Natco VW Installation And Operating Instructions Manual page 23

IV. SOOT IN FLUEWAYS OR IN TUBES, OR
NOXIOUS FUMES INDICATIVE OF BAD
COMBUSTION
Possible Cause
A. Combustion air supply to heater
room is inadequate.
B. Stack or vent is blocked or
restrictive.
C. Severe down draft is causing
spillage of flue products into room.
D. Gas pressure to burners is
excessive.
E. Heater not fitted for the fuel being
supplied.
F. Heater installed at high altitude
without proper derating.
What To Do
A. Check air supply opening. Look
for debris in screen or louvre
which covers combustion air
opening, or for material blocking
the opening.
B. Look for blocked stack and
excessive number of elbows in
stack or excessive length of
horizontal runs.
C. Check for (1) proper vent cap on
stack; (2) adequate height of
stack above roof; (3) equipment
exhausting air from inside of
building; and (4) proper
installation of draft diverter.
D. Check gas pressure with
nanometer, and adjust with
heater firing at full rate.
E. See nameplate for correct fuel.
F. Installations at altitudes in excess
of 2000 ft. above sea level are
subject to jurisdiction of the local
inspection authorities.
V. WATER DRIPPING
IN FIREBOX
Possible Cause
Tub in heat exchanger has
overheated and ruptured.
23
What To Do
A tube failure is almost always
caused by (a) scale formation in the
tube or (b) inadequate water flow
through the boiler.