BURNER CONTROL and OPERATION
AIR CONTROLS
Air Regulator
The flow of combustion air into the burner is controlled by a multiple-aperture rotary type damper,
fitted to the burner casing within the air inlet silencer on the right hand side of the burner.
Air Damper Motor
In all cases, the air damper is controlled by a servomotor containing adjustable limit switches for the
low and high fire positions.
The single spill-back burners employ a Landis & Staefa SQM10 motor, as shown on Page 11. This
motor activates the damper through an adjustable cam and cable system, and is mounted above the
air inlet on all models.
Air Diffuser
The air diffuser is fitted to the front of the burner assembly, within the flame tube (refer to the
Appendix). This diffuser controls the combustion air flow and creates a pressure drop across the
burner head, promoting good fuel/air mixing and flame stability.
Air Pressure Switch
The air pressure switch is located on the left side of the burner casing. Its function is to ensure that
combustion air flow is adequate under all operating conditions.
Air flow failure at any stage beyond the first few seconds of the pre-purge sequence will result in
burner lockout.
GAS CONTROLS
A typical gas train fitted is shown on page 12.
High Gas Pressure Switch
A high gas pressure switch is fitted at the outlet of the gas train to ensure that any increase in gas
supply pressure above the level needed to maintain the set conditions results in a safe burner
shutdown. In most cases, high gas pressure would indicate a fault with the air/gas ratio controller.
The pressure switch, which is fitted with an illuminated fault indicator and manual reset button, is
factory set to the maximum value. Final adjustment of the setting of this switch is described in the
section on Commissioning.
Low Gas Pressure Switch
Provision of a low gas pressure switch is required by European Standard EN676 – Automatic forced
draught burners for gaseous fuels. The pressure switch is fitted to all burners which carry the CE
marking but it may not be fitted to non-CE marked burners.
The low gas pressure switch monitors inlet gas pressure and ensures that any decrease in gas
pressure below the value needed to maintain satisfactory combustion results in a safe burner
shutdown. Final adjustment of the setting of this switch is described in the Section on Commissioning.
Gas Valve Train
In addition to the pressure switches noted above, the gas control train includes an air/gas ratio
controller, automatic safety shut-off valves and a governor in the start gas line. A manual isolation
valve must be fitted at the inlet to the gas train during installation. This valve must be in the closed
position when firing the burner on oil.
.
MDFL 3300 & MDFL 4000 Issue 2 08/08
Page 10
Summary of Contents for MDFL 3300
Page 16: ...MDFL 3300 MDFL 4000 Issue 2 08 08 Page 15 VALVE PROVING SYSTEM LDU 11 Standard fitting...
Page 30: ...MDFL 3300 MDFL 4000 Issue 2 08 08 Page 29 MODULATING CAM BOX...
Page 43: ...Electrode Setting Details MDFL 3300 MDFL 4000 Issue 2 08 08 Page 42 All dimensions in mm...
Page 48: ...NOTES MDFL 3300 MDFL 4000 Issue 2 08 08 Page 47...
