VENT SYSTEM MODIFICATION
When an existing boiler is removed from a common venting system, the common venting
system is likely to be too large for the proper venting of the appliances remained connected
to it. If this situation occurs, the following test procedure must be followed:
At the time of removal of an existing boiler, the following steps shall be followed with
each appliance remaining connected to the common venting system placed in operation,
while the other appliances remaining connected to the common venting system are not in
operation.
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 in 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 damper.
D. Place in operation the appliance being inspected. Follow the lighting instructions.
Adjust 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 or pipe.
F. After it has been determined that each appliance remaining connected to the common
venting system properly vents when tested as outlined above, return doors, windows,
exhaust fans, fireplace dampers and any other gas burning appliance to their previous
conditions of use.
G. Any improper operation of the common venting system should be corrected so the
installation conforms with the latest revision of the National Fuel Gas Code, ANSI Z223.1.
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 appendix G in the latest revision of the National Gas Fuel Code, ANSI Z223.1.
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