A.O. Smith FMD 40 Manuale Utente

19

This water heater has been factory equipped to operate with the 
type gas indicated in the “EQUIPPED FOR” area of the model rating 
plate located near the gas control valve/thermostat. The indicated 
gas may be either Natural or Propane (L.P.). By following the 
conversion instructions in this manual or the instructions near the 
gas control valve/thermostat, the water heater must be converted if 
it is to be used with the opposite gas. DO NOT USE THIS WATER 
HEATER WITH ANY GAS OTHER THAN THE ONE LISTED ON 
THE MODEL RATING PLATE. Failure to use the correct gas can 
cause problems which can result in DEATH, SERIOUS BODILY 
INJURY, OR PROPERTY DAMAGE. If you have any questions or 
doubts consult your gas supplier or gas company. 

To convert from Propane (L.P.) gas to Natural gas, follow the “Fuel” 
Conversion Instructions “From Natural Gas to Propane (L.P.) Gas” 
section except in Step 5, use orifi ce “E”, marked “NAT.”. In Step 6 
use pilot orifi ce “G”, brass color and in Step 8 turn control screw 
“B” in Figure 12 clockwise ( 

  ) to stop. Screw must be in “OUT” 

position for Natural Gas.

See “Instruction Label” for orifi ce sizes and information below.

Orifi ce size: #52 Propane (L.P.) / #40 for Natural , 
if converted - Natural Rate: 30,000 BTU.

Orifi ce size: #51 for Propane (L.P.) / #38 for Natural,
if converted - Natural Rate: 32,000 BTU.

Orifi ce size: #51 for Propane (L.P.) / #35 for Natural, 
if converted - Natural Rate: 38,000 BTU.

Maximum Supply Pressure:
 

10.5” W.C. for Natural Gas.

 

13” W.C. for Propane (L.P.) Gas.

Minimum Supply Pressure:
       5” W.C. for Natural Gas.
      11” W.C. for Propane (L.P.) Gas.