Checking And Adjusting Input - A.O. Smith HW 300 Instruction Manual

CHECKING AND ADJUSTING INPUT

Fire and Explosion Hazard
Under no circumstances should the
input exceed the rate shown on the
boiler's rating label.
Overfiring could result in fire or
explosion.
Gas and carbon monoxide detectors are
available.
Breathing Hazard - Carbon Monoxide Gas
Under no circumstances should
the input exceed the rate shown
on the boiler's rating label.
Overfiring could result in damage to
the boiler's and sooting.
Gas and carbon monoxide detectors
are available.
Breathing carbon monoxide can cause brain damage or
death. Always read and understand instruction manual.
1. Follow steps 1 thru 6 of the OPERATING INSTRUCTIONS
on Page 31.
2. Attach a pressure gauge or a manometer to the manifold
pressure tapping and refer to Table 16 for correct manifold
pressure.
3. Follow steps 7 thru 11 of the OPERATING INSTRUCTIONS.
4. Use this formula to "clock" the meter. Be sure that other gas
consuming appliances are not ON during this interval.
3600 x H = Btuh
T
Btuh = The approximate actual input rate.
T = Time in seconds to burn one cubic foot of gas.
H = Heating value of the fuel gas in Btu per cubic foot of gas.
EXAMPLE:
T = 9.0 seconds/ft
3
H = 1050 Btu/ft (natural gas)
3
Btuh = ?
Gas flow through meter:
3600 x 1050 = 420,000 Btuh
9.0
Small changes in the input rate may be made by adjusting the
manifold pressure, refer to Gas manifold pressure regulators
on Page 25. Under no circumstances should you exceed the
maximum input rate for the boiler given in Table 3 on Page 7.
5. Repeat steps 1 thru 6 of the OPERATING INSTRUCTIONS.
6. Remove the pressure gauge or manometer from the manifold
pressure tapping. Replace the screw-in plug in the manifold
pressure tap.
7. Repeat steps 7 thru 11 of the OPERATING INSTRUCTIONS
on Page 31. The boiler will resume normal operation.
When the boiler is operating at full capacity, or full gas input,
it should consume 1 cu. ft. of gas in approximately the time
indicated in Table 16.
TABLE 16. CONSUMPTION RATE (REFER TO OPERATING
AT FULL INPUT OR FULL CAPACITY)
TIME TO CONSUME 1 CU. FT. OF GAS
HEATING
TYPE
VALUE
GAS
BTU/FT. HW-300 HW-399 HW-420 HW-520 HW-670
Natural 12.6
1050
Propane 30.0
2500
Minor variances from input on rating plate can be corrected by
adjustment of gas pressure regulators. Refer to Gas manifold
pressure regulators on Page 25.
The inlet gas pressure must not exceed or be less than the
values shown on rating plate.
28
(SECONDS)
9.5 9.0 7.3 5.7
22.6 21.4 17.3 13.4