AER Benchmark Platinum Series User guide

Benchmark Series Pre-Installation Venting & Combustion Air
TAG-0022_0Z AERCO International, Inc. •100 Oritani Dr. •Blauvelt, New York 10913 Page 1of 51
GF-2050 Phone: [phone]/2018
VENTING & COMBUSTION AIR GUIDE
Natural Gas, Propane and Dual Fuel Modulating and Condensing Boilers
Latest Update: 9/14/2018
VENT
STARTER
SECTION
EXHAUST MANIFOLD
BOILER BODY
PRE-INSTALLATION APPLICATION GUIDE
APPLIES TO MODELS:
•BMK 750
•BMK 1000
•BMK 1500
•BMK 2000
•BMK 2500
•BMK 3000
•BMK 5000
•BMK 6000

Benchmark Series Pre-Installation Venting & Combustion Air
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TABLE OF CONTENTS
1. General .......................................................................................................................... 3
2. Approved Vent Materials ................................................................................................ 3
3. Code Required Vent Terminations.................................................................................. 4
4. Combustion Air Supply................................................................................................... 6
5. Combustion Air from WITHIN the Building...................................................................... 7
6. Combustion Air from OUTSIDE the Building................................................................... 7
7. Two-Permanent-Openings Method (USA Only).............................................................. 8
8. One Permanent Opening Method..................................................................................11
9. Opening a Louver Through the Benchmark Boiler.........................................................12
10. Direct Vent/Ducted Combustion Air...............................................................................12
11. Exhaust Vent and Combustion Air Systems ..................................................................13
12. Gross Natural Draft........................................................................................................13
13. Acceptable Pressure Ranges........................................................................................14
14. Exhaust Fans ................................................................................................................14
15. Corrections for Altitude..................................................................................................14
16. Manifolded Systems......................................................................................................14
17. Elbow Quantity and Separation .....................................................................................14
18. Exhaust Muffler Guidelines............................................................................................15
19. Vent & Combustion Air System Design Requirements...................................................16
20. Condensate Removal....................................................................................................20
21. Individually Vented Systems..........................................................................................21
21.1 BMK 1500 Example:...................................................................................................22
22. Manifolded Ducted Combustion Air ...............................................................................23
23. Common Vent Breeching (Manifolded)..........................................................................25
24. Pressure Drop and Draft Data Tables............................................................................27
24.1 Discharge Flue Vent Pressure Drop............................................................................27
24.2 Ducted Combustion Air Duct Pressure Drop...............................................................29
24.3 Gross Natural Draft.....................................................................................................43
24.4 Altitude Correction ......................................................................................................49
24.4 Round vs Square Duct................................................................................................50

