Burnham 8HE Series User guide

1111924-01 - 2/23
8HE Multiple Boiler Application Instructions
Commercial Boilers
WARNING
This manual must only be used by a qualified heating installer/service technician. BEFORE installing, read all
instructions in this manual and all other information shipped with the boiler. Post all instructions and manuals
near the boiler for reference by service personnel. Perform steps in the order given. Failure to comply could
result in severe personal injury, death or substantial property damage.
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Series 8HE
Multiple Boiler Application Instructions for
www.burnhamcommercial.com

2111924-01 - 2/23
8HE Multiple Boiler Application Instructions
The following defined terms are used throughout this manual to bring attention to the presence of hazards of various
risk levels or to important information concerning the life of the product.
HAZARD DEFINITIONS
IMPORTANT INFORMATION - READ and save these instructions for reference.
NOTICE: Indicates special instructions on
installation, operation, or service which are
important but not related to personal injury
hazards.
DANGER
Indicates a hazardous situation that, if not
avoided, will result in death or serious injury.
CAUTION
Indicates a hazardous situation that, if not
avoided, could result in minor or moderate
injury.
WARNING
Indicates a hazardous situation that, if not
avoided, could result in death or serious injury.
DANGER
DO NOT store or use gasoline or other flammable vapors or liquids in the vicinity of this or any other
appliance.
If you smell gas or fuel oil vapors, do not try to operate the burner/boiler system. Do not touch any electrical
switch or use any phone in the building. Immediately call the gas or oil supplier from a remotely located
phone.
Burner/boiler systems produce steam or hot water in a pressurized vessel by mixing extremely flammable
gaseous, liquid or solid fuels with air to produce combustion and very hot products of combustion.
Explosions, fires severe personal injury, death and/or property damage will result from improper, careless or
inadequate installation, operation or maintenance of fuel-burning and boiler equipment.
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3111924-01 - 2/23
8HE Multiple Boiler Application Instructions
WARNING
•Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury
or loss of life. Failure to follow all instructions in the proper order can cause personal injury or death. Read and
understand all instructions, including all those contained in component manufacturers manuals which are provided
with the appliance before installing, starting-up, operating, maintaining or servicing this appliance. Keep this
manual and literature in legible condition and posted near appliance for reference by owner and service technician.
•These boilers require regular maintenance and service to operate safely. Follow the instructions contained in the
Series 8HE Installation, Operating and Service Instructions.
•Installation, maintenance, and service must be performed only by an experienced, skilled and knowledgeable
installer or service agency.
•All heating systems should be designed by competent contractors and only persons knowledgeable in the layout
and installation of hydronic heating systems should attempt installation of any boiler.
•It is the responsibility of the installing contractor to see that all controls are correctly installed and are operating
properly when the installation is completed.
•Installation is not complete unless a pressure relief valve is installed into the specified tapping on the top of
appliance - See the Series 8HE Installation, Operating and Service Instructions for details.
• These boilers are NOT suitable for installation on combustible flooring.
•Do not tamper with or alter the boiler or controls. Retain your contractor or a competent serviceman to assure that
the unit is properly adjusted and maintained.
•Inspect boilers at least once a year - preferably at the start of the heating season to remove soot and scale. The
inside of the combustion chamber should also be cleaned and inspected at the same time.
•Have Burner and Controls checked at least once a year or as may be necessitated. Do not operate unit with
jumpered or absent controls or safety devices. Do not operate unit if any control, switch, component, or device
has been subject to water.
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8HE Multiple Boiler Application Instructions
WARNING
•Appliance materials of construction, products of combustion and the fuel contain alumina, silica, heavy metals,
carbon monoxide, nitrogen oxides, aldehydes and/or other toxic or harmful substances which can cause death or
serious injury and which are known to the state of California to cause cancer, birth defects and other reproductive
harm. Always use proper safety clothing, respirators and equipment when servicing or working nearby the appliance..
•These boilers contain very hot water under high pressure. Do not unscrew any pipe fittings nor attempt to disconnect
any components of this boiler without positively assuring the water is cool and has no pressure. Always wear
protective clothing and equipment when installing, starting up or servicing this boiler to prevent scald injuries. Do
not rely on the pressure and temperature gauges to determine the temperature and pressure of the boiler. This
boiler contains components which become very hot when the boiler is operating. Do not touch any components
