Bryant 310A Installation, Start--Up, Operating, And Service And Maintenance page 36

NOTE: If orifice hole appears damaged or it is suspected to have
been redrilled, check orifice hole with a numbered drill bit of
correct size. Never redrill an orifice. A burr- -free and squarely
aligned orifice hole is essential for proper flame characteristics.
4. Verify natural gas input rate by clocking meter.
NOTE: Gas valve regulator adjustment cap must be in place for
proper input to be clocked.
a. Turn off all other gas appliances and pilots served by
the meter.
b. Run furnace for 3 minutes in heating operation.
c. Measure time (in sec) for gas meter to complete 1 re-
volution and note reading. The 2 or 5 cubic feet dial
provides a more accurate measurement of gas flow.
d. Refer to Table 11 for cubic ft. of gas per hr.
e. Multiply gas rate (cu ft./hr) by heating value (Btu/cu
ft.) to obtain input.
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
input is achieved. Reinstall regulator seal cap on gas valve.
5. Set temperature rise. The furnace must operate within the
temperature rise ranges specified on the furnace rating
plate. Do not exceed temperature rise range specified on
unit rating plate. Determine the temperature rise as fol-
lows:
NOTE: Blower access door must be installed when taking
temperature rise reading. Leaving blower access door off will
result in incorrect temperature measurements.
a. 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 par-
ticularly important with straight- -run ducts.
b. When thermometer readings stabilize, subtract return- -
air temperature from supply- -air temperature to determ-
ine air temperature rise.
NOTE: Blower access door must be installed for proper
temperature rise measurement.
NOTE: If the temperature rise is outside this range, first check:
S Gas input for heating operation.
S Derate for altitude if applicable.
S Return and supply ducts for excessive restrictions
causing static pressures greater than 0.50- -in. wc.
S Dirty filter.
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.
c. Adjust air temperature rise by adjusting blower speed.
Increase blower speed to reduce temperature rise.
Decrease blower speed to increase temperature rise.
d. Turn thermostat down below room temperature and
remove blower access door.
e. To change motor speed selection for heating, remove
blower motor lead from control HEAT terminal (See
Fig. 25.) Select desired blower motor speed lead from
one of the other terminals and relocate it to the HEAT
terminal (See Table 10 for lead color identification).
Reconnect original lead to SPARE terminal.
Table 10—Speed Selection
COLOR
White Common
Black
Yellow{ Med --- High
Blue* Med --- Low
Red*
* 1/5 HP motor models: BLUE to HEAT, RED to SPARE
{ Not available on 1/5 HP motors.
NOTE: Continuous blower is the HEAT speed.
f. Repeat steps a through e.
g. When correct input rate and temperature rise is
achieved, turn gas valve ON/OFF switch to OFF.
h. Remove manometer or similar device from gas valve.
i. Reinstall manifold pressure tap plug in gas valve.
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.
j. Reinstall blower access door if removed.
k. Turn gas valve ON/OFF switch to ON.
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.
6. Set thermostat heat anticipator.
a. Mechanical thermostat - - Set thermostat heat anticipat-
or to match the amp. draw of the electrical components
in the R- -W circuit. Accurate amp. draw readings can
be obtained at the wires normally connected to ther-
mostat subbase terminals, R and W. The thermostat
anticipator should NOT be in the circuit while measur-
ing current. (1.) Remove thermostat from subbase or
from wall. (2.) Connect an amp. meter as shown in
Fig. 49 across the R and W subbase terminals or R and
W wires at wall.
(3.) Record amp. draw across terminals when furnace
is in heating and after blower starts.
(4.) Set heat anticipator on thermostat per thermostat
instructions and install on subbase or wall.
b. Electronic thermostat: Set cycle rate for 4 cycles per
hr.
7. Adjust blower off delay The blower off delay has 4 ad-
justable settings from 90 sec to 180 sec. The blower off
delay jumpers are located on the furnace control board.
(See Fig. 25.) To change the blower off delay setting,
move the jumper from one set of pins on the control to the
pins used for the selected blower off delay. Factory off
delay setting is 120 sec.
8. Set airflow CFM for cooling Select the desired blower
motor speed lead for cooling airflow. See Table 5- -Air De-
livery- -CFM (With Filter). See Table 10 for lead color
identification.
36
SPEED AS SHIPPED
BLW
High COOL
SPARE
SPARE
Low HEAT