Bryant 581B installation instructions Rated Gas Inputs at Indicated Manifold Pressures, Orifices

Table 5 Ð Rated Gas Inputs at Indicated Manifold Pressures

	NUMBER	GAS SUPPLY PRESSURE				MANIFOLD		NATURAL GAS		PROPANE*
UNIT			(in. wg)			PRESSURE
581B	OF	Natural		Propane		(in. wg)		Ori®ce	Heating Input	Ori®ce	Heating Input
	ORIFICES
		Min	Max	Min	Max	Natural	Propane	Drill Size	(Btuh)²	Drill Size	(Btuh)²
	2	4.0	13.6	5.0	13.0	3.5	3.5	33	72,000	43	72,000
036-072**	3	4.0	13.6	5.0	13.0	3.5²²	3.5²²	33	115,000²²	43	115,000²²
	3	5.0	13.6	5.0	13.0	3.5	3.5	30	150,000	38	150,000

*When a 581B unit is converted to liquid propane (LP), the burners must be modi®ed with accessory LP Kit.

²Based on altitudes from sea level up to 2000 ft above sea level. For altitudes above 2000 ft, reduce input rating 4% for each 1000 ft above sea level. In Canada, from 2000 ft above sea level to 4,500 ft above sea level, derate the unit 10%.

**581B036 with 150,000 Btuh input not available.

²²581B036115 at high ®re operation. At low ®re, manifold pressure is 1.8 in. wg, and heating input is 82,000 Btuh. 581B048-072150 at high ®re operation. At low ®re, manifold pressure is 2.2 in. wg, and heating input is 120,000 Btuh.

Table 6 Ð Altitude Compensation* Ð Units 581B036-072

	72,000 AND 115,000		150,000 BTUH
	BTUH NOMINAL INPUT		NOMINAL INPUT
ELEVATION	Natural	Liquid	Natural	Liquid
(ft)	Gas	Propane	Gas	Propane
	Ori®ce	Ori®ce	Ori®ce	Ori®ce
	Size²	Size²	Size²	Size²
0-2,000	33	43	30	38
2,000	34	43	30	39
3,000	35	44	31	40
4,000	36	44	32	41
5,000	36	44	33	42
6,000	37	45	34	43
7,000	37	45	35	43
8,000	38	46	36	44
9,000	39	47	37	44
10,000	41	48	38	45
11,000	43	48	39	45
12,000	44	49	40	46
13,000	44	49	41	47
14,000	45	50	42	47

*As the height above sea level increases, there is less oxygen per cubic foot of air. Therefore, heat input rate should be reduced at higher altitudes.

²Ori®ces are available through your local distributor or branch.

NOTE: The gas manifold is equipped with a plug located ap- proximately 5 in. down from the gas valve which may also be used to connect the manometer.

3.Record number of seconds for gas meter test dial to make one revolution.

4.Divide number of seconds in Step 3 into 3600 (number of seconds in 1 hour).

5.Multiply result of Step 4 by the number of cubic ft shown for one revolution of test dial to obtain cubic ft of gas ¯ow per hour.

6.Multiply result of Step 5 by Btu heating value of gas to obtain total measured input in Btuh. Compare this value with heating input shown in Table 1. (Consult the local gas supplier if the heating value of gas is not known.)

EXAMPLE: Assume that the size of test dial is 1 cubic ft, one revolution takes 33 seconds, and the heating value of the gas is 1050 Btu/ft3, then proceed as follows:

1.33 seconds to complete one revolution.

2.3600 4 33 = 109

3.109 x 1 = 109 ft3 of gas ¯ow/hr

4.109 x 1050 = 114,450 Btuh input

If the desired gas input is 115,000 Btuh, only a minor change in the manifold pressure is required.

Observe manifold pressure and proceed as follows to adjust gas input:

1.Remove cover screw over regulator adjustment screw on gas valve. See Fig. 31.

2.Turn regulator adjustment screw clockwise to increase gas input, or turn regulator adjustment screw counter- clockwise to decrease input. Manifold pressure must be between 3.2 and 3.8 in. wg on high-®re, two-stage units.

WARNING: Unsafe operation of the unit may result if manifold pressure is outside this range. Personal in- jury or unit damage may result.

3.Replace cover screw cap on gas valve.

4.Turn off gas supply to unit.

5.Remove manometer from pressure tap.

6.Replace pipe plug on gas valve or manifold.

7.Turn on gas to unit.

8.Check for leaks.

Fig. 31 Ð Burner Tray Details

Measuring Manifold Pressure Ð LP Gas Units

The main burner ori®ces on LP gas unit are sized for the unit rated input when the manifold pressure is 3.5 in. wg (high- ®re on two-stage units).

Proceed as follows to adjust gas input on an LP gas unit:

1.Turn off gas to unit.

2.Remove pipe plug on outlet of gas valve or manifold.

3.Connect manometer.

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