unless they are cool.
•All appliances must be properly vented and connected to an approved vent system in good condition. Do not
operate boilers with the absence of an approved vent system.
•These boilers need fresh air for safe operation and must be installed so there are provisions for adequate combustion
and ventilation air.
•The interior of the venting and air intake systems must be inspected and cleaned before the start of the heating
season and should be inspected periodically throughout the heating season for any obstructions. Clean and
unobstructed venting and air intake systems are necessary to allow noxious fumes that could cause injury or loss
of life to vent safely and will contribute toward maintaining the boiler’s efficiency.
•These boilers are supplied with controls which may cause the boiler to shut down and not re-start without service.
If damage due to frozen pipes is a possibility, the heating system should not be left unattended in cold weather;
or appropriate safeguards and alarms should be installed on the heating system to prevent damage if the boiler
is inoperative.
•This boiler is designed to burn natural gas only. Do not use gasoline, crankcase drainings, or any oil containing
gasoline. Never burn garbage or paper in this boiler. Do not convert to any solid fuel (i.e. wood, coal). All flammable
debris, rags, paper, wood scraps, etc., should be kept clear of the boiler at all times. Keep the boiler area clean
and free of fire hazards.
•Float type low water cutoff devices require annual inspection and maintenance. Refer to manufacturer's instructions.
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NOTICE: All Series 8HE cast iron boilers are designed, built, marked and tested in accordance with the ASME
Boiler and Pressure Vessel Code, Section IV, Heating Boilers. An ASME Data Label is factory applied to each
8HE jacket, which indicates the boiler Maximum Allowable working Pressure (MAWP). Each cast iron section
is permanently marked with the MAWP listed on the boiler’s ASME Data Label. The MAWP for all Series 8HE
Boiler is 50 psi (Water Only).
It is common and acceptable practice to install these boilers in lower pressure systems, below the boiler
MAWP. Therefore, in addition to Safety Relief Valves set for 50 psi, Burnham also offers Safety Relief Valves set
for 30 psi (By Special Order Only).
CAUTION
Series 8HE Boilers are NOT suitable for direct installation on combustible flooring.
Refer to the 8HE Installation, Operating and Service Instructions for Installation Instructions for Floor Shields
that are available and required for combustible floor installations.
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8HE Multiple Boiler Application Instructions
Important Product Safety Information:
Refractory Ceramic Fiber Product
WARNING
Some boiler components use materials that contain refractory ceramic fibers (RCF). RCF has
been classified as a possible human carcinogen. When exposed to elevated temperatures, RCF
may change into crystalline silica, a known carcinogen. When disturbed as a result of servicing
or repair, these substances become airborne and, if inhaled, may be hazardous to your health.
Avoid breathing RCF particulates and dust.
Precautionary Measures:
•Do not handle RCF parts or attempt any service or repair work involving RCF without wearing the following
protective gear:
1. A properly fitting National Institute for Occupational Safety and Health (NIOSH)-certified air-
purifying respirator with a filter efficiency of at least 95%. Respirator should also include a full
facepiece when handling used RCF. Other types of respirators may be required depending on site
conditions. Current NIOSH recommendations may be found on the NIOSH website
http://www.cdc.gov/niosh/homepage.html. NIOSH-approved manufacturers, respirators and
associated user instructions are listed on the NIOSH website.
2. Long sleeved, loose fitting clothing that is sufficiently tight around potential entry points for RCF
dust.
3. Gloves.
4. Eye protection, such as goggles, safety glasses with side shields, or full facepiece.
•Take steps to assure adequate ventilation.
•Handle RCF carefully to minimize airborne dust. Use hand tools whenever possible.
•Dampen used RCF with light water spray prior to removal to prevent airborne dust.
•Do not use compressed air or dry sweeping for clean-up. Frequently clean work area with a vacuum or by
wet sweeping to minimize debris accumulation.
•Vacuum work clothes before leaving work area. Wash work clothes separately from other laundry and
rinse washing machine after use to avoid contaminating other clothes.
•Wash all exposed body areas gently with soap and water after contact.
•Discard used RCF components by sealing in an airtight plastic bag or container.Refer to local, regional,
state or provincial regulations to identify applicable disposal requirements.
First Aid Procedures:
•Eye contact: Flush with water for at least 15 minutes. Do not rub eyes. Seek immediate medical attention
if irritation persists.
•Skin contact: Wash affected area gently with soap and water. Do not rub or scratch affected skin. Seek
immediate medical attention if irritation persists.
•Nose and throat contact: If these become irritated, leave the area and move to a location with clean fresh
air. Drink water and blow nose. Seek immediate medical attention if symptomspersist.
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http://www.cdc.gov/niosh/homepage.html

