Midco J121-DS - Manual (Page 6)

from reaching an explosive level, periodically purge the incineration
chamber as described in Step 5.
9. Observe the ignitor flame. If it is weak, screw in the Ignitor regulator adjustment
to increase the pressure. If it is excessively rich and large or floating from the
ignitor tip, back off the regulator adjustment to reduce the pressure. Set the
ignitor to a stable blue flame which burns firmly within the ignitor tip. Check
flame current with a micro-ammeter and adjust Ignitor Regulator slowly for
highest steady 2 or more microamps.
CAUTION: When adjusting the regulator, take note of the supply
pressure. If gas supply pressure is below its specified range during
adjustment, an over-fire condition could result when pressure returns to
normal, particularly if the regulator adjustment screw is BOTTOMED
OUT. ALWAYS confirm that at least the minimum rated pressure is being
supplied to the ignitor during regulator adjustments, and NEVER BOTTOM
OUT regulator screw. Operate air shutter throughout range to confirm
Ignitor stability. Try several relights. Refer to Table 4.
10. Remove the input adjuster cap (see Figure 3) and, with the Ignitor and Main
Flame on, turn the Main Gas Input Adjusting Screw (see Figure 4) until the
desired input rating is reached (refer to Table 2). Turning of adjustment screw
counterclockwise increases gas flow; clockwise reduces flow. If Main Flame
gas pressure requires adjustment, refer to SECTION V PIPING SUPPLY.
11. Reset the Blower Air Shutter to match the intended input, i.e.; full open for
maximum, closed for minimum or partially open for midrange. The Blower Air
Shutter is factory set wide open. Adjust as necessary when, with combustion air
available in the incineration chamber, it is desirable to increase the flame
length, or to restrict the amount of excess air discharged into the incineration
chamber when the burner input is below
450 MBH.
6
Part 1 Installation
PROPANE Gas
2,500 BTU / Cu. Ft.
(with 5/8" Main Gas Port)
NATURAL Gas
1,000 BTU / Cu. Ft.
(with Main Gas Tube
only, no Gas Port)
GAS PRESSURE AT MAIN AUTOMATIC VALVE (INCHES WATER COLUMN)
Manifold Gas Pressure in Inches W. C. Manifold Gas Pressure in Inches W. C.
Input in MBH Input in MBH
Table 2 Firing Rate Curves
Part 1
Installation
Continued