A
DJM3
IOM-17
19 of 27 Mar 99 R3
2.
Bring voltage to gas valve at 2.25 VDC and adjust the
spring activated low fire
adjustment
located in the head with the electric modulator (smaller screw under cap) to achieve the
same O
2
reading as the one achieved at 0 VDC (16.8% to 17.5% O
2
). After this is complete
then adjust the Curve Matching pot as described in point 5 above.
Pilot Set Up (High Turndown Burner)
1.
On high turndown units, ensure air tube to pilot is free of debris and blockages and then set
pilot pressure to 3.5" WC.
2.
Pilot set up is not as critical on the high turndown burner as there is not as much heat on it
as on the regular burner.
Standard (Round) Burner
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.
Turn on the service switch (dipswitch 5).
2.
Set manual firing Pot Hi Service (located next to the + terminal) to high fire. Adjust the high
fire input to the correct clocked rate. 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
Low fire blower input is 40% of high fire blower input.
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 Low Fire Pot to 1850
10 RPM (30.5 Hz).
After setting up the low fire, adjust the curve matching pot as described in point 5 above.
