Instructions / Assembly

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7. If the burner stays running, the system is operational.
8. If the (LED indicator for R7184 control; green LED for
7505 control) is off, check the cad cell assembly after
disconnecting the line voltage. See Table 9.
COMPONENT FUNCTIONS
Combustion Blower Centrifugal Switch
The electric motor for the blower which supplies combustion
air to the burner is equipped with a centrifugal switch wired
in series with the burner controls. This switch is normally
open until the speed of the blower motor closes it thereby
powering the burner controls. The burner controls will not
function until the blower motor is operating at full speed.
Fan Switch
The FAN ON and OFF switch is located on top of the control
box. This switch provides either automatic operation of
the blower through the thermostat or continuous blower
operation.
Fan Limit Switch
The fan limit switch closes and turns on the main blower
after a period of burner ON time when thermostat calls
for heat. The fan limit switch opens after the thermostat
is satisfi ed. The blower operates a period of burner OFF
time and turns the blower off.
Gas Burner Controls
The gas valve lever can be set to ON or OFF, as shown
in Figure 14 (page 21). When in the ON position, gas
fl ow through the gas valve is allowed when the valve is
energized electrically. When in the OFF position, gas fl ow
is completely shut off.
Supply Air Limit Switch
The supply air limit switch is the safety device that prevents
the furnace from exceeding the maximum allowable outlet
temperature.
Auxiliary Limit
This furnace is equipped with an auxiliary manual reset
limit. This limit will trip in the event of a blower motor failure.
If the limit trips, reset the limit by fi rmly pressing the red
button in the center of the limit. The limit is located on the
left hand side of the blower assembly. If the limit will not
reset, continues to trip, or the blower does not function,
notify your servicing contractor.
Honeywell R7184 Control
Indicator LED Status
On
Cad cell is sensing fl ame
(could be fl ame or stray light)
Off Cad cell is not sensing fl ame
Flashing (1/2 sec. on, 1/2 sec. off) Lockout/Restricted Lockout
Flashing (2 sec. on, 2 sec. off) Recycle
Beckett 7505 Control
Light color On Continuously Flashing
Red Restricted (Hard) Lockout Soft Lockout
Green
Cad cell is sensing fl ame (could be fl ame or stray light) Recycle
Yellow
Pump prime mode or reset button currently held for
15+ sec.
N/A
Table 8. Cad Cell Fault Conditions
Table 9. Cad Cell Resistance when sensing fl ame
Honeywell R7184
LED Flashes (Ohms) Cad Cell Resistance
1 0-400
2 400-800
3 800-1600
4 >1600
Burner will not start and the LED indicator is fl ashing
at 2 seconds on, 2 seconds off for R7184 (or the green
LED is fl ashing for 7505).
• Hold the reset button down for 1 - 2 seconds. If LED
indicator continues to fl ash, wait for 60 - 70 seconds.
If it still continues to fl ash, replace the primary control.
• Honeywell R7184 control: To check cad cell
resistance, press and release the button during the
run mode, with the igniter off. The LED will fl ash to
indicate the cad cell resistance. For proper burner
operation, it is important that the cad cell resistance
is under 1600 Ohms. See Table 9.
• Beckett 7505 control: To check cad cell resistance,
unplug the cad cell leads (yellow wires) from the control.
Measure the resistance with a meter in the conventional
way (when a fl ame is present). For proper burner
operation, it is important that the cad cell resistance
is under 1,600 Ohms.
Control Module Status Indicator
Gas Furnace
• One fl ash - the inducer centrifugal switch is stuck closed.
• Two fl ashes - the signal was not received by the control
that the inducer centrifugal switch had closed within the
time.
• Three fl ashes - a failed ignition attempt, a gas valve
error, or a false fl ame sensed during the warm up period.
A false fl ame condition occurs when the fl ame sensor
senses a fl ame without a fl ame present. If a false fl ame
occurs, the control will only return to normal operation
after the false fl ame condition is no longer present.
• Four fl ashes - the control senses a failure within the
control board.
Oil Furnace
The indicator lights on the oil primary control provides
lockout, recycle, and cad cell indications. See Table 8.