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8HE Multiple Boiler Application Instructions
1Air for Ventilation and Combustion
CAUTION
Do not store flammable liquids, combustible
materials, or potential combustion air
contaminants in boiler area.
WARNING
Provide combustion and ventilation air in
accordance with section "Air for Combustion
and Ventilation", of National Fuel Gas
Code, ANSI Z223.1/NFPA 54, or applicable
requirements of local building codes.
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1.1 Insufficient ventilation air may cause incomplete
combustion, poor ignition, accumulation of soot
in the boiler, or the production of toxic gases.
Many service calls for dirty boilers, nuisance
lock outs, noisy ignition, or obnoxious odors are
traceable to insufficient ventilation air.
1.2 The information below is from the National Fuel
Gas Code, ANSI Z223.1/NFPA 54. See NFPA 54
for further details.
1.3 Determine the boiler input required to the
system. Determine load of the heated space
using methods contained in the ASHRAE
Handbook or other engineering methods. If
domestic water heater is to be added, calculate
the added boiler capacity as described in
paragraph 3.21 of this manual. Size boilers per
total net rating as shown on Table 1-2.
1.4. Determine Required Room Volume
Air openings are required for all boiler rooms
smaller than 50 ft.3/ 1,000 Btu/hr.
If it is known or suspected that the air infiltration
rate is less than 0.4 ACH (air changes per hour),
the minimum required room volume is calculated
using the formula:
Adjacent rooms may be included in the boiler
room volume if the adjacent room(s) are
communicating directly (no doors) or have
internal air openings sized per Table 1-1.
1.5 .Determine Free Area of Air Openings
Size air openings for the total appliance input
as shown in Table 1-1. See also Figure 1-3 and
Figure 1-4.
Upper Opening or Single Opening – Opening
shall commence within 12 in. of the top of the
enclosure. See also paragraph 1.7.h.
Lower Opening – Opening shall commence
within 12 in. of the bottom of the enclosure. See
also paragraph 1.7.h.
1.6 Louvers, Grilles, and Screens - The required
size of openings for combustion, ventilation, and
dilution air shall be based on the net free area
of each opening. Where the free area through
a design of louver, grille, or screen is known, it
shall be used in calculating the size opening
required to provide the free area specified.
Where the louver and grille design and free
area are not known, it shall be assumed that
wood louvers have 25 percent free area, and
metal louvers and grilles have 75 percent free
area. Nonmotorized louvers and grilles shall be
fixed in the open position. Screens shall not be
smaller than 1/4 in. mesh.
Free Area of Each Air Opening* Air Opening Type
1 in2/ MBH Indoor Air Two Openings Combining Space on the Same Story.
2 in2/ MBH Combining Spaces in Different Stories.
1 in2/ 4 MBH (0.25in2/ MBH)
Outdoor Air
Two Openings
Vertical Ducts or Direct Communication
(vertical or horizontal).
1 in2/ 2 MBH (0.5 in2/ MBH) Horizontal Ducts.
1 in2/ 3 MBH (0.33 in2/ MBH)** Single Opening Vertical or Horizontal Ducts or Direct
Communication (vertical or horizontal).
* Use total input from all appliances.
** Single opening free area must also be not less than sum of areas of all vent connectors in space.
Table 1-1: Air for Combustion and Ventilation
Room Volume
Required per
1,000 Btu/hr
=21
ACH

