Due to changes in UL requirements, the Comfort Plus units are equipped as of July 1st, 2019 with contactors that only open when a system has a core charging high limit switch open. These contactors provide a secondary means of interrupting heating elements. Previously, the same relays that were used for core temperature regulation could also be used for safety control as long as they passed a 250,000 cycle test at rated current and voltage. UL recently removed this 250,000 cycle allowance.
The addition of the definite purposes contactors also affected the electrical panel painted cover by shifting the circuit breakers up slightly.
If the core temperature gets above a normal range, any one of the series connected core charging high limit switches can interrupt the line voltage power going to the system's definite purpose contactor and relay expansion board(s), triggering a "core fail" condition.