Benchmark Series Pre-Installation Venting & Combustion Air
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1. General
The AERCO Benchmark gas-fired boiler is a high efficiency, forced draft, hydronic-heating unit
with unique venting capabilities. All Benchmark venting options (which include horizontal and
vertical discharges, direct vent, and manifolded vent breeching), typically exceed the
capabilities of competing combustion equipment. These and other features enable Benchmark
boilers to provide extremely high thermal efficiencies and optimum temperature control under
widely varying conditions. It is therefore critical that the flue gas vent and combustion air
system be designed to maintain these objectives.
Benchmark’s high efficiency is achieved through air/fuel modulation and the release of energy
from the moisture condensing in the combustion products. Because condensation can occur
in the exhaust vent system, means must be provided to remove the moisture accumulation.
Each Benchmark model is fitted with a condensate removal trap, as indicated in Figures 1a –
1d, which illustrate the air inlet, vent connections and condensate removal connections for the
BMK 750 (0.75 MMBTU), BMK 1000 (1.0 MMBTU), BMK 1500 (1.5 MMBTU), BMK 2000
(2.0 MMBTU), BMK 2500 (2.5 MMBTU), BMK 3000 (3.0 MMBTU), BMK 5000 (5.0 MMBTU)
and BMK 6000 (6.0 MMBTU) models.
The design guidelines in this bulletin provide broad latitude while meeting the objectives of
safety, longevity and optimum performance.
2. Approved Vent Materials
The Benchmark boiler is a Category II and IV appliance, which requires special attention to
exhaust venting and combustion air details. The exhaust vent MUST be UL listed for use with
Category II and IV appliances. The following materials are allowed:
•BMK 1500 to BMK 6000 boilers can use polypropylene, AL29-4C, and other stainless
steel* vent venting materials. PVC and CPVC are NOT allowed.
•BMK 750 and BMK 1000 boilers can use PVC, CPVC, polypropylene, AL29-4C, and
other stainless steel* vent materials. This is due to the smaller size producing lower
exhaust operating temperatures.
* NOTICE: UL1738 listed material is a minimum requirement for stainless steel vent to be used
with AERCO Benchmark boilers.
DISCLAIMER: It is the responsibility of the design engineer and installing contractor to ensure
all vent system designs and installations follow industry best practices with proper pitch,
support, and drainage to prevent failure. While UL1738 is the industry standard guideline for
venting, it is highly recommended that exhaust vent passing through confined or enclosed
horizontal building spaces be made of AL29-4C as the most corrosion resistant vent material
currently available.
Flue System Requirements – Minimum Thickness for AL29-4C
Diameter Wall Thickness Diameter Wall Thickness Diameter Wall Thickness
3" (7.6 cm) 0.015" (0.38 mm) 9" (22.9 cm) 0.020" (0.51 mm) 20" (50.8 cm) 0.024" (0.61 mm)
4" (10.2 cm) 0.015" (0.38 mm) 10" (25.4 cm) 0.020" (0.51 mm) 22" (55.9 cm) 0.024" (0.61 mm)
5" (12.7 cm) 0.015" (0.38 mm) 12" (30.5 cm) 0.020" (0.51 mm) 24" (61.0 cm) 0.024" (0.61 mm)
6" (15.2 cm) 0.015" (0.38 mm) 14" (35.6 cm) 0.020" (0.51 mm) 26" (66.0 cm) 0.034" (0.86 mm)
7" (17.8 cm) 0.015" (0.38 mm) 16" (40.6 cm) 0.020" (0.51 mm) 28" (71.1 cm) 0.034" (0.86 mm)
8" (20.3 cm) 0.015" (0.38 mm) 18" (45.7 cm) 0.024" (0.61 mm) 30" (76.2 cm) 0.034" (0.86 mm)

Benchmark Series Pre-Installation Venting & Combustion Air
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If needed, a PVC Vent Adapter is provided in the Spares Kit included with each BMK 750 and
BMK 1000 boiler. Proper clearances to combustibles must be maintained per UL and the vent
manufacturer requirements. The UL, National Fuel Gas Code (ANSI Z223.1/ NFPA54)1and
CSA B149.1-10 guidelines are often the basis for state and local codes. AERCO's
recommendations follow the guidelines of these agencies, unless more stringent codes govern
the installation site. The venting and combustion air systems must meet all applicable code
requirements.
All Canada installations must comply with CSA B149.1 installation code.
3. Code Required Vent Terminations
The guidelines provided in this bulletin should be followed to comply with AERCO, UL, NFPA 54
(National Fuel Gas Code, ANSI Z223.1) and in Canada: CSA B149.1-10 recommendations and
regulations.
Vent terminations must be at least 4 feet (1.22 m) below, 1 foot (0.30 m) above or 4 feet (1.22
m) removed horizontally from any window, door or gravity air inlet of a building. Such
terminations must extend beyond the outside face of the wall by at least 6 inches (15.2 cm).
The bottom of the vent termination must be at least 12 inches (30.5 cm) above both finished
grade and any maximum snow accumulation level to avoid blocking the vent or air intake. The
vent termination must be least 3 feet (0.91 m) above any forced-air building inlet within 10 feet
(3.05 m). Design must prevent flue gases from recirculating through the boiler air intake.
Vents must not terminate over public walkways or areas where condensate or vapor could
create a nuisance or be detrimental to the operation of regulators, meters or related equipment.
Discharges must not be located in high wind, wind-blocked areas or corners, or be located
directly behind vegetation. Discharges in these locations may cause the flue pressures to
fluctuate and result in flame instability. As a general rule, designs should minimize wind effects.
Wall and roof penetrations must follow all applicable codes and the vent manufacturer's
instructions. Vents must never be installed at less than required clearances to combustible
materials, as enumerated in UL, NFPA, CSA B149.1-10 or local codes "Double-wall" or
'Thimble" assemblies are required when vents penetrate combustible walls or roofs.
Vertical discharges must extend at least 3 feet (0.9 M) above the roof through properly flashed
penetrations, and at least 2 feet (0.61 m) above any object within a 10 foot (3.05 m) horizontal
distance.
Vertical and horizontal discharges must be designed to prevent rain from entering the vent.
Large-mesh screens can be applied to protect against the entry of foreign objects but the 'free
area' should be at least twice the flue cross-sectional area.
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 280 °F (138 °C), 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. Vents may enter the stack through the bottom or side. All
side connections must enter at a 45-degree connection in the direction of flow and must enter at
different elevations, with the smallest vent connection at the highest elevation. Benchmark vents
must not be connected to other manufacturer’s equipment.
The exhaust vent must be pitched upward toward the termination by a minimum of ¼ inch per
foot (21 mm per m) of length. Condensate must flow back to the Benchmark unit freely, without
accumulating in the vent.

