Check Safety Controls - Bryant 987MA Installation, Start-Up, Operating And Service And Maintenance Instructions

To lock the furnace in Intermediate Heat:
1. Turn SW1- -2 OFF and SW4- -2 ON at the furnace control.
2. Connect a jumper across R and W/W1 at the thermostat
terminals at the furnace control.
3. Allow the burners to ignite and the blower to turn on.
4. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in Intermediate Heat:
1. Remove jumpers from R and W/W1.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of Set up switch SW1- -3. When set to
ON, airflow is raised 18% for Minimum Heat and for
Intermediate Heat. Factory default position is OFF.
5. Turn 115 VAC power on.
6. Re- -check Minimum Heat Temperature Rise .
To lock the furnace in Maximum Heat:
1. Connect a jumper across R and W/W1 and W2 at the
thermostat terminals at the furnace control.
2. Allow the burners to ignite and the blower to turn on.
3. Allow the supply temperature to stabilize and verify the
proper rise range.
If the temperature rise is too high or too low in Maximum Heat:
1. Remove jumpers from R and W/W1.
2. Wait until the blower off delay is completed.
3. Turn 115 VAC power off.
4. Check the position of Set up switch SW1- -4. When set to
OFF, airflow is raised 9% for Minimum Heat, 7% for
Intermediate Heat and 15% for Maximum Heat. Factory
default position is ON.
5. Turn 115 VAC power on.
6. Re- -check Minimum Heat Temperature Rise.
After the temperature rise has been verified:
1. Remove jumpers from thermostat terminals.
2. Allow the blower off delay to complete.
3. Turn Set up switches SW1- -2 and SW4- -2 to the OFF posi-
tion.
4. Install blower door.
WARNING
!
FIRE HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Reinstall manifold pressure tap plug in gas valve to prevent
gas leak.
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
mid- -point of rise range or slightly above.
f. Proceed to "Set Blower Off Delay" before installing
blower door.
Adjust Blower Off Delay (Heat Mode)
a. Remove blower door if installed.
b. Turn Dip switch SW- -7 or SW- -8 ON or OFF for desired
blower off delay. (See Table 17 and Fig. 34 , 54 and 63.)
Adjust Cooling Airflow - - Single Stage and High
Stage Cooling
The ECM blower can be adjusted for a range of airflow for Low
Speed or High Speed cooling. See Table 7- -Air Delivery - - CFM
(With Filter ). Depending on the model size, the cooling airflow
can be adjusted from 1.5 to 6 tons based on 350 CFM ton.
The cooling airflow is adjusted by turning Setup switches SW2- -1,
SW2- -2 and SW2- -3 either ON or OFF. Select the required airflow
from Table 7. Table 7 is based on 350 CFM per ton. For other
CFM per ton setup switch selections. See Fig. 34 and Fig. 54 and
Fig.63.
NOTE: 6 ton airflow will truncate at 2200 CFM on applicable
models. For a complete explanation of cooling airflow, refer to the
section titled "Sequence of Operation."
Adjust Continuous Fan Airflow/Low Speed
Cooling Airflow
The ECM blower motor can be adjusted for continuous fan speeds
different than heating or cooling fan speed. See Table 7 - - Air
Delivery - - CFM (With Filter). Select the required continuous fan
airflow from Fig. 54 and Table 7. Other airflow options are
available via SW4- -3. See Table 7.
The continuous fan speed is also the fan speed for low speed
cooling when furnace is used with a 2- -speed cooling unit. Adjust
the Continuous Fan CFM to match the airflow required for low
speed cooling. Select the required airflow from Fig. 54. For other
CFM per ton setup switch selections. (See Fig. 34 and Fig. 54.)
The airflow selected for low speed cooling will also be the airflow
used for continuous fan.
The continuous fan speed can be further adjusted at the thermostat
using the "Comfort Fan" select function. Changing the continuous
fan speed at the thermostat DOES NOT change the low speed
cooling airflow selected at the control board.
Adjust Thermostat Heat Anticipator.
a. Mechanical thermostat. Set thermostat heat anticipator to
match the amp. draw of the electrical components in the
R- -W/W1 circuit. Accurate amp. draw readings can be ob-
tained at the wires normally connected to thermostat sub-
base terminals, R and W. The thermostat anticipator should
NOT be in the circuit while measuring current.
(1.) Set SW1- -2 switch on furnace control board to ON.
(2.) Remove thermostat from subbase or from wall.
(3.) Connect an amp. meter as shown in Fig. 52 across
the R and W subbase terminals or R and W wires
at wall.
(4.) Record amp. draw across terminals when furnace is
in minimum heat and after blower starts.
(5.) Set heat anticipator on thermostat per thermostat
instructions and install on subbase or wall.
(6.) Turn SW1- -2 switch OFF.
(7.) Install blower door.
b. Electronic thermostat: Set cycle rate for 3 cycles per hr.

Check Safety Controls

The flame sensor, gas valve, and pressure switch were all checked
in the Start- -up procedure section as part of normal operation.
1. Check Main Limit Switch
This control shuts off combustion system and energizes air- -
circulating blower motor, if furnace overheats. By using this
method to check limit control, it can be established that lim-
it is functioning properly and will operate if there is a re-
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