A.O. Smith 3400 - Manual (Page 40)

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PIPE SIZES FOR PROPANE GAS
Make sure to contact the gas supplier for pipe sizes, tanks, and
100% lockup gas pressure regulator.
PURGING GAS LINE
Gas line purging is required with new piping or systems in which
air has entered. Gas purging should be performed per NFPA 54
for US and CAN B149.1 for Canada.
CHECK GAS SUPPLY INLET PRESSURE
CSA or UL listed flexible gas connections are acceptable, but
make sure that the line has adequate capacity to allow your boiler
to fire at full rate. Consult with local codes for proper installation
or service procedures.
Do not adjust or attempt to measure gas control valve outlet
pressure. Attempting to alter or measure the gas control valve
outlet pressure could result in damage to the valve, causing
potential severe personal injury, death, or substantial property
damage.
Make sure the gas piping are sized for the proper flow and length
of pipe, to avoid excessive pressure drop. The gas meter and
the gas regulator must be properly sized for the total gas load.
Perform the below steps when checking inlet gas supply:
1. Turn the main power switch to the “OFF” position.
2. Shut off gas supply.
3. Remove the 1/8" pipe plug on the main gas shutoff valve
and install a suitable 1/8" fitting (field supplied) for the
manometer tubing. Place the tubing of the manometer over
the tap once the 1/8" fitting is installed.
4. Slowly turn on the gas supply.
5. Ensure inlet pressure is within specified range.
6. If the gas pressure is out of range, contact the gas utility, gas
supplier, qualified installer or service agency to determine
the necessary steps to provide proper gas pressure to the
control.
CHECK FOR GAS LEAKS
Before operating the boiler, make sure to check the floor near and
around the boiler for gas odorant or any unusual odor. Remove
the top access panel and check for odor in the interior of the
boiler enclosure. Do not start the boiler if there is any indication
of a gas leak. Use an approved leak detection solution and repair
any leaks at once.
In the case of propane boilers, the supplier mixes an odorant
with the propane to make its presence detectable. But in some
instances, the odorant can fade, and the gas may no longer have
an odor. Before operating the boiler, make sure the propane
supplier verify the correct odorant level in the gas.
Do not adjust or attempt to measure gas control valve outlet
pressure. The gas control valve is factory set for the correct
outlet pressure. This setting is suitable for natural gas and
propane, requiring no field adjustment. Attempting to alter or
measure the gas control valve outlet pressure could result in
damage to the valve, causing potential severe personal injury,
death, or substantial property damage.