Benchmark Series Pre-Installation Venting & Combustion Air
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Figure 1a: BMK 750/1000 Figure 1b: BMK 1500/2000
Figure 1c: BMK 2500/3000 Figure 1d: BMK 5000/6000
AIR INLET
AIR INLET
AIR INLET
AIR INLET
EXHAUST VENT
CONNECTION EXHAUST VENT
CONNECTION
EXHAUST VENT
CONNECTION
EXHAUST VENT
CONNECTION
CONDENSATE
TRAP
CONDENSATE
TRAP
CONDENSATE
TRAP
CONDENSATE
TRAP

Benchmark Series Pre-Installation Venting & Combustion Air
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4. Combustion Air Supply
The Benchmark boilers require the following combustion air volumes when operated at full
capacity.
UNIT VOLUME at 60°F (15.6°C)
BMK 750 165 SCFM (4.67 m3/min)
BMK 1000 200 SCFM (5.66 m3/min)
BMK 1500 325 SCFM (9.20 m3/min)
BMK 2000 500 SCFM (14.16 L/min)
BMK 2500 600 SCFM (16.99 m3/min)
BMK 3000 700 SCFM (19.82 m3/min)
BMK 5000 1167 SCFM (33.05 m3/min)
BMK 6000 1400 SCFM (39.64 m3/min)
These flows MUST be accommodated. Air supply is a direct requirement of NFPA, CSA B149.1-
10 (Canada) and local codes that should be consulted for correct design implementation.
In equipment rooms containing other air-consuming equipment ― including air compressors
and other combustion equipment ― the combustion air supply system must be designed to
accommodate all such equipment when all are operating simultaneously at maximum capacity.
Combustion air intakes must be located in areas that will not induce excessive (>0.10" W.C. (25
Pa)) intake air pressure fluctuations. Designs should take into account equipment blowers and
exhausts when using room air for combustion.
Intakes must be located to prevent infiltration of chlorides, halogens or any other chemicals that
are detrimental to the operation of combustion equipment. Common sources of these
compounds are swimming pools, degreasing compounds, salts, plastic processing and
refrigerants. When the environment contains these types of chemicals, the air MUST be
supplied from the outdoors using direct-vent/ducted-combustion ductwork.
Air intakes must not be located in the proximity of garages, industrial and medical hood venting,
loading docks or refrigerant vent lines. Boilers must not be installed in the proximity of activities
that generate dust if that dust can enter the boiler intake. Boilers must be located to prevent
moisture and precipitation from entering combustion air inlets.
When a boiler is used, temporarily, to provide heat during ongoing building construction or
renovation, accumulated drywall dust, sawdust and similar particles can:
•Accumulate in the unit’s combustion air intake and block combustion air flow
•Accumulate over the burner surface and restrict flow of air/fuel mixture
In these situations, AERCO requires 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.
Combustion air temperatures as low as -30 °F (-34.4 °C) can be used without affecting the
integrity of the equipment; however, the combustion settings may require adjustment to
compensate for site conditions.

