DJM2.4 MANUAL
16
Oct 00 R2
NOTE:
Our design discharge temperature range is 30 to 140ºF, with about 55-75
being the usual set point.
Maxitrol Discharge Sensor/Selector
If the system uses a Maxitrol set point, the set point is that indicated on the TD114 dial. There is
also a calibration pot on the back of the Maxitrol dial. Its correct setting is such that the
resistance across the Maxitrol terminals 1 and 3 should be 10,000 ohms with the set point at 77°F
(25°C). The Maxitrol TS114 temperature sensor (calibrated to 10,000 ohms at 77 degrees also)
changes about 40 ohms per °F. As the sensor gets hotter, the resistance falls. If there is a long
wire run it may be best to calibrate the dial against a known sensor temperature due to wire
resistance.
XIV.
BURNER SET UP
Burner Selection
The DJM2.4 is designed for use with either the standard circular DJ burner or the rectangular
shaped high turndown burner. Turn the board over to the backside. There is a jumper wire
located next to terminal "PV1" on the bottom backside of the board. If the DJM2.4 is to be used
with the high turndown burner this wire must be cut.
Combustion Set Up
The DJM2.4 is designed to operate with both the standard
(round burner plate)
and High
Turndown
(rectangular)
Burners. Cutting a jumper wire located next to terminal “PV1” makes the
selection. For high turndown burner operation, the jumper wire must be cut.
There are two pots located close to terminal SP, which affect the burner set up. These pots are to
be adjusted only by a qualified service technician using proper combustion analysis equipment.
Pot 7
(second pot from the right)
is the curve matching pot. The curve matching pot is used to
match the modulating gas valve opening curve and the combustion blower fan curve. There are
three Maxitrol valves that can be used with the DJM2.4. Each of these gas valves has slightly
different opening characteristics. The curve matching pot is to be adjusted to compensate for
these differences.
Pot 8
(first pot from the right-labelled MINSP)
is the low fire RPM adjustment pot. This pot is used
to provide some adjustment to the low fire combustion air. The low fire motor speed is
adjustable from 1150 to 1400 RPM
(high turndown)
and 1800 to 2000
(standard burner)
. The
recommended settings for the low fire speed are 1250 for the high turndown burner and 1830
for the standard burner.
NOTE
:
The light off RPM is fixed, non-adjustable. Adjusting the low fire speed will
have not effect on the light off speed.
Preview of Combustion Set Up
There are two burners available:
THE STANDARD
(or Round)
BURNER
Limited to about 2.5:1 turndown.
Summary of Contents for ENGINEERED AIR DJM2.4
Page 3: ...DJM2 4 MANUAL 3 Oct 00 R2 ...