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8HE Multiple Boiler Application Instructions
1Air for Ventilation and Combustion (continued)
Motorized louvers shall be interlocked with each
appliance so they are proven in the full open
position prior to main burner ignition and during
main burner operation. Means shall be provided
to prevent the main burner from igniting should
the louver fail to open during burner startup and
to shut down the main burner if the louvers close
during burner operation.
1.7 Combustion Air Ducts
a. Ducts shall be constructed of galvanized
steel or a material having equivalent corrosion
resistance, strength, and rigidity.
b. Ducts shall terminate in an unobstructed
space, allowing free movement of combustion
air to the appliances.
c. Ducts shall serve a single space.
d. Ducts shall not serve both upper and lower
combustion air openings where both such
openings are used. The separation between
ducts serving upper and lower combustion air
openings shall be maintained to the source of
combustion air.
e. Ducts shall not be screened where
terminating in an attic space.
f. Horizontal upper combustion air ducts
shall not slope downward toward the source
of combustion air.
g. The remaining space surrounding a chimney
liner, gas vent, special gas vent, or plastic
piping installed within a masonry, metal, or
factory built chimney shall not be used to
supply combustion air.
h. Combustion air intake openings located
on the exterior of the building shall have
the lowest side of the combustion air intake
openings located at least 12 in. vertically from
the expected snow height.
1.8 Combination Indoor and Outdoor Combustion
Air. The use of a combination of indoor and
outdoor combustion air shall be in accordance
with the following:
a. Indoor openings. Where used, openings
connecting the interior spaces shall comply
with Table 1-1.
b. Outdoor opening(s) shall be located in
accordance with Section 1.5.
c. Outdoor opening(s) size. The outdoor
opening(s) size shall be calculated in
accordance with the following:
i. The ratio of the interior spaces shall
be the available volume of all
communicating spaces divided by
the required volume.
ii. The outdoor size reduction factor
shall be 1 minus the ratio of interior
spaces.
iii. The minimum size of outdoor
opening(s) shall be the full size of
outdoor opening(s) calculated in
accordance with Table 1-1, multiplied
by the reduction factor. The
minimum dimension of air openings
shall not be less than 3 inches.
1.9 Mechanical Combustion Air Supply - Where all
combustion air is provided by a mechanical
air supply system, the combustion air shall be
supplied from outdoors at the minimum rate
of 0.35 ft3/min/1000 Btu/hr for all appliances
located within the space.
Where exhaust fans are installed, additional air
shall be provided to replace the exhausted air.
Each of the appliances served shall be
interlocked to the mechanical air supply system
to prevent main burner operation where the
mechanical air supply system is not in operation.
Where combustion air is provided by the
building’s mechanical ventilation system, the
system shall provide the specified combustion
air rate in addition to the required ventilation air.

8111924-01 - 2/23
8HE Multiple Boiler Application Instructions
1Air for Ventilation and Combustion (continued)
Table 1-2: Recommended Number of Boilers
Total Input MBH Total Gross Output*
MBH
Total Net Output**
MBH
Boiler Qty.
805HE 806HE
239 201 175 1 0
299 251 218 0 1
478 402 350 2 0
538 452 393 1 1
598 502 436 0 2
717 603 525 3 0
777 653 568 2 1
837 703 611 1 2
897 753 654 0 3
956 804 700 4 0
1016 854 743 3 1
1076 904 786 2 2
1136 954 829 1 3
1196 1004 872 0 4
1255 1055 918 4 1
1315 1105 961 3 2
1375 1155 1004 2 3
1435 1205 1047 1 4
1495 1255 1090 0 5
1554 1306 1136 4 2
1614 1356 1179 3 3
1674 1406 1222 2 4
1734 1456 1265 1 5
1794 1506 1308 0 6
* Total Gross Output based on 84% Combustion Efficiency
** Total Net Output based on piping and pickup allowance of 1.15.
1.10 Example: A 3 story apartment house needs a
total boiler capacity including domestic water
heating, of 1,250,000 Btu/Hr net rating. Boiler
room is 20 feet long, 10 feet wide with a clear
ceiling of 12 feet. Typical 0.4 ACH air filtration
rate, similar in layout to Figure 1-4.
a. Find boiler combination with closest total net
output from Table 1-2:
Input = 1,734 MBH. (5) 806HE and (1) 805HE.
b. Determine if the room size is adequate without
adding openings for additional air:
Room Volume = 20 ft x 10 ft x 12 ft = 1.4 ft3/MBH
MBH Input 1734 MBH
Since 1.4 ft3/ MBH < 50 ft3/MBH, additional air is
required.
c. Find Required Free Area of each opening
from Table 1-1:
1 in2/ 4 MBH * 1734 MBH = 434 in2.

