750-204
Profire D/LND
4-7
4.6 — Linkage: Modulating Motor
4.5.6 — Nozzle Line Heater
1. Remove the cover that encloses the thermostat and interlock switch. The pointer controls the thermostat set-
ting. The knurled knob controls the cold oil interlock switch.
2. The thermostat pointer should be set at position 6 and then raised or lowered as required. Higher numbers
indicate higher temperatures. Let the unit run before making further adjustments. The thermostat governing
the nozzle line heater element is set lower than the thermostat governing the oil heater in the circulating loop.
3. The cold oil interlock switch is controlled by the small brass knurled knob under the pointer. This is set to pre-
vent the burner from starting until proper oil temperature is attained. Set it below the oil thermostat setting. If
the cold oil interlock is set higher than the oil temperature, the burner will not run.
4. Replace the cover.
FIGURE 4-2. Pointer and Knob
4.6 — Linkage: Modulating Motor
The linkage consists of adjustable cams, levers, rods and ball joints that transmit motion from the modulating
motor to the air damper, gas butterfly valve, and oil metering unit. When properly adjusted, coordinated move-
ment of the air and fuel control devices provide proper fuel/air ratios through the firing range. In linkage adjust-
ments, several important factors serve as guides:
• The modulating motor must be able to complete its full travel range. Restrictions will damage the motor and/
or the linkage.
• Lever and rod adjustments should be made with the motor in the low fire position.
NOTE: Be sure the manifold is filled with oil prior to startup.
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