EngA ENGINEERED AIR DJM2.4, Installation, Operation And Maintenance Manual, Page: 21 / 37

DJM2.4 MANUAL
21 Oct 00 R2
Standard (Round) Burner
Most standard turndown DJ units will employ one of the following Maxitrol modulating DC volt
gas valves. Note that there is an orifice where the pilot gas line is connected to the pilot air tube.
This orifice is sized to the BTU and altitude requirements of the burner. It must be free of dirt and
burrs to operate properly. If there are problems lighting or proving the pilot that do not appear
to be related to the ignition/flame supervision device then carefully clean and inspect this orifice
from both the gas tube and air tube side. If a burr exists it is usually best to remove it by pushing
it into the air tube from the gas tube with a small pin or orifice drill, then break it off by inserting
a file or other object into the air tube.
Most standard turndown DJ units will employ one of the following Maxitrol modulating DC volt
gas valves:
Series 20 - M520, M620 These valves do not have high fire regulators. High fire
pressure is set up at the appliance regulator. If used on the
standard burner, the low fire adjustment located on the
bottom side of the valve is to be adjusted fully clockwise
(no
bypass) .
Series 50 - M550, M650, ES350 These valves do not have high fire regulators. High fire
pressure is set up at the appliance regulator. This series of
valve has been replaced with the M520/620 series.
ES345D-L This valve has a built in high fire regulator.
High Fire Set Up
1.
Place a jumper across the DJM2.4 terminals “SV and SR” to force the control into a
manual firing mode.
2.
Set manual firing pot #4 labelled “SER” (located near the middle of the panel) to high fire.
3.
Ensure correct inlet fuel pressure. Adjust the high fire manifold pressure to that listed on
the rating plate. Adjust the combustion air slider or inlet damper until the high fire O
2
reading is between 3.5 and 4.2%.
Low Fire Set Up
Standard Burner Low Fire Set Up 2.5:1 turndown
Low Fire Input is 40% of High Fire Input
The low fire procedure set up is similar to that for the high turndown burners noted
above. Adjust pot 4
(CONT) to low fire CCW and follow the set up for the high turndown
burner, except use the following values. 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 8
(MINSP) to 1850 ±10 RPM (30.5 Hz) . Note that for this speed range the high turndown
jumper on the back of the board is not to be cut.