dunphy TAD4, Operating Manual

Page: 53 / 165

Operating Instructions For TD/TAD4 Dual Fuel Burner
June 13 53 of 165 TD/TAD4 Manual Rev 4
5.2 Start -up Sequence
When a fuel selection is made and the ‘burner select’ signal is given to start up the burner, the
controller performs the sequence described below. If a gas profile is selected and the safety valve
proving function is selected, the controller will perform safety valve pressure proving concurrently
with the start-up sequence.
State
no. State name Description
0.
Non-volatile
lockout
All fuel valve outputs are OFF and the Alarm output is ON until
muted. The burner is held in this state until all faults are
removed.
1.
Burner off
The burner is checked to make sure that it has switched off
completely. Testing includes - main fuel safety valves closed, no
flame signal and no air pressure’ signal. The controller will
remain in this state until there is a call for heat from the PID
system.
2. Wait for purge The controller waits for both a burner select (PE9 ON) and a
fuel/air profile to be selected. Progression to stage 3 or 5 maybe
held off by external influences, e.g. Digital Communications
control or digital input controlled by an external circuit.
3. Open fuel valve If gas firing and safety valve proving are selected, the gas valve
servo motor is moved ‘open’ for five seconds to allow any gas
in the test section to be vented easily during the proving
sequence.
4. Hold fuel valve The fuel motor is held in position until step 1 of the safety valve
proving sequence (open main valve 2, or vent valve) is
completed.
5. Prove closed
positions If gas is selected, the gas valve proving sequence begins. The
fuel and air motors are moved to closed position until they stop.
The final positions are compared with the closed positions
stored in memory when the profile is commissioned.
6. Prove air
pressure The burner motor output is set ON and air pressure prove time
(t1) is initiated. The selected motors are moved ‘open’ towards
the purge position. If the ‘fan start early’ option parameter has
been set then the motors will not move until the option time has
expired.
7. Prove purge
positions When the air pressure prove time has elapsed, the air pressure
switch must give a ‘pressure’ signal or the controller will
lockout the burner and move to stage 0. If primary air is
selected, then both primary and secondary air pressure signals
must be ON to prove air pressure. The selected motors are
driven ‘open’ until they reach their commissioned purge
position.