What is the difference between the McDonnell & Miller 2 and 2-M switches

protecting the system from dangerous exhaust build-up or blocked vent conditions

it maintains tight close-off integrity (up to 0

specifically selected for its resilience in standard air

Lochinvar & A.O. Smith 100133618 Pump 320735-701 What is the difference betweenThe Lochinvar and A. O. Smith 100133618 is a heavy duty 3 4 HP circulator pump engineered for demanding hydronic heating and commercial water heating applications. Specifically designed for high head requirements, this centrifugal pump maintains consistent flow rates across complex piping geometries, ensuring optimal heat transfer within the heat exchanger. This OEM replacement pump is a direct fit for various Lochinvar Knight and Copper Fin models,