25
Installation and operation manual
–
DTHR-V9-2020
Step 3 -
Pre-Purge (S40)
The blower starts and set to 100% of its capacity for about 60 seconds then a 10 seconds timer to let
the fan speed slow down before the burner ignition. When complete the
burner ignition
step is
enabled.
Step 4 -
Burner ignition (S60)
The blower speed is reduced to the ignition setting. The flame safeguard will light the pilot and then
the main burner. The
flame stabilization
is allowed once the burner status is received
Step 5 -
Flame stabilization (S70)
A 10 seconds delay is set to let the flame stabilize. Once the time delay is reached the
modulation
step is allowed and the modulation gas valve can operate.
Step 6
–
Modulation (S80)
With the burner in operation, the gas valve and the blower modulation begin. Modulating gas valve
and the blower follow the request signal value. According to the gas valve position the blower
modulates following an air/gas relation curve (pre-set into the PLC memory) to achieve an accurate
clean combustion.
Notice:
•
The unit model is pre-set at factory with the correct air/gas relation. You can fine tune
this relation on the PLC screen at the air/gas relation set-up page at level 1.
• The gas valve
input signal can be different from the heating demand (ex: heating
demand 8 Vdc can gives 7.1 Vdc to the gas valve) following a capacity curve.
•
If the burner modulation request signal is lower than 2.3VDC the
low fire
step is
enabled.
Step 7
-
Low fire (S90)
The burner is in low fire mode during about 240 seconds at a blower and gas valve fixed position. At
the end of the timer, the Post-purge step is enabled.
However
, if within the timer delay the burner modulation requests become greater than 2.3VDC,
the sequence returns to the
Modulation
step 6.
