International comfort products R8MXL Installation Instructions Manual page 32

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 temperat-
ure 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.
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.
Disconnect 115−v electrical power and install lockout
tag before changing speed tap.
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 particularly important with straight−run ducts.
b. When thermometer readings stabilize, subtract re-
turn−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 heating operation.
(2.) Derate for altitude if applicable.
(3.) Return and supply ducts for excessive restric-
tions causing static pressures greater than
0.50−in. w.c.
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
Figure 25) Select desired blower motor speed lead
from one of the other terminals and relocate it to the
HEAT terminal (See Table 5 for lead color identifica-
tion). Reconnect original lead to SPARE terminal.
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.
32
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.
FURNACE OVERHEATING HAZARD
Failure to follow this caution may result in reduced
furnace life.
Recheck temperature rise.
specified on the rating plate. Recommended operation
is at the mid−point of rise range or slightly above.
Specifications are subject to change without notice.
Figure 41 − Gas Control Valve
Figure 42 − Orifice Hole
WARNING
!
CAUTION
!
It must be within limits
A06666
BURNER
ORIFICE
A93059
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