Bryant 987MA Installation, Start-Up, Operating And Service And Maintenance Instructions page 66

1. Make sure the gas supply is turned off to the furnace and at
the electric switch on the gas valve.
2. Remove the 1/8 inch NPT plug from the outlet pressure tap
on the gas valve.
3. Connect a manometer to the outlet pressure tap on gas
valve.
4. Turn on furnace power supply.
5. Turn gas supply manual shutoff valve to ON position.
6. Turn furnace gas valve switch to ON position.
7. Jumper the R to W/W1 and W2 thermostat connections at
the furnace control board.
8. After the main burners ignite and the blower starts, confirm
Maximum Heat manifold pressure is correct, based on the
manifold pressure tables in the installation instructions.
9. To adjust the Maximum Heat manifold pressure, slowly turn
adjusting screw counterclockwise to decrease manifold
pressure or clockwise to increase manifold pressure. Turn
adjustment no more than one click per second until you
obtain the required manifold pressure. See Fig. 53.
10. Main burner flame should be clear blue, almost transparent.
11. After adjusting the Maximum Heat manifold pressure,
remove jumpers across thermostat connections to terminate
the call for heat.
12. Wait for blower off-delay to finish then reset 115- -v power
to furnace.
Adjust Manifold Pressure - - Minimum Heat
To adjust manifold pressure to obtain input rate for Minimum Heat:
1. Turn SW1- -2 ON and SW4- -2 must be OFF.
2. Jumper R and W/W1 thermostat connections on control to
start furnace.
3. After the main burners ignite and the blower starts, confirm
Minimum Heat manifold pressure is correct, based on the
manifold pressure tables in the installation instructions.
4. To adjust the Minimum Heat manifold pressure, slowly turn
adjusting screw counterclockwise to decrease manifold
pressure or clockwise to increase manifold pressure. Turn
adjustment no more than one click per second until you
obtain the required manifold pressure. See Fig. 53.
5. After adjusting the manifold pressure, remove jumpers
across thermostat connections to terminate the call for heat.
Wait until the blower off delay is completed.
6. Move setup switch SW1- -2 to the OFF position.
7. Turn gas supply manual shutoff valve to OFF position.
8. Turn off furnace power supply.
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.
9. Remove manometer from the inlet pressure tap of the gas
valve.
10. Apply pipe dope sparingly to end of inlet gas pipe plug and
re-install in the gas valve.
11. Re-install cap over adjustment screw on the top of the gas
valve.
Clocking The Meter
Verify natural gas input rate by clocking meter.
NOTE: Contact your HVAC distributor or gas supplier for metric
gas meter Tables, if required.
1. Turn off all other gas appliances and pilots served by the
meter.
2. Move setup switches SW1- -2 to ON position and SW4-2 to
OFF. This keeps furnace locked in low--heat operation
when only W/W1 is energized or high heat operation when
R to W/W1 and W2 are jumpered.
3. Jumper R to W/W1 and W2. Run furnace for 3 minutes in
maximum heat operation.
4. Measure time (in sec) for gas meter to complete one
revolution and note reading. The 2 or 5 cubic feet dial
provides a more accurate measurement of gas flow.
5. Refer to Table 20 for cubic ft. of gas per hr. Multiply gas
rate cu ft./hr by heating value (Btuh/cu ft.) to obtain input
rate.
6. If clocked rate does not match required input from Step 5,
increase manifold pressure to increase input or decrease
manifold pressure to decrease input. Repeat steps 3 through
5 until correct maximum heat input is achieved. See Fig.
62.
7. Remove jumpers across thermostat connections to terminate
the call for heat. Wait until the blower off delay is
completed then reset 115- -v power to furnace.
8. Jumper R and W/W1 thermostat connections on control to
start furnace.
NOTE: Setup switches SW1- -2 must be ON and SW4- -2 must be
OFF. This keeps furnace locked in minimum heat operation when
R to W/W1 is energized. Repeat items 3 through 6 for minimum
heat operation until minimum heat input is achieved
9. Restore furnace to normal operating condition.
10. Remove jumpers across thermostat connections to termi- -
nate the call for heat. Wait until the blower off delay is
completed.
11. Disconnect 115 VAC power to furnace.
12. Turn gas valve ON/OFF switch to OFF.
13. Remove water column manometer or similar device from
manifold pressure tap (if still connected).
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.
14. Replace manifold pressure tap plug to gas valve.
15. Turn gas valve ON/OFF switch to ON.
16. Move setup SW1- -2 on furnace control to position required
for attached thermostat (OFF for single-stage thermostats,
ON for two-stage thermostats).
17. Check for gas leaks and verify furnace operation.
Adjust Temperature Rise
NOTE: Blower door must be installed when taking temperature
rise reading. Leaving blower door off will result in incorrect
temperature measurements, due to possible changes in duct static
pressure and airflow.
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