Lochinvar & A.O. Smith 100277936 Pressure Switch

The Lochinvar & A.O. Smith 100277936 Pressure Switch is a critical safety component designed for precise differential pressure sensing in high-efficiency condensing boilers and water heaters. Engineered with a specific set point of -0.75" W.C. (PF), this 0.75 pressure switch ensures the combustion air blower is generating sufficient draft before allowing the ignition sequence to proceed. As a direct Lochinvar PRS1011 replacement, it maintains the integrity of the flue gas sensing circuit, preventing operation under hazardous venting conditions. This OEM pressure switch is built to withstand the cycling demands of commercial and residential hydronic systems. When troubleshooting Lochinvar error codes related to air proving, verifying the diaphragm integrity and contact continuity of this A.O. Smith 100277936 is a standard diagnostic step. It provides a reliable millivolt signal to the integrated boiler control, ensuring the fan inducer is venting properly during the pre-purge cycle.

Key Benefits

• Direct Replacement: This unit is the exact functional equivalent for the PRS1011, ensuring zero-modification installation on compatible mounting brackets.
• Precise Calibration: Factory-set at -0.75" Water Column to meet strict negative pressure requirements for safe combustion.
• Enhanced Durability: Engineered with materials resistant to the corrosive environment of condensing furnace exhaust and moisture.
• Reliable Proving: Minimizes nuisance lockouts by providing consistent electrical closure when the inducer motor reaches the required RPM.

Common Questions

Can I use a switch with a different set point if the -0.75" W.C. is unavailable?
No. Using a switch with an incorrect pressure rating can lead to incomplete combustion, frequent ignition failure, or unsafe operating conditions. Always match the water column rating on the manufacturer's label.

What are the symptoms of a failing 100277936 pressure switch?
Common signs include the blower motor running without the burner igniting, or the controller displaying an "Air Proving Switch Open" or "Fan Proving" fault code.

Is this switch compatible with both Lochinvar and A.O. Smith units?
Yes, this OEM part is a shared component used across several brands under the A.O. Smith parent company, including certain Lochinvar Knight and Armor models.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.