A.O. Smith 200 Instruction Manual page 23

PURGING OF GAS LINE
Gas line purging is required with new piping or systems in which
air has entered.
PURGING SHOULD BE PERFORMED BY PERSONS
EXPERIENCED IN THIS TYPE OF GAS SERVICE TO AVOID RISK
OF FIRE OR EXPLOSION. PURGE DISCHARGE MUST NOT
ENTER CONFINED AREAS OR SPACES WHERE IGNITION CAN
OCCUR. THE AREA MUST BE WELL VENTILATED AND ALL
SOURCES OF IGNITION MUST BE DEACTIVATED OR REMOVED.
BEFORE PLACING THE BOILER IN OPERATION, CHECK FOR
GAS LEAKAGE. USE A SOAP AND WATER SOLUTION OR OTHER
MATERIAL ACCEPTABLE FOR THE PURPOSE OF LOCATING GAS
LEAKS. DO NOT USE MATCHES, CANDLES, FLAME OR OTHER
SOURCES OF IGNITION FOR THIS PURPOSE.
THE GAS VALVE MUST HAVE BEEN IN THE OFF POSITION FOR AT
LEAST 5 MINUTES. This waiting period is an important safety
step. Its purpose is to permit gas that may have accumulated in
the combustion chamber to clear. IF YOU DETECT GAS ODOR AT
THE END OF THIS PERIOD DO NOT PROCEED WITH LIGHTING.
RECOGNIZE THAT GAS EVEN IF IT SEEMS WEAK, MAY INDICATE
PRESENCE OF ACCUMULATED GAS SOMEPLACE IN THE AREA
WITH RISK OF FIRE OR EXPLOSION. SEE THE FRONT PAGE
FOR STEPS TO BE TAKEN.
INLET GAS PRESSURE
The inlet gas pressure is measured by removing the low gas
pressure switch located on the main gas manifold which is
upstream of the unit's combination gas valves. The maximum
value specified in the table must not be exceeded. The minimum
values shown in table 17 must be maintained under both load and
no load conditions (static and dynamic). The combination gas
valves supplied with the boiler are for low pressure service. If
upstream pressure exceeds 14.0" W.C., an intermediate gas
pressure regulator of the lockup type must be installed.
TABLE 17.
Inlet Gas Pressure
Max. Inlet Pressure (Inches W.C.)
Min. Inlet Pressure (Inches W.C.)
MANIFOLD PRESSURE
The manifold gas pressure is measured at the pressure tap on
the downstream side of the combination gas valve(s). For natural
gas the Manifold Pressure should measure 3.5" W.C. For propane
(LP) gas, the pressure should read 10" W.C.
IMPORTANT
UNDER NO CIRCUMSTANCES SHALL THE GAS PRESSURE
MEASURED AT THE BURNER MANIFOLD EXCEED THAT STATED
ON THE BOILER RATING PLATE. OVERFIRING WILL RESULT IN
DAMAGE TO THE BOILER, AS WELL AS INCREASED RISK OF
FIRE, SOOTING AND ASPHYXIATION.
ADJUSTMENTS
ON INITIAL STARTUP SOME ADJUSTMENTS ARE NECESSARY.
1. CHECK MANIFOLD AND INLET GAS PRESSURES.
CAUTION
WARNING
Nat. Gas Prop. Gas
14.0 14.0
6.0 11.0
2. CHECK THE INPUT. SEE SECTIONS "INLET GAS PRESSURE:"
AND SEE NATIONAL FUEL GAS CODE, ANSI Z223.1 OR CAN/
CSA - B149.1 AND .2 (AND LATEST ADDENDA) FOR
PROCEDURES.
HOT WATER TEMPERATURES REQUIRED FOR AUTOMATIC
DISHWASHER AND LAUNDRY USE CAN CAUSE SCALD
BURNS RESULTING IN SERIOUS PERSONAL INJURY AND/OR
DEATH. THE TEMPERATURE AT WHICH INJURY OCCURS VARIES
WITH THE PERSON'S AGE AND TIME OF EXPOSURE. THE
SLOWER RESPONSE TIME OF CHILDREN, AGED OR DISABLED
PERSONS INCREASES THE HAZARDS TO THEM. NEVER ALLOW
SMALL CHILDREN TO USE A HOT WATER TAP, OR TO DRAW
THEIR OWN BATH WATER. NEVER LEAVE A CHILD OR DISABLED
PERSON UNATTENDED IN A BATHTUB OR SHOWER.
THE WATER HEATER SHOULD BE LOCATED IN AN AREA WHERE
THE GENERAL PUBLIC DOES NOT HAVE ACCESS TO SET
TEMPERATURES.
It is recommended in domestic hot water applications that lower
water temperatures be used to avoid the risk of scalding. It is
further recommended, in all cases, that the water temperature be
set for the lowest temperature which satisfies the user's hot water
needs. This will also provide the most energy efficient operation of
the boiler and minimize scale formation in the heat exchanger,
thus prolonging the life of the boiler.
SETTING THE WATER HEATER TEMPERATURE AT 120°F (49°C)
WILL REDUCE THE RISK OF SCALDS. Some states require
settings at specific lower temperatures. Table 18 below shows the
approximate time-to-burn relationship for normal adult skin.
TABLE 18. Risk of Scalds
Temperature
Setting
Over 170°F (77°C)
160°F (71°C)
150°F (66°C)
140°F (60°C)
130°F (54°C)
120°F (49°C) or less
USE ANTI-SCALD VALVE(S) in the hot water system to reduce the
risks of scalding at points of use such as lavatories, sinks and
bathing facilities.
23
DANGER
Time to Produce 2nd & 3rd
Degree Burns on Adult Skin
Nearly instantaneous
About 1/2 second
About 1-1/2 seconds
Less than 5 seconds
About 30 seconds
More than 5 minutes