Page 17 - Webster Service Manual

plished by using a solenoid valve which cuts off the flow
of oil instantly on shut-down.
Since the use of a solenoid is often costly for some
installations, Webster offers the M34DK-3 as a fast
shut-off alternative. In this unit the valve opens and
closes at approximately 2, 400 rpm fan speed. At this
speed the air pattern is well established, both in the
tube and in the chamber, and the burner operates with-
out a smoke plume, eliminating pulsation on starts and
stops. The volume of air delivered by the fan at such a
speed provides the oxygen necessary for complete
combustion insuring clean, quiet operation when the
burner is set at maximum efficiency.
Checking Seal Leaks
Seal leaks generally do not occur; they are caused. It
must be remembered that a seal can be operated under
conditions ranging from high vacuum to pressure (psi).
Where there is a head of oil over the fuel unit, a pres-
sure gauge can be installed in the suction port of the
unit to check head pressure. If the head pressure is
over 3 psi an oil safety valve (OSV) should be installed
in the suction line between the oil tank and the unit.
This also holds true where there are pressurized lines
leading to the fuel unit, such as a series of suspended
furnaces being served by a supply pump.
REMEMBER: To comply with NFPA standards, fuel unit
inlet pressures must be limited to 3 psi.
If Pump Doesn't Work, Check for Air Leaks
of start-up problems are due to air leaks in the suction
line. Be sure to double check for air leaks if there a re
problems with poor cutoff, noisy operation, or erratic fire.
To inspect for air leaks, check to be sure return line is
submerged. Also, check all fittings, all joints, and the
optional inlet plugs for tightness.
Check for air leaks:
Return line must be submerged
Check all fittings
Check all joints
Check optional inlet plugs
DO NOT use compression fittings
of start-up problems are due to air leaks in the suc-
tion line . . . So check
and doubt check
for air