dunphy TD - Page 120

Operating Instructions For TD/TAD4 Dual Fuel Burner
June 13 120 of 165 TD/TAD4 Manual Rev 4
Shortly after the start of «t1», the air pressure switch must change over from
terminal 13 to terminal 14.
- Otherwise lockout
- Start of air pressure check
At the same time, terminal 14 must be live since the ignition transformer will be
powered and the fuel released via this current path.
On completion of the prepurge time, the burner control will drive the air damper
to the low-fire position via terminal 10, which is determined by the changeover
point of auxiliary switch «m». During the positioning time, the sequence switch
stops again. A short time later, the motor of the sequence switch will be
switched to the control section of the burner control. This means that, from now
on, positioning signals delivered to terminal 8 have no impact on the burner’s
further startup sequence (and on subsequent burner operation):
t5 Interval
- On completion of «t5», power is fed to terminal 20; at the same time, control
outputs 9...11 and input 8 are galvanically separated from the unit’s control
section.
- The LFL1... is now protected against return voltages from the power
control loop.
- The startup sequence of the LFL1… ends with the release of «LR» at terminal 20
- After a number of idle steps (steps with no change of the contact position), the
sequence switch switches itself off
Expanding flame burners
TSA Ignition safety time
On completion of «TSA», a flame signal must be present at terminal 22. It must not
be interrupted until controlled shutdown takes place
- otherwise lockout
t3 Pre-ignition time
Release of fuel via terminal 18
t4 Interval «BV1 – BV2» or «BV1 - LR»
- On completion of «t4», terminal 19 is live
- That powers «BV2» connected to the actuator’s auxiliary switch «v»
Control sequence under fault conditions and lockout indication
In the event of any kind of fault, the sequence switch will stop and, with it, the lockout indicator.
The symbol above the indicator’s reading mark gives the type of fault: