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19
2 Venting (continued)
Common venting systems may be too large when an existing
unit is removed.
At the time of removal of an existing appliance, the following
steps shall be followed with each appliance remaining connected
to the common venting system placed in operation, while other
appliances remaining connected to the common venting system
are not in operation.
1. Seal any unused opening in the common venting system.
2. Visually inspect the venting system for proper size and
horizontal pitch. Make sure there is no blockage or
restriction, leakage, corrosion and other unsafe conditions.
3. If possible, close all building doors and windows. Close all
doors between the space in which the appliances remaining
connected to the common venting system are located and
other building spaces.
4. Turn on clothes dryers and any other appliances 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.
5. Close fire place dampers.
6. Place in operation the unit being inspected. Follow the
lighting instructions. Adjust thermostat so unit will operate
continuously.
7. 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.
8. After making sure that each appliance remaining connected
to the common venting system properly vents when tested
as above, return doors, windows, exhaust fans, fireplace
dampers and other gas burning appliances to their previous
conditions of use.
9. Correct any improper operation of the common venting
system so that the installation conforms to the latest edition
of the National Fuel Gas Code, ANSI Z223.1, in Canada,
the latest edition of CAN/CGA-B149 Installation Code for
Gas Burning Appliances and Equipment. When resizing any
portion of the common venting system, resize to approach
the minimum size as determined using the appropriate
tables of the latest edition of the National Fuel Gas Code,
ANSI Z223.1, in Canada, the latest edition of CAN/
CGA-B149 Installation Code for Gas Burning Appliances
and Equipment.
A masonry chimney must be properly sized for the installation of
a high efficiency gas-fired appliance. Venting of a high efficiency
appliance into a cold or oversized masonry chimney can result
in operational and safety problems. Exterior masonry chimneys,
with one or more sides exposed to cold outdoor temperatures,
are more likely to have venting problems. The temperature of
the flue products from a high efficiency appliance may not be
able to sufficiently heat the masonry structure of the chimney
to generate proper draft. This will result in condensing of flue
products, damage to the masonry flue/tile, insufficient draft and
possible spillage of flue products into an occupied living space.
Carefully inspect all chimney systems before installation.
Masonry chimney installation
A masonry chimney must be carefully inspected to determine
its suitability for the venting of flue products. A clay-tile-
lined chimney must be structurally sound, straight and free of
misaligned tile, gaps between liner sections, missing sections of
liner or any signs of condensate drainage at the breaching or
clean out. If there is any doubt about the condition of a masonry
chimney, it must be relined with a properly-sized and approved
chimney liner system.
Inspection of a masonry chimney
Follow all vertical venting termination information for
clearances and location under Vertical Vent Termination
Clearances and Location, page 16.
Vertical vent termination clearances and
location
Installation & Service Manual
Venting of high efficiency appliances into a
masonry chimney without a sealed stainless
steel liner can result in operational and safety
problems. Any breaks, leaks, or damage to
the masonry flue/tile will allow spillage of
the positive pressure flue products from the
chimney. These flue products can easily
escape into an occupied living space causing
a health hazard. If there is any doubt about
the condition of a masonry chimney, or
its acceptability for use after insertion of
a corrosion resistant liner system, consult
with local code officials.
CAUTION