A flame safety system is a combination of several sensors, valves, and a flame monitor computer to manage them all. The exact combination of these changes system to system, and more or less are required for different regions and for different uses and heat out puts. For example, the AGA codes for Australia are far stricter than the NFPA86 codes used for the US and require several more components and a more complex monitoring system.
Flame Monitor
The flame monitor is the brains of a flame safety system. It reads inputs from the various sensors, and sends output signals at the correct time. It decides when the valves are opened to let gas in, when the blower turns on, and when everything is shut down in case of an error.
Dungs/Eclipse MPA
This is the flame monitor we’ve used for the past 5 years. It has a display that shows error codes, and is programmable so that we can use it for several different systems. The MPA also has a communications function so that it can “talk” to our OnSite server, allowing remote access and explanations of error codes present.
Quick Displays:
Plus and Back: Error memory
Hold Reset for 4 seconds for hard reset, in case of F04 error
Plus and Reset: Info Display, UV Scanner Signal
Minus and Back: Resets display to normal
Veriflame
This is the flame monitor we used on equipment about 5 years old and older. It has several lights that indicate errors, and will flash an LED to indicate more error codes. It has a set of DIP switches inside that allow some different settings. While we no longer use the veriflame, we still sell replacements and repairs.
Other Components
Dual Valves
The dual valves are two solenoid valves that work together to ensure safety. When the MPA detects a fault from one of the sensors, it will close the valves. When the fault has been corrected and the system is reset, the MPA will open the valves and allow gas to the burner after the startup sequence. Also referred to as DSSOV, Dual Safety Shut Off Valves
UV Scanner
The UV scanner detects when flame is present and relays this information to the MPA. This can also be accomplished by a flame rod, which is less expensive but requires more frequent replacement and maintenance.
Air Pressure Switch
The air pressure switch detects whether the air line has pressure and relays this information to the MPA. No pressure indicates the butterfly valve has been closed or the blower is not functioning.
Gas Pressure Switches
The high and low gas pressure detect if the gas pressure is above or below their set points and relays this information to the MPA.
Sequence of Operations
1) System check: Safety shutoff valves should be closed, air pressure switch should be open (no a pressure detected), UV signal should not exist, and interlocks loop (consisting of high and low gas pressure switches, high limit switch, and any other switches such as a ventilation interlock or CO sensor)
2) Pre-purge: The blower alone is energized and purges the combustion chamber including ports and flues to clear any gas from the atmosphere. During this phase, the air pressure switch must sense air and close. The default pre-purge duration is 30 seconds, but essentially the entire interior volume of the equipment must be replaced 4-5 times (depending on regional codes) with fresh air during this period.
3) Trial-for-Ignition (TFI): If present, a pilot safety valve opens while the spark plug is energized: to ignite the flam, and the UV scanner is expected to detect a flame within 5-15 seconds depending on regional codes. If no pilot valve is used, the main safety shutoff valves will open at this time. In some cases, ignition is performed manually during the TFI. If no flame is detected within the TFI period, the system shuts down and must be reset.
4) Operation: If a flame is detected during the TFI, the main safety shutoff valves open, and the system will fire until it is interrupted by either the operator or the flame supervisor due to any system sensors becoming unsatisfied. If the flame signal is too weak or lost at any point, the system will shut down within 1-3 seconds depending on regional codes.
5) Shutdown: The Veri-Flame’s LED indicators and MPA’s digital display will indicate system status or error codes which can be cross-referenced in the troubleshooting section of this manual.
For more information, please refer to the component-specific manuals.
