Burnham Series 5B - Manual (Page 54)

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and the relay will lock out on safety within
15 seconds.
Assuming the pilot on the opposite side is
burning, the gas valves on that side will
open and main flame will be ignited on that
side only.
7
. EP CONTROL SYSTEM – 5006B thru 5014B
The EP Control System utilizes an 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 continues as long as there is a “call for
heat” (intermittent electrically ignited pilot).
The RM7890A Relay Module 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 valves to open on “call for heat” for that will shut
down main burners within 0.8 second if pilot flame is
not “proved”. Relay Module will lockout 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 Manual Main Shut-off Valve and
all Pilot Valves have been off for at least five
minutes.
(2) Set Operating and Limit Controls to desired
settings.
(3) Turn Manual Main Shut-off Valve and Pilot
Valve to Open Position.
(4) Turn on Main Electric Switch and Service
Switch – Pilot will automatically light main
burners.
SEQUENCE OF OPERATION EP - See Fig. 48
b. NORMAL OPERATION - 5006B thru 5014B
(1) When the operating control calls for heat,
terminal #6 of RM7890A Relay is energized.
(2) A component check circuit in the RM7890A
Relay is activated which, checks the electronic
network in the relay.
(3) Terminals #8 and #10 of the relay are energized.
Terminal #8 opens pilot line solenoid valve
supplying gas to pilot. Terminal #10 energizes
ignition transformer creating electric spark
ignition at pilot.
(4) Flame rod circuit between Q179C pilot and
RM7890A proves presence of pilot flame
electronically.
(5) Terminal #10 to ignition transformer is de-
energized.
(6) Terminal #9 is energized and supplies power to
the main gas valves.
(7) Main gas valves open and main burners are
lighted by pilot.
(8) When operating control is satisfied, terminals
#6 and #9 are de-energized. Main Gas Valves
and pilot line solenoid valve are all de-energized
and main burner 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 in relay is interrupted thus de-energized
terminal #9 and #8 in relay which de-energizes
main gas valves and pilot valves. Main gas
burners and pilot burners are immediately
extinguished. Normal operation can be resumed
when the cause of safety switch malfunction
is corrected. Make sure all manual resets are
activated where involved.
(2) PILOT FAILURE
(a) Pilot failure can occur during the start of
operating cycle of the boiler. Any pilot
failure, on the Q179C electronic pilot, after
ignition of pilot flame will close the main
gas valves in 0.8 second.
(b) For 15 seconds after failure of the Q179C
pilot, the relay through terminals #8 and #10
will try to establish pilot flame. If not pilot
flame can be sensed by the flame rod circuit,
terminal #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.
SecTiON iV - OPeRATiON (continued)