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7.2 Common Exhaust Venting
Common Vent Exhaust:
If this boiler is replacing one which was part of a common venting system, it
is likely that the vent is to large to vent the appliances still attached to it. To prevent
this, at the time of removal, the following steps shall be followed with each appliance
remaining connected to the common venting system. Place each appliance in
operation, while the other appliances remaining connected to the common venting
system are not in operation.
1. Seal any unused openings in the common venting system.
2. Visually inspect the venting system for proper size and horizontal pitch and
determine there is no blockage or restriction, leakage, corrosion or other deficiencies
which could cause an unsafe condition.
3. Insofar as practical, close all building doors and windows and all doors between the
space in which the appliance remaining connected to the common venting system
is located and other spaces of the building . Turn on any appliance not connected
to the common vent system. Turn on all exhaust fans except for summer exhaust
fans. Close the fireplace damper if applicable.
4. Place in operation the appliance being inspected. Follow the lighting instructions.
Adjust thermostat so appliance will operate continuously.
5. Test for spillage at the barometric damper opening after 5 minutes of main burner
operation. Use the flame of a match or candle, or smoke from a cigarette, cigar or
pipe.
6. After it has been determined that each appliance remaining connected to the
common venting system properly vents when tested as outlined above, return
the doors, windows, exhaust fans, fireplace dampers and any other gas-burning
appliance to their previous condition of use.
7. Any improper operation of the common venting system should be corrected so the
installation conforms with the National Fuel Gas Code, ANSI Z223.1 and/or CAN/CGA
B149, Installation Codes. 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 in Part 11 of the National Fuel Gas Code,
ANSI Z223.1, and/or CAN/CGA B149, Installation Codes.
For boilers connected to gas vents or chimneys, vent installations shall be in
accordance with part 7, Venting of Equipment, of the National Fuel Gas Code, ANSI
Z223.1 or Section 7, Venting Systems and Air Supply for Appliances, of the CAN/CGA B149,
Installation Codes, or applicable provisions of the local building codes.
Vent connectors serving appliances vented by natural draft shall not be
connected into any portion of mechanical draft systems operating under positive
pressure.
7.3 Exhaust Venting With Gas
