Allied Air Enterprises Upflow specifications Determining Furnace Input Natural Gas Only

The gas control (Figure 13) has two separate pressure regulator adjustment screws, one for 1st stage (marked "LO") and the second one for 2nd stage (marked "HI"). The adjusting screws are positioned on either side of the barbed fitting. The pressure regulator adjustment is sensitive: one turn of the adjusting screw will result in a relatively large change in manifold pressure. Turn regulator-adjusting screws IN (clockwise) to increase pressure, OUT (counterclockwise) to decrease presure.

Set the unit on high fire and adjust the 2nd stage high fire pressure regulator to the required setting. Disconnect the violet wire from the "HI" terminal on the gas control and the burners will drop down to the 1st stage low fire, then adjust the 1st stage pressure regulator setting as required. Gas input must never exceed the value shown on the furnace rating label. These units are equipped for rated input at manifold pressures of 2.3" w.c. (1st stage) and 3.5" w.c. (2nd stage) for natural gas. When these furnaces have been converted for use with LP (propane) gas, the manifold pressures are 6.4" w.c. (1st stage) and

10.0" w.c. (2nd stage). After proper adjustments, reconnect violet wire and furnace should go up to 2nd stage high fire. Turn OFF gas, replace manifold pressure tap pipe plug, regulator adjustment vent cap, and turn ON gas.

At higher altitudes and varying heating valves, manifold pressure or orifice changes maybe required. Consult Tables 7 and 8 for appropriate values. Failure to follow this warning could lead to a hazardous furnace operating condition and result in serious bodily injury or loss of life.

Determining Furnace Input - Natural Gas Only

NOTE: All access doors must be in place when checking gas input.

1.Turn OFF all other gas appliances (except for pilot burners) served by the same gas meter.

2.With furnace operating in full heat cycle, note how many seconds it takes for one full revolution of the smallest dial on the meter. Typically, this will be a 1/2 - or - 1 - cubic foot test dial.

3.Using the number of seconds for one revolution and the size of the meter dial, determine the cubic foot per hour of gas flow by using the formula provided below or Table 5.

Number of Dial Revolutions x Cubic Foot/Revolution x 3600

Cubic Ft/Hr =

Time (in seconds) Required for Number of Timed Revolutions

TABLE 5

Gas Rate (Cubic Feet per Hour)

	TEST DIAL				TEST DIAL
Seconds for				Seconds for
	1/2	1	2		1/2	1	2
One	Cubic	Cubic	Cubic	One	Cubic	Cubic	Cubic
Revolution	Feet	Foot	Feet	Revolution	Feet	Foot	Feet
10	160	360	720	36	50	100	200
12	150	300	600	38	47	95	190
14	129	257	514	40	45	90	180
16	113	225	450	42	43	86	172
18	100	200	400	44	41	82	164
20	90	180	360	46	39	78	156
22	82	164	325	48	37	75	150
24	75	150	300	50	36	72	144
26	69	138	276	52	35	69	138
28	64	129	258	54	34	67	134
30	60	120	240	56	32	64	128
32	56	113	226	58	31	62	124
34	53	106	212	60	30	60	120

4.Calculate the furnace input using the following formula:

BTUH = Cubic Ft/Hr x BTU/Cubic Foot

The local gas supplier should be able to provide the heating value of the gas, in BTU/cubic foot. If a specific value is not available, use 1000 BTU/cubic foot for Natural gas or 2500 BTU/cubic foot for Propane (LP).

Furnace input should be maintained within ± 2% of the value on the rating plate or appropriate altitude derate. Adjust manifold pressure or change orifices size if required.

5. Calculate the unit's actual input rate.

Example: If the heating value of the natural gas is 1015 Btu/cu. and it takes 60 seconds to burn 2 cu. ft. of gas then:

Input = 1015 Btu/cu. ft. X 1 rev X 2 cu. ft./rev. X 3600 60 sec.

Input = 121,800 Btu/hr.

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