Lochinvar & A.O. Smith 100208661 Flow Switch
The Lochinvar & A.O. Smith 100208661 Flow Switch, also identified by part number 781621 or alias FS8-W, is a heavy-duty liquid flow switch engineered for precise proof-of-flow detection in high-efficiency commercial boiler systems and water heaters. Designed as a direct HVAC replacement part for the McDonnell & Miller FS8-W, this unit features a durable stainless steel #3 paddle configuration to ensure reliable contact closure once the system pump achieves the required differential pressure. It is a critical safety component for Lochinvar Knight and A.O. Smith Legend boilers, preventing dry-fire conditions by verifying active circulation before allowing the ignition sequence to proceed.
This flow switch kit is fully compatible with multiple Lochinvar models, including the AWN286PM, OKL501, and OKL701 series. It serves as a necessary upgrade for units originally utilizing the WTR2211 or 100173715 components. For HVAC technicians performing heating system repair, this switch provides a standard 1-inch NPT connection and is rated for high-temperature hydronic applications. Whether you are troubleshooting a flow switch lockout or conducting annual boiler maintenance, installing this OEM-spec control switch ensures the Smart System control board receives the necessary proving signal to maintain peak operational efficiency without nuisance shutdowns.
Key Benefits- Broad Compatibility: Matches specifications for Lochinvar and A.O. Smith commercial units, replacing legacy part numbers WTR2211 and 100173715.
- Optimized Flow Sensing: Includes a factory-sized #3 paddle designed to trigger at specific GPM thresholds required for condensing water heaters.
- Safety Integration: Directly interfaces with boiler control boards to provide a hard-wired safety interlock against low-flow conditions.
- Rugged Construction: Built to withstand the constant cycling and thermal stress found in commercial HVAC environments.
What was the previous part number for this flow switch?
This kit replaces the older 100173715 and WTR2211 part numbers frequently found in older Lochinvar Knight manuals.
Will this work if my boiler shows a "Flow Switch" fault code?
Yes, if your Lochinvar Smart System or A.O.-Smith DiaScan display indicates a flow error despite the pump running, this replacement flow switch is the primary component to inspect for mechanical failure or scale buildup.
How do I test the 100208661 during a service call?
Technicians should check for continuity across the switch terminals while the pump is active. If the paddle is deflected by water flow but the circuit remains open, the 100208661 flow switch requires immediate replacement.
This item is not eligible for free shipping.
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.
Original: $295.73
-65%$295.73
$103.51Lochinvar & A.O. Smith 100208661 Flow Switch
The Lochinvar & A.O. Smith 100208661 Flow Switch, also identified by part number 781621 or alias FS8-W, is a heavy-duty liquid flow switch engineered for precise proof-of-flow detection in high-efficiency commercial boiler systems and water heaters. Designed as a direct HVAC replacement part for the McDonnell & Miller FS8-W, this unit features a durable stainless steel #3 paddle configuration to ensure reliable contact closure once the system pump achieves the required differential pressure. It is a critical safety component for Lochinvar Knight and A.O. Smith Legend boilers, preventing dry-fire conditions by verifying active circulation before allowing the ignition sequence to proceed.
This flow switch kit is fully compatible with multiple Lochinvar models, including the AWN286PM, OKL501, and OKL701 series. It serves as a necessary upgrade for units originally utilizing the WTR2211 or 100173715 components. For HVAC technicians performing heating system repair, this switch provides a standard 1-inch NPT connection and is rated for high-temperature hydronic applications. Whether you are troubleshooting a flow switch lockout or conducting annual boiler maintenance, installing this OEM-spec control switch ensures the Smart System control board receives the necessary proving signal to maintain peak operational efficiency without nuisance shutdowns.
Key Benefits- Broad Compatibility: Matches specifications for Lochinvar and A.O. Smith commercial units, replacing legacy part numbers WTR2211 and 100173715.
- Optimized Flow Sensing: Includes a factory-sized #3 paddle designed to trigger at specific GPM thresholds required for condensing water heaters.
- Safety Integration: Directly interfaces with boiler control boards to provide a hard-wired safety interlock against low-flow conditions.
- Rugged Construction: Built to withstand the constant cycling and thermal stress found in commercial HVAC environments.
What was the previous part number for this flow switch?
This kit replaces the older 100173715 and WTR2211 part numbers frequently found in older Lochinvar Knight manuals.
Will this work if my boiler shows a "Flow Switch" fault code?
Yes, if your Lochinvar Smart System or A.O.-Smith DiaScan display indicates a flow error despite the pump running, this replacement flow switch is the primary component to inspect for mechanical failure or scale buildup.
How do I test the 100208661 during a service call?
Technicians should check for continuity across the switch terminals while the pump is active. If the paddle is deflected by water flow but the circuit remains open, the 100208661 flow switch requires immediate replacement.
This item is not eligible for free shipping.
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.
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Description
The Lochinvar & A.O. Smith 100208661 Flow Switch, also identified by part number 781621 or alias FS8-W, is a heavy-duty liquid flow switch engineered for precise proof-of-flow detection in high-efficiency commercial boiler systems and water heaters. Designed as a direct HVAC replacement part for the McDonnell & Miller FS8-W, this unit features a durable stainless steel #3 paddle configuration to ensure reliable contact closure once the system pump achieves the required differential pressure. It is a critical safety component for Lochinvar Knight and A.O. Smith Legend boilers, preventing dry-fire conditions by verifying active circulation before allowing the ignition sequence to proceed.
This flow switch kit is fully compatible with multiple Lochinvar models, including the AWN286PM, OKL501, and OKL701 series. It serves as a necessary upgrade for units originally utilizing the WTR2211 or 100173715 components. For HVAC technicians performing heating system repair, this switch provides a standard 1-inch NPT connection and is rated for high-temperature hydronic applications. Whether you are troubleshooting a flow switch lockout or conducting annual boiler maintenance, installing this OEM-spec control switch ensures the Smart System control board receives the necessary proving signal to maintain peak operational efficiency without nuisance shutdowns.
Key Benefits- Broad Compatibility: Matches specifications for Lochinvar and A.O. Smith commercial units, replacing legacy part numbers WTR2211 and 100173715.
- Optimized Flow Sensing: Includes a factory-sized #3 paddle designed to trigger at specific GPM thresholds required for condensing water heaters.
- Safety Integration: Directly interfaces with boiler control boards to provide a hard-wired safety interlock against low-flow conditions.
- Rugged Construction: Built to withstand the constant cycling and thermal stress found in commercial HVAC environments.
What was the previous part number for this flow switch?
This kit replaces the older 100173715 and WTR2211 part numbers frequently found in older Lochinvar Knight manuals.
Will this work if my boiler shows a "Flow Switch" fault code?
Yes, if your Lochinvar Smart System or A.O.-Smith DiaScan display indicates a flow error despite the pump running, this replacement flow switch is the primary component to inspect for mechanical failure or scale buildup.
How do I test the 100208661 during a service call?
Technicians should check for continuity across the switch terminals while the pump is active. If the paddle is deflected by water flow but the circuit remains open, the 100208661 flow switch requires immediate replacement.
This item is not eligible for free shipping.
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.