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5. Combustion Air from WITHIN the Building
Where combustion air will originate from within the building, air must be provided to the
equipment room from two permanent openings to an interior room (or rooms). Openings
connecting indoor spaces must be sized and located in accordance with the following:
•Each opening must have a minimum free area of 1 inch2per 1,000 BTU/hr (2,200
mm2/kW) of total input rating of all appliances in the space, but not less than 100 inch2
(0.06 m2).
•One opening must commence within 12 inches (300 mm) of the top of the enclosure,
and one opening must commence within 12 inches (300 mm) of the bottom. (See
Figure 2).
Figure 2: All Combustion Air from Adjacent Indoor Spaces through Indoor Combustion
Air Openings
6. Combustion Air from OUTSIDE the Building
Outdoor combustion air must be provided through opening(s) to the outdoors in accordance with
the methods described below. The minimum dimension of air openings must not be less than
3 inches (76 mm). The required size of the openings for combustion air must be based upon
the net free area of each opening. When the free area through a louver, grille, or screen is
known, it must be used to calculate the opening size required to provide the free area specified.
For additional details, consult NFPA 54, or in Canada, CSA B149.1-10, paragraphs 8.4.1 and
8.4.3.

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7. Two-Permanent-Openings Method (USA Only)
Two permanent openings must be provided; one commencing within 12 inches (304 mm) of the
top of the enclosure and one commencing within 12 inches (304 mm) of the bottom. The
openings must communicate directly ― or by ducts ― with the outdoors, or spaces that freely
communicate with the outdoors, as show on the following pages:
1. When communicating directly with the outdoors, or when communicating to the outdoors
through vertical ducts, each opening must have a minimum free area of 1 inch2per
4,000 BTU/hr (550 mm2/kW) of total input rating of all appliances in the space (see
Figures 3 and 4).
Figure 3: All Combustion Air From Outdoors - Inlet Air From Ventilated Crawl
Space and Outlet Air to Ventilated Attic

Benchmark Series Pre-Installation Venting & Combustion Air
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Figure 4: All Combustion Air from Outdoors - Through Ventilated Attic
2. When communicating with the outdoors through horizontal ducts, each opening must
have a minimum free area of 1 inch2per 2,000 BTU/hr. (1100 mm2/kW) of total input
rating of all appliances in the space (see Figure 5).

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Figure 5: All Combustion Air from Outdoors Through Horizontal Ducts

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8. One Permanent Opening Method
One permanent opening must be provided, commencing within 12 inches (300 mm) of the top
of the enclosure. The appliance must 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. The
opening must communicate with the outdoors directly or through a vertical or horizontal duct to
the outdoors or spaces that freely communicate with the outdoors (as shown in Figure 6) and
must have a minimum free area as follows:
•1 inch2per 3,000 BTU/hr (700 mm2/kW) of the total input rating of all appliances
located in the space.
Figure 6: All Combustion Air from Outdoors Through Single Combustion Air Opening

