If you observe low suction pressure along with high superheat and a frosted expansion valve inlet while the head pressure remains relatively normal

How does a duplex pump alternator work

Precise Superheat Regulation: High-grade diaphragm ensures consistent refrigerant flow

OEM Fitment: Precision-stamped aluminized steel ensures exact alignment with existing burner manifold and collector box footprints

preventing excessive stacking during peak demand periods

Caleffi ZVR103 Relay 320788-704 If you observe low suctionThe Caleffi ZVR103 is a high performance 3 zone valve relay designed for professional contractors managing multi zone hydronic heating systems. Engineered for seamless integration, the ZVR103 serves as a direct technical replacement for the HPZC103, providing a robust interface between low voltage 2, 3, and 4 wire thermostats and boiler equipment. This hydronic zone valve controller features a standard 40 VA transformer, which is field expandable to