Troubleshooting guide

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vent cap.
4. Blockage. Check the system for blockage by removing the cap, and
looking down into the vent with a flashlight. Check for bird nests, debris,
rodents, insects, or other obstructions. If nothing is found, inspect the entire
system for physical damage.
5. Downdraft. Downdrafts are generally caused by the system's termination
being too close to an adjacent wall, parapet, or other structure. If the cap is within
eight feet of such an obstruction, it must also be at least two feet above it. Also insure
that the top is at the height prescribed for your roof pitch in Table 2. Inadequate
combustion air is also a major cause of downdraft problems. Appliances like
clothes dryers or other exhausting appliances in the same utility room can cause
downdraft problems.
6. Condensate/Corrosion. Continuous condensate can cause corrosion
(rusting) of vents, tops, appliance draft hoods, and other components of the system,
as well as the inside of the appliance. This situation can be extremely
dangerous, and corrective action must be taken immediately. Common
causes of corrosion are listed below: If in doubt call a professional to inspect the
vent.
(a) If the vent system is located in an area where spray cans or solvents are
used extensively, (laundry areas, or paint shops, for example), the halogenated
compounds get into the combustion air. When they are burned, they form
compounds that cause corrosion. The corrective action in this case, is to isolate the
appliance, and get the air supply from outside, or an uncontaminated area.
(b) Condensate may be caused by incorrect sizing of the vent system.
Follow the procedures in the various sizing publications to obtain the correct sizes
for connectors and vents. Other causes are: excessive lateral runs, too many
elbows, cold attics and crawl spaces, and large areas of the exterior portions of the
venting system exposed to cold weather. As a general rule, laterals should be held
to a minimum, and be no longer than 75% of the vertical height of the system.
Condensate may initially appear as beads on the outside of the connector or vent.
7. Construction. Laterals, offsets, and vertical components should be
securely supported with wall straps, as previously described. Components of
the vent which are in occupied areas should be enclosed to prevent accidental
contact and damage to the vent system. Insure that insulation, building materials,
or debris do not extend into the required clearance spaces. In cold climates,
the exterior portions of the vent should be enclosed in a chase. Outside portions
of the vent system with may be painted with high temperature paint to help