Front diagnostic lights - Switchable priority - Built in priority protection - Simplified wiring - Premium sealed relays - Compact design - Fuse protected - 100% Factory tested - Isolated end switch - Contractor friendly PC board layout - Universal thermostat compatibility - 24 volt power output for hard wired thermostats - Field replaceable transformer - Add on power control plug - Built in post purge and pump exercise functions - Switchable primary circulator output - Two boiler contacts - Expandable up to 20 zoning panels (up to 120 zones if all are 6 zone panels) - Interface with EXP zone valve controls - UL Approved