All installations and services must be performed by qualified service personnel.
GAS PRESSURE CHART FOR CMA* MODEL FURNACES
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.
D. BURNER ADJUSTMENT
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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