Electrical And Sequence Of Operations; Control Differential - Burnham LEDV SERIES Installation & Service Instructions Manual

V. Electrical and Sequence of Operations
A
. ELECTRICAL
1. Install wiring and ground boiler in accordance with
requirements of authority having jurisdiction, or in
absence of such requirements the National
Electrical Code, ANSI/NFPA 70, and/or the CSA
C22.1 Electric Code.
2. A separate electrical circuit should be run from the
main electrical service with a fused disconnect
switch in the circuit.
3. Wiring should conform to Figure 15.
B
. SEQUENCE OF OPERATIONS
1. General. A call for heat by the thermostat
energizes the L8148A limit control which in turn
energizes the R8184P primary control to turn on
the burner. The circulator will operate as long as
there is a call for heat. If the call for heat is not
satisfied and the high limit setting is reached, the
circulator will continue to operate, and the burner
will stop until the high limit circuit is closed by a
drop in boiler water temperature.
2. L8148A Combination Limit control.
The switching action within the L8148A control
has one setting, the high limit. The switching relay
is controlled by the low voltage room thermostat.
On a call for heat, the relay contacts close to
complete the line voltage circulator circuit and also
the burner circuit if the boiler water temperature is
below the high limit setting. The high limit switch
shuts off the burner if boiler water temperature
exceeds the high limit setting. See Figure 14.
3. R8184P Oil Primary Control.
The R8184P operates the oil burner motor, solenoid
oil valve, and the ignition transformer in response
to a call for heat from the L8148A limit control.
a. A call for heat will energize the burner motor
and ignition transformer.
b. After a 15 second pre-purge period, in which
time a draft is established in the flueways, the
oil valve is opened.
c. If the burner ignites within 15 seconds from the
time the oil valve opens and the CAD cell senses
a flame, the burner will operate until the call for
heat is satisfied or the setting of the high limit is
reached.
d. A manual reset button is provided to reset the
safety switch after lockout.
e. When the call for heat ends, or the CAD cell
fails to sense a flame, the oil valve will close.
The combustion blower will continue to operate
for a postpurge period of approximately two (2)
minutes.
4. CAD Cell.
The Beckett AFII burners used on the LEDV Series
are supplied with a C554A Cadmium Sulfide (cad
cell) Flame Detector to monitor the burner flame
and shut down the burner on ignition failure or on
flame failure during the run cycle. On either
failure, the manual reset button on the R8184P will
be tripped.
Figure 14: Control Differential
18