18
5.3 Denitions
1.
Coaxial piping – Exhaust and air intake pipe have a
common axis.
5 - COMBUSTION AIR AND VENT PIPING
2.
Twin Pipe – Exhaust and intake air are separate
pipes, can be terminated using single wall
5.2 Removal of Existing Boiler From Common Vent
System
When existing boiler is removed from common venting
system, common venting system is likely to be too large
for proper venting of appliances remaining connected to
it.
After removal of existing boiler, following steps shall be
followed with each appliance remaining connected to
common venting system placed in operation, while other
appliances remaining connected to common venting
system are not in operation:
• Seal any unused openings in common venting
system.
• Visually inspect venting system for proper size and
horizontal pitch. Determine there is no blockage or
which could cause an unsafe condition.
• When practical, close all building doors, windows,
and all doors between space in which appliances
remaining connected to common venting system are
located and other spaces of building. Turn on clothes
dryer and any appliance not connected to common
venting system. Turn on exhaust fans, such as range
hoods and bathroom exhaust so they will operate at
maximum speed. Do not operate summer exhaust
• Turn on appliance being inspected. Follow lighting
instructions. Adjust thermostat so appliances will
operate continuously.
• Test for spillage at draft hood relief opening after
match or candle, smoke from cigarette, cigar or pipe.
• Determine each appliance remaining connected to
common venting system properly vents when tested
as outlined above. Then return doors, windows,
exhaust fans and any other gas-burning appliance to
their previous condition of use.
• Any improper operation of common venting system
should be corrected so installation conforms with
National Fuel Code, ANSI Z223.1/NFPA 54 and/or
Natural Gas and Propane Installation Code, CAN/
CSA B149.1. When re-sizing any portion of common
venting system, common venting system should be
re-sized to approach minimum size as determined
using appropriate tables in Chapter 13 of the National
Fuel Gas Code, ANSI Z223.1/NFPA 54 and/or Natural
Gas and Propane Installation Code, CAN/CSA B149.1.
240013375 REV A, [07/01/2021]
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