Service manual

A DJM3.2 MANUAL
The low fire procedure set up is similar to that for the high turndown burners noted above. The
difference is the maximum allowable CO at low fire is 200 PPM. The low fire O
2
reading should be
between 10.9% to 11.3%. The combustion slider is different than the high turndown slider. It is a
plate that slides between the blower outlet and the burner box. The low fire RPM is adjusted using
Pot Low Fire to 1850 ±10 RPM (30.5 Hz).
After setting up the low fire, adjust the curve matching pot as described in points 5 and 6 above.
Pilot Set Up for DJ Series Standard Burners
Do not set up pilot until you are confident the burner is operating with correct air/fuel mixture.
1. Ensure the pilot tube is free of debris and blockages.
2. On standard round burners, set pilot as per the following
procedure.
• Install a 10,000-ohm resistor in series with the flame
rod circuit.
• Connect a DC voltmeter across the resistor.
• The reading will be in millivolts if your meter does not
auto scale.
MV mete
r
I
g
n Control
10,000 ohms
• Connect a manometer to the pilot line.
• Run the burner on main flame for a few minutes to have the burner plate warm.
• Leave the pilot on but turn the main gas off. You will have to jumper the DJM3.2 terminals
1 and P to do this and remove the wire from terminal 3.
• As low pilot gas pressure can damage the ceramics, reduce the pilot gas pressure to 2.5
inches and immediately return it to a higher pressure. This is to ensure the pilot gas
regular responds properly.
• Adjust the pilot valve regulator to a pressure in excess of 4.5 inches pressure.
• Slowly reduce the pilot gas pressure while watching both the pressure and the voltmeter.
The millivolt reading should be increasing. At the point where it begins to fall you should
stop reducing pressure and return to the high spot.
NOTE: The fall in pressure could only be as small as a couple of millivolts. This point
should be between 4.5 and 2.5 inches pilot pressure.
NOTE: Some smaller burners (DJ40 250,000 BTUH and smaller), may need to have a
screw placed through the pilot air tube to reduce the amount of air to the pilot.
This reading is used to determine the adjustment that will usually give the best pilot lighting
and proving strength. However, care must be taken to not adjust the reading for pilot gas
pressure below 2.5 inches water column pressure or you will break the pilot ceramics.
Next, visually observe the pilot flame. It should be visible at a minimum of 3 of the holes
around the pilot. If the pilot cannot be seen then it is likely burning too deep into the pilot box.
If this is occurring check that the gasket on the pilot assembly is forming a tight seal. Also
ensure that the burner is located in the center of the burner tube. If it is mounted too low then
too much air can flow over the top of the burner and affect the pilot.
Too large a gap.
Raise burner plate
up to centre.
OK
Page 33 Revised: 3/11/99