Mueller A17921 Manifold 320788-703 or light oil

or light oil

and phase imbalance

or if the system exhibits rapid cycling

Always verify the 4 cell gasket configuration against your specific furnace model number before installation to ensure total pressure switch stability and combustion safety

Ensure the porcelain is clean of carbon deposits

Mueller A17921 Manifold 320788-703 or light oilThe Mueller A17921 ReliefMaster is a heavy duty change over manifold engineered for high demand industrial and commercial refrigeration applications. This HVACR manifold features a 1 2" NPTFE (National Pipe Thread Fuel Extended) inlet and 1 2" NPTFI (National Pipe Thread Fuel Injection) outlets, providing a secure, leak proof transition for dual relief valve setups. With a design pressure (MAP) of 700 psig and a broad operating temperature range of