Bryant 340MAV United States, Ðaltitude Derate Multiplier for U.S.A, Canada, Ðgas Rate CU FT/HR

f.Look through sight glass in burner enclosure and check burner flame. Burner flame should be clear blue, almost transparent. (See Fig. 45.)

BURNER FLAME

BURNER

MANIFOLD

A89020

Fig. 45ÐBurner Flame

3. Verify natural gas input rate by clocking gas meter.

NOTE: Be sure all pressure tubing, combustion-air and vent pipes, and burner enclosure front are in place when checking input by clocking gas meter.

a.Calculate high-altitude adjustment (if required).

UNITED STATES

At altitudes above 2000 ft, this furnace has been ap- proved for a 2% derate for each 1000 ft above sea level. See Table 10 for derate multiplier factor.

TABLE 10ÐALTITUDE DERATE MULTIPLIER FOR U.S.A.

ALTITUDE	% OF	DERATE MULTIPLIER
(FT)	DERATE	FACTOR FOR U.S.A.*
0Ð2000	0	1.00
2001Ð3000	4Ð6	0.95
3001Ð4000	6Ð8	0.93
4001Ð5000	8Ð10	0.91
5001Ð6000	10Ð12	0.89
6001Ð7000	12Ð14	0.87
7001Ð8000	14Ð16	0.85
8001Ð9000	16Ð18	0.83
9001Ð10,000	18Ð20	0.81

* Derate multiplier factor is based on midpoint altitude for altitude range.

EXAMPLE:

100,000 Btuh input furnace installed at 4300 ft.

Furnace Input		Derate		Furnace Input Rate
Rate at	X	Multiplier	=	at Installation
Sea Level		Factor		Altitude
100,000	X	0.91	=	91,000

CANADA

→At installation altitudes from 2000 to 4500 ft, this furnace must be derated 5% by an authorized Gas Conversion Station or Dealer. To determine correct input rate for altitude, see example above and use 0.95 as derate multiplier factor.

b.Turn off all other gas appliances and pilots.

c.Start furnace and let operate for 3 minutes.

d.Measure time (in sec) for gas meter test dial to complete 1 revolution.

Ð40Ð

e.Refer to Table 11 for cu ft of gas per hr.

TABLE 11ÐGAS RATE (CU FT/HR)

SECONDS	SIZE OF TEST DIAL			SECONDS	SIZE OF TEST DIAL
FOR 1	1	2	5	FOR 1	1	2	5
REVOLUTION	cu ft	cu ft	cu ft	REVOLUTION	cu ft	cu ft	cu ft
10	360	720	1800	50	72	144	360
11	327	655	1636	51	71	141	355
12	300	600	1500	52	69	138	346
13	277	555	1385	53	68	136	340
14	257	514	1286	54	67	133	333
15	240	480	1200	55	65	131	327
16	225	450	1125	56	64	129	321
17	212	424	1059	57	63	126	316
18	200	400	1000	58	62	124	310
19	189	379	947	59	61	122	305
20	180	360	900	60	60	120	300
21	171	343	857	62	58	116	290
22	164	327	818	64	56	112	281
23	157	313	783	66	54	109	273
24	150	300	750	68	53	106	265
25	144	288	720	70	51	103	257
26	138	277	692	72	50	100	250
27	133	267	667	74	48	97	243
28	129	257	643	76	47	95	237
29	124	248	621	78	46	92	231
30	120	240	600	80	45	90	225
31	116	232	581	82	44	88	220
32	113	225	563	84	43	86	214
33	109	218	545	86	42	84	209
34	106	212	529	88	41	82	205
35	103	206	514	90	40	80	200
36	100	200	500	92	39	78	196
37	97	195	486	94	38	76	192
38	95	189	474	96	38	75	188
39	92	185	462	98	37	74	184
40	90	180	450	100	36	72	180
41	88	176	439	102	35	71	178
42	86	172	429	104	35	69	173
43	84	167	419	106	34	68	170
44	82	164	409	108	33	67	167
45	80	160	400	110	33	65	164
46	78	157	391
				112	32	64	161
47	76	153	383
				116	31	62	155
48	75	150	375
				120	30	60	150
49	73	147	367

f.Multiply gas rate (cu ft/hr) X heating value (Btu/cu ft) using natural gas heating value from local gas utility/supplier.

EXAMPLE: (0Ð2000 ft altitude)

Furnace input from rating plate is 100,000 Btuh. Btu heating input = Btu/cu ft X cu ft/hr Heating value of gas = 975 Btu/cu ft

Time for 1 revolution of 2-cu ft dial = 70 sec Gas rate = 103 cu ft/hr (from Table 11)

Btu heating input = 103 X 975 = 100,425 Btuh

In this example, the orifice size and manifold pressure adjustment is within ±2 percent of the furnace input rate.

B.Set Temperature Rise

CAUTION: Temperature rise must be within limits specified on unit rating plate. Recommended operation is at midpoint of rise or above. Failure to follow this caution may result in condensing or overheating the heat ex- changers.

Determine and adjust air temperature rise as follows:

1.Place thermometers in return and supply ducts as close to furnace as possible. Be sure thermometers do not see heat exchanger so that radiant heat does not affect readings. This practice is particularly important with straight-run ducts.

2.When thermometer readings stabilize, subtract return-air temperature from supply-air temperature to determine air temperature rise.