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Preferred Instruments

Preferred Instruments manufactures microprocessor based controllers, instruments, and electric actuators for combustion and process applications. Preferred Instruments also manufactures oil tank gauging and leak detection equipment. A major component of the Instrument group sales is from control systems integration and personal computer based Supervisory Control and Data Acquisition systems. Preferred Utilities' industrial factory is located in Danbury, CT

Quanta Flame 5004-M Flame Safeguard Controller

This flame safeguard controller is designed for single burner process heat applications such as ovens, furnaces, kilns, and dryers. The controller accepts one or two scanners per burner. Unlike other flame safeguard controllers that require a multitude of amplifiers, programmers, and purge timers, the Preferred 5004-M has just one processor with a built-in universal amplifier that accepts UV, self-checking UV scanner inputs, as well as flame rod inputs. In addition, Purge times and Main Trial For Ignition (MTFI) times are field-selectable.


Controller Functions

False Flame Detection: The controller will Lockout if flame is detected during Standby or Purge.

Safe Start Check: During every burner startup sequence, the controller performs hardware & software self-tests to verify it’s internal circuitry is functioning properly. The controller verifies the safety relay, ignition relay, pilot relay, and the main fuel valve relays are functioning properly. If the “check for power failure” function is selected and power was interrupted during a firing cycle, upon power up the control will Lockout.

Check for Limits Bypassed: If the “Check for limits bypassed” function is selected, before beginning Purge, the controller ensures the Limits Made input is de-energized, and waits for up to 60 seconds for the Limits Made input to be de-energized. (The fan motor starter interlock and minimum air pressure switch should not be made before the fan is powered. This function will detect if these limits have been bypassed.)

Proof of Valve Closure (POVC): The controller will Lockout if the main fuel valves are not proven closed during Standby, Purge and Pilot Trial for Ignition (PTFI). The controller will also Lockout if the main fuel valves close when the burner is firing.

Proven High Fire / Purge: Proves that the high fire position and purge air flow interlocks are made before Purge can begin, and requires these interlocks to be made throughout the Purge period. If these interlocks open during the Purge period for more than 30 seconds (cumulative), the controller will lockout. If running interlocks are not made continuously throughout the Purge period, the control will lockout after 5 minutes. This ensures a proper Purge cycle.

Proven Low Fire / Ignition: Proves the low fire position prior to Ignition and light off of the burner. If low fire proving switch is not made within 5 minutes the control will Lockout.

Selectable Pilot Trial for Ignition (PTFI) Time: DIP switches allow selection of a 3, 5, or 10 second timing.

Early Spark Termination / Pilot Verification: The ignition transformer spark is de-energized at the end of PTFI while the pilot valve continues to be energized for 5 seconds before the main fuel valves are energized. This ensures the sensor is not recognizing spark as a (false) flame and the pilot flame is stable without a spark, before lighting the energizing the mail fuel valves.

Selectable Main Trial for Ignition (MTFI) Time: The default MTFI time is 10 seconds. Some No. 6 oil burners may require a 15 second MTFI to allow extra time for the cold oil to flow to the burner. Energizing terminal 27 changes the MTFI time from 10 seconds to 15 seconds.

Pilot Test Mode: In this mode, after the completion of PTFI, the ignition transformer is de-energized, the pilot valve remains energized, and the controller will not attempt to open the main fuel valves. If the flame sensor stops detecting a flame the controller will Lockout. This mode permits the technician to examine and adjust the pilot flame.

Modbus Communications: The operation of the 5004-M-85 can be monitored via the RS485 Modbus communications link. Modbus also provides access to the Historical Data in the 5004-M: the last 6 Lockout reasons, burner Run hours, and burner Start cycles.


  • Interfaces to ultraviolet, ultraviolet self-check or flame rod sensors.
  • Single or Dual Flame Sensors
  • Field Selectable Purge Time
  • RS485 Modbus Communication
  • Plug-in Field Wiring Terminals
  • Remote/Local reset from Lockout state



Enclosure: 7” L x 5” W x 2” D

Weight:  2 lbs

Operating Temperature:  -40° F to +140° F (-40° C to +60° C); UV scanners -20° C to 60° C


Voltage: 120 VAC +10% – 15%, 50/60 Hz

Power Consumption:  2 VA

Flame Failure Response Time: 2.5 to 3.5 seconds

Purge Time: 30, 60, 90, 150, 180, 300, 450, or 900 seconds (DIP switch selectable)

Pilot Trial for Ignition Time: 3, 5, or 10 seconds (DIP switch   selectable)

Flame Sensor Inputs (2): Ultraviolet, Flame Rod


Microprocessor Flame Safeguard Controller: Controller shall be U.L. recognized for single burner boiler applications. It shall accept inputs from one or two flame detectors without external circuitry. The controller shall be capable of accepting inputs from ultraviolet, self-checking ultraviolet, and flame rod detectors without changing controller hardware. Purge timing, Pilot Trial for Ignition (PTFI) timing, and other control functions shall be DIP switch selectable.

Flame Safeguard Controller Hardware: Controller and included flame amplifier circuity shall be microprocessor-based and include the following as a minimum:

  • Removable LCD display for status information and trouble-shooting
  • Optional remote display
  • Sequence status LEDs on the controller faceplate including Start Limits (green), Fan On (yellow), Pilot (yellow), Main (yellow), Flame Fail (red), Safety Interlock (red),  Alarm (red) Power (red), Flame (red), Low Fire (green), High Fire (red), Automatic (yellow)
  • Plug-in field wiring terminals
  • Test jacks for direct flame intensity measurement (0-5 VDC)

Flame Safeguard Functions: The controller shall cycle the burner from Standby, through Purge, supervised Pilot Trial for Ignition, Main Flame Trial for Ignition and Release to Modulate states. De-energization of pre-ignition interlocks, running interlocks, or loss of flame signal shall result in the safe shutdown of the burner. Additional control functions shall include:

  • False Flame detection during Standby and Purge modes.
  • Field selectable check for limits bypassed during startup.
  • Field selectable Lockout or Recycle on loss of AC power.
  • Field selectable Purge timing from 30 to 900 seconds (by DIP switch).
  • Field selectable Pilot Trial for Ignition (PTFI) timing from 3 to 10 seconds (by DIP switch)
  • Field selectable Main Trial for Ignition (MTFI) timing (by powering digital input)

Digital Communication: The flame safeguard controller shall be capable of Modbus RTU communications via RS-485 bus.

Manufacturer: The flame safeguard controller shall be model 5004-M manufactured by Preferred Utilities Mfg. of Danbury, CT.