37
Boiler Blowdown Solenoid Valve Does Not Drain
If your steamer has an automatic blowdown drain
valve, when the blowdown button is depressed, the
boiler blowdown valve opens. If your steamer has a
manual blowdown drain valve, close it. The water
contained in the boiler, being under pressure, should
be blown through this valve and be noticeably visible
exhausting out the steamer drain. If the blowdown
operation appears to function sluggishly or not at all,
considerable scalant may be lodged in the drain pipe
and/or the valve. Disconnect the valve from the drain
line and inspect both the valve and the drain pipe
fixed to the boiler. If considerable scalant or lime
build-up is apparent, then not only the valve, but also
the boiler and water level control must be thoroughly
cleaned. Refer to “Water Is Not Being Supplied To
Boiler” for cleaning procedure of valve and “Removal
of Scalants from Boiler.”
Boiler Achieves Pressure Slower Than Normal
If the boiler requires more than 15 minutes to achieve
normal operating pressure (6 to 7 psi), then assume
that heavy build-up of scalant has completely coated
the interior of the boiler. The insulating effect of the
scalant hampers heat transfer.
Unbolt and remove the hand hole cover plate and
gasket assembly. Examine interior of boiler, and if
scalant and/or lime build-up is apparent, follow
procedure for removal of scalants from boiler.
If considerable scalant is evident, then both the boiler
blowdown solenoid valve and the water level control
must also be examined.
GAS GENERATORS
The pilot thermocouple supplies power to the gas
valve. A gas pressure regulating valve is an integral
part of the gas control valve and is set for 3.5" Water
Column for natural gas and 10" Water Column for
propane gas. Limited adjustment is provided by a
screw under the cap screw located at the top of the
control body. Turn the screw clockwise to increase
the gas pressure to the main burner.
The pilot burner flame is controlled by an adjustable
valve (under cap screw behind the dial of the
combination control valve). Turn clockwise to
decrease pilot flame. Pilot flame should be a steady
blue flame which envelopes the thermocouple tip.
Pilot flame should be about 1" long. A pilot orifice
fitting is located at the bottom of the pilot and is the
hexagon fitting to which the gas supply tubing to the
pilot is attached.
The main burners are lanced port steel burners (5 or
7 burners, depending on the unit) and have adjustable
air shutters. Fixed orifice-type hoods are used to
establish the gas flow to each burner. Set each
burner air shutter opening just large enough to
eliminate any yellow tip in the burner flame.
Pilot, Thermocouple or Main Burners
To remove the pilot assembly, disconnect thermocouple
and pilot gas supply tubing from the combination control
valve and remove the two screws holding the pilot to
its bracket.
To remove main burners, lift burner and move it to the
rear to clear the orifice hood, then lower front end of
burner and bring it forward under the manifold pipe.
If pilot keeps going out, first check visually for proper
pilot flame. Check to see that unusually strong floor
drafts are not interfering with proper heating of the
thermocouple by the pilot flame. If the pilot flame is
not the proper height, adjust it. If adjustment does not
result in a pilot flame of proper size, then gas is not
flowing properly to the pilot. Check for a plugged pilot
orifice, a kinked or plugged pilot gas supply tube, a
problem in the combination control valve, or for low or
high gas supply pressure. The pilot operates at gas
supply pressure. The pressure regulator in the
combination control valve regulates only the pressure
of gas to the main burner.
If the pilot flame is correct and there are no drafts,
then the problem is in the thermocouple or the
combination control valve. Check the thermocouple
with a millivoltmeter. If a meter is not available,
replace thermocouple with a new one as a check. The
connection of the tubing from the thermocouple tip to
the control valve is an electrical connection and must
be clean. Do not use any sealing compound on the
threads. With a wrench, tighten the nut finger tight
plus
1
⁄4 turn. DO NOT OVERTIGHTEN this nut. To
check a thermocouple with a millivoltmeter, make a
closed circuit check first (an adapter is required).
Closed circuit reading should be 13 to 26 MV.
