Smith Cast Iron Boilers GB250 SERIES - Manual (Page 17)

17
5. Boilers are shipped from the factory with the primary air
shutters on the main bur ner wide open. It is
recommended these air shutters be left in the wide open
position unless there is lifting of the flame above the
burner ports. If there is lifting, the air shutters should be
gradually closed until the lifting is eliminated. it may also
be necessary to adjust the primary air shutters if the input
rate is reduced by a change in the orifices.
6. After burner has been in operation for about 10
minutes, check gas input rate to boiler as follows:
a. Make sure all appliances served by the meter are
turned off during timing of gas input rate to the boiler.
b. Measure the time in seconds that it takes for the
boiler to use 10 cubic feet of gas. Divide 36,000 by the
number of seconds (this is the number of cubic feet of
gas used per hour). Multiply this figure by the heating
value of the gas to obtain Btu input per hour.
Example: A GB250-7 boiler takes 2 minutes to use 10
cubic feet of natural gas. The local utility indicated the
heating value of the natural gas being supplied is 1000
Btu/cu ft. Therefore:
2 minutes = 120 seconds.
36,000
X 1000 = 300,000 Btu/hr
120
Therefore, the boiler input is correct.
NOTE: Before calculating the input of the heating
equipment, obtain the heating value of the gas from
the local utility.
7. If input needs to be corrected, adjust combination gas
valve pressure regulator. (Regulator is factory set at 3-
1/2" W.C. for natural gas and 10" W.C. for propane.) Turn
adjusting screw clockwise to increase gas flow (increase
input). Turn adjusting screw counterclockwise to decrease
gas flow (decrease input). In no case should final manifold
pressure setting vary more than + .3" from factory-set
pressures. If rated input cannot be obtained with
adjustment, gas supply pressure or orifice size may be
cause. Consult local utility and Smith.
8. Gas burner orifices supplied with boiler have been
carefully designed to provide correct gas input rate for
most gas conditions typically found in the U.S. and
Canada. Occasionally, however, local gas
characteristics may not allow unit to be properly
adjusted for input. If this is the case, local utility or
Smith may recommend orifices be changed. When
changing orifices follow the procedures detailed in
Section 4 of this manual.
9. Start and stop burners several times by raising and
lowering the thermostat setting.
10. After boiler has been firing long enough to raise
boiler pressure above minimum setting of the primary
pressuretol limit, check limit by turning its setting from
maximum to minimum setting. This should turn boiler
off. Return limit to desired setting. GB250-8 and
GB250-9 also have a secondary pressuretrol (located to
the right of the primary pressuretrol when facing the
front of the boiler). DO NOT READJUST THE
SECONDARY PRESSURETROL (it is factory-set and
sealed at 15 psig).
11. Check boiler safety shutoff controls.
a. For boilers with standing pilot, with boiler firing,
disconnect thermocouple lead from the valve. The
valve should close.
b. For boilers with intermittent pilot, with boiler firing,
disconnect wire connected to the "PV" terminal on the
Honeywell S8600 control. The gas valve should
close.
12. On initial start-up and prior to each heating season,
boiler must be cleaned (see "Steam Boiler Cleaning
Instructions" in Section 4 of this manual).
CAUTION: Never leave the job with yellow burning
flames. This condition indicated poor combustion
and will quickly carbonize the boiler, reducing
efficiency and boiler life. It may also be an indication
of improper venting or combustion air supply. If
unable to adjust flame properly, consult your local
utility.