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9. Opening a Louver Through the Benchmark Boiler
A louver can be opened using the auxiliary relay contacts of the Benchmark boiler. These
contacts are provided by a single pole double throw (SPDT) relay that is energized when there
is a demand for heat and is de-energized after that demand is satisfied. The relay contacts are
rated for 120 VAC at 5 amps, resistive.
NOTE
Do NOT power the louver directly using the Auxiliary Relay. An
external relay (supplied by others) must be employed for this
purpose. The boiler power cannot support external accessories.
If the louver features a proof-of-open switch, it must be connected to the boiler’s delayed
interlock. The delayed interlock must be closed for the unit to fire. If the louver requires time to
open, a time-delay must be programmed to hold the start sequence of the boiler long enough for
the proof-of-open switch to make (Parameter: Aux Start On Delay — programmable from 0 to
120 seconds). 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, delayed interlock and the
Aux Start On Delay parameter, refer to the Benchmark boiler’s Operations and Maintenance
manual.
If an AERCO Control System (ACS) is being used to manage a multiple boiler installation, the
louver must be opened using the System Start Relay of the ACS. Refer to the ACS Operations
and Maintenance Manual, GF-131, for wiring connections and further details.
10. Direct Vent/Ducted Combustion Air
The Benchmark is approved for direct vent installation; i.e., it can draw all combustion air from
the outdoors through a metal or PVC duct connected between the Benchmark unit(s) and the
outdoors. This configuration is useful for situations in which room air is insufficient or otherwise
unsuitable for combustion. The minimum ducted combustion-air duct sizes for the Benchmark
boilers are as follows:
•BMK 750 = 6-inch diameter (15.2 cm)
•BMK 1000 = 6-inch diameter (15.2 cm)
•BMK 1500 = 6-inch diameter (15.2 cm)
•BMK 2000 = 8-inch diameter (20.3 cm)
•BMK 2500 = 8-inch diameter (20.3 cm)
•BMK 3000 = 8-inch diameter (20.3 cm)
•BMK 5000 = 14-inch diameter (35.6 cm)
•BMK 6000 = 14-inch diameter (35.6 cm)
In many installations, the combustion air duct can be manifolded for multiple unit applications.
The length and restriction of the ducted combustion duct directly impact the size, length and
restriction of the discharge venting. The direct vent air intake must be located at least 3 feet (0.9
m) below any vent termination within 10 feet (3.1 m).
A screen with mesh size not smaller than 1” x 1” (2.54 mm x 2.54 mm) must be installed at the
inlet of the ducted combustion air duct.

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IMPORTANT NOTES:
1. PLEASE CONSULT THE AERCO FACTORY FOR ALL APPLICATIONS UTILIZING
COMMON DUCTED COMBUSTION AIR WITH COMMON BREECHING OF
EXHAUSTS.
2. AERCO BOILERS AND AERCO WATER HEATERS MAY SHARE COMMON
COMBUSTION AIR AND EXHAUST BREECHING. OTHER CONFIGURATIONS, NOT
DEPICTED IN THIS GUIDE, ARE POSSIBLE. IF YOU INTEND TO IMPLEMENT ANY
OF THESE OPTIONS, PLEASE CONTACT YOUR LOCAL AERCO REPRESENTATIVE
OR THE AERCO FACTORY FOR PROJECT SPECIFIC VENTING AND COMBUSTION
AIR CONFIGURATIONS.
11. Exhaust Vent and Combustion Air Systems
The Benchmark supports several venting and combustion air options, and although the
application parameters vary, there are basic similarities among all systems. Tables 1 through 5
at the end of this Guide address the pressure drop of most applicable vent and duct fittings and
sizes. The losses in the vent exit and air duct entrance are also included.
It should be noted that flow and vent or duct diameter have the most significant effects on
overall system pressure drop. When using fittings or terminations not listed in Tables 1, 2 and 3,
consult the device manufacturer for actual pressure drop values. If a rectangular duct is to be
used, consult Table 5 for a round diameter duct size that has the identical pressure drop per
length of rectangular duct.
The pressure drop values in Table 1b and 1c are in equivalent feet of 8 inch (20.3 cm) diameter
exhaust vent. Note that 1 equivalent foot (0.3 equivalent m) of 8 inch (20.3 cm) diameter vent
is equal to 0.00546-inch W.C. (1.36 Pa).
The pressure drop values used in Table 1a are in equivalent feet of 6 inch (15.2 cm) diameter
exhaust vent. Note that 1 equivalent foot (0.3 equivalent m) of 6 inch (15.2 cm) diameter vent
is equal to 0.00581-inch W.C. (1.45 Pa).
12. Gross Natural Draft
Flue gases have a lower density (and are lighter) than air and will rise, creating "gross natural
draft." Gross natural draft is created when flue gases exit the vent at an elevation above the
Benchmark boiler. The amount of draft depends upon the height of the stack and the difference
between the flue gas temperature and the surrounding air temperatures (densities). Gross
natural draft values for stacks at various heights above the Benchmark unit are presented in
Table 3, Part 1 and Part 2. These draft values are based on an installation site at sea level.
Adding the gross natural draft (negative) to the vent and air system pressure drop (positive)
determines if the total system will be positive pressure or negative pressure ("net natural draft").
As with most combustion equipment, negative pressure (net natural draft) systems should be
treated differently from positive pressure systems when the discharge vents are manifolded.
Note that sidewall vent terminations, as well as some vertical terminations, are positive pressure
systems.
Contact your AERCO sales representative or AERCO International for design assistance
and approval when designing manifolded exhaust vent systems.
CAUTION!
Do NOT install a non-sealed draft control damper.

