Lochinvar & A.O. Smith 100208231 Fuse

The Lochinvar & A.O. Smith 100208231 Fuse is a critical 3.15 Amp 250V slow-blow glass fuse designed specifically for the protection of integrated control boards in high-efficiency commercial boilers and water heaters. As a direct OEM replacement part, this 5x20mm cartridge fuse ensures the sensitive electronics of the Lochinvar Knight and Armor series, as well as various A.O. Smith Cyclone models, remain protected from overcurrent events and transient surges. Unlike standard fast-acting fuses, the time-delay characteristics of the 100208231 allow for the momentary inrush current required by fans and pumps without nuisance tripping. When diagnosing a "No Power" or "Blank Display" condition on a Smart System control board, checking this fuse is a primary troubleshooting step. This high-quality ceramic or glass-bodied fuse meets strict UL and CSA standards, maintaining the operational integrity and safety clearances of the original manufacturer specifications for HVAC control circuit protection.

• Precise Overcurrent Protection: 3.15A rating specifically calibrated for Lochinvar control board safety.
• Time-Delay Functionality: Prevents premature failure caused by motor start-up rushes in HVACR systems.
• OEM Compatibility: Exact replacement for A.O. Smith 100208231 and Lochinvar FUS2003, ensuring proper fit and conductivity.
• Standardized Form Factor: 5x20mm dimensions allow for quick installation in standard board-mounted fuse holders.

What causes the 100208231 fuse to blow repeatedly?
Recurring failure of the 3.15 amp fuse typically indicates a short circuit in the 24V transformer or a grounded wire in the blower motor or igniter circuit. Always meg-ohm the combustion blower and check for moisture on the control board before replacing.

Can I use a fast-acting fuse instead of this slow-blow model?
No. A fast-acting fuse will likely blow immediately upon the induction load of the fan or the energizing of the transformer. The 100208231 slow-blow fuse is required to handle HVAC control circuit inrush currents.

Is this fuse compatible with Lochinvar Knight and Armor units?
Yes, this is the standardized replacement fuse for most Lochinvar and A.O. Smith commercial units utilizing the 100208231 or 100109923 part numbers.

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.