Bryant 355M-40-4 Ðgas Rate CU FT/HR, Set Temperature Rise, Set Thermostat Heat Anticipator

TABLE 14ÐGAS 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

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.

Furnace must operate within range of temperature rise specified on the unit rating plate. Determine air temperature rise as follows:

1.Place thermometers in return and supply ducts as near 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.

NOTE: Temperature rise can be determined for low-fire opera- tion by placing setup switch SW-2 on control center in ON position. For high-heat operation, place setup switch SW-2 in OFF position and jumper R-W2 on control center. DO NOT forget to return setup switch to OFF position and remove R-W2 jumper upon completion of testing. (See Fig. 25 for switch and terminal location.)

3.This furnace is capable of automatically providing proper airflow to maintain the temperature rise within the range specified on unit rating plate. If temperature rise is outside this range, proceed as follows:

a.Check gas input for low- and high-heat operation.

b.Check derate for altitude if applicable.

c.Check all return and supply ducts for excessive restric- tions causing static pressure greater than 0.5-in. wc.

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d. Ensure bypass humidifier switch (BPH) setup switch SW-3 on control center is in ON position when a bypass humidifier is used. (See Fig. 25 for switch location.)

e. Check Troubleshooting Guide for Variable-Speed 2-Stage Electronic Condensing Furnaces.

C. Set Thermostat Heat Anticipator

The thermostat heat anticipator must be set to match the amp draw of components in the R-W/W1 circuit. Accurate amp draw measurements can be obtained at the thermostat subbase terminals R and W.

Fig. 50 illustrates an easy method of obtaining thermostat amp draw measurements. The amp reading should be taken after blower motor has started and furnace is operating in low heat.

1.To operate furnace in low heat, turn setup switch SW-2 to ON position (See Fig. 25) and connect ammeter leads across thermostat subbase R-W.

2.See thermostat manufacturer's instructions for adjusting the heat anticipator and for varying heating cycle length.

NOTE: When using an electronic thermostat, set cycle rate for 3 cycles per hr.

3.Return setup switch SW-2 to OFF position and replace thermostat on subbase.

THERMOSTAT SUBBASE TERMINALS WITH THERMOSTAT REMOVED (ANITICIPATOR, CLOCK, ETC.,

MUST BE OUT OF CIRCUIT.)

HOOK-AROUND

AMMETER

R Y W G

10 TURNS

FROM UNIT 24-V

CONTROL TERMINALS

EXAMPLE:	5.0 AMPS ON AMMETER	=	0.5 AMPS FOR THERMOSTAT
	10 TURNS AROUND JAWS		ANTICIPATOR SETTING

A96316

Fig. 50ÐAmp Draw Check with Ammeter

CHECK SAFETY CONTROLS

I.CHECK PRIMARY LIMIT CONTROL

This control shuts off the combustion control system and energizes the air-circulating blower motor if furnace overheats.

1.The recommended method of checking this limit control is to gradually block off return air after furnace has been operating for a period of at least 5 minutes.

2.As soon as limit control has shut off burners, a 33 fault code will appear on control center.

3.The return-air opening should be unblocked to permit normal air circulation.

By using this method to check the limit control, it can be established that the limit is functioning properly and the furnace will operate safely if there is a restricted return-air supply or motor failure. If the limit control does not function during this test, the cause must be determined and corrected.