DJM2.4 MANUAL
6 Oct 00 R2
III. GENERAL
The DJM2.4 is a programmed logic controller designed for use with the Engineered Air DJ series of
heaters. The DJM2.4 is designed to be backward compatible with the original DJM and DJM2
controllers. Like the original controllers, the DJM2.4 uses a variable speed combustion blower and
an electro-mechanical modulating gas valve (usually Maxitrol). The combustion blower speed and
the gas valve's flow rate are modulated based on temperature requirements and the programmed
operating curves programmed into the DJM2.4.
The major differences between the original DJM and the DJM2 are:
Improved temperature control.
Improved burner management logic.
Built-in status lights to assist with trouble shooting.
Ability to support the new high turndown burner (See Burner Selection on page 16).
Service Mode
NOTE: The DJM2.4 is a discharge temperature control. It is not primarily designed to
have a reset signal attached to it. The discharge set point can not be reset
from room, ambient, or BMS signals. It is not recommended but if a second
control is connected to the DJM2.4 it will respond to the control with the
greatest signal. If direct reset control is required, the DJM3 controller should
be used.
Basic Features
The basic features of the DJM2.4 include the following:
1. Proportional and Integral (PI) temperature control.
2. Can be used with the Johnson TE 6000 sensor and internal DJM2 set-point pot. It is not
compatible with the TE 6100 room sensor/set-point.
3. Has a provision for a heat switch. (Terminal HS needs 24 VAC from the same voltage source as H
for heat to operate. Jump H to HS if no heat switch is in circuit.)
4. Can be used with both standard and high turndown DJ burners simply by cutting a jumper wire.
(See Burner Selection on page 16).
5. Can be used with combustion blower motors up to 0.6 HP.
NOTE: The combustion fan motor is a special motor, and not just any motor will
work. It is a 3450 RPM PSC motor designed for modulation with CW rotation
shaft end.
6. Easier burner set up and trouble shooting. Features such as diagnostic indicating lights, service
pot, and test terminals are designed to assist service personnel.
7. To reduce ground isolation problems, optical isolation was added to the digital and BMS inputs.
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