Burnham Series 5B - Manual (Page 52)

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failure on one OP Control System occur, the other OP
Control System would not be affected. Thus main
burners on the unaffected side would ignite on a “call
for heat” and would continue to operate until the
operating control was satisfied.
The OP Control System utilizes an RM7890C
microprocessor based integrated burner control and
a Q179D Rectification Pilot (standing or continuous
burning pilot) to which has been added to a Q309
Thermocouple. The RM7890C Primary Control is a
non-programming, amplifying relay which when used
with the Q179D Pilot provides solid state electronic
Flame Safeguard Protection during a “call for heat”
pilot failure. Main burners will shut down within 0.8
seconds and the RM7890C will lock out on safety
shutdown within 15 seconds. Should a pilot failure
occur during the “off” cycle, the thermocouple will cool
and within 45 to 90 seconds, will cause the L62GB-3C
Pilot Safety Switch to which it is connected, to break
the electrical circuit to the main gas valves as well as
shut off the flow of gas to the pilot. Thus 100% shut-
off is achieved.
a. LIGHTING INSTRUCTIONS
(1) Make sure all Manual Main Shut-off Valves and
all Pilot Valves have been off for at least five
minutes.
(2) Set Operating and Limit Controls to desired
settings.
(3) Turn on Main Electric Switch and Service
Switch.
(4) Open pilot valve on one side of boiler. Depress
button on L62GB-3C Pilot Safety Switch to
which it is connected and light pilot with match.
Continue to hold button in for one minute
or until pilot remains lighted after button is
released. Light pilot on opposite side of boiler
using same procedure.
(5) Press reset button on each RM7890C relay.
(6) Open Manual Main Shut-off Valves – main
burners will light.
Proceed to Paragraph 15 - Minimum Input
Adjustments (for diaphragm “Lo-Hi-Lo” or
motorized type gas valves)
SEQUENCE OF OPERATION OP – See Fig. 47
b. NORMAL OPERATION – 5015B thru 5026B
(1) When the operating control calls for heat,
terminal #6 of each RM7890C Burner Control is
energized.
(2) A component check circuit in each RM7890C is
activated which checks the electronic network of
the relay.
(3) Flame rod circuit between each Q179D pilot and
terminal “11” on its respective RM7890C proves
presence of flame electronically at its Q179D
pilot.
(4) Terminal #9 on each RM7890C is energized
supplying power to its respective main gas
valves.
(5) Main gas valves open and main burners are
ignited by the pilot flames.
(6) When operating control is satisfied, terminals
#6 and #9 on the RM7890C relays are de-
energized, main gas valves close and main
burners are extinguished.
(7) The Q179D pilots continue to burn.
c. SAFETY SHUTDOWN
(1) SAFETY SWITCH CIRCUIT
If limit control, Low Water Cut-off or any
other electrical safety switch opens, power
to terminal #6 and all other terminals on both
RM7890C relays are interrupted. Main Gas
Valves are thus de-energized and main gas
burners are immediately extinguished. Standing
pilot flames in the Q179D pilots will continue to
burn.
(2) PILOT FAILURE
(a) Flame rod supervision of the Q179D pilots
occur only during the operating cycle (call
for heat) since it is during this period that
the control is energizing the RM7890C
relays. If pilot failure occurs during this
period on one of the Q179D pilots, the main
gas valves controlled by that particular
RM7890C will close in 0.8 seconds. The
RM7890C will lockout on safety within 15
seconds. The burners controlled by the other
RM7890C will continue to burn.
(b) If pilot failure occurs on one of the Q179D
pilots during the “off” cycle of the operating
control, there will be no electronic flame rod
supervision since neither RM7890C relay
is energized during the “off” cycle. This is
due to utilization of a thermocouple in each
Q179D modified pilot which controls its
own pilot safety switch. This thermocouple
will cool in 45 to 90 seconds de-energizing
the pilot safety switch, which interrupts
the circuit between terminal #9 and the gas
valves and also shuts off the flow of gas to
the pilot. Thus 100% shut-off is achieved.
If the operating control calls for heat
during this period, the RM7890C relay will
immediately sense “no flame” on the pilot
SecTiON iV - OPeRATiON (continued)