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Pre-Installation Application Guide
MFC Series Boiler
Vent and Combustion Air Guide
Applies to Models 3000 through 10000
Exhaust venting, combustion air and piping
requirements for MFC Series boilers
Other documents for this product include:
OMM-0104 GF-148 MFC-Series User Manual
OMM-0108 GF-148-IN MFC-Series Installation Manual
TAG-0077 GF-148-E MFC-Series Electrical Power Guide
TAG-0078 GF-148-G MFC-Series Gas and #2 Oil Supply Guide
TAG-0081 GF-148-B MFC-Series Boiler Application Guide
Disclaimer
The information contained in this manual is subject to change without notice
from AERCO International, Inc. AERCO makes no warranty of any kind with
respect to this material, including, but not limited to, implied warranties of
merchantability and fitness for a particular application. AERCO International is
not liable for errors appearing in this manual, not for incidental or consequential
damages occurring in connection with the furnishing, performance, or use of
these materials
• GF-148-V • 3/29/2023
TAG-0080_OG
Heating and Hot Water Solutions
USA: T: (845) 580-
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© 2020 AERCO
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Table of Contents
Related Manuals for Watts AERCO MFC Series
Summary of Contents for Watts AERCO MFC Series
- Page 1 Pre-Installation Application Guide MFC Series Boiler Vent and Combustion Air Guide Applies to Models 3000 through 10000 Exhaust venting, combustion air and piping requirements for MFC Series boilers Other documents for this product include: OMM-0104 GF-148 MFC-Series User Manual OMM-0108 GF-148-IN MFC-Series Installation Manual TAG-0077 GF-148-E MFC-Series Electrical Power Guide TAG-0078 GF-148-G MFC-Series Gas and #2 Oil Supply Guide TAG-0081 GF-148-B MFC-Series Boiler Application Guide...
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Page 2: Table Of Contents
MFC Series Boiler Vent and Combustion Air Guide Table of Contents General ..........................3 Approved Vent Materials ....................3 Code Required Vent Terminations ..................4 Combustion Air Supply ...................... 5 4.1 Combustion Air from WITHIN the Building ..............6 4.2 Combustion Air from OUTSIDE the Building .............. 7 4.3 Two-Permanent-Openings Method (USA Only) ............ -
Page 3: General
MFC Series Boiler Vent and Combustion Air Guide 1. General or fuel oil-fired (backup) The AERCO MFC gas-fired boiler is a high efficiency, forced draft, hydronic-heating unit with unique venting capabilities. All MFC venting options (which include horizontal and vertical discharges, direct vent, and manifolded vent breeching), typically exceed the capabilities of competing combustion equipment. -
Page 4: Code Required Vent Terminations
MFC Series Boiler Vent and Combustion Air Guide 3. Code Required Vent Terminations The guidelines provided in this bulletin should be followed to comply with AERCO, UL, NFPA 54 NFPA 31, (National Fuel Gas Code, ANSI Z223.1), and in Canada: CSA B149.1-10 recommendations and regulations. -
Page 5: Combustion Air Supply
MFC Series Boiler Vent and Combustion Air Guide If the vent system is to be connected to an existing stack, the stack must be UL listed for Category II and IV appliances (capable of 350F, positive pressure and condensing flue gas operation). Masonry stacks must be lined, and the vent penetration must terminate flush with, and be sealed to, this liner. -
Page 6: Combustion Air From Within The Building
MFC Series Boiler Vent and Combustion Air Guide In these situations, AERCO recommends that a disposable air intake filter be installed, temporarily, above the boiler combustion air inlet. Air filters may be required year-round in instances in which dust or debris can enter the combustion air tube. Consult the boiler Operations and Maintenance Manual for details. -
Page 7: Combustion Air From Outside The Building
MFC Series Boiler Vent and Combustion Air Guide 4.2 Combustion Air from OUTSIDE the Building Outdoor combustion air shall be provided through opening(s) to the outdoors in accordance with the methods described below. The minimum dimension of air openings shall not be less than 3 inches (80 mm). - Page 8 MFC Series Boiler Vent and Combustion Air Guide Figure 4: All Combustion Air from Outdoors - Through Ventilated Attic • When communicating with the outdoors through horizontal ducts, each opening shall have a minimum free area of 1 inch per 2,000 BTU/hr. (1100 mm /kW) of total input rating of all appliances in the space (see Figure 5).
