Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
AFUE DEFINITION, RATINGS
AGE of CHIMNEYS & FIREPLACES
AGE of HEATERS, BOILERS, FURNACES
BACKDRAFTING HEATING EQUIPMENT
BOILER COMPONENTS & PARTS
BOILER CONTROLS & SWITCHES
BOILER NOISE SMOKE ODORS
BOILER OPERATING PROBLEMS
BOOKSTORE - InspectAPedia
CARBON DIOXIDE - CO2
CARBON MONOXIDE - CO
CHIMNEY INSPECTION DIAGNOSIS REPAIR
COMBUSTION AIR for TIGHT buildings
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
COMPLETE COMBUSTION, Stoichiometric
CREOSOTE FIRE HAZARDS
DEFINITION of HEATING & COOLING TERMS
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECT VENTS / SIDE WALL VENTS
DRAFT HOODS - gas fired
DRAFT MEASUREMENT, CHIMNEYS & FLUES
DRAFT REGULATORS, DAMPERS, BOOSTERS
FIRE SAFETY CONTROLS
FIREPLACES & HEARTHS
FLAME COLOR, BLUE vs YELLOW COMBUSTION
FLOODED HEATING EQUIPMENT REPAIR
FLUE SIZE SPECIFICATIONS
FLUE VENT CONNECTORS
FUEL OIL TYPES & CHARACTERISTICS
FUEL UNIT, HEATING OIL PUMPS
FURNACE CONTROLS & SWITCHES
GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
HEATING LOSS DIAGNOSIS-BOILERS
HEATING LOSS DIAGNOSIS-FURNACES
HEATING OIL PIPING TROUBLES
HEATING OIL TANKS
HEATING SYSTEM NOISES
HEATING SYSTEM TYPES
HIGH EFFICIENCY BOILERS/FURNACES
HOT WATER HEATERS
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
GAS LP & NATURAL GAS SAFETY HAZARDS
MANUALS & PARTS GUIDES - HVAC
Natural Gas Combustion
NO HEAT - BOILER
NO HEAT - FURNACE
NOISE, DUCT VIBRATION DAMPENERS
NOISE, HEATING SYSTEMS
NOISE, WATER HEATER
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS FROM HEATING SYSTEMS
OIL BURNER FUEL UNIT
OIL BURNER INSPECTION & REPAIR
OIL BURNER NOISE SMOKE ODORS
OIL BURNER SOOT & PUFFBACKS
OIL FILTERS on HEATING EQUIPMENT
OIL FUEL TYPES & CHARACTERISTICS
OIL HEAT FIRE SAFETY CONTROLS
OIL LINE CLOGGING FIX
OIL LINE QUICK STOP VALVES
OIL LINE SAFETY VALVES, OSVs
OIL FILL PIPE LEAKS
OIL PUMP FUEL UNIT
PLASTIC Plexvent / Ultravent RECALL
PULSE COMBUSTION HEATERS
RELIEF VALVE LEAKS
RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - STEAM TP VALVES
RELIEF VALVES - Water Heaters
Reset Switch - Heater Primary Control
Reset Switch Broken - Quick RepaiR
RESET SWITCH - ELECTRIC MOTOR
Reset Switch - Stack Relays
SAFETY, HEATING INSPECTION
SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOOT on OIL FIRED HEATING EQUIPMENT
SPILL SWITCHES - Flue Gas Detection
STACK RELAY SWITCHES
STAIN DIAGNOSIS on BUILDING INTERIORS
STEAM HEATING SYSTEMS
THERMAL EXPANSION of HOT WATER
THERMAL EXPANSION of MATERIALS
THERMAL MASS in BUILDINGS
THERMOSTATS, HEATING / COOLING
THERMOSTATS, WATER HEATER
TRANSITE PIPE CHIMNEYS & FLUES
VIDEO GUIDES: Heating System Videos
WINTERIZE A BUILDING
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
ZONE VALVES, HEATING
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.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
Guide to Inspecting Barometric Dampers or Draft Regulators on Oil Fired Heaters, Furnaces, Boilers, Water Heaters
This article series answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects.
[Click to enlarge any image]
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.
Details 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 DIAGNOSIS REPAIR and FLUE VENT CONNECTORS, HEATING EQUIPMENT 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.
Barometric dampers are devices used to regulate the draft on oil-fired heating equipment such as furnaces, boilers, or water heaters. The barometric damper or draft regulating device we are discussing here is normally used only on oil-fired heating equipment, not on gas-fired equipment. The equivalent draft control on gas fired heating systems is discussed at Furnace Draft Hood on gas fired equipment.
