International comfort products F8MVL Installation Instructions Manual page 39

5. Verify natural gas input rate by clocking meter.
a. Turn off all other gas appliances and pilots served
by the meter.
b. Move setup switch SW1−2 to ON position. This
keeps furnace locked in low−heat operation.
c. Jumper R to W/W1.
d. Run furnace for 3 minutes in low−heat operation.
e. Measure time (in sec) for gas meter to complete 1
revolution and note reading. The 2 or 5 cubic feet
dial provides a more accurate measurement of gas
flow.
f. Refer to Table 12 for cubic ft. of gas per hr.
g. Multiply gas rate cu ft./hr by heating value (Btuh/cu
ft.) to obtain input. If clocked rate does not match
required input from Step 1, increase manifold pres-
sure to increase input or decrease manifold pressure
to decrease input. Repeat steps b through e until
correct low−heat input is achieved. Re−install low
heat regulator seal cap on gas valve.
h. Move setup switch SW1−2 to OFF position and
jumper R to W/W1, and W2. This keeps furnace
locked in high−heat operation. Repeat items d
through g for high−heat operation.
6. Set Temperature Rise
NOTE: Blower access door must be installed when taking
temperature rise reading. Leaving blower access door off will
result in incorrect temperature measurements.
CAUTION
!
FURNACE DAMAGE HAZARD
Failure to follow this caution may result in shorten
furnace life.
Set air temperature rise within limits specified on the
rating plate to prevent reduced life of furnace
components. Operation is within a few degrees of the
mid−point of rise range when setup switch SW1−4 is
OFF.
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in overheating
the heat exchangers or condensing flue gases in heat
exchanger areas not designed for condensate.
Temperature rise must be within limits specified on
unit rating plate. Operation is within a few degrees of
midpoint of rise range when setup switch SW1−4 is
OFF.
When setup switch SW1−4 is ON, operation will be near the
high end of the rise range for improved comfort.
Furnace must operate within ranges of temperature rise
specified on the furnace rating plate. Determine air
temperature rise as follows:
a. Place thermometers in return and supply ducts as
near furnace as possible. Be sure thermometers do
not see heat exchanger so that radiant heat does
not affect readings. This practice is particularly im-
portant with straight−run ducts.
b. When thermometer readings stabilize, subtract re-
turn−air temperature from supply−air temperature to
determine air temperature rise.
441 01 2122 01
NOTE:
operation by placing setup switch SW1−2 on furnace control in
ON position. For high−heat operation, place setup switch
SW1−2 in OFF position and jumper R−W2 on furnace control.
DO NOT forget to return setup switch to OFF position and
remove R−W2 jumper upon completion of testing.
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. It must be within limits
specified
operation is at the mid−point of rise range or slightly
above.
7. Set Blower Off Delay
Specifications are subject to change without notice.
Temperature rise can be determined for low−heat
c. This furnace is capable of automatically providing
proper airflow to maintain the temperature rise within
the range specified on furnace rating plate. If tem-
perature rise is outside this range, proceed as fol-
lows:
(1.) Check gas input for low− and high−heat opera-
tion.
(2.) Check derate for altitude if applicable.
(3.) Check all return and supply ducts for excessive
restrictions causing static pressure greater than
0.5−In. W.C.
(4.) Ensure Low Heat Rise Adjust switch SW1−3 on
furnace control is in ON position when a bypass
humidifier is used. (See Figure 26 for switch
location.)
(5.) Make sure proper model plug is installed.
d. Remove thermostat jumpers and release blower
access door switch.
e. Repeat Steps a through c as required to adjust for
high heat temperature rise.
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 Figure 48)
WARNING
!
j. Remove thermostat jumper wire from furnace control
board.
k. Turn gas valve ON/OFF switch to ON.
CAUTION
!
on the rating plate.
l. Proceed to Step 6, "Set Blower Off Delay" before
installing blower access door.
a. Remove blower access door if installed.
b. Turn Dip switch SW−7 or SW−8 ON or OFF for de-
sired blower off delay. (See Table 9 and Figure 26
and Figure 55)
Recommended
39