Burnham K50 manual Safety Switch Circuit, Pilot Failure

5.EO CONTROL SYSTEM – 5006B thru 5014B

The EO Control System utilizes an RA890F Protectorelay and a Q179D Rectification Pilot (standing or continuous burning pilot) to which has been added a Q309 thermocouple. The RA890F Protectorelay

Primary Control is a non-programming, amplifying relay which, when used with the Q179D Pilot, provides solid state electric Flame Safeguard Protection during a “call for heat” pilot failure. Main burners will

shut down within 0.8 second and the Protectorelay will lock out on safety shutdown within 15 seconds. Should a pilot failure occur during the “off” cycle, the thermocouple in the Q179D pilot will cool and, within 45 to 90 seconds, will cause the L62GB-3C Pilot

Safety Switch to which it is connected, to break the electrical circuit to the main gas valves, as well as shut off the flow of gas to the pilot. Thus, 100% shut-off is achieved.

a. LIGHTING INSTRUCTIONS

(1)Make sure Manual Main Shut-off Valve and

Pilot Valve have been off for at least five minutes.

(2)Set Operating and Limit Controls to desired setting.

(3)Turn on Main Electric Switch and Service Switch.

(4)Turn Pilot Valve to Open Position.

(5)Depress button on L62GB-3C Pilot Safety

Switch and hold lighted match to pilot, holding button in for one minute or until pilot remains lighted after button is released.

(6)Press reset button on RA890F relay.

(7)Open Manual Main Shut-off Valve – main burners will light.

Proceed to Paragraph 15- Minimum Input Adjustments (for diaphragm “Lo-Hi-Lo” or motorized type gas valves)

SEQUENCE OF OPERATION EO – see Fig. 46

b.NORMAL OPERATION – 5006B thru 5014B

(1)When the operating control calls for heat, terminal #6 of RA890 Relay is energized.

(2)A component check circuit in the RA890 Relay is activated which checks the electronic network of the relay.

(3)Flame rod circuit of the RA890 and Q179D proves presence of pilot flame electronically.

(4)Terminal #5 is energized and supplies power to the main gas valves.

(5)Main gas valves open and main burners are lighted by pilot.

(6)When operating control is satisfied, terminals #6 and #5 are de-energized, Main Gas Valves close and main burners are extinguished.

(7)The pilot continues to burn.

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- energizing terminal #5 in Relay. Main Gas Valves are thus de-energized and main gas burners are immediately extinguished. The pilot will continue to burn. 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)Flame rod supervision of pilot occurs only during the operating cycle (call for heat) of the operating control since the RA890 relay is only energized by the operating control.

If failure occurs during this period, the main gas valves close and the main gas burners are extinguished within 0.8 second. After

15 seconds the relay will lock out on safety shutdown.

(b)If the pilot failure occurs during the “off” cycle of the operating control, the RA890 relay will not be powered thru terminal #6, therefore, there is no electronic flame rod supervision. This is due to the utilization of a thermocouple in the Q179D modified pilot. This thermocouple will cool in 45 to 90 seconds allowing the pilot line safety valve to close. This shuts off the flow of gas to the pilot. It is in this manner that 100% shut-off is achieved. If the operating control calls for heat during this period the RA890 relay will immediately sense “no flame” on pilot and will lockout as described in paragraph (a) above.

d.SHUTDOWN INSTRUCTIONS

(1)Close manual shut-off valve and pilot valve.

(2)Turn off main electric switch.

6.EO CONTROL SYSTEM 5015B thru 5026B

The 5015B thru 5026B boilers utilize two EO Control

Systems that are interconnected electrically thru all operating and safety controls. Should any of the aforementioned controls break the power supply circuit, both EO control systems would be de-energized. The succeeding paragraph describes the function and operation of each EO Control System. Should a pilot failure on one EO Control System occur, the other EO 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 EO Control System utilizes an RA890F Protectorelay and a Q179D Rectification Pilot (standing or continuous burning pilot) to which has been added

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