On oil fired equipment the barometric damper, or draft regulator is typically a round Tee inserted in the flue vent connector between the heating appliance and the chimney. The face of the tee contains a round "door" with an adjustable weight.
The service technician adjusts the weight to control the swing or opening of this door which in turn controls the amount of excess air that can enter the flue and chimney when the oil burner is operating.
The draft regulator in our photo shown just above is not working - and has been deliberately jammed - indicating that something else is wrong, probably a chimney problem or an oil burner operating problem: the technician was unable to get enough draft, so s/he defeated the regulator - this is not a good idea, as we'll explain below.
For a detailed guide to inspecting draft regulators and barometric dampers please see How to Inspect a Barometric Damper.
As combustion continues (the fuel is mixed with air and burned), a mix of air and combustion gases continues onwards, moving out of the combustion chamber, up through the boiler or furnace heat exchanger, through the flue vent connector ("stack pipe or flue pipe" and on into the chimney where these gases are finally vented outside, usually above the building roof.
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 ?
Chimney draft is not constant. While above we described how we measure draft inside of heating equipment and on the way to the chimney where (we hope) combustion gases are to be vented safely outside, the "draft" that the oil burner and furnace or boiler experience are not constant.
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.
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 , and Tjernlund  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.
Barometric damper location: a barometric damper will work properly to regulate draft and reduce backdrafts in a variety of locations in relation to the heating appliance and the chimney. [Images at left are courtesy Field Controls.]
Details are at DRAFT MEASUREMENT, CHIMNEYS & FLUES. Excerpts are just below.
Normally we measure draft at two locations: over the fire or in the combustion chamber. The draft we typically see on oil fired heating equipment like water heaters, boilers and heating furnaces is
The sketch at left showing a barometric damper on oil fired heating equipment (heating boilers or water heaters) was provided courtesy of Carson Dunlop Associates.
In the breech we want to see about -0.05 inches WC pressure. If the breech draft is too low the combustion process and venting process may be inadequate, and if the draft measured in the breech is lower than the draft measured over the fire, the oil burner and combustion chamber are operating under pressure - which is often a problem on residential heating systems since few of them are designed to work this way. Thanks to L. - for correcting our WC pressure data.
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.
In general the draft regulator is set to the lowest draft that gives good combustion and proper oil burner operation. Higher wastes energy.
While the heating equipment is operating at normal temperature, the draft is set to a number specified by the oil burner manufacturer, so we can only give approximate settings in this discussion. To find the proper weight setting to control the draft regulator, the heating service technician will make three measurements:
It is the position of the weight along a moveable scale, usually by screwing the weight in or out, or by sliding the weight along a scale (see our photo), that adjusts how far the draft regulator door will open in response to these three conditions described above. It's basically a principle of leverage -the weight is moved closer to or farther out from the axis of rotation of the moving draft regulator door.
When the barometric draft regulator door is more open, it is admitting more building air into the flue and reducing the draft seen by the heating appliance. When the draft regulator door is more closed, it is admitting less building air into the flue and is thus increasing the draft seen by the heating appliance.
So do not change the barometric draft control's weight setting unless you're a trained service technician who knows when, where, how, and why to measure draft at an oil fired heating appliance.
Weight location & adjustment on barometric draft controls
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
Why we Measure Carbon Dioxide CO2 as Well as Draft when Adjusting the Draft Regulator
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). 
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.
Draft Regulator Inspection Points, List of Defects & Signs of trouble with a barometric damper or draft regulator and what they mean
For a detailed guide to inspecting draft regulators and barometric dampers and for example of additional draft regulator defects, failures, misadjustments, please see DRAFT REGULATOR SOOT INSPECTION.
Loose or Damaged Draft Regulator (Barometric Damper) Parts or Improper Draft Regulator Installation Points
Field-installed draft regulator tee vs. using a factory tee
Is the draft regulator a field-installed retrofit unit (below left) or does it connect to a factory-built Tee (below right)?
Retrofit draft regulator opening size: Why do we care if the damper is mounted on a field built tee or a factory tee? The draft regulator at above left is a field add-on that is installed using a two-piece eared collar provided by the manufacturer.
The compnents are installed by assembling the two halves of the collar and by cutting a a hole in the existing length of flue vent connector pipe. The eared collar is mounted over the hole in the flue vent connector and the draft regulator is mounted to the collar opening. The size of the hole to be cut is determined by making a trace-mark inside of the mounting collar when the collar is held against the face of the flue vent connector in its destined location. On occasion we find that the hole cut in the pipe was too small (improper draft regulation) or too large (leaky connections).
