North American Tempest® High Velocity Burner Operation
a flame (UV) is detected. This can be a problem when the controller responds to the spark but there is no actual flame. For this reason, it is often necessary to use additional timers and relays to prevent premature shut down of the spark igniter. Halfwave ignition transformers will prevent UV sensing of the spark during trial for ignition, but they supply lower amperage to the igniter with produces a cooler spark that may not reliably ignite burners over as wide a range of inputs or air/fuel ratios as a conventional transformer.
PRINCIPLES OF CONVENTIONAL 4441 OPERATION
On most 4441 burners the air enters the burner from the back and is distributed around the outside of the stabilizer cup. Fuel is also connected to the back of the burner, but on the centerline. The fuel enters the inside of the stabilizer cup, where the first small amounts of air is added to the fuel. An ignition spark starts the combustion process, and the base of the flame stabilizes inside the cup. Additional air is added in multiple stages to the fuel and flame as it moves through the burner towards the tile exit. This air staging helps to keep the flames oxygen content low, and the air that flows around the stabilizer cup and flame helps to control the temperatures inside the burner. Because the flame burns in the stabilizer cup and inside the tile it can be monitored with a flame supervision system. Before the flame leaves the burner, the tile tapers to a nozzle which increases the flames velocity as it exits the tile. The final fuel / air reaction happens in the furnace where the high velocity flame entrains furnace gases into the burning flame envelope.
— Relight: Tempest® burners require spark for re-ignition. They will not relight reliably from a hot tile or furnace.
— Control: Excellent performance with all control systems; StepFire™, on-ratio and fuel-only turndown. A limiting orifice valve must be installed in gas supply line within 1 ft. (30 cm) of burner (generally the closer the better). A ratio regulator should ideally be within 4 ft. (122 cm) of burner. Even in cases where a motorized valve is used for fuel control, a limiting orifice valve that takes at least 10"w.c. (6 osi) of pressure drop must be installed close to the burner. Failure to install the valve could cause stability problems as the gas flow is modulated.
4441 OPERATION INSTRUCTIONS
— Combustion Air: 00.3-41.6"w.c. (0.08-10.3 kPa) air pressure, max 350°F (177°C). Most sizes are available in a hot air version that can operate with 800°F (427°C) combustion air. Sizes -3 through -4-B are available as standards and special versions of the larger sizes are available but without complete flow documentation. — Fuel: Natural gas for all burner sizes, propane gas versions are available in the -1 thru -4-B sizes. Gas pressure varies per size with 19"w.c. (4.7 kPa) is maximum required at design capacity, for 27.7"w.c. (6.9 KPA) combustion air pressure, at stoichiometric ratio. — Flame Supervision: Flame rod or UV detector Consult National Safety Standards and insurance underwriters for specific flame supervision requirements. Flame supervisory components must be ordered separately. See the parts list table for correct flame rod part number. — Ignition: Direct spark (no pilot) with 6000 V transformer. Lighting not recommended above 27.7"w.c. (6.9 kPa) main air pressure. Always energize the spark before the gas or with the gas as the flame lights most reliably in an excess air condition as the gas transitions from off to its set point. On systems that use UV flame supervision, UV radiation generated by the spark igniter can often be “seen” by the UV detector through reflection off the burner internals or the burner tile. Many flame relay controls turn off the spark when
< 1.0'
Limiting Orifice Valve
— Piping: In cross-connected systems, the design, selection, and system installation must consider pressure drop through the components to avoid excessive pressure drop in the gas line between the ratio regulator and the burner. Consider the gas pressure required at the burner to achieve the desired heat release (i.e. gas flow). For more detailed information on cross- connected control systems, see Sheet 7218-2 Instructions, Bulletin 7216 and the Practical Pointers Book. — “A” tiles: 4441 burners with the “A” style self-supporting tiles may be shipped with the tiles separate from the burner mounting to prevent tile damage. Attaching the tiles in field conditions is relatively easy. See Sheet 4441-2 which ships with “A” series burners for detailed instructions.
Bulletin 4441 page 3
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