The Field Controls 2722701 6RC Draft Regulator Control with Collar is a barometric draft control engineered for oil-fired, coal-fired, and wood-burning residential and commercial heating appliances.
This 6-inch unit counteracts the unpredictable forces of barometric pressure shifts, ambient temperature swings, and wind loading to hold flue draft steady within a calibrated range of .02" to .08" W.C., ensuring complete combustion and measurable fuel savings in hydronic boilers, forced-air furnaces, and stoker systems.
Why Unstable Draft Destroys Combustion Efficiency—& How the 6RC Fixes It Permanently
Combustion in any oil burner, coal stoker, or solid-fuel appliance depends on a consistent, negative pressure gradient drawing combustion air through the fire and exhaust gases up the flue. When that gradient fluctuates—because a cold front drops barometric pressure, a wind gust pressurizes the structure, or a warm afternoon reduces the chimney's natural draw—the burner reacts immediately.
Too much draft pulls excess air through the combustion zone, diluting the flame and lowering flue gas temperatures, which tanks thermal efficiency. Too little draft allows combustion gases to linger, raises smoke numbers, and risks positive pressure puffing into the mechanical room. Neither condition is acceptable to a heating professional aiming for peak system performance and clean combustion test results.
The 2722701 6RC addresses this directly through a precisely machined, counterweighted damper gate that swings open in response to excess negative pressure, admitting dilution air into the flue passageway only as needed to hold the setpoint. The mechanism requires no electricity, no signal wire, and no controller—it operates on pure mechanical balance, making it immune to power outages and control board failures that sideline more complex systems.
This model ships as standard equipment on many leading oil-fired boiler and furnace brands, a testament to its long-standing reputation among OEM engineers who need a field-proven, low-maintenance solution to draft variability.
6-Inch Barometric Damper Construction: 24-Gauge Ring & Gate with 26-Gauge Collar
The 2722701's damper ring and pivoting gate are fabricated from 24-gauge galvanized steel, providing the stiffness necessary to hold geometric accuracy across years of thermal cycling without warping or developing pivot slop that would compromise sensitivity. The included mounting collar is 26-gauge material—slightly thinner to facilitate the field-bending installation technique specified in Field Controls' installation protocol, where collar tabs are cut at ½-inch intervals and bent outward to form a mechanically locked, tight joint against the flue pipe sidewall.
This gauge pairing is not arbitrary. The heavier gate and ring maintain the precise pivot geometry that makes the .02"–.08" W.C. adjustment range achievable and repeatable. A gate that racks or binds in its pivot points cannot respond linearly to draft changes, and calibration becomes meaningless.
The collar's B-dimension clearance for the 6-inch RC size is specified at 1-7/8 inches—the minimum distance the collar opening must provide to prevent the swinging gate from intersecting the main flue passageway during operation. Installers using a sheet metal tee instead of the supplied collar must verify this dimension before securing the assembly.
What Makes the 6RC's Adjustable Counterweight System So Sensitive to Draft Setpoint?
The heart of the 6RC's control authority is a sliding adjustment weight mounted on a calibrated bracket marked at positions 2, 4, 6, and 8, corresponding to draft settings of .02", .04", .06", and .08" inches of water column respectively. Moving the weight along the slot changes the torque resisting gate opening, which directly sets the flue draft level at which the gate begins admitting dilution air.
This sensitivity is exceptional. Field Controls' own documentation notes that the control requires the use of draft gauges and combustion instrumentation during setup—not because installation is complicated, but because the mechanism responds to changes smaller than the human senses can detect. A trained HVAC technician using a digital manometer can dial the gate to within fractions of a hundredth of an inch of water column.
For vertical flue installations, the weight rides the right-hand slot as shipped. Horizontal flue orientation requires relocating the weight to the left-hand slot—a 30-second adjustment made with a single fastener that reconfigures the control's gravitational reference so the gate responds correctly regardless of flue pipe routing.
Positioning the 2722701 for Optimal Draft Control Performance in the Flue System
Placement within the vent system has a direct bearing on how well the 6RC maintains setpoint under dynamic conditions. Field Controls specifies that the control should be located as close to the appliance as practical—proximity to the appliance reduces the volume of flue gas between the burner and the regulator, which tightens response time when draft conditions change.
