37
A06666
Fig. 47
---
Gas Control Valve
BURNER
ORIFICE
A93059
Fig. 48
---
Orifice Hole
6. Set thermostat heat anticipator.
a. Mechanical thermostat -- Set thermostat heat anticipat-
or 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 connected to ther-
mostat subbase terminals, R and W. The thermostat
anticipator should NOT be in the circuit while measur-
ing current. (1.) Remove thermostat from subbase or
from wall. (2.) Connect an amp. meter as shown in
Fig. 48 across the R and W subbase terminals or R and
W wires at wall.
(3.) Record amp. draw across terminals when furnace
is in heating and after blower starts.
(4.) Set heat anticipator on thermostat per thermostat
instructions and install on subbase or wall.
b. Electronic thermostat: Set cycle rate for 4 cycles per
hr.
R Y W G
10 TURNS
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
(ANITICIPATOR, CLOCK, ETC.,
MUST BE OUT OF CIRCUIT.)
HOOK-AROUND
AMMETER
EXAMPLE: 5.0 AMPS ON AMMETER
10 TURNS AROUND JAWS
= 0.5 AMPS FOR THERMOSTAT
ANTICIPATOR SETTING
FROM UNIT 24-V
CONTROL TERMINALS
A96316
Fig. 49
---
Amp. Draw Check With Ammeter
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
CAUTION
!
7. Adjust blower off delay The blower off delay has 4 ad-
justable settings from 90 sec to 180 sec. The blower off
delay jumpers are located on the furnace control board.
(See Fig. 25.) To change the blower off delay setting,
move the jumper from one set of pins on the control to the
pins used for the selected blower off delay. Factory 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 De-
livery--CFM (With Filter). See Table 9 for lead color iden-
tification.
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 en-
ergizes air--circulating blower motor, if furnace overheats.
By using this method to check limit control, it can be es-
tablished that limit is functioning properly and will operate
if there is a restricted duct system or motor failure. 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.
d. Burners will re--light when furnace cools down.
2. Check draft safeguard switch.
The purpose of this control is to cause the safe shutdown
of the furnace during certain blocked vent conditions.
PG
8J
/M
