Burnham Series 5B Installation, Operating And Service Instructions page 56

a. OPERATING 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
setting.
(3) Turn all Manual Main Shut-off Valves and Pilot
Valves to Open Position.
(4) Turn on Main Electric Switch and Service
Switch. Pilots will automatically light main
burners.
SEQUENCE OF OPERATION EP – See Fig. 45
b. NORMAL OPERATION – 5015B thru 5026B
1. When the operating control calls for heat,
terminal #6 of each RM7890A is energized.
2. A component check circuit in each RM7890A is
activated which checks the electronic network of
the relay.
3. Terminals #8 and #10 of each RM7890A relay
are energized. Terminal #8 opens the pilot line
solenoid valve supplying gas to the Q179C pilot.
Terminal #10 energizes ignition transformer
creating electric spark ignition at the Q179C
pilot.
4. Flame rod circuit between each Q179C pilot and
terminal "11" on its respective RM7890A proves
presence of flame electronically at its Q179C
pilot.
5. Terminal #10 of each RM7890A and the ignition
transformer connected to it is de-energized.
6. Terminal #9 on each RM7890A is energized
supplying power to its respective main gas
valves.
7. Main gas valves open and main burners are
ignited by the pilot flames.
8. When the operating control is satisfied, terminals
6 and all other terminals on both RM7890A
relays are de-energized. The main gas valves
and pilot valve for each gas train are closed
and main burners and pilot burner flames are
extinguished.
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 RM7890A
relays are interrupted de-energizing the main
gas valves and pilot valves and the main gas
burners and pilot burners are immediately
56
SecTiON iV - OPeRATiON (continued)
extinguished. Normal operation can be resumed
when the cause of the safety switch malfunction
is corrected. Make sure all manual resets are
activated where applicable.
(2) PILOT FAILURE
(a) Pilot failure can occur during the start and
operating cycle of the boiler. Any pilot
failure on either of the Q179C Electronic
Pilots, after ignition of pilot flame will close
the pilot valve and the main gas valves
controlled by that particular RM7890A relay
in 0.8 second. The burners controlled by the
other RM7890A will continue to burn.
(b) For 15 seconds after failure of a Q179C
pilot, the relay through terminals #8 and #10
will attempt to re-establish pilot flame. If no
pilot flame can be sensed by the flame rod
circuit in 15 seconds, terminals #8 and #10
are de-energized, and the relay will lock out
on safety.
(c) Pilot failure is caused by the following:
(1) Complete loss of gas supply.
(2) Poor ignition spark caused by low
voltage, poor ground connection, faulty
wiring, and possibly a defective ignition
transformer.
(3) Low gas pressure will prevent flame rod
circuit from sensing pilot flame properly.
(4) Unusually strong secondary air drafts
can blow the pilot flame away from the
flame rod momentarily causing nuisance
shutdown.
(5) A pilot line solenoid valve will not open
because of faulty wiring, low voltage, or
possibly the valve is defective.
(6) A defective RM7890A may be the cause
but items (1) thru (5) should be followed
first. Refer also to RM7890A relay
literature furnished with the control.
(d) By referring to the Sequence of Operations
step by step operation of the system can
be controlled and the cause of pilot failure
can be readily found. After the cause of
pilot failure has been corrected, resume
normal operation by following the Lighting
Instructions.
(3) SHUTDOWN INSTRUCTIONS
(a) Close manual shut-off valves and pilot
valves.
(b) Turn off main electric switch.