DJM2.4 MANUAL
17 Oct 00 R2
No jumper to be cut on DJM2.
Light off speed about 2700 RPM.
Modulation between 1850 and 3400 RPM.
THE HIGH TURNDOWN (Rectangular) BURNER
Capable of 15:1 turndown.
You must cut the jumper on the back of the DJM2 board. It is located next to terminal “P”
on the bottom of the board.
Light off speed about 2300 RPM.
Modulation between 1150 and 3400 RPM.
Note carefully which “M” series valve is in use.
FOR EITHER BURNER
When measuring combustion, ensure probe of analyser inserts fully into the flue
connection to the heat exchanger. Measuring at the flue outlet may be a diluted reading
due to air mixing into the flue.
First set up high fire
Then set up low fire
Adjust midrange firing (curve matching pot)
Adjust pilot
NOTE: If combustion is not set correctly it can result improper burning which may
produce products of combustion that smell, carbon and or an excessive
amount of water in the flue. Care should be taken to set burners up properly.
Note that temperature of the air and fuel may have a great affect on the set
up you select. If both the combustion air and the fuel are at a constant
temperature throughout the heating season, once combustion is set it should
remain similar through the season. However, this usually only occurs on
indoor units. Setting up an outdoor unit is not the same as setting up a unit or
a boiler inside a building.
When a unit is located outside, it is subject to different temperatures of combustion air and
fuel through the season. These temperatures affect the densities, thus affecting the resulting
combustion process. In some instances units that operate with 3% oxygen at -40° ambient
temperatures will be found to operate at 9% oxygen on an 80°F day. How the gas line is run
(indoors or across the roof) is the largest contributor to this problem.
It is better to have a burner that runs clean and doesn’t produce a lot of water from the flue
throughout the season then to set up for best efficiency. Also we recommend that the probe
for combustion analysis be placed directly into the heat exchanger outlet rather then in the
flue. This is because air can enter into the bottom of the flue and dilute readings in the flue.
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