Speed Selection - International comfort products N8MSN Installation Instructions Manual

EXAMPLE 2: (0−2000 ft. (0−610 M) altitude)
For 22,000 Btuh per burner application use Table 15.
Heating value = 1000 Btuh/cu ft.
Specific gravity = 0.62
Therefore: Orifice No. 43*
Manifold pressure: 3.7−in. w.c.
*Furnace is shipped with No. 43 orifices. In this example all
main burner orifices are the correct size and do not need to
be changed to obtain proper input rate.
3. Adjust manifold pressure to obtain correct input rate.
a. Turn gas valve ON/OFF switch to OFF.
b. Remove manifold pressure tap plug from gas valve.
(See Figure 41)
c. Connect a water column manometer or similar
device to manifold pressure tap.
d. Turn gas valve ON/OFF switch to ON.
e. Manually close blower door switch.
f. Set thermostat to call for heat.
g. Jumper R and W thermostat connections on fur-
nace control board to start furnace.
h. Remove regulator seal cap and turn regulator ad-
justing screw counterclockwise (out) to decrease
input rate of clockwise (in) to increase input rate.
i. Install regulator seal cap.
j. Leave manometer or similar device connected and
proceed to Step 4.
NOTE: DO NOT set manifold pressure less than 3.2−in. w.c.
or more than 3.8−in. w.c. for natural gas at sea level. If
manifold pressure is outside this range, change main burner
orifices or refer Table 15 or 16.
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
revolution and note reading. The 2 or 5 cubic feet
dial provides a more accurate measurement of gas
flow.
d. Refer to Table 13 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 temperat-
ure rise as follows:
32
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. Ra-
diant 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: Blower access door must be installed for proper
temperature rise measurement.
NOTE: If the temperature rise is outside this range, first
check:
Gas input for heating operation.
Derate for altitude if applicable.
Return and supply ducts for excessive restrictions
causing static pressures greater than 0.50−in. w.c.
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 temperat-
ure rise. Decrease blower speed to increase tem-
perature rise.
d. Turn thermostat down below room temperature and
remove blower access door.
e. To change motor speed selection for heating, re-
move 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 12 for lead color
identification). Reconnect original lead to SPARE
terminal.
Table 12—Speed Selection
COLOR SPEED
White Common
Black
Yellow {
Med-High
Blue Med-Low
Red
{
NOTE:
Yellow available on 4 speed motor only
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.
AS SHIPPED
BLW
High COOL
SPARE
HEAT
Low SPARE
441 01 1402 02