the 138-18-021-04 is specifically calibrated for the RPC series

Built with a durable black silicone jacket

using this genuine HVAC manifold part eliminates the guesswork associated with aftermarket alternatives

providing an essential safety barrier against "dry fire" conditions

By utilizing this HVAC gas supply line

Hydrolevel 1100 Low Water Cut-Off 320788-704 the 138-18-021-04 is specifically calibratedThe Hydrolevel 1100 (Part Number 45 1100) is a 24Vac compact low water cut off engineered specifically for residential boiler protection in space constrained installations. This probe type LWCO utilizes advanced electronic water level sensing to protect hydronic systems from dry fire conditions. Featuring an automatic reset function, it restores the burner circuit once a safe water level is detected. The control includes a dedicated burner circuit