Siemens LME7 Series Technical Instructions page 132

Technical Instructions
Document No. LME-1000
Honeywell Modutrol IV with the LME75 (continued)
5. Output X2-09.3 de-energizes and output X2-09.2 energizes in phase 36. These actions
de-energize relay CR-1 and energize relay CR-3. Normally open contact CR-1A opens,
removing the connection that was keeping the mod motor to high fire. Since normally
open contact CR-2 remains open, the mod motor drives to the low fire position. Once
the mod motor reaches the low fire position, the low fire proving switch closes, and
actuator feedback input X2-09.4 is energized.
6. If the jumper for direct ignition is not installed, the LME75 progresses through phases
40, 42, and 44 without any change to the mod motor. During these phases, the LME75
lights off the pilot and establishes a flame signal. The mod motor remains at the low fire
position, and actuator feedback input X2-09.4 is required to remain energized during
these phases, proving that the mod motor is at the low fire position through the light-off
sequence.
7. Main valve outputs X7-04.4 and X7-02.3 are energized in phase 50 (for piloted burners)
or phase 40 (for non-piloted burners). Input X5-03.3 is energized, which has no effect.
Output X2-09.3 is de-energized, so normally open contact CR-1B remains open, and
relay CR-2 remains de-energized. The mod motor remains at the low fire position. The
LME75 lights off the main burner and progresses through the end of phase 52 like this.
8. The LME75 transitions to operation phase oP. During phase oP, power on input
X5-03.3 is directly transmitted to output X2-09.3, causing relay CR-1 to energize.
Normally open contact CR-1B closes, energizing relay CR-2. Normally open contact CR-2
closes, allowing the modulation signal (0-135 Ohm or 4-20 mA) to control the mod
motor. Normally closed contact CR-2 opens, preventing the connection of terminals R
and B on 0-135 Ohm mod motors or terminals F and - on 4-20 mA mod motors. During
phase oP, the mod motor is controlled by an external control signal, and the LME75
does not require any type of position feedback.
9. The LME75 loses the call for heat and transitions to phase oP1. Output X2-09.2 is
energized to drive the mod motor to low fire before shutting the fuel valves. Once the
mod motor reaches the low fire position, the low fire proving switch closes, and
actuator feedback input X2-09.4 is energized.
10. Postpurge (phase 74) occurs at low fire. No outputs are energized that would allow the
mod motor to move off of low fire. No actuator position feedback is required during
postpurge.
Appendix A Page 10
LME Series
SCC Inc.