A.O. Smith 3400 - Manual (Page 18)

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TABLE 8.
SINGLE UNIT INSTALLATION, SUGGESTED GAS PIPE
SIZING. MAXIMUM EQUIVALENT PIPE LENGTH (IN FEET).
BTU
Input
2” 2-1/2” 3” 4”
Nat Pro Nat Pro Nat Pro Nat Pro
920,000 125 200 200 ----- ----- ----- ----- -----
1,300,000 80 175 175 ----- ----- ----- ----- -----
1,700,000 40 100 100 ----- ----- ----- ----- -----
1,999,900 30 80 80 200 200 ----- ----- -----
2,600,000 20 50 50 125 150 ----- ----- -----
3,400,000 10 30 30 70 90 200 ----- -----
Natural gas 1000 Btu/ft^ 3 , 0.63 specific gravity @ 0.5 in. w.c. pressure drop.
Propane gas 2500 Btu/ft^ 3 , 1.50 specific gravity @ 0.5 in. w.c. pressure drop.
CORROSIVE MATERIALS AND CONTAMINATION
SOURCES
Products to avoid: (Not all inclusive list)
• Spray cans containing chloro/fluorocarbons
• Permanent wave solutions
• Chlorinated waxes/cleaners
• Chlorine-based swimming pool chemicals
• Calcium chloride used for thawing
• Sodium chloride used for water softening
• Refrigerant leaks
• Paint or varnish removers
• Hydrochloric acid/muriatic acid
• Cements and glues
• Antistatic fabric softeners used in clothes dryers
• Chlorine-type bleaches, detergents, and cleaning
solvents found in household laundry rooms
• Adhesives used to fasten building products and other
similar products
Areas likely to have contaminants:
• Dry cleaning/laundry areas and establishments
• Swimming pools
• Metal fabrication plants
• Beauty shops
• Refrigeration repair shops
• Photo processing plants
• Auto body shops
• Plastic manufacturing plants
• Furniture refinishing areas and establishments
• New building construction
• Remodeling areas
Common household products, pool and laundry products may
contain fluorine or chlorine compounds. When these chemicals
come in contact with the boiler, they react and can form strong
acids. The acid can spoil the boiler wall, causing serious damage
and may result in flue gas spillage or boiler water leakage into
the building.
If the above mentioned contaminants and corrosive materials
chemicals are present near the location of the boiler, make sure
to remove the boiler permanently or relocate air inlet and vent
terminations to other areas.
Fittings and unions in gas line must be of metal to metal type.
Apply joint compounds (pipe dope) sparingly and only to the
male threads of pipe joints. Do not apply compound to the first
two threads. Use compounds resistant to the action of liquefied
petroleum gases. The boiler and its gas connection must be leak
tested before placing the boiler in operation.
GAS SUPPLY LINE SIZING
The gas piping installation must be capable of supplying the
maximum probable gas demand without excessive pressure loss.
Depending on local practices, the ALLOWABLE PRESSURE
LOSS between the gas meter, or service regulator and each
appliance is generally 0.3 or 0.5 inches of water column (0.075
or 0.124 kPa).
For single boiler installation, refer to Table 7 and Table 8 to size
iron pipe or equivalent gas supply line size to be used with single
unit.
For multiple boiler installation or installations of a single boiler
with other gas appliances, please refer to Table 9 and Table 10
on Page 20 to size iron pipe or equivalent gas supply line. These
tables are taken from the current edition of the National Fuel Gas
Code, ANSI Z223.1/NFPA 54 or the Natural Gas and Propane
Installation Code, CAN/CSA B149.1.
• Table 9 is based on a pressure drop of 0.5 inches water
column (0.124 kPa), and a gas with a specific gravity of
0.60 and a heating value of 1,000 BTU/ft 3 , approximately
that of Natural Gas.
• Table 10 is based on a pressure drop of 0.5 inches water
column (0.124 kPa), and a gas with a specific gravity of
1.53 and a heating value of 2,500 BTU/ft3, approximately
that of Propane Gas.
Where it is necessary to use more than the average number of
fittings (i.e., elbows, tees and valves in gas supply line) use a
pipe larger than specified to compensate for increased pressure
drop.
Table 7 and Table 8 shows the maximum equivalent gas pipe
length for a single unit installation. It does not take into account
other appliances that may be connected to the gas line.
For installation of multiple units, or instances where several
appliances are connected to the same line, use Table 9 and
Table 10 for proper sizing.
TABLE 7.
SINGLE UNIT INSTALLATION, SUGGESTED GAS PIPE
SIZING. MAXIMUM EQUIVALENT PIPE LENGTH (IN FEET).
BTU
Input
2” 2-1/2” 3” 4”
Nat Pro Nat Pro Nat Pro Nat Pro
920,000 70 150 175 ----- ----- ----- ----- -----
1,300,000 40 100 100 200 ----- ----- ----- -----
1,700,000 20 60 70 150 200 ----- ----- -----
1,999,900 20 50 50 100 150 ----- ----- -----
2,600,000 10 30 30 70 90 200 ----- -----
3,400,000 ----- ----- 20 40 50 125 200 -----
Natural gas 1000 Btu/ft^ 3 , 0.60 specific gravity @ 0.3 in. w.c. pressure drop.
Propane gas 2500 Btu/ft^ 3 , 1.50 specific gravity @ 0.3 in. w.c. pressure drop.