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13. Acceptable Pressure Ranges
For individually vented units, the exhaust system must be designed so that pressure measured
at every point is in the range from -0.25” W.C. to +0.81” W.C. (-62 Pa to 202 Pa). For common
vented units, the exhaust system must be designed so that pressure measured at every point is
in the range from -0.25” W.C. to +0.25” W.C. (-62 Pa to 62 Pa). Pressures below -0.25” W.C.
(-62 Pa) (more negative) may cause flame instability. Pressures above +0.25” W.C. (62 Pa) for
common vented units, or +0.81 W.C. (202 Pa) for individually vented units (more positive), will
prevent flue gases from exiting.
14. Exhaust Fans
If the Benchmark boiler’s exhaust system incorporates an exhaust fan, the system designer
must size the vent pipe diameters, select the fan and determine the location of the fan sensor to
maintain a -0.25” W.C. to +0.25” W.C. (-62 Pa to 62 Pa) pressure range at the outlet of each
boiler. Also, the designer must ensure that the exhaust fan material is acceptable for use with
Category IV appliances.
15. Corrections for Altitude
Table 4 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.
16. Manifolded Systems
In many instances it may be practical to connect multiple units using a manifolded vent or
exhaust configuration. However, when multiple units are connected by a manifolded air intake
or exhaust vent, the operation of a given unit can be affected by the others, if the venting or
combustion air system is not designed properly. Properly designed common vent and air supply
systems can be installed that will prevent "operational interaction" between units.
Do not use static regain method on common ductwork, but rather, use one duct size for
the common run (See Figure 13).
Contact your AERCO sales representative or AERCO International for design assistance
and approval when designing manifolded exhaust vent systems.
17. Elbow Quantity and Separation
The quantity and angle of elbows and the distances between them can influence the system’s
exhaust and combustion air pressures, as well as its acoustical behavior. Designers should
consider minimizing the quantity of elbows in the design and the use of angles less than 90°,
whenever possible. Five or fewer elbows are recommended for individual venting/connections;
five or fewer are recommended for common sections. The minimum distance required
between two elbows is 5 feet (1.5 m).

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18. Exhaust Muffler Guidelines
Benchmark boilers require an exhaust muffler when installed in a noise-sensitive application
and when the exhaust vent ducting is relatively short in length. The following criteria must be
used to determine when to include a field-installed muffler in a Benchmark installation:
•The exhaust is sidewall vented and the vent is terminated in close proximity to
residences, offices, hotel/hospital rooms, classrooms etc.
OR
•The total vertical and horizontal section of exhaust vent is less than 25 linear feet
(7.6 m) in length from the last unit, and the vent terminates in close proximity to
residences, offices, hotel/hospital rooms, classrooms etc.
Figure 7: Flanged AERCO Exhaust Muffler
For manifolded exhaust systems, the total vertical section length includes both horizontal and
common vertical; individual boiler vertical connectors are included in the determination as well.
EXAMPLE: For an installation that has a 20 foot (6 m) common vertical, 5 foot (1.5 m)
common horizontal after the last boiler, and each boiler has a 10 foot (3.1 m) vertical
connector, the total section linear length considered is 35 feet (10.7 m). Because this length
is greater than 25 linear feet (7.6 m), a muffler is not 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 (3.1 m) common
vertical, 5 foot (1.5 m) common horizontal after the last boiler and each boiler has an 8 foot
(2.4 m) vertical connector, the total section linear length considered is 23 feet (4.0 m).
Because this is less than 25 linear feet (7.6 m), an attenuator is required.
Contact your local AERCO sales representative for more information on the AERCO
exhaust muffler.

