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Other Unit Adjustments
Primary Limit
The primary limit is located on the heating compartment
vestibule panel. This limit is factory set and require no ad-
justment.
Flame Rollout Switches (Two)
These manually reset switches are located on the burner
box.
Pressure Switches (Two)
The pressure switches are located in the heating com-
partment on the combustion air inducer. These switches
check for proper combustion air inducer operation before
allowing ignition trial. The switches are factory-set and re-
quire no adjustment. Pressure switch tubing installation is
critical for safe operation. See FIGURE 54.
PRESSURE SWITCH TUBING INSTALLATION
High-Fire
Pressure
Switch
Cold End
Header Box
Low-Fire
Pressure
Switch
Gas Valve
1 - Black tubing from front port on low-fire pressure switch to
positive port on the gas valve.
2 - Red and black tubing from rear port on low-fire pressure
switch to the negative port on the gas valve.
3 - Red and black tubing from front port on high-fire pressure
switch to negative port on cold end header box.
4 - Black tubing from rear port on high-fire pressure switch to
positive port on cold end header box.
FIGURE 54
3
4
2
1
Page 54
Temperature Rise
After the furnace has been started and supply and return
air temperatures have been allowed to stabilize, check the
temperature rise with the unit operating at 100 percent fir-
ing rate. See "Duct System" on page 9 for installing
the optional discharge air sensor used to measure tem-
perature rise. Sensor is shipped with the unit. If necessary,
adjust the blower speed to maintain the temperature rise
within the range shown on the unit nameplate. See TA-
BLE 23 for allowable heating speeds. Increase the blower
speed to decrease the temperature. Decrease the blower
speed to increase the temperature rise. Failure to adjust
the temperature rise may cause erratic limit operation.
Electrical
1 - Check all wiring for loose connections.
2 - Check for the correct voltage at the furnace (furnace
operating).Correct voltage is 120VAC + 10%.
3 - Check amp-draw on the blower motor with
innerlower panel in place.
Motor Nameplate__________Actual__________
Electronic Ignition
The integrated control has an added feature of an inter-
nalWatchguard control. The feature serves as an auto-
matic reset device for ignition control lockout caused by
ignition failure. This type of lockout is usually due to low
gas line pressure. After one hour of continuous thermostat
demand for heat, the Watchguard will break and remake
thermostat demand to the furnace and automatically reset
the control to begin the ignition sequence.
Exhaust and Air Intake Pipe
1 - Check exhaust and air intake connections for
tightness and to make sure there is no blockage.
2 - Are pressure switches closed? Obstructed exhaust
pipe will cause unit to shut off at pressure switches.
Check termination for blockages.
3 - Reset manual flame rollout switches on burner box
cover.
Heating Sequence of Operation
The integrated control initiates a pressure switch calibra-
tion at the initial unit start-up on a call for heat. The ignition
control will also initiate a calibration any time main power
is turned off and back on and a heating demand is pres-
ent . Additional calibrations may be initiated by the ser-
vice technician during field test sequence. The following
heating sequence of operation assumes completion of a
successful calibration.
NOTE - The thermostat selection DIP switch on the inte-
grated control is factory-set in the "TWO-STAGE" position.
Applications Using a Two-Stage Thermostat
A - Heating Sequence -- Control Thermostat Selection
DIP switch in "Two-Stage" Position (Factory Setting)
1 - On a call for heat, thermostat first-stage contacts
close sending a signal to the integrated control. The
integrated control runs a self-diagnostic program
and checks high temperature limit switches for
normally closed contacts and pressure switches
for normally open contacts. The combustion air
inducer is energized at ignition speed, which is
approximately the same as the inducer speed at 70
percent firing rate.
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