Siemens LMV3 series Technical Instructions page 213

LMV Series
Pilot Valve Proving (continued)
Option 3 Sequence of Operation
1. The LMV3 is in standby. All valves are closed and all relay contacts are as shown in the
electrical schematic. Main gas valve V1 terminal X8-02.1 is effectively connected to PV1,
and main gas valve V2 terminal X7-01.3 is effectively connected to PV2.
2. The LMV3 receives a call for heat. The SV terminal (X6-03.3) energizes with the blower,
which has no effect. The LMV3 drives to prepurge position.
3. During prepurge, the valve proving sequence takes place on the pilot valves only. PS-
VP2 (the Pressure Switch Valve Proving between the pilots) is effectively connected to
the valve proving terminal (X9-04.2). The setpoint of PS-VP2 should be set for half of
the inlet pressure to the pilot valves.
4. The LMV3 drives to ignition position. The ignition transformer output (X4-02.3)
energizes, thereby energizing the CR-2 coil, and latching the CR-1 coil from the power
supplied from X6-03.3. The main gas valve V1 terminal (X8-02.1) is connected to main
gas valve V1, and the main gas valve V2 terminal (X7-01.3) is connected to main gas
valve V2. The pilot valve terminal (X7-02.3) is connected to both PV1 and PV2. Also, PS-
VP1 is now connected to the valve proving terminal (X9-04.2).
5. The LMV3 continues to light off and runs as normal, with the CR-1 coil latched in.
6. Upon shutdown, the LMV3 proceeds directly into valve proving on shutdown. The SV
terminal (X6-03.3) is still energized, so the main valves will go through valve proving
using PS-VP1. The setpoint of PS-VP1 should be set for half of the main inlet pressure.
7. After valve proving on shutdown is complete, the SV terminal (X6-03.3) de-energizes
and the CR-1 circuit unlatches.
Option 3 Important Notes
1. Separate pressure switches for the pilot valves and main valves are required.
2. All four valves are tested independently.
3. Valve proving must be done on both startup and shutdown of the boiler.
4. CR-1 should be a force-guided safety relay
SCC Inc. Page 21
Technical Instructions
Document No. LV3-1000
Appendix A