DJM2.4 MANUAL
10 Oct 00 R2
SLOW FLASH There is a heat call but the heat switch is open. (HS terminal).
IRREGULAR FLASH Terminals SV and SR are jumpered. The unit is in service mode.
LED 3 (Flame Relay or Ignition Enabled)
OFF The flame relay or ignition control device is not energized.
ON The flame relay or ignition control device is energized. The ignition
control device now has the responsibility to light the pilot flame, prove
the pilot flame, and energizing the main valve.
IX. BASIC BURNER OPERATION
Blower and Dampers
The DJM2.4 has no control of the dampers and supply air blower. They will be controlled by devices
external to the DJM2.4.
Burner
The basic burner-operating scheme is as follows.
1. Nothing happens until there is a call for heat and all the required heating operating conditions
are met. (Example: heat switch turned on.)
NOTE: During Service Mode operation or safety operation, this step is ignored.
2. When a heating call is received, before the combustion air blower is allowed to start, the
combustion blower tachometer (Hall effect speed sensor) is checked for a false signal. If no
signal is present, the combustion air blower is started.
3. After the combustion blower is started, the DJM waits until the blower reaches the correct pre-
purge speed (Approximately 3450 RPM).
4. When the correct speed is obtained, the pre-purge time delay is started. While the combustion
fan is operating in the pre-purge mode, the heat exchanger is purged of any unwanted gases
that may be present.
5. After the pre-purge cycle is complete, the combustion blower speed slows down to an
intermediate ignition speed. (For the standard round burner this is 2700 RPM, for the
rectangular high turndown burner is 2300 RPM.)
6. The DJM2.4 relay contacts across DJM2.4 terminals “CFR” and “FR” close to allow the flame
relay or ignition control device to be energized. The flame relay or ignition control device lights
the pilot by activating a spark and opening the pilot solenoid valve (which receives it's power
from the ignition control and the power passes through the DJM2.4 contacts "PV1" and "PV2").
The ignition control proves the pilot flame and then energizes the main gas valve. At the same
time the main gas valve is energized, a "feedback" signal is fed to the DJM2.4 on terminal
"VFB24" or “VFB120” depending on the gas valve voltage.
NOTE: At all times the combustion blower speed is continuously monitored. If any
problem is detected, the burner is shut off and the control logic goes to step 3.
To Next Page
Loading...