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8HE Multiple Boiler Application Instructions
1Air for Ventilation and Combustion (continued)
Figure 1-3: Ventilation Air Provided from Inside Building
Figure 1-4: Ventilation Air Provided from Outdoors

10 111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting
WARNING
Asphyxiation Hazard.
•Failure to vent this boiler in accordance with these
instructions could cause products of combustion
and/or carbon monoxide to enter living space,
resulting in severe personal injury, death or
substantial proper damage.
•Vent installation shall be in accordance with local
codes, authority having jurisdiction, National Fuel
Code - ANSI Z223.1/NFPA 54, ASHRAE Handbook,
or applicable requirements of the local building
codes.
•Inspect existing chimney before installing boilers.
•Maintain clearances to vent piping and draft hood.
•Do notalter boilerdraft hoodor placeany obstruction
or non-approved damper in the breeching or vent
system.
!
WARNING
Vent system must not experience signs of
continuous wetness.
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2.1 Avoiding Flue Gas Condensation
Masonry chimneys, and in particular exterior masonry
chimneys, are more susceptible to the formulation of
condensate. If a masonry chimney experience signs
of continuous wetness, a listed metal liner must be
installed or an alternate vent system must be used. All
masonry chimneys must use either a clay tile liner or
listed metal liner.
Recommend use of listed metal chimney liner with
external masonry chimneys.
For external masonry chimneys that do not include a
listed metal chimney liner:
• Recommend double wall vent connectors
and double wall vent manifolds. Use only
double wall material on long runs.
• For common vent installations with 5 or 6
boilers, recommend sequencing boilers
to fire minimum of 2 boilers simultaneously.
Up to eight boilers may be vented into a
single vent system if a minimum of two
boilers are fired simultaneously. See also
Section 5 – Controls.
See also Section 3, Water Piping, for methods to
avoid flue gas condensation from low return water
temperatures.
2.2 General
Vent systems are generally less flexible in design
location than are water pipes, gas pipes or electrical
lines. To avoid conflicts for a given location, design
and layout the vents in this section before proceeding
to other sections of this manual. If the factory
fabricated water manifolds are to be used, boilers
should be laid out with 28½ in. spacing.
Vent terminations - provide clearances as shown
in Figure 2-3 and Figure 2-4 to minimize adverse
wind effects or pressure areas which may reduce
or impede vent flow. A UL Listed vent cap is also
recommended to minimize adverse wind effects.
Follow manufacturer’s instructions of venting system
components in addition to National Fuel Gas Code
- ANSI Z223.1/NFPA 54, ASHRAE Handbook, or
applicable requirements of local building codes.
Vent system design must address the following:
• Support of lateral runs so that vent pipe does
not sag.
• Support of common vent where it passes thru
a ceiling or roof.
• Firestops
• Flashing and storm collars.
• Guying or bracing of common vent pipe
above roof.
• Securing and gas tightness of joints.
• Lightning arrester if top of metal vent is one of
the highest points on the roof.
• Support of common vent where it passes thru
a ceiling or roof.
• Proper insertion of vent connection at
masonry chimney – vent should enter
chimney at a point above the extreme bottom
of chimney – vent should be flush with inside
of chimney and sealed (see Figures 1-3 and
1-4).
• Never connect a gas vent to a chimney
serving a fireplace unless the fireplace has
been permanently sealed.
• Never pass any portion of a vent system thru
a circulating air duct or plenum.
2.3 Clearances
See Table 2-2 for minimum clearances around
boilers to combustible materials and for service
access. Provide thimbles through combustible
construction.