A field-installed damper mounting "tee" like the one at above left is secured to the flue vent connector by two sheet metal screws, one on either side (red circle). If these screws are loose, stripped, or if the vent connector itself is corroded and rusty, the whole regulator assembly can fall off of the system - an unsafe event for obvious reasons.
The factory tee shown in our photo at above right (orange arrow) is secured to the boiler top and the flue vent connector (green arrow above the tee) using three sheet metal screws.The draft regulator assembly(blue arrow) is also secured to the opening of the tee (at right) by one or in some cases more than one sheet metal screws. Inspect to make sure that the SMS are all in place and that the parts are not loose nor rattling..
Loose-rattling draft regulator?
Interesting is that someone must have had trouble with this damper falling out or rattling, as they used adhesive-backed foil tape (blue arrow) to secure the regulator assembly to the field-installed tee. The adhesive tape shown by our arrow is a clue to heating system operating history, or it might mean that the installer didn't know how or where to install the sheet metal screw (at the top and bottom of the regulator mounting ring) to secure it to the tee. Or maybe s/he was out of sheet metal screws. Any clue suggesting unusual installation like this is an orange alert flag: look further for odd or improper workmanship.
Soot & Debris inside the flue vent connector
This photo (left) shows how, simply by pushing open the draft regulator swinging door to inspect inside the unit you can reliably identify a field-installed cut-in draft regulator instructions - notice the bent-over tabs (green arrows) that were cut and adjusted by the technician.
As we elaborate at DRAFT REGULATOR SOOT INSPECTION, this heater is also dirty (red arrow) and has not been properly maintained.
Screws Required to Secure Tee to Flue Vent Connector & Draft Regulator Assembly to Tee
The flue vent tee photo (below left) shows two of three sheet metal screws required to secure the tee assembly to the boiler top; three more screws are used to secure the tee to the flue vent connector ("stack pipe", not shown here) as well as three more (some instructions permit two) screws to secure the draft regulator assembly to the tee opening.
Our photos above show one of the screws required to secure the draft regulator assembly to the flue vent tee .
Usually we find that it's a tight fit jamming the draft regulator assembly into the tee opening, but we still install the factory recommended screws.
Vibration during heating equipment operation or the banging caused by rough heating boiler starts (mini "puff-backs") or other wear and tear can otherwise loosen the whole assembly.
At left we show where the draft regulator is missing one of its securing screws. There are several reasons why a screw might be missing:
The mounting screw was forgotten at initial installation
The mounting screw was removed to adjust the damper to proper level position, then the tech dropped the screw, it rolled under the boiler, and s/he didn't have another screw handy;
The service tech removed screws during cleaning (more likely at a flue vent connector not at the damper) and was in a rush to leave the job.
A close look at this photo shows that the damper position has been adjusted (to correct an out-of-level condition. We can just see the originally-drilled screw hole in the damper assembly (red arrow) just above the original screw insertion hole (blue arrow) in the flue vent tee. Our orange arrow points to a 3/16" gap between the draft regulator fully-in raised stamping and the edge of the tee opening - not a serious concern as long as the device is properly secured.
Check the Draft Regulator Door Hinge Pins
Our photos below (and my red pencil) point to the hinge pin that allows the flapper door of the barometric damper (or draft regulator) to swing freely. For the unit to operate properly the door needs to move freely in response to changes in draft in the flue. If the pins are bent, rusted, jammed, or field-modified (say a lost pin is replaced by a finishing nail) the draft regulator may not work properly and may even be unsafe.
Check the Draft Regulator Weight Assembly
Check that the weight assembly is present. You should see the bracket and adjustable weight on the outside of the draft regulator door (above my red pencil in the photo at below left). Now tip the hinged door open and check that the interior weight (red arrow in our photo at below right) is also in place. If the inside weight has been lost it may have fallen into the boiler or furnace. If the outside draft control weight is missing look for it on the floor next to those missing sheet metal screws we mentioned earlier. Without the weights it is unlikely that a barometric damper can do its job properly.
Note: some draft regulator controls do not use weights on both sides of the control door.
Now use your finger or a tool to gently push the barometric flapper door open and let go - it should swing freely and should not jam open nor jam shut.
Check the Operating Environment for the Heating Equipment
Even a perfectly-installed draft regulator cannot overcome other combustion air, draft, chimney, or boiler/furnace operating defects from other causes.