Clearance requirements are equally important. A minimum of 18 inches must separate the 2722701 from any stack switch or primary safety control to prevent drafting action from triggering nuisance lockouts. An 18-inch clearance to combustible ceilings and walls is also mandatory under the installation specification. The control must not be installed in a room physically separated from the heating appliance—doing so decouples the mechanical room's air pressure from the regulator's sampling environment and invalidates the control's ability to stabilize overfire draft.
Front face plumb orientation is non-negotiable. The pivot points must be perfectly level whether the flue runs horizontal, vertical, or at a slope. A spirit level applied to the front face before tightening the collar's clamping screws confirms proper alignment and protects the gate's swing arc from binding against the collar ring.
Fuel Compatibility: Oil, Coal, Wood & Stoker Applications All Within the 6RC's Operating Range
The Field Controls 2722701 handles oil-fired atmospheric burners, pressure-jet oil burners, coal stoker systems, hand-fired solid-fuel appliances, and wood-burning boilers without modification—a flexibility that makes it the single-unit answer for heating contractors servicing mixed-fuel mechanical rooms or multi-fuel boiler installations.
For oil burner applications, the overfire draft target typically falls between .02" and .03" W.C. after the burner has operated for at least five to ten minutes and flue temperatures have stabilized. Some burner models require higher overfire draft—always defer to the burner manufacturer's installation documentation for the specific setpoint. CO₂ readings and smoke spot tests confirm that the draft control is holding the combustion zone in the optimal air-to-fuel ratio range.
Coal stoker operation demands that adjustment occur while the stoker runs with a normal fuel bed depth and the stoker fan set to its approximate operating position. The recommended stoker overfire draft setpoint is -.04" W.C. with the stoker running, adjusted to eliminate puffing at startup without introducing excess air that would drop efficiency. Hand-fired coal and wood plants typically target -.06" in cold weather, with the understanding that milder conditions warrant pulling the setpoint down to prevent appliance overheating.
How Does the 6RC's Collar Installation Method Create a Permanent, Sealed Flue Connection?
The tab-and-bend collar mounting system included with the 2722701 creates a mechanical interlock between the collar and the flue pipe sidewall that outperforms adhesive or tape-only connections under thermal expansion stress. The process begins by bending the two front corner ears of the collar outward 90 degrees at ¼ inch behind the single hole on the mounting straps, then threading clamping screws through those ears to pre-assemble the collar body.
After marking the collar outline on the flue pipe and cutting the opening approximately ½ inch inside that outline, a series of ½-inch-spaced radial cuts from the hole edge to the outline marks creates a ring of tabs. Those tabs bend outward into the interior of the collar, forming a mechanical lock that prevents the collar from backing out of the pipe under vibration or thermal cycling. The clamping screws then draw the collar tight against the pipe exterior.
When the existing flue pipe is fabricated from material too rigid to bend—heavy-gauge black iron or certain stainless liners—the opening diameter can be cut to within ½ inch of the collar's inside diameter, with the gap sealed using high-temperature RTV silicone or UL-listed high-temperature foil tape rated for the application temperature. This approach maintains draft integrity while accommodating field conditions the standard tab method cannot address.
Residential & Commercial Sizing: Why the 6-Inch RC Covers the Most Common Flue Pipe Diameter in Domestic Heating
A 6-inch round flue connection is the dominant pipe size in domestic oil-fired boilers and furnaces from 100,000 to 200,000 BTU/h input, as well as in mid-range coal stoker systems and wood boiler applications in this output class. The 2722701's nominal capacity of 28.3 square inches cross-sectional area aligns precisely with 6-inch round pipe geometry, ensuring no restriction to flue gas flow when the gate is in the fully closed position during low-draft conditions.
This sizing alignment matters because an undersized damper creates backpressure that mimics blocked flue conditions, forcing the burner to operate against resistance. An oversized damper allows uncontrolled dilution air entry when the gate swings partially open, reducing the precision of draft regulation. The 6RC's 6-inch match to the flue pipe eliminates both failure modes in a single selection.
For heating contractors managing residential retrofit projects on mid-century homes originally equipped with larger coal-burning boilers later converted to oil, the 6-inch 2722701 fits the existing flue infrastructure without requiring flue liner replacement—a cost consideration that makes it a first-choice specification for older home mechanical system upgrades.