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Page 9: One Permanent Opening Method
MFC Series Boiler Vent and Combustion Air Guide 4.4 One Permanent Opening Method One permanent opening shall be provided, commencing within 12 inches (300 mm) of the top of the enclosure. The appliance shall have clearances of at least 1 inches (25 mm) from the sides and back of the appliance, and a clearance of 6 inches (150 mm) from the front. -
Page 10: Direct Vent/Ducted Combustion Air
MFC Series Boiler Vent and Combustion Air Guide If the louver features a proof-of-open switch, it can be connected to the boiler’s Enable/Disable terminals. The Enable/Disable terminals must be closed for the unit to fire. If the proof-of-open switch does not prove within the programmed time frame, the boiler will shut down. For wiring connections and further details regarding the auxiliary relay and limit circuit, refer to the MFC Series boiler Operations and Maintenance manual. - Page 11 MFC Series Boiler Vent and Combustion Air Guide Figure 7: Air Inlet Adapter for MFC 3000 (P/N 201044004) TAG-0080_OG • GF-148-V • Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST 3/29/2023 Page 11 of...
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Page 12: Exhaust Vent And Combustion Air Systems
MFC Series Boiler Vent and Combustion Air Guide 6. Exhaust Vent and Combustion Air Systems The MFC Series supports several venting and combustion air options, and although the application parameters vary, there are basic similarities among all systems. Tables 4 through 8 in Section 19 at the end of this Guide address the pressure drop of most applicable vent and duct fittings and sizes. -
Page 13: Corrections For Altitude
MFC Series Boiler Vent and Combustion Air Guide 10. Corrections for Altitude Table 7 in Section 19 lists correction factors for installation altitudes above sea level. These factors must be applied to both the natural draft and pressure drops of vent and air ducts. The pressure drop through vents and combustion air ducts will increase at higher elevations, while the natural draft will decrease. -
Page 14: Vent And Combustion Air System Design Requirements
MFC Series Boiler Vent and Combustion Air Guide required. For manifolded ducted combustion, the total section length includes both horizontal and common vertical; individual boiler vertical connectors are included in the determination. EXAMPLE: For a manifolded ducted combustion that has a 10-foot common vertical, 5-foot common horizontal after the last boiler and each boiler has an 8-foot vertical connector, the total section linear length considered is 23 feet. -
Page 15: Individually Vented Systems
MFC Series Boiler Vent and Combustion Air Guide The condensate trap assembly is located directly below the exhaust manifold. Plastic hose should be connected to the trap assembly and run to drain. Care should be taken to avoid hose kinks and to avoid raising the hose above the trap assembly. - Page 16 MFC Series Boiler Vent and Combustion Air Guide horizontal run, 20 feet of vertical run 2) A rain cap termination 3) A 10-inch diameter ducted combustion air duct with two 90° elbows and 50 feet of run MFC Series Pressure Drop Calculation 10-INCH DIAMETER EXHAUST VENT PRESSURE Two 90°...
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Page 17: Manifolded Ducted Combustion Air
MFC Series Boiler Vent and Combustion Air Guide 17. Manifolded Ducted Combustion Air For systems using manifolded ducted combustion ductwork, use the longest length of common duct and the individual branch to the furthest boiler to calculate the pressure drop. Figure 8a: Individual Vents –... - Page 18 MFC Series Boiler Vent and Combustion Air Guide Figure 8b: Individual Vents – Acceptable Installations NOTES: For high wind, wind blocked sites, a tee may be installed at the fresh air inlet. The leg of the tee connects to the combustion air intake. On the flue vent side, a tee or exit cone (velocity cone) may be utilized in place of a rain cap for high wind or wind blocked sites.
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Page 19: Common Vent Breeching (Manifolded)
MFC Series Boiler Vent and Combustion Air Guide 18. Common Vent Breeching (Manifolded) Connections to common vent breeching or duct work must be accomplished with a 45° elbow in the direction of flow in the main breeching. “Tees” should not be used to accomplish these connections - see Figure 9a. - Page 20 MFC Series Boiler Vent and Combustion Air Guide Figure 10 illustrates the preferable “transition vent section” when making the 45° connection into a main. The main can also remain at one diameter, as long as it is sized for the total number of units vented and the 45°...
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Page 21: Pressure Drop And Draft Data Tables
MFC Series Boiler Vent and Combustion Air Guide 19. Pressure Drop and Draft Data Tables TABLE 4: Discharge Flue Vent Pressure Drop (Eq. Ft.) Single MFC 3000 Boiler (Assuming 180°F Water Temperature and 20°F Rise at Sea Level) FLUE STRAIGHT EXIT LOSS EXIT LOSS FLUE VENT... - Page 22 MFC Series Boiler Vent and Combustion Air Guide TABLE 4: Discharge Flue Vent Pressure Drop (Eq. Ft.) Single MFC 8000 Boiler (Assuming 180°F Water Temperature and 20°F Rise at Sea Level) FLUE STRAIGHT EXIT LOSS EXIT LOSS FLUE VENT 90° ELBOW 45°...