Check the service tag for the maintenance history of the equipment and for clues about a history of problems (repeated service calls for the same complaint); check the area around the heater for soot, oil spills, or an obvious lack of combustion air (tiny room, no air inlets).
In a forensic investigation of a heating system problem I'd be worried about why the bottom portion of the older (blue) service tag has been torn off (photo above left). The service company doesn't want to leave the equipment with no service tag - that itself is a red flag. But what information did someone want me to not-see?
Our boiler top dust photo (above right) and my finger show that 6 1/2 months of operation and dust (July 1 to January 15) of this oil fired boiler has produced almost no soot blow-out. In fact the system is almost too clean - I wondered if it was running with excess combustion air - staying clean but maybe giving up on efficiency, thus increasing the building's heating cost.
More draft regulator defects are described in detail at Questions & Answers about inspecting and adjusting the barometric damper below in this article and also at DRAFT REGULATOR SOOT INSPECTION where we provide details about what you may see when inspecting the draft regulator interior or the flue that it serves.
Barometric dampers or draft regulators (synonyms) are sold in a variety of sizes for residential and larger commercial heating systems. Draft regulator sizes are specified in inches, representing the diameter of the moving regulator door assembly.
Draft regulators are sized to match the flue vent connector to which they are mounted - in turn implying that the draft regulator will also be properly sized for the operating requirements (and draft requirements) of the heating appliance as well. That is, if the chimney and flue are too large or too small for the heating appliance the installation is improper and may be unsafe as well.
Sizes of draft regulators range from as small as 3-inch in diameter up to at least 32-inches in diameter. Prices for draft regulators range from under $50. U.S. to over $600. U.S. Larger sizes of barometric dampers, such as the Field 20-inch unit, retail (in 2013) for about $530. U.S.
Definitions: What's the difference between a flue damper, duct damper, a fire damper, and a draft regulator?
Don't confuse an automatic flue vent damper with two other "damper" devices: a heating system automatic duct damper or a duct fire damper.
An automatic flue damper is a device which closes the heating flue when the furnace or boiler is "off" so that we won't continue to lose building heat up the chimney - it's a device to reduce heating costs and save on heating oil consumption.
When the heating system has turned off at the end of an "on" cycle of burning fuel, the automatic flue damper electric (see sketch above and photo at left) motor turns a baffle inside of the flue vent connector pipe to a position "across" the pipe so that the airflow inside the pipe is blocked or stopped.
What is an automatic duct damper and how do they work?
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.
What is an Automatic Fire Damper in Ductwork and how do they work?
A draft inducer is a booster fan that increases the flow of combustion gases up a chimney. T
hey 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.
What is a Barometric Draft Control and how do they work?
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
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
What is the Significance of Soot production or soot blow-back stains at the Damper or Draft Regulator
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.
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.
When the oil burner is not operating, should the damper door be closed?
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.
Reply: Generally, yes, at rest, the damper door is shut. But here are some things that might make it open:
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. 
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.
Here are some things that might explain why the barometric damper is hanging open even when the heater is not running:
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.
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.
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.
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.
Question: our draft regulator door gets "stuck" then bursts open with a loud explosion noise - scary!
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.
Reply from reader Lionel Scott
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.
Reply from DF: a sticky barometric damper door is easily repaired but that's not the whole problem here - watch out for dangerous boiler or furnace puffback
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.
Question: I smell exhaust fumes after the oil burner shuts off. How can I track down that problem?
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
Reply: have an expert inspect and fix any chimney, flue, or flue vent connector or draft regulator problems; check the oil burner for improper shutdown.
Question: the chimney cleaner vacuumed through the damper and damaged it
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
Reply: repair the barometric damper or replace it; have the chimney and heating appliance properly cleaned and serviced
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.
And if all that disassembly were performed, it would be easier then to vacuum the chimney base directly.
Damper parts on floor = very poor workmanship
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.
Sue for CO poisoning risk? Focus on safety first!
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.
Question: Draft regulator placement
The picture of the hot water heater shows the draft regulator installed at the end of the tee which makes for a possible exhaust leak should be perpendicular to pipe.
I invented a improved draft regulator patent #2459368
I have been asked to prove how much heat a properly set up barometric draft regulator can lose. I have been under the impression that it is 15 to 20% of the total fuel bill. Can anyone help? 11/27/2011
- Lionell Scott
Lionel Scott - thanks for your comments below. I agree completely.
Thanks for your interest in the Venturi Draft Regulator, If you would like to have an actual regulator to test i would be glad to send one.
