chimney base. Now that might be all that was needed, provided that the service tech had some reason to be confident that the rest of the chimney was clean and unblocked. Say by inspection using a mirror and light? But it's difficult to look up into a chimney thoroughly - it's like peering into a black abyss.
Finding your damper damaged and the counter weight on the floor is prima-facae evidence of an incompetent technician. No responsible person would leave equipment in that condition. I'd give the heating or chimney company service manager a polite call asking that they send someone with better training and work habits to repair the damper and to inspect the chimney, and if your heater was supposed to have been cleaned, to perform that task too.
About suing your contractor for CO poisoning, I understand that you're rightly annoyed, but in my OPINION that's a costly waste of time and source of unnecessary aggravation for you as well as everyone else. Focus first on making sure that your heating system is properly serviced and safe. It would be in my OPINION a big mistake to start by hiring a lawyer while leaving the heating system in an unsafe condition.
Questions & Answers about draft regulators and barometric dampers on heating equipment; Questions & Answers about inspecting and adjusting the barometric damper or draft regulator on oil fired heating equipment
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CARBON MONOXIDE - CO
CARBON MONOXIDE WARNING
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CHIMNEYS & Flues - Asbestos Transite Pipe
Chimney Draft & Performance
Draft: Thermal Performance of Chimneys
Chimney Height & Clearance
Chimney Too Short
Masonry Chimney Roof Clearance
Adjacent Metal Chimney Separation
Chimney Height for Types L & Type B Vents
Chimney Height Extensions
Wood burning Fireplace Roof Clearance
COMBUSTION AIR
COMBUSTION AIR for TIGHT buildings
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
COMPLETE COMBUSTION, Stoichiometric
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DRAFT HOODS - gas fired
DRAFT MEASUREMENT, CHIMNEYS & FLUES
DRAFT REGULATORS, DAMPERS, BOOSTERS
Purpose of Barometric Draft Regulator
Measure Draft
Barometric Damper Defect List
How to Inspect a Barometric Damper
Automatic Vent Dampers
Define flue damper, duct damper, & fire damper
Draft Inducer Fans
Also see OIL BURNERS and OIL BURNER NOISE SMOKE ODORS
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An automatic duct damper is a mechanical device, usually controlled by a room thermostat, which opens or closes a metal baffle inside of a warm air (or cool air) heating (or cooling) duct in order to provide multiple heating zone control in a building. You can see photographs of and read about manual and automatic heating and air conditioning zone dampers at ZONE DAMPER CONTROLS. |
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A draft inducer is a booster fan that increases the flow of combustion gases up a chimney. They are used when there is a problem with the chimney or heating equipment installation that prevents natural draft from working adequately. We discuss draft inducer or "draft boosting" fans for heating systems (and maybe for some fireplaces) in detail at Draft Inducer Fans. |
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A barometric draft control, also called a "damper" or barometric damper, is a hinged, weighted door on an opening at a heating flue. The door opens or closes to let extra air into the flue to assure that the draft in the flue remains constant at the proper setting needed for proper heating system operation. Barometric dampers are discussed in detail beginning at DRAFT REGULATORS, DAMPERS, BOOSTERS |
Dirk Faegre, Camden, Maine (207) 232-9494 is a certified BPI energy auditor and certified Envelope technician who kindly suggested draft regulator and flue vent connector inspection defect additions 6 Sept 09
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