Check Safety Controls - International comfort products N8MSN Installation Instructions Manual

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 anti-
cipator 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 con-
nected to thermostat subbase terminals, R and W.
The thermostat anticipator should NOT be in the
circuit while measuring current. (1.) Remove ther-
mostat from subbase or from wall. (2.) Connect an
amp. meter as shown in Figure 43 across the R
and W subbase terminals or R and W wires at wall.
(3.) Record amp. draw across terminals when fur-
nace is in heating and after blower starts.
(4.) Set heat anticipator on thermostat per thermo-
stat instructions and install on subbase or wall.
b. Electronic thermostat: Set cycle rate for 4 cycles
per hr.
7. Adjust heat off delay The heat off delay has 4 ad-
justable settings from 90 sec to 180 sec. The heat off
delay jumpers are located on the furnace control board.
(See Figure 25) To change the heat off delay setting,
move the jumper from one set of pins on the control to
the pins used for the selected heat off delay. Factory
heat 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
Delivery−CFM (With Filter). See Table 12 for lead color
identification.
Figure 41 - Gas Control Valve
441 01 1402 02
Figure 43 - Amp. Draw Check With Ammeter
EXAMPLE:
Step 4 —Check Safety Controls
The flame sensor, gas valve, and pressure switch were all
checked in the Start−up procedure section as part of normal
operation.
1. Check Main Limit Switch(es)
This control shuts off combustion control system and
energizes air−circulating blower motor, if furnace over-
heats. By using this method to check limit control, it can
be established that limit is functioning properly and will
operate if there is a restricted duct system or motor fail-
ure. If limit control does not function during this test,
cause must be determined and corrected.
a. Run furnace for at least 5 minutes.
b. Gradually block off return air with a piece of card-
board or sheet metal until the limit trips.
c. Unblock return air to permit normal circulation.
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d. Burners will re−light when furnace cools down.
2. Check draft safeguard switch.
The purpose of this control is to cause the safe shut-
down of the furnace during certain blocked vent condi-
tions.
Figure 42 - Orifice Hole
BURNER
ORIFICE
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
(ANITICIPATOR, CLOCK, ETC.,
MUST BE OUT OF CIRCUIT.)
HOOK-AROUND
AMMETER
R Y W G
10 TURNS
FROM UNIT 24-V
CONTROL TERMINALS
= 0.5 AMPS FOR THERMOSTAT
5.0 AMPS ON AMMETER
ANTICIPATOR SETTING
10 TURNS AROUND JAWS
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