Boyertown Furnace RSM 500 Installation, Operation And Maintenance Manual page 18

Conventional System
(1) Stage Heat (2) Cool ECM Motor
"O" Terminal to be energized for Cooling Only
Humidistat breaks on high humidity. Jumper "R"-"DH" if not used.
Heat Pump (1) Stage Heat (1) Stage Cool PSC Motor - Furnace Auxiliary Heat
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