Carrier 58CTA Installation And Service Instructions Manual page 39

DESIRED HEATING MODE
BLOWER OFF DELAY (SEC.)
90
120
150
180
e. Re-install high-fire adjustment caps.
f. Leave manifold or similar device connected and proceed to
Step 7.
NOTE: DO NOT set high-heat manifold pressure less than 3.2-in.
wc or more than 3.8-in. wc for natural gas. If manifold pressure is
outside this range, change main burner orifices.
7. Verify natural gas high heat input rate by clocking meter.
NOTE: Gas valve regulator adjustment caps 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 for 3 minutes in high-heat operation.
c. Measure time (in sec) for gas meter to complete 1 revolu-
tion and note reading.
d. Refer to Table 10 for cubic ft of gas per hr.
e. Multiply gas rate cu ft/hr by heating value (Btu/cu ft) to
obtain input.
NOTE: Using the 2 cu. ft. or 5 cu. ft. gas meter dial provides
greater accuracy in verifying gas input rate.
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 tempera-
ture 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 tem-
perature 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.
Table 12—2 Stage Furnace Blower OFF Delay Setup Switch
SETUP SWITCH
SW-2
OFF
OFF
ON
ON
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).
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury.
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. 32.) Select desired blower motor speed lead from 1 of
the other terminals and relocate it to the HI-HEAT termi-
nal. DO NOT use the low-heat tap that was already set.
(See Table 8 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. (See Fig
52.)
→
FIRE HAZARD
Failure to reinstall manifold pressure tap plug in gas valve
could result in fire, explosion, 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 install-
ing blower access door.
→
FURNACE OVERHEATING HAZARD
Failure to properly set air temperature rise may cause exces-
sive furnace temperatures and shorten 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.
9. Set Blower Off Delay
a. Remove Blower Access Door if installed.
37
SETUP SWITCH
SW-3
OFF
ON
OFF
ON