LMV Series Technical Instructions
Document No. LV3-1000
SCC Inc. Page 19 Appendix A
Pilot Valve Proving (continued)
Option 2 Sequence of Operation
1. The LMV3 is in standby. All valves are closed and all relay contacts are as shown in the
electrical schematic.
2. The LMV3 receives a call for heat. The SV terminal (X6-03.3) energizes with 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 X9-04.2 as normal. The setpoint of
the PS-VP should be set for half of the inlet pressure.
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. At the same time, one of the CR-1 contacts opens, thereby
closing the PVLT and closing the PVLT POC switch. Note that the PVLT POC switch must
be closed before the pilot valves open.
5. The LMV3 continues light off and runs as normal, with the CR-1 coil latched in and the
PVLT closed.
6. Upon shutdown, the SV terminal (X6-03.3) de-energizes, which un-latches the circuit.
The PVLT remains closed until the next start up.
Option 2 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. Inlet pressure and pilot pressure must be similar (within ~30%) to have a valid test for all
four valves.
3. Valve proving must be done on startup only.
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