Installation Tooling & Pre-Commissioning Checklist for the Field Controls 2722701
The 6RC's successful commissioning requires a defined set of instruments and preparatory steps before the adjustment weight is ever moved:
- Digital or analog draft gauge capable of resolving .01" W.C. increments—required to set overfire draft and verify flue draft at the control location
- Combustion analyzer reading CO₂ percentage and smoke spot number—confirms the draft setpoint produces complete combustion without excess air dilution
- Spirit level for confirming front face plumb and pivot point level regardless of flue orientation
- High-temperature RTV silicone or UL-listed foil tape rated for flue temperatures if rigid pipe prevents tab-bend collar installation
- Sheet metal snips and drill for cutting the collar opening and making the radial tab cuts in the flue pipe
The burner must be running and thermally stable—typically five to ten minutes into operation—before the adjustment weight position is finalized. Setting draft on a cold flue produces a reading that shifts once the flue reaches operating temperature, requiring a second calibration pass.
Stoker, Hand-Fired & Multi-Fuel System Integration with the 6RC Draft Regulator
Where the 6RC genuinely separates itself from single-fuel draft controls is in its capacity to serve the same unit across oil burner, coal stoker, and hand-fired solid-fuel applications without any component swaps. The barometric operating principle is fuel-agnostic—the gate responds to flue draft pressure regardless of whether that draft is produced by an oil atomizing gun burner, an underfeed stoker auger, or a hand-fired grate with an active solid fuel bed.
For stoker systems, the adjustment sequence differs from oil burner procedure. The stoker fan must be set to approximately its correct operating position before the weight is moved, and a normal fuel bed depth must be established. Draft set too low on a stoker system allows the fuel bed to gas back through the fire door at startup; too high a draft setting pulls heat through the system before the stoker can transfer it into the water or air distribution system.
Hand-fired plants operating in mild weather or banking mode benefit from the 6RC's ability to work in conjunction with a check damper and partially closed ash pit draft door, giving the operator multiple layers of combustion air management without any of those auxiliary controls interfering with the 6RC's automatic draft stabilization function.
Frequently Asked Questions
Q: How does the 2722701 6RC's .02"–.08" W.C. adjustment range compare to the requirements of most domestic oil burners, and can the weight be set accurately without professional instrumentation?
A: Most domestic oil burners target overfire drafts of .02" to .03" W.C., placing the typical setpoint at the lower end of the 6RC's range. Because the control is sensitive enough to respond to sub-.01" pressure changes, Field Controls' installation specification explicitly requires a calibrated draft gauge during adjustment. Attempting to set the weight by feel or by observing flame characteristics alone produces unreliable results and risks a combustion efficiency or safety issue.
Q: Will the Field Controls 2722701 work correctly if the flue pipe runs at an angle rather than strictly horizontal or vertical?
A: Yes—the 6RC accommodates sloping flue installations, provided the front face of the control is installed plumb and the pivot points are level regardless of the pipe's angle. The weight slot selection (right slot for vertical, left slot for horizontal) applies to the extremes; for angled flues, the installer uses a spirit level on the pivot axis to confirm level, which is the functional requirement regardless of the pipe's roof angle. Consult the appliance manufacturer's flue requirements to confirm the sloped routing is acceptable for the appliance type before placing the regulator.
Q: Can the 2722701's collar be reused if the flue pipe is replaced during a boiler upgrade, or does replacement require a new collar and hardware?
A: The supplied 26-gauge collar uses a destructive tab-bend installation method that permanently deforms the collar tabs into the flue pipe opening. Removal without damaging the collar is not practical in most cases. When a flue pipe section is replaced, Field Controls' recommended approach is to install a fresh collar assembly to ensure the tab-lock joint integrity and proper B-dimension clearance. Attempting to reuse a collar that has been removed introduces the risk of air leaks at the collar-to-pipe interface that degrade the draft control's precision.
Plumbing Supply & More: Your Source for Field Controls Draft Regulation Solutions
Plumbing Supply & More carries the complete Field Controls draft regulator lineup, including the 2722701 6RC with Collar, backed by knowledgeable product support for heating contractors and facility managers who need the right draft control matched to their specific appliance and flue configuration.
With decades of experience supplying professional-grade HVAC and combustion control components, Plumbing Supply & More connects qualified installers with the Field Controls products specified by OEM manufacturers across residential and light commercial heating applications ensuring every draft regulator order arrives ready for precise, code-compliant installation.
