Dual Fuel Operation - Siemens LMV5 Series Technical Instructions

Technical Instructions
Document No. LV5-8000
VFD Bypass (continued)

Dual Fuel Operation

1. When the "Fuel Select Switch" is in gas mode, the coil for CR3 is energized, preventing
the LMV52 from running oil. Motor contactors K1 and K2 are energized and power
flows through the VFD to the motor. Auxiliary contactors on K1 and K2 prevent motor
contactor K3 from energizing. The gas select terminal (X4-01.1) on the LMV52 is
energized, and the LMV52 operates on gas.
2. When the "Fuel Select Switch" is in oil mode, the coil for CR2 is energized which
prevents the LMV52 from running gas. Motor contactors K1 and K2 are de-energized
and no power flows to the VFD. Power runs directly to the motor through bypass
contactor K3 once the fan output (X3-01.1) is energized in phase 22. An auxiliary
contactor on K3 prevents motor contactors K1 and K2 from energizing. The oil select
terminal (X4-01.2) on the LMV52 is energized, and the LMV52 operates on oil.
3. When the "Fuel Select Switch" is in off mode, terminal X5-03.1 is de-energized,
preventing the LMV52 from running.
4. Once the fan turns on in phase 22 while running either fuel, the coil for CR1 is energized.
The normally open contacts for CR1 close, latching the current fuel in place until the fan
turns off after phase 78.
5. If direct start is activated and a fuel changeover is required, turn the "Fuel Select
Switch" to off. Wait for the LMV52 to get back to standby (phase 12). Switch the "Fuel
Select Switch" to the desired fuel.
Appendix A Page 42
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