User guide

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satised.
 TheEPControlSystemutilizesandRM7890ARelay
ModuleandaQ179CRecticationPilot,whichin
additiontoapilotburnerandrectifyingamerodame
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ameisproven,ignitionstopsbutpilot
ame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ameisnot“proved”.
Relay Module will lock out on safety shutdown within
15secondsifthereisapilotamefailureonstartor,if
duringthe“run”cycle,pilotame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ve
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ame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ames.
8.Whentheoperatingcontrolissatised,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ames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)