Adjusting The M-Series Air Tube Combinations

840-1-2The Beckett M-Series of air tube combinations were introduced in the mid-1980’s. Appliance designs were changing to improve efficiencies, the European-style boilers with more restrictive heat exchangers and “cooler” combustion chambers were being introduced. These appliance designs sometimes required an alternative to the F-type retention head design to optimize performance.

The key to the M-Series’ high performance is in their recessed head designs. Notice how the V head in Figure 2 is further back from the end of the air tube than the F head is in Figure 1. This protects the flame base and gives cleaner, more stable combustion in certain applications.

The M-Series designs use two styles of retention heads. The first style is the L1 head (for “locked” or “low”), which is locked in place and used on appliances with low firing rates. The second style is the V1 head (for “variable”). This head has a variable position, and is used for higher firing rates.

The M-Series can handle many different situations, but they must be adjusted correctly in order to provide the high performance of which they are capable. Proper adjustment is very important. To make set-up easier and right the first time, follow these step-by-step instructions regarding how to adjust the L1 (“locked”) head and the V1 (“variable”) head.

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ADJUSTING THE L HEAD: MA, MB, and MC Air Tube Combinations

  1. Be sure to shut off electrical power to the burner. If it is not already accessible, remove the burner from the appliance (or open the combustion chamber door, if applicable) so that you can access the end of the air tube.
  2. 840s2Loosen the splined nut and the 5/16″ hex head screw that holds the escutcheon plate in place.
  3. 840s3Using a Beckett T-500 of T-231 gauge, hold it so that you can read the inch markings. Line up the edge of the gauge with the leading edge of the L head, and move the nozzle line assembly until the end of the air tube is at the 1-3/8 inch mark (▼).
  4. 840s4Tighten the 5/16″ hex head screw and the splined nut. The “Z” dimension of your L head is now properly adjusted.

ADJUSTING THE V HEAD: MD, ME, MK, And ML Air Tube Combinations

  1. Be sure to shut off electric power to the burner. If it is not already accessible, remove the burner from the appliance (or open the combustion chamber door, if applicable) so that you can access the end of the air tube.
  2. 840st2Loosen the splined nut, acorn nut, and 5/16″ hex head screw.
  3. 840st3Move the adjusting plate assembly so that the “0” on the plate aligns with the mark on the housing, and tighten the 5/16″ hex head screw.
    NOTE: The copper fuel connector tube will need to be adjusted to match the nozzle line assembly position.
  4. 840st4Using the Beckett T-500 or T-231 gauge, hold it so that you can read the inch markings. Move the nozzle line assembly until the end of the air tube is at the 1-3/4 inch mark (▼), while the leading edge of the V head is lined up with the edge of the T-gauge.
  5. 840st5Tighten the acorn nut and splined nut. This fixes the “0” head setting position of the adjusting plate. The “Z” dimension of your V head is now properly adjusted at the “0” head setting.
    NOTE: After setting the “Z” dimension for the first time (or with a new nozzle line assembly), you will not need to do anything further with the acorn nut.
  6. 840st6To change the head setting for different firing rate, simply loosen the splined nut and 5/16″ hex head screw only. Adjust the nozzle line assembly by pulling the adjusting plate outward and positioning it to the desired numerical setting. Re-tighten the splined nut and 5/16″ hex head at the new setting.

Pro Tip

Many experienced servicemen have found it useful to mark their “Z” dimension location on the burner itself when using the F-type or L1 heads. After adjusting the nozzle line assembly, simply mark the escutcheon plate’s location on the burner housing with a marking pen, sharp screwdriver, or any other marking or etching device. The next time you need to move or remove the nozzle line assembly, you will not have to remove the burner to reset the “Z” dimension (unless you change the nozzle line assembly).