Armstrong World Industries 242 AHALT390-1 Orifices, Normal, High, Orifice Size, Model, Altitude

	ACCESSORIES		Magic-Pak: HW/HWC
7-16
	BTU/HR	=	Cubic Feet Per Revolution x 3600 x Heating
	INPUT		# Seconds Per Revolution	Value

The heating value of your gas can be obtained from your local utility.

With proper manifold pressure achieved, cycle main burners on and off. Ignition and extinction should be smooth and quiet. Burning back at the orifice or flame popping back to the orifice can be corrected by adjusting the air shutter to soften the flame.

Regulator - Propane

The furnace has a regulator in the gas valve. A regulator is also required on the propane tank. Another regulator may be required at the house or the unit.

The minimum permissible gas supply pressure to the furnace is 11" W.C. for the purpose of input adjustment.

If at any time ignition is slow and the burner does not seem to be operat- ing correctly, check manifold pressure. It should be between 10" to 10.5" W.C.

The furnace is designed to obtain rated input at 10.0" W.C.

To check this pressure:

1.Turn off the gas valve.

2.Remove the plug on the valve.

3.Install a water manometer.

Turn gas valve “ON”. If manifold pressure must be adjusted, remove cap from pressure regulator and turn adjustment screw clockwise to increase pressure, counterclockwise to reduce pressure. After checking pressure, turn gas off, remove the manometer fitting and replace the pipe plug and regulator cap. Put furnace in operation and leak check plug for leaks using a soapy solution.

With proper manifold pressure achieved, cycle main burners on and off. Ignition and extinction should be smooth and quiet. Burning back at the orifice or flame popping back to the orifice can be corrected by adjusting the air shutter to soften the flame.

TABLE 7-8	AHALT390-1 Orifices
	Normal	High	High	Orifice Size
Model		Altitude	Altitude
	Input
Size		Input	Output
	Btuh			Natural	Propane
		Btuh	Btuh
26HW/HWC	26,000	23,400	18,000	55	65
38HW/HWC	38,000	24,200	27,000	54	64
51HW/HWC	51,000	45,900	36,000	54	63	SRM-
64HW/HWC	64,000	57,600	45,000	53	63
						HW/HWC

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