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5−Burner Control (A3) & Transformer (T1)
−1 through −4 units
The burner control, along with the matching cad cell, proves
flame and controls the burner. After the cad cell closes a circuit
to the burner control, the burner control de−energizes the safe
ty switch heater to allow the unit to operate normally. The
burner control allows 45 seconds for the cad cell to close. If the
cad cell remains open after the 45 second time frame, the
burner control locks out. The burner control must be manually
reset by depressing the red reset button on top of the burner
control.
Transformer (T1) is part of the burner control. T1 provides
24VAC to the low voltage components in the unit and to the
thermostat.
6−Burner Control (A3) −5 units
All O 23, OHR23 and OF23 −5 units are equipped with a burn
er control R7184B manufactured by Honeywell. The burner
control, along with the matching cad cell, proves flame and
controls the burner. An LED on the control shows unit status.
See table 5 for status codes. After the cad cell closes a circuit
to the burner control, the burner control de−energizes the safe
ty switch heater to allow the unit to operate normally. When
there is a call for heat the control performs a 2 to 6 second
delay safety check. Once this is established a 15 second pre−
puge will follow. The valve then opens for a 15 second trial for
ignition. If flame is not sensed during the 15 second trial, the
control shuts down and must be manual re−set. After three
consecutive lockouts the control goes into restricted lockout.
Once flame is established after 10 seconds of run time, the ig
niiton shuts off.
If flame is lost during the heat cycle the control will shut
down the burner and begin a 60 second recycle delay. Af
ter 60 seconds the control repeats the ignition process. If
flame is lost three consecutive times during a single ther
mostat demand the control goas into restricted lockout.
Reset button
If the control lockouts three consecutive times the control
will go into restricted lockout. To reset control hold down
the reset button for 30 seconds until the LED flashes twice.
At any time the burner motor is energized, press and hold
the reset button to disable the buner. The burner will re
main disabled as long as the reset button is held and return
to operational once the button is released.
TABLE 5
LED
STATUS
On
Flame sensed
Off
Flame not sensed
Flashing
(1/2 sec on1/2 sec off)
Lockout /
Restricted Lockout
Flashing
(2 sec on 2 sec off)
Recycle
7−Heat Shutoff Relay (K125)
−1 and −2 units only
Heat shutoff relay K125 is a SPST N.O. relay, with a 24V
coil. K125 is located on the vestibule and wired in series
with the burner. When secondary limit S21 or primary limit
S10 open, the circuit breaks opening K125 contacts which
in turn de−energizes the burner.
8−Cad Cell (R26)
Together the cad cell and the burner control prove flame.
The cad cell senses the presence of burner light (less re
sistance) to close a circuit to the burner control.
IMPORTANT−Burner should not be installed so it is ex
posed to direct sunlight or electric bulb light. If the cell
is exposed to light on start up, the burner will not oper
ate.
O23, OHR23 & OF23 −5 Units Only
Resistance for the cad cell can be checked while the burn
er is firing and after ignition is off. Press (1/2 second or
less) and release the reset button. The LED will flash 1 to 4
times depending on the cad cell resistance. The cad cell
resistance should read less than 1600 Ohms. See table 6.
TABLE 6
O23, OHR23 & OF23 −5 UNITS
LED FLASHES
RESISTANCE
1
0 − 400Ohms
2
400 − 800 Ohms
3
800 − 1600 Ohms
4
1600 Ohms
