LMV Series Technical Instructions
Document No. LV3-1000
SCC Inc. Page 23 Appendix A
Purge Proving (continued)
2. Set parameter 211 (fan run-up time) approximately 5 seconds longer than the amount
of time that it takes for the proving switch to close after the fan turns on at the
beginning of phase 22.
Operation
1. In phase 22, the blower motor output (X3-05.1) energizes, powering the common side of
the proving switch.
2. By the end of phase 24, the combustion air pressure input (X3-02.1) must be energized
or the LMV3 will lockout.
3. Once the proving switch closes, relay CR-1 energizes and the two normally-open
contacts close.
4. The contact wired in parallel with the proving switch latches power to relay CR-1 as long
as the blower is on.
5. The other contact wired to line (X3-02.2) completes the circuit to the combustion air
pressure input (X3-02.1), provided that the combustion air switch is also closed. At this
point, the purge proving is complete and the LMV3 will progress to phase 30 (prepurge).
6. After postpurge is completed (phase 78), the blower motor output (X3-05.1) de-
energizes, removing power from relay CR-1 and breaking the latch circuit.
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