0
0
all combustion products. If the vent system does not 
provide enough draft, combustion products will spill into 
the building from the draft hood relief opening. If spillage 
of combustion products occurs, check the vent system,
the combustion and ventilation openings and make sure 
the boiler room is never under negative pressure.
Failure to provide adequate
venting can result in severe
injury or death.
4. Exterior Vents 
a) If the vent is outside, make sure it is insulated
sufficiently to ensure adequate draft.
5. Vent Sizing: 
a) Individual vents: Use vent piping the same diameter
as the boiler vent connection. The minimum height 
is I0 feet above the bottom of the draft hood (relief 
opening). The vent must also extend above the roof 
or any obstiructions as outlined in the current edition 
of the National Fuel Gas Code, ANSI 
Z223.1/NFPA54 or as required by local codes.
b) Combined vent- breeching:
• The recommended sizing in Section 14, "Boiler
Ratings and Dimensions", in this Manual is based 
on a minimum chimney or vent height of 20 feet
and a maximum horizontal run of 6 feet to the 
chimney with no more than one 90-degree
standard elbow.
• The minimum area of the chimney serving two or 
more appliances must be at least the area of the
largest chimney connector plus 50% of the total 
area of all other appliance connectors.
• The vent connector must be single wall steel or 
Type B double wall vent pipe. The vent connector 
must be Type B double wall if it is located in or
passes through cold areas. The vent connector 
must extend into, but not beyond, the inside wall
of the chimney.
6. Vent Connection to Boiler (Figure 6): 
a) Provide at least a three foot rise in the vent
connection on the boiler.
b) The vent system should provide a draft of at least
0.02" w.c. measured at the vent connections.
c) Support the weight of the vent system indepently of
the boiler draft hood. The draft hood is not designed 
to carry structural loading.
d) Provide support ofthe vent connector (breeching] at
maximum 12 foot intervals to prevent sagging and 
to provide a minimum upward slope of I/4" per foot.
e) Do not connect the vent for this boiler into any vent
system which operates with positive pressure.
f) Use Type B double-wall pipe for vents which run
through unheated spaces.
7.
Removing an existing boiler from a common vent: At the
time for removal of an existing boiler, the following steps 
shall be followed with each appliance connected to the
common venting system placed in operation, while the 
other appliances remaining connected to the common
venting system are not in operation.
Recommendedsizingfor chimneyand connectorsis 
based on maximum 6 foot connectorlength and
maximumone 90 degree elbow.
Frovidesuppo_for I_lz_taJ secl_s to preventsagging• 
Slopeve_tconnectorupw_d min 1/4 inch perfoot --
T
Connlz_tor must notprotrudeinlo chimney •
Boi)erven_c0nnect0r shCuldbeh_ghet
than 0tha:connectedapp_ances
I_Do not obs_ct draft.hood openfn_
Figure 6: Vent Connection
a) Seal any unused openings in the common venting
system.
b) Visually inspect the venting system for proper size
and horizontal pitch and determine there is no 
blockage or restriction, leakage, corrosion and other
deficiencies which could cause an unsafe condition.
c) Insofar as is practical, close all building doors and
windows and all doors between the space in which 
the appliances remaining connected to the common
venting system are located and other spaces of the 
building. Turn on clothes dryers and any appliance
not connected to the common venting system. Turn 
on any exhaust fans, such as range hoods and
bathroom exhausts, so they will operate at 
maximum speed. Do not operate a summer exhaust
fan. Close fireplace dampers.
d) Place in operation the appliance being inspected.
Follow the lighting instructions. Adjust the 
thermostat so appliance will operate continuously.
e) Test for spillage at the draft hood relief opening after 5
minutes of main burner operation. Use the flame of a 
match or candle, or smoke from a cigarette, cigar orpipe.
f) After it has been determined that each appliance
remaining connected to the common venting system 
propedy vents when tested as outlined above, return 
doors, windows, exhaust fans, fireplace dampers 
and any other gas-burning appliance to their 
previous condition of use.
g) Any improper operation of the common venting
system should be corrected so the installation
conforms with the current edition of the National 
Fuel Gas Code, ANSI Z223.1/NFPA54. When
resizing any portion of the common venting system, 
the common venting system should be resized to 
approach the minimum size as determined using the
appropriate tables located in the chapter "Sizing of 
Category I Venting Systems" in the current edition
ofthe National Fuel Gas Code, ANSIZ223.1/NFPA54.