6.2 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 restrictions, leakage,
corrosion and other deficiencies 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 fan. Close fireplace dampers.
• Turn on appliance being inspected. Follow lighting instructions. Adjust thermostat so appliances will operate continuously.
• Test for spillage at draft hood relief opening after 5 minutes of main burner operation. Use flame of 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.
Figure 6-1 - Venting Support
6.3 Definitions
1.
Coaxial piping – Figure 6-2 exhaust and air intake pipe have a common axis.
2.
Twin Pipe – Figure 6-3 Exhaust and intake air are separate pipes, can be
terminated using single wall terminals from the vent manufacturer or field built
configuration using elbows or tees.
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