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19. Vent & Combustion Air System Design Requirements
The minimum exhaust vent and combustion air duct sizes for Benchmark Low NOx boilers
models are as follows:
Minimum Diameter
Model Combustion Air Duct Exhaust Vent Diameter
BMK 750 6 inch (15.2 cm)
6 inch (15.2 cm)
BMK 1000 6 inch (15.2 cm)
6 inch (15.2 cm)
BMK 1500 6 inch (15.2 cm)
6 inch (15.2 cm)
BMK 2000 8 inch (20.3 cm) 8 inch (20.3 cm)
BMK 2500 8 inch (20.3 cm) 8 inch (20.3 cm)
BMK 3000 8 inch (20.3 cm) 8 inch (20.3 cm)
BMK 5000
BMK 6000 14 inch (35.6 cm) 14 inch (35.6 cm) (<9ppm NOxOptional Calibration)
* 12 inch (30.5 cm) optional (Standard <20ppm NOx emissions only)
* Optional 12 inch (30.5 cm) diameter exhaust venting requires a 12” (30.5 cm) vent adapter. Consult
your local AERCO sales representative or vent manufacturer or AERCO International for more
information on the 12” (30.5 cm) adapter.
A 1/4-inch (6.35 mm) NPT combustion test hole is provided on each unit’s exhaust manifold
connection (See Figures 8a, 8b, 8c and 8d). A 24 inch (61 cm) length of straight vent is
required downstream of the exhaust manifold, as illustrated in these figures.
The vent system should always be pitched up 1/4 inch per foot (21 mm per m) of run towards
the vent termination to enable condensate to drain back to the unit for disposal. Low spots in the
vent must be avoided. Periodic inspection must be performed to assure correct drainage.
Benchmark vents must not be interconnected to those of other manufacturers' equipment.
Horizontal vent and ductwork must be supported to prevent sagging, in accordance with local
code and the vent manufacturer’s requirements. Vertical vent and ductwork must be supported
to prevent excessive stress on the horizontal runs. The exhaust manifold and inlet air adapter
must never be used as weight-supporting elements. The supports must be so arranged and the
overall layout designed to assure that stresses on the vent and combustion air connections are
minimized.
The vents and combustion air ducts may be insulated in accordance with the vent
manufacturer's instructions and local codes.

Benchmark Series Pre-Installation Venting & Combustion Air
TAG-0022_0Z AERCO International, Inc. •100 Oritani Dr. •Blauvelt, New York 10913 Page 17 of 51
GF-2050 Phone: [phone]/2018
Figure 8a: Ducted Combustion Connection for
BMK 750 & BMK 1000 Boilers
Figure 8b: Ducted Combustion Connection for
BMK 1500 & BMK 2000 Boilers
AIR INLET DIAMETER MINIMUM
•BMK 2000 = 8” (20.3 cm)
•BMK 1500 = 6” (15.2 cm)
AIR INLET
6” (15.2 cm)
DIAMETER MINIMUM

Benchmark Series Pre-Installation Venting & Combustion Air
Page 18 of 51 AERCO International, Inc. •100 Oritani Dr. •Blauvelt, New York 10913 TAG-0022_0Z
9/14/2018 Phone: [phone] GF-2050
Figure 8c: Ducted Combustion Connection for
BMK 2500 & BMK 3000 Boilers
Figure 8d: Ducted Combustion Connection for
BMK 5000 & 6000 Boilers
AIR INLET
14” (35.6 cm)
MINIMUM DIAMETER
ALTERNATE 8” or 10” (20.3
cm or 25.4 cm)
MINIMUM AIR INLET,
1 EACH SIDE
(ONLY ON BMK 2500/3000)
AIR INLET MINIMUM DIAMETER
•BMK 2500 = 8” (20.3 cm)
•BMK 3000 = 8” (20.3 cm)