11111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
2.4 Determine the input required to the system. See
Section 1.3 and Table 1-2.
2.5 Individual Vents
Individual vents are highly recommended if
the job site conditions allow. Individual vents
are particularly useful in boiler rooms having
a low ceiling height. Individual vents are easy
to design and in many cases result in the
lowest installed cost. They also are the most
dependable in operation and less susceptible to
condensation than are combined vents.
Install individual vents per National Fuel Code -
ANSI Z223.1/NFPA 54.
2.6 Common Vents
See Section 2.1, "Avoiding Flue Gas
Condensation", and see Figures 2-3 through 2-8
and Table 2-9.
Combined vents will perform satisfactorily if strict
design procedures are followed. Referring to
Table 2-10, note that a connector rise of at least
one foot is required. Where the vent dampers are
mounted vertically, include damper height in the
connector rise. A connector rise of three feet is
desirable.
Keep horizontal laterals as short as possible.
Place the first boiler as close to the chimney as
practical.
The horizontal vent manifold is an extension of
the vertical common vent.
2.6.1 Common Vent Sizing
Size the common vent CV per Table 2-9. Note
that the CV diameter applies to both the chimney
and the vent manifold / lateral.
Size the vent connector diameter CN per Table
2-10.
If a tapered or graduated manifold vent is
desired, use the same procedures above for
sizing the intermediate manifold diameter
but for the total input of the boilers served by
intermediate tapered or graduated manifold
vent.
Within Table 2-9 are several entries of NR.
This means that the combination involved is
not recommended. The most common reason
for a combination to be designated NR is that
condensation inside the vent pipe is likely to
occur. This is particularly true of single wall vent
pipe.
If a masonry chimney is desired, the minimum
cross sectional area of the chimney is found in
Table 2-11 as a function of the vent diameter.
Confirm adequate ceiling height. Referring to
Table 2-10, note that a connector rise of at least
one foot is required. Where the vent dampers are
mounted vertically, include damper height in the
connector rise. A connector rise of three feet is
desirable. Thus, to make the desired connector
rise and have space for the manifold vent, the
minimum boiler room ceiling height must be
equal to:
32½ in. Boiler Height
+ D Drafthood Height
+ F Minimum Connector Rise (include the
height of vertically mounted vent
dampers)
+ CV Manifold Diameter
+ 6 in. Clearance
= Minimum Ceiling Height
If the minimum ceiling height above is not
available, common vents will not perform
satisfactorily and should not be used.
2.6.2 Example of Common Venting:
Start with the previous example of a 3 story
apartment building that will use five 806HE and
one 805HE boiler.
For a common vent layout as shown in Figure
2-3 use Table 2-9 to find the common vent size,
CV, at 1734 MBH input. Common Vent required
is 15 ft. high, 18 in. Diameter Double Wall. Single
Wall Vent is Not Recommend.
Find vent connector using Table 2-10. For Type
B connectors with 3 ft. rise, 805HE uses 8 in.
diameter and 806HE uses 9 in. connector.
Calculate minimum ceiling height.
32½ in. Boiler Height
+ 27 13/16 in. Height to Outlet of Drafthood, D
+ 36 in. Desired Conn. Rise, F (incl. damper hgt)
+ 18 in. Manifold Diameter, CV
+ 6 in. Clearance
~ 10 ft.1 in. Minimum Ceiling Height
An eleven foot clear ceiling height will work. With
only one elbow, no correction is necessary. The
design of a constant diameter manifold vent is
complete. Mark these vent and connector sizes
on the drawing of the boiler room.

12 111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
2.6.3 The above procedure is based on data found
in the ASHRAE Handbook, Equipment Volume,
Chapter 35. The basic chimney equation is
expressed as follows:
where: I = Operating heat input, BTUH.
di = Inside diameter of the common vent or
manifold vent.
M = Mass flow input ratio, lb. of products per
1000 BTU of fuel burned. A value of 1.54 was
used based on 5.3% CO2after dilution.
∆P = Pressure difference or loss in the system acting
to cause flow, inches of water. Use 0.37 inches
water per 100 ft. of pipe.
B = Sea level barometer used —29.92 in. Hg.
K = Resistance loss coefficients, dimensionless.
Tm = Average absolute temperature in vent system
at average conditions (add 460° to vent
temperature).
If system conditions do not fall within the limit of
the tables, vent sizes must be calculated using
the chimney equation above as described in the
ASHRAE Handbook. The values in Tables 2-3,
2-4, and 2-5 should not be extrapolated.
If a tapered or graduated manifold vent is
desired, such as in Figure 2-4, the horizontal and
vertical portion of the vent serving all six boilers
is also complete with the above. However, to
size the manifold vent at an intermediate position
such as CV2 in Figure 2-7, use Table 2-9 for the
MBH Input of the boilers served by that position
of the manifold vent The Input MBH of each
boiler can be determined from Figure 2-1. In this
case CV2 serves three boilers for a combined
input of 897 MBH. Find CV2 = 14 in. diameter
double wall manifold section.
I = 4.13 X 105 X
M[ ∆P x B
K x Tm ]0.5
(di)2X

