Bryant 120 instruction manual Speed Selection, Color Speed AS Shipped

If clocked rate does not match required input from Step 1, increase manifold pressure to increase input or decrease manifold pressure to decrease input. Repeat steps b through e until correct high heat input is achieved. Re-install high-heat regulator seal cap on gas valve.

8.Set high heat temperature rise.

Jumper R to W/W1 and W2 to check high-gas-heat temperature rise. Do not exceed temperature rise ranges specified on furnace rating plate for high heat. The furnace must operate within the temperature rise ranges specified on the furnace rating plate.

Determine the air temperature rise as follows:

NOTE: Blower access door must be installed when taking temperature rise reading. Leaving blower access door off will result in incorrect temperature measurements.

a.Verify the furnace is operating in high heat per Step 6. Place thermometers in return and supply ducts as close to furnace as possible. Be sure thermometers do not see radiant heat from heat exchangers. Radiant heat affects temperature rise readings. This practice is particularly important with straight-run ducts.

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

NOTE: If the temperature rise is outside this range, first check: (1.) Gas input for low-and high-heat operation.

(2.) Derate for altitude if applicable.

(3.) Return and supply ducts for excessive restrictions causing static pressures greater than 0.50-in. wc.

(4.) Dirty filter.

c. Adjust air temperature rise by adjusting blower speed. Increase blower speed to reduce temperature rise. Decrease blower speed to increase temperature rise. For high heat, speed selection can be med-high, med (5-speed blowers only), or med-low (factory setting).

!WARNING

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal injury or death.

Disconnect 115-v electrical power before changing speed tap.

d.To change motor speed selection for high heat, remove blower motor lead from control HI-HEAT terminal. (See Fig. 34.) Select desired blower motor speed lead from 1 of the other terminals and relocate it to the HI-HEAT terminal. DO NOT use the low-heat tap that was already set. (See Table 13 for lead color identification). Reconnect original lead to SPARE terminal.

e.Repeat steps a thru e.

f.When correct high heat input rate and temperature rise is achieved, turn gas valve ON/OFF switch to OFF.

g.Release Blower Access Door switch.

h.Remove manometer or similar device from gas valve.

i.Re-install manifold pressure tap plug in gas valve (use 3/16 in. head allen wrench). (See Fig 54.)

!WARNING

FIRE HAZARD

Failure to reinstall manifold pressure tap plug in gas valve could result in personal injury, property damage or death.

Reinstall manifold pressure tap plug in gas valve to prevent gas leak.

j. Remove thermostat jumper wire from furnace control board.

k.Turn LHT switch OFF.

l.Turn gas valve ON/OFF switch to ON.

m.Proceed to Step 9, “Set Blower Off Delay” before installing blower access door.

!CAUTION

FURNACE OVERHEATING HAZARD

Failure to follow this caution may result in reduced furnace life.

Recheck temperature rise. It must be within limits specified on the rating plate. Recommended operation is at the midpoint of rise range or slightly above.

9.Set Blower Off Delay

a.Remove Blower Access Door if installed.

b.Turn Dip switch 2 and 3 ON or OFF for desired blower off delay. (See Table 14 and Fig 34.)

10.Set thermostat heat anticipator.

a.Mechanical thermostat - Set thermostat heat anticapator to match the amp. draw of the electrical components in the R-W/W1 circuit. Accurate amp. draw readings can be obtained at the wires normally connected to thermostat subbase terminals, R and W. The thermostat anticipator should NOT be in the circuit while measuring current. (1.) Set LHT switch on furnace control board to ON.

(2.) Remove thermostat from sub-base or from wall.

(3.) Connect an amp. meter as shown in Fig. 56 across the R and W subbase terminals or R and W wires at wall.

(4.) Record amp. draw across terminals when furnace is in low heat and after blower starts.

(5.) Set heat anticipator on thermostat per thermostat instructions and install on subbase or wall.

(6.) Turn LHT switch OFF.

(7.) Install blower access door.

b. Electronic thermostat: Set cycle rate for 3 cycles per hr.

11.Set airflow CFM for cooling

Select the desired blower motor speed lead for cooling airflow. See Table 5-Air Delivery-CFM (With Filter). See Table 13 for lead color identification.

Table 13 – Speed Selection

COLOR	SPEED	AS SHIPPED
White	Common	BLW
Black	High	COOL
Yellow	Med--- High	SPARE
Orange†	Med	SPARE
Blue	Med--- Low	HI--- HEAT
Red	Low*	LO HEAT

*Continuous---blower speed---as shipped default { Not all models equipped with 5 speed motors

312A

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