Revision Notes:
Revision A (PCP# 3000023718 / CN# 500013605)
initial release.
Revision B (PCP #3000027910 / CN #500017507) reflects the addition
of the 3501 model, updates made to the Check Flame and Combustion
Section on page 18, and the wiring and ladder diagrams.
Revision C (PCP #3000029182 / CN #500018624) reflects the addition
of the 2501 - 3001 and 4001 - 6001 models.
MM #100302418_DIR #2000555704 Rev C
11/18