- Page 23 MFC Series Boiler Vent and Combustion Air Guide TABLE 5: Ducted Combustion Air Duct Pressure Drop Eq. Ft.) for MFC 3000 MMBTU Boiler Inlet Duct OUTSIDE AIR TEMPERATURE (°F) Duct Section & No. Type Boilers -30 °F -15 °F 0 °F 20 °F 40 °F 60 °F...
- Page 24 MFC Series Boiler Vent and Combustion Air Guide TABLE 5: Ducted Combustion Air Duct Pressure Drop (Eq. Ft.) for MFC 4000 MMBTU Boiler Inlet Duct OUTSIDE AIR TEMPERATURE (°F) Duct Section & No. Type Boilers -30 °F -15 °F 0 °F 20 °F 40 °F 60 °F...
- Page 25 MFC Series Boiler Vent and Combustion Air Guide TABLE 5: Ducted Combustion Air Duct Pressure Drop (Eq. Ft.) for MFC 5000 MMBTU Boiler Inlet Duct OUTSIDE AIR TEMPERATURE (°F) & No. Duct Section Type -30 °F -15 °F 0 °F 20 °F 40 °F 60 °F...
- Page 26 MFC Series Boiler Vent and Combustion Air Guide NOTES: 1) Calculation assumes 1170 scfm per boiler at full fire rate 2) Units for "Straight Run" pressure drop values are (eq. ft. / foot) 3) Units for "Elbows" and "Ent. Loss" are (equivalent feet / item) TAG-0080_OG •...
- Page 27 MFC Series Boiler Vent and Combustion Air Guide TABLE 5: Ducted Combustion Air Duct Pressure Drop (Eq. Ft.) for MFC 6000 MMBTU Boiler Inlet Duct OUTSIDE AIR TEMPERATURE (°F) Duct Section & No. Type -30 °F -15 °F 0 °F 20 °F 40 °F 60 °F...
- Page 28 MFC Series Boiler Vent and Combustion Air Guide TABLE 5: Ducted Combustion Air Duct Pressure Drop (Eq. Ft.) for MFC 8000 MMBTU Boiler Inlet Duct OUTSIDE AIR TEMPERATURE (°F) Duct Section & No. Type -30 °F -15 °F 0 °F 20 °F 40 °F 60 °F...
- Page 29 MFC Series Boiler Vent and Combustion Air Guide TABLE 5: Ducted Combustion Air Duct Pressure Drop (Eq. Ft.) for MFC 10000 MMBTU Boiler Inlet Duct Duct Section OUTSIDE AIR TEMPERATURE (°F) & No. Type -30 °F -15 °F 0 °F 20 °F 40 °F 60 °F...
- Page 30 MFC Series Boiler Vent and Combustion Air Guide TABLE 6: Gross Natural Draft for 6000 – 10000 Boilers (Inch. W.C.) STACK OUTSIDE AIR TEMPERATURE (°F) HEIGHT (FT) -30°F -15°F 0°F 20°F 40°F 60°F 80°F 100°F 120°F 0.024 0.022 0.021 0.018 0.016 0.014 0.011...
- Page 31 MFC Series Boiler Vent and Combustion Air Guide TABLE 6: Gross Natural Draft for 3000 – 5000 Boilers (Inch. W.C.) STACK OUTSIDE AIR TEMPERATURE (°F) HEIGHT (FT) -30°F -15°F 0°F 20°F 40°F 60°F 80°F 100°F 120°F 0.024 0.022 0.021 0.018 0.016 0.014 0.011...
- Page 32 MFC Series Boiler Vent and Combustion Air Guide TABLE 7: Altitude Correction Site Elevation Altitude Correction Factor (feet above sea level) (CF) 0.982 1000 0.964 1500 0.947 2000 0.930 2500 0.913 3000 0.896 3500 0.880 4000 0.864 4500 0.848 5000 0.832 5500 0.817...
- Page 33 MFC Series Boiler Vent and Combustion Air Guide Change Log: Date Description Changed by Rev D: DIR 17-004: Added optional air intake adapter figures (new section 5.1), corrected example calculation (section 16.1), corrected figure 11/22/2017 Chris Blair numbering, added and corrected table numbering, renumbered sections, updated formatting per current standard.