Burnham K50 manual Proceed to Paragraph 15- Minimum Input

burners on the unaffected side would ignite on a “call for heat” and would continue to operate until the operating control was satisfied.

The EE Control System utilizes and RA890F Protectorelay 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 RA890F Protectorelay 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” or that will shut down main burners within 0.8 second if pilot flame is not “proved”. Protectorelay 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 #3 terminal in the Protectorelay 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 settings.

(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.

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Adjustments (for diaphragm “Lo-Hi-Lo” or motorized type gas valves)

SEQUENCE OF OPERATION EE – See Fig. 50

a.NORMAL OPERATION – 5015B thru 5026B

1.When the operating control calls for heat, terminal #6 of each RA890F Protectorelay is energized.

2.A component check circuit in each RA890F Protectorelay is activated which checks the electronic network of the relay.

3.Terminals #3 and #4 of each RA890F relay are energized. Terminal #3 opens the pilot line solenoid valve supplying gas to the Q179C pilot. Terminal #4 energizes ignition transformer creating electric spark ignition at the Q179C pilot.

4.Flame rod circuit between each Q179C pilot and terminal “F” on its respective RA890F proves

presence of flame electronically at its Q179C pilot.

5.Terminal #4 of each RA890F and the ignition transformer connected to it is de-energized.

6.Terminal #5 on each RA890F 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 RA890F 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 RA890 Relays is 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

Pilots, after ignition of pilot flame will close the pilot valve and the main gas valves controlled by that particular RA890F relay in 0.8 second. The burners controlled by the other RA890F will continue to burn.

(b)For 15 seconds after failure of a Q179C pilot, the relay through terminals #3 and #4 will attempt to re-establish pilot flame. If no pilot flame can be sensed by the flame rod circuit in 15 seconds, terminals #3 and #4 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. 59