Sequence Of Operation; Important Notes - Siemens LMV5 Series Technical Instructions

LMV Series
Pilot Valve Proving (continued)
Option 1 Sequence of Operation
1. The LMV5 is in standby. All valves are closed and all relay contacts are as shown in the
electrical schematic.
2. The LMV5 receives a call for heat. The SV terminal (X9-01.1) energizes before the
blower, energizing the PVLT (Pilot Valve Leak Test). The PVLT opens, and connects the
volumes between the pilot valves and main valves. The PVLT POC switch also opens,
preventing the operation of the pilot valves.
3. During prepurge, the main valve proving sequence takes place as normal. The PS-VP
(Pressure Switch - Valve Proving) is wired to terminal X9-03.2 as normal. The setpoint of
the PS-VP should be set for half of the inlet pressure.
4. The LMV5 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 X9-01.1. At the same time, one of the CR-1 contacts opens, thereby
closing the PVLT valve and closing the PVLT POC switch. Note that the PVLT POC switch
must be closed before the pilot valves open.
5. The LMV5 continues light off and runs as normal, with the CR-1 coil latched in and the
PVLT valve closed.
6. Upon shutdown, the SV terminal (X9-01.1) de-energizes, which un-latches the circuit.
The PVLT valve remains closed until the next start up.
Option 1 Important Notes
1. The proof of closure switch on the PVLT ensures that gas is unable to flow between the
pilot and main valves before the pilot attempts to light.
2. All four valves are tested at the inlet pressure, which is the pressure that they normally
operate at. The PS-VP should be set for half of the inlet pressure which provides a valid
test for all four valves.
3. Valve proving must be done on startup only.
SCC Inc. Page 23
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Technical Instructions
Document No. LV5-8000
Appendix A