Carrier HH19ZA190 Limit Switch 321894-709 'NoPP' signifies that there is

'NoPP' signifies that there is no pre-purge period

How do I troubleshoot a pilot that will not stay lit

identifying underlying issues before restarts

No Differential Pressure Required: The internal pilot-operated design ensures the valve opens reliably from zero PSI up to its maximum rating

Carrier HH19ZA190 Limit Switch 321894-709 'NoPP' signifies that there isThe Carrier HH19ZA190 Limit Switch is a critical safety component engineered for precise thermal monitoring in residential and commercial HVAC furnace systems. This temperature actuated switch is designed to protect equipment and ductwork from overheating by interrupting the electrical circuit when the high limit threshold is reached. Specifically calibrated with a 190F Open and 150F Close thermal profile, it serves as a reliable flame rollout switch