Aprilaire 4977 Relay 321894-706 this reversible filter drier is

this reversible filter drier is fully compatible with R-410A

This is the recommended direct replacement

Industrial-Grade Durability: Built to withstand high-temperature environments inside heat exchangers and burner boxes

Replacing these internal components during scheduled maintenance is far more cost-effective than a total valve swap and significantly reduces potential downtime

The Robertshaw 1980-018 utilizes a high-grade copper and nickel alloy core for maximum millivolt output and electrical conductivity

Aprilaire 4977 Relay 321894-706 this reversible filter drier isThe Aprilaire 4977 Relay is a high performance 24v Coil DPDT Relay designed for seamless integration within advanced HVACR systems. This versatile double pole double throw relay serves as a critical HVAC control component, allowing for the simultaneous management of two independent circuits. Engineered for Aprilaire humidifiers and air cleaners, this 24 volt switching relay ensures precise electrical isolation and reliable secondary hardware