Benchmark Series Pre-Installation Venting & Combustion Air
TAG-0022_0Z AERCO International, Inc. •100 Oritani Dr. •Blauvelt, New York 10913 Page 19 of 51
GF-2050 Phone: [phone]/2018
Figure 9a: Vent Starter Section – Left Side View
BMK 750 & BMK 1000 (Left) & BMK 1500 & BMK 2000 (Right)
Figure 9b: Vent Starter Section – Left Side View
BMK 2500 & BMK 3000 (Left) & BMK 5000/6000 (Right)
VENT
STARTER
SECTION
VENT
STARTER
SECTION
EXHAUST MANIFOLD
EXHAUST MANIFOLD
ANALYZER
PROBE PORT
CONDENSATE
DRAIN
MIN. 24”
(61.0 cm)
STRAIGHT
VENT
STARTER
MIN. 24”
(61.0 cm)
STRAIGHT
VENT
STARTER
EXHAUST MANIFOLD
CONDENSATE
DRAIN
MIN. 24”
(61.0 cm)
STRAIGHT
VENT
STARTER
VENT
STARTER
SECTION
VENT
STARTER
SECTION
EXHAUST MANIFOLD
ANALYZER
PROBE PORT
ANALYZER
PROBE PORT
ANALYZER
PROBE PORT
CONDENSATE
DRAIN
CONDENSATE
DRAIN
BOILER BODY
BOILER BODY
BOILER BODY
BOILER BODY
MIN. 24”
(61.0 cm)
STRAIGHT
VENT
STARTER

Benchmark Series Pre-Installation Venting & Combustion Air
Page 20 of 51 AERCO International, Inc. •100 Oritani Dr. •Blauvelt, New York 10913 TAG-0022_0Z
9/14/2018 Phone: [phone] GF-2050
20. Condensate Removal
The exhaust vent system must be pitched back toward the Benchmark unit by a minimum of 1/4
inch per foot (21 mm per m) of duct length to enable condensate to drain back to the unit for
disposal. Low spots in the vent must be avoided to prevent the condensate from collecting.
The condensate trap assembly is located directly below the exhaust manifold. Plastic hose must
be connected to the trap assembly and run to drain. Care must be taken to avoid hose kinks
and to avoid raising the hose above the trap assembly. Condensate must flow freely to drain.
The condensate-to-drain run must not be hard-piped so the trap can be removed periodically for
maintenance purposes.
If the condensate must be lifted above the trap assembly to a drain, it must be drained into a
sump. From there, a pump can lift the condensate away.
Each unit will produce the following approximate condensate quantities in the full condensing
mode:
•BMK 750 = 6 gallons (22.7 L) per hour
•BMK 1000 = 8 gallons (30.3 L) per hour
•BMK 1500 = 9 gallons (34.1 L) per hour
•BMK 2000 = 10 gallons (37.9 L) per hour
•BMK 2500 = 15 gallons (56.8 L) per hour
•BMK 3000 = 20 gallons (75.7 L) per hour
•BMK 5000 = 33 gallons (124.9 L) per hour
•BMK 6000 = 40 gallons (151.4 L) per hour
Condensate drain systems must be sized for full condensing mode.
In multiple boiler applications, it is common to manifold these drains together in a plastic pipe
manifold to a floor drain. Condensate manifolds must be large enough to handle the anticipated
flow and must be properly secured and protected. Manifolds are generally located behind the
boilers so that short runs of plastic tubing into the manifold can be used for the condensate
drain. A base drain must be installed at the bottom of vertical common flue piping.
The pH level of the condensate produced by Benchmark boilers ranges between 3.0 and 3.2.
The installation must be designed in accordance with local codes that specify acceptable pH
limits. If required, any type of commercially available neutralizer may be used.