EngA ENGINEERED AIR DJM2.4, Installation, Operation And Maintenance Manual, Page: 27 / 37

DJM2.4 MANUAL
27 Oct 00 R2
above, the temperature rise would only be about 80 degrees to give a final discharge
temperature of about 50
° at about 11,800 CFM at high fire.)
Improper Burning

Plugged 12 AO6 vent orifice ( on units equipped with one on regulator ).

Modulating valve sticks.

Incorrect burner setup.
Improper Burning After Changing Combustion Motor Or Fan
If the fan is located at a different spot on the motor shaft, it changes the airflow pattern and
quantity. The quantity is changed by the size of the gap changing around the fan inlet. This
allows more or less air to “leak” from the fan discharge side back to the fan inlet.
Temperature Swings and Temperature Control Issues
If the DJM2.4 is a slave to a C-TRAC and temperature swings are evident, refer to notes in section
XVIII about “DJM2.4 Slaving From C-TRAC” for proper control set up parameters.
Next, re discharge air temperature sensor location: Engineered Air mounts the discharge air
temperature sensor in the unit at the time of manufacture. This has been successful in
eliminating loss of sensors when they are shipped loose to be field mounted. In some
applications due to air flow patterns created by many factors (including duct layout) this location
may not represent an average duct temperature. Most discharge temperature sensors can be
relocated into the duct work to correct problems of temperature stratification, etc.
Last but by no means least is the application of a BMS sensor in the discharge by a control
contractor. Engineered Air suggests that both our sensor and the BMS sensor should be located
within ½” of each other. If this is not done there can be great discrepency in the readings
between the two sensors. Also if there is a discharge air temperature duct sensor from the BMS it
should only be used to transfer the duct temperature to the computer screen and / or activate
desired alarms. DO NOT --- repeat DO NOT program the BMS discharge duct temperature sensor
to do any reset functions on Engineered Air controls that are operating in a discharge sensor
mode. (controls such as C-TRAC, M-TRAC, G-TRAC, DJM, H-TRAC etc) BMS reset can only be
performed from room, return air or ambient sensor locations.
Ignition Failure During Morning Start Up
What happens if ignition fails on morning start-up?
The following is a generalization of what the DJM2.4 lights do.

If heat call light comes on:

Combustion fan starts, purge light comes on.

Purge cycle completes - purge light goes off.

Ignition enable light comes on.

Now if ignition failure occurs:

Ignition enable light stays on.