Question: Questionable reader reports improper chimney & heater service led to Carbon Monoxide fatalities
The guy who cleaned my chimney stuck the vacuum into my damper causIng me to almost lose my entire family to carbon monoxide poisoning o called the guy back and he laugh at me - Alexander Delarge 12/16/2011
My boiler just exploded causing thousands of dollars worth of damage called the boiler company and they told me it's not their problem because it was cleaned by a unqualified chimney cleaner . The cleaner laugh at me over the phone and told me to [... obscenities deleted] - Alexander Delarge 12/24/2011
Alexander, although subsequent posts suggest that you are making up the claim above, nevertheless it merits comment. One would imagine that even if the heating service technician was not competent or did something improper, it sounds as if the problem was more complex than you describe. Just putting a vacuum into a barometric damper itself would not cause carbon monoxide fatalities. More likely there was incorrect cleaning, incorrect heating equipment service, a blocked chimney, or a combustion air fault - or some similar and dangerous condition.
Question: barometric damper slams shut
I have a burnham v8 series domestic boiler and the boiler shuts down the Field control barometric damper slams shut when the boiler shuts off. What can cause this problem? - Guy Triano 1/19/2012
Question: pros and cons of direct vented chimneys?
please state all risks or negatives of a non chimney boiler onside of home through wall with fan as opposed to regular roof chimney. Our chimney being blocked 5 feet away by 6 story building wall of neighbor. need to correct it. advise please - Susan Borchardt 10/22/12
Question: omitting the barometric damper is usually a bad idea
Hi - I just had a brand new oil boiler/burner installed (Smith Series 8 boiler) and the technician did not install a barometric draft control at the flue pipe. I have never seen a boiler without it. He explained that I do not need one because when he tested it he saw that I have enough draft (0.2 to 0.4). My upstairs neighbor's boiler that sits right next to mine is the exact same model. It was installed last year with a draft control. I compared the draft test results and they are identical, so this is making no sense to me. Is it really ok not to have a draft control on my flue pipe? And what about access to cleaning the flue pipe? They really can't get into the flue pipe without taking it apart every time, so that can't be good either.
We do not agree with what your service tech told you - it was an incomplete and incorrect reply. Even if a tech sees "perfect" draft at a chimney at a particular time, weather temperature, wind, and other conditions will change constantly at any building site, meaning that draft conditions will change too. In turn, that means that while the heating equipment may run, it is impossible to tune it and set it for proper and economical condition under those varying conditions if there is no way to regulate the draft seen by the heating equipment.
Typically when we see a system with no barometric damper we infer that there was a chimney with marginal or inadequate draft.
Question: my barometric damper is always open
I have a oil furnace with direct-venting through a vertical wall. My barometric damper is always open and allows cold outside air to enter the basement when the furnace is not running. Is this proper? We have had the service techs of two different companies here and when I mentioned it to them, neither of them made any comment. Can I replace this part myself, or do I need to find still another furnace repair company? - Paul Hallisey<paul.e.hallisey@gm 1/15/2013
Question: oil burner locks out & I hear a wailing noise
I an experienced plumber/pipefitter who is experiencing some puzzling problems with my boiler. I had my Weil McLain GTO 5 boiler, QB 180 burner cleaned and serviced about a month ago. At that time it was running fine. The night after it was cleaned the burner started locking out a few times a day and night. I have tried to get the one who serviced it to come back but with no success. I then started to apply the limited knowledge of burners I have and I noticed a slight waining sounds come from the burner just before it would spit and sputter, then lock out. I bought a new oil pump, insatlled it, and I am still experiencing the same problem. Only now it will run fine for 5 minutes and then the flame will blow out and then come back, with that happening just before the burner shuts off, sometimes without locking out the control. I have adjusted the gap and air flow to the specs of my boiler. I will say the nozzle is a 1.10 and my model calls for a 1.20 but the help at the supply house said that wouldnt matter. My next step is to replace the primary control or opening up the fan motor to inspect that. Anyone with some insight please share! - Ryan Darvalics 1/18/2013
Ryan, I don't want to guess at what's wrong with your heater with so little information, but
Changing the fuel unit for a new one before diagnosing the problem can be a costly and unnecessary step. For example, a leak in the oil piping, a clogged filter, even a simple clogged fuel unit strainer can cause ignition problems - not reasons to change the whole fuel unit.
You can read further about oil burner troubleshooting at OIL BURNER INSPECTION & REPAIR and at OIL BURNER NOISE SMOKE ODORS but I would stop shotgunning, installing new parts, before we have an accurate diagnosis of what's wrong.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References