Burnham Series 5B - Manual (Page 57)

57
(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
the 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.
8 . EP CONTROL SYSTEM – 5015B thru 5026B
The 5015B thru 5026B boilers utilize two EP control
systems that are interconnected electrically thru all
operating and safety controls. Should any of the
aforementioned controls break the power supply circuit,
both EP control systems would be de-energized. The
succeeding paragraphs describe the function and
operation of each EP Control System. Should a pilot
failure on one EP Control System occur, the other EP
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 EP Control System utilizes and RM7890A Relay
Module and a Q179C Rectification Pilot, which in
addition to a pilot burner and rectifying flame rod flame
detector to prove pilot, includes an ignition electrode
for spark ignition of the pilot. A Webster 612-6A7
Transformer supplies the high voltage spark potential.
Once pilot flame is proven, ignition stops but pilot
flame continues as long as there is a “call for heat”
(intermittent electrically ignited pilot).
The RM7890A Primary Control is a non-programming
amplifying relay which when used with the Q179C
Pilot provides solid state electronic Flame Safeguard
Protection that will not allow the main gas valve to
open on “call for heat” or that will shut down main
burners within 0.8 second if pilot flame is not “proved”.
Relay Module will lock out on safety shutdown within
15 seconds if there is a pilot flame failure on start or, if
during the “run” cycle, pilot flame is not re-established.
Since #8 terminal in the Relay Module is de-energized
at end of safety switch timing, a solenoid valve in the
pilot line will close and thus 100% shut-off is achieved.
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.
Proceed to Paragraph 15 - Minimum Input
Adjustments (for diaphragm “Lo-Hi-Lo” or
motorized type gas valves)
SEQUENCE OF OPERATION EP – See Fig. 49
a. 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.
b. 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
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
SecTiON iV - OPeRATiON (continued)