c. Adjust air temperature rise by adjusting blower speed. Increase blower speed to reduce temperature rise. Decrease blower speed to
increase temperature rise.
WARNING: Disconnect the electrical power before changing the speed tap. Failure to follow this warning could result
in personal injury.
d. To change blower motor speed selections for heating mode, remove blower motor lead from control board HEAT terminal. (See Fig.
11.) Select desired blower motor speed lead from 1 of the other terminals and relocate it to HEAT terminal. See Table 10 for lead color
identification. Reconnect original lead on SPARE terminal.
Follow this same procedure for proper selection of COOL speed selection.
CAUTION: Recheck temperature rise. It must be within limits specified on unit rating plate. Recommended operation
is at midpoint of rise or above.
3. Set thermostat heat anticipator.
The thermostat heat anticipation must be set to match the amp draw of the electrical components in the R-W circuit. Accurate amp draw
readings can be obtained at thermostat subbase terminals R and W. Fig. 17 illustrates an easy method of obtaining the actual amp draw.
The amp reading should be taken after the blower motor has started. See the thermostat manufacturer’s instructions for adjusting the heat
anticipator and for varying the heating cycle length.
NOTE:
When using an electronic thermostat, set cycle rate for 3 cycles per hr.
E.
Check Safety Controls
The flame sensor, gas valve, and pressure switch were all checked in the Start-up Procedures section as part of normal operation.
1. Check primary limit control.
This control shuts off the combustion control system and energizes the circulating-air blower motor if the furnace overheats.
The preferred method of checking the limit control is to gradually block off the return air after the furnace has been operating for a period
of at least 5 minutes. As soon as the limit has shut off the burners, the return-air opening should be unblocked. By using this method to
check the limit control, it can be established that the limit is functioning properly and operates if there is a motor failure.
2. Check draft safeguard switch.
The purpose of this control is to permit the safe shutdown of the furnace during certain blocked vent conditions.
Table 9—Canadian Orifice Size
GAS
SEA LEVEL 0-2000 FT
HIGH ALTITUDE
2000-4500 FT
Natural
43
44
Propane
54
55
Table 10—Speed Selector
COLOR
SPEED
FACTORY
ATTACHED TO
Black
High
COOL
Yellow
(When present)
Medium-High
SPARE
Blue
Medium-Low
HEAT
Red
Low
SPARE
White
Common
COM
Fig. 17—Amp Draw Check With Ammeter
A80201
R
Y W G
10 TURNS
THERMOSTAT SUBBASE
TERMINALS WITH
THERMOSTAT REMOVED
HOOK-AROUND
VOLT/AMMETER
EXAMPLE:
5.0 AMPS ON AMMETER
10 TURNS AROUND JAWS
= 0.5 AMPS FOR THERMOSTAT SETTING
FROM UNIT 24-VOLT
TERMINAL BLOCK
—19—
