Bryant 340MAV GAS Rate CU FT/HR, Speed Selector, Blower OFF Delay Setup Position

EXAMPLE: (0—2000 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 12)

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 furnace rating plate. Recommended opera- tion is at midpoint of rise range or slightly above. Failure to follow this caution may result in primary and second- ary heat exchangers failure.

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.

3.Adjust temperature rise by adjusting blower speed. Increase blower speed to reduce temperature rise. Decrease blower speed to increase temperature rise.

TABLE 12—GAS 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	124	29	58	145

TABLE 13—SPEED SELECTOR

		FACTORY-
COLOR	SPEED	SHIPPED
		CONNECTION
Black	High	Cool
Yellow (When Present)	Medium High	Spare
Blue	Medium Low	Heat
Red	Low	Spare
White	Common	COM

TABLE 14–BLOWER OFF DELAY SETUP POSITION

PINS	1 AND 2	2 AND 3	3 AND 4	4 AND 5
Time (in sec)	90	120	150	180

WARNING: Disconnect 115-v electrical power before changing speed tap. Failure to follow this warning could result in personal injury.

4.To change blower motor speed selections for heating mode, remove blower motor lead from control center HEAT terminal. (See Fig. 31.) Select desired blower motor speed lead from 1 of the other motor leads and relocate it to HEAT terminal. See Table 13 for lead color identification. Recon- nect original lead on SPARE terminal.

Follow this same procedure for proper selection of COOL speed selection.

C.Blower Off Delay (Heat Mode)

The blower off delay has 4 adjustable settings from 90 sec to 180 sec. (See Table 14.) The blower off delay jumpers are located on the furnace control board (See Fig. 31). To change the blower off delay setting, move the jumper from one set of pins on the control board to the pins used for the desired blower off delay. Factory blower off delay setting is 120 sec.

D. Set Thermostat Heat Anticipator

When using a nonelectronic thermostat, the thermostat heat anticipator must be set to match amp draw of the electrical components in R-W circuit. Accurate amp draw readings can be obtained at thermostat subbase terminals R and W. Fig. 53 illustrates an easy method of obtaining actual amp draw. The amp reading should be taken after blower motor has started and furnace is heating. Connect ammeter wires as shown in Fig. 53.

The thermostat anticipator ahould NOT be in the circuit while measuring current. If thermostat has no subbase, the thermostat must be disconnected from R and W wires during current measurement. See thermostat manufacturer’s instructions for ad- justing heat anticipator and for varying heating cycle length.

For an electronic thermostat, set cycle rate for 3 cycles per hour.

CHECK SAFETY CONTROLS

This section covers the safety controls that must be checked before the installation is complete. The flame sensor, gas valve, and pressure switch were all checked in the Start-up procedure section as part of normal operation.

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