Thermo Products CMA2-75N Manual Do Utilizador

 
 

                          

SUPPLY PRESSURE 

MANIFOLD PRESSURE 

NAT 

MAX 14” WC 

MIN 4.5” WC 

3.5 + .3” WC 

PROPANE 

MAX 14” WC 

MIN 11” WC 

10.0” + .3” WC 

 

TABLE 3 

 

This gas furnace is equipped with a fixed orifice sized for the manifold 
pressure shown on the rating label.  The input can only be increased, or 
decreased, by adjusting the manifold pressure.  Remove the 1/8" threaded 
pipe plug located on the gas manifold.  
 
Use a U tube manometer or recently calibrated pressure gage to measure 
the pressure.  To adjust the pressure, remove the screw cap from the 
regulator on  the gas valve and using the adjustment screw.  Decrease the 
pressure by turning the screw counterclockwise or increase it by turning 
the screw clockwise.   
 

:  ADJUSTMENTS TO THE LISTED PRESSURE MUST NOT 

EXCEED 0.3" WC.  A 0.3" WC adjustment will increase or decrease the 
input approximately 4.0%.   
 
Replace screw (cap) when adjustment is complete. 
The correct input can be assumed if the furnace manifold pressure is the 
same as that shown on the rating label if a gas meter is not available for 
natural gas or the unit is installed on an unmetered propane gas supply. 
Shut off the gas supply to the furnace.  Remove the pressure gage and re-
install the pipe plug using a thread compound resistant to the action of LP 
gases. 
If the rated input cannot be obtained with the present orifice at the correct 
pressure, your local gas supplier may assist in sizing the proper orifice.  
Thermo Products Engineering Department will gladly assist in sizing the 
orifice if you provide them with the heating value in BTU per cubic foot and 
the specific gravity of the fuel gas. 

 

 

This unit is designed to not require any burner adjustment. The flames should be 
checked by looking through the sight glass located on the burner box. Burner 

 

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