13111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
Figure 2-1: Boiler Dimensions
Rear, Sides, Drafthood
& Vent Connector
Top of
Jacket Front Side-by- Side 1,2
Back-
to-Side
Back-to-
Back2
Front-to-
Front2
To Combustible
Construction 6 in. 36 in. 18 in. N/A N/A N/A N/A
Recommended
for Servicing N/A 36 in. 24 in. 1 in. 1 in. 26" 36 in.
N/A: Not Applicable
1 - 28.5 in. when using prefabricated water manifolds.
2 - Also consult local codes for minimum spacing of multiple boilers.
Table 2-2: Minimum Installation Clearances Around Boilers

14 111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
Figure 2-3: Constant Diameter Manifold Vent

15111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
Figure 2-4: Graduated Manifold Vent

16 111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
Figure 2-5: Dual Constant Diameter Manifold Vent

17111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
Figure 2-6: Constant Diameter Manifold with Laterals in Vent Connectors

18 111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
Figure 2-7: Graduated Manifold
Figure 2-8: Constant Diameter Manifold

19111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
Diameter of Common Vent & Manifolds (CV), inches
Boiler Qty Total
Input
MBH
H - Total Vent Height (ft.)
805HE 806HE 6 10 15 20 30
DW SW DW SW DW SW DW SW DW SW
2 0 478 14 14 12 12
12 12 12 12 10 10 1 1 538
14 120 2 598
16 16 14 123 0 717
14 14
14 14
2 1 777
16 16
14
1 2 837
18 18
14
0 3 897
16 16
4 0 956
3 1 1016
NR NR
18 18
16 16
2 2 1076
1 3 1136
16
0 4 1196
18 18 16
4 1 1255
NR
3 2 1315
NR
18
2 3 1375
18
1 4 1435
0 5 1495
NR 18
4 2 1554
NR 18
3 3 1614
2 4 1674
NR1 5 1734 NR
0 6 1794
Table 2-9: Vent Diameter for Common Venting
Table Notes:
• DW = Double Wall Type B or Type L Vent. SW = Single Wall Vent
• NR = Not Recommended. Vent Diameter would exceed 7 times area of drafthood outlet.
• Table based on ASHRAE Handbook formulas/tables.
• Values based on pipe fitting flow resistance of (1) elbow in vent connector, (1) tee at
vertical transition to chimney, and typical chimney cap.
• Values based on manifold lateral max. length between chimney and closest boiler of 10
ft., or 1/2 in. total height, which is greater. See dimensional figures.

20 111924-01 - 2/23
8HE Multiple Boiler Application Instructions
2Venting (continued)
Vent Connector Diameters for Common Venting, (CN), inches
Total Vent
Height (ft.)
Connector Rise
(ft.)
805HE 806HE
Double Wall Single Wall Double Wall Single Wall
6
1 10 10 12 NR
2 9 9 10 10
38899
8
1 9 9 10 10
2 9 9 10 10
38899
10
1 9 9 10 10
29999
38899
15
1 9 9 10 10
28899
38899
20
1 9 9 10 10
28899
38889
30
1 9 9 9 10
28899
37888
50
18899
28889
37788
Table Notes:
• Vent Connector Diameters for Common Venting per ANSI Z223.1/NFPA 54.
• Lateral max. length is 1.5 ft. per inch diameter per ANSI Z223.1/NFPA 54.
Table 2-10: Vent Connector Diameters for Common Venting, inches