McDonnell & Miller 354089 Switch Assembly
The McDonnell & Miller 354089 Switch Assembly, also designated as the Model SWA-150S-M, is a critical replacement component engineered specifically for Series 150S and 157S low water cut-offs and pump controllers. For technicians servicing steam boilers, this snap-action switch assembly is the standard for maintaining precise liquid level control and ensuring high-limit safety. Featuring a manual reset mechanism, this assembly requires professional intervention after a low water condition, preventing the burner from cycling until the system is checked. This switch is rated for applications up to 150 psi and is designed for a direct fit on modern "S" prefix head mechanisms, providing a significant upgrade in reliability over older mercury-style iterations.
When installing the SWA-150S-M manual reset switch, verify the manufacturing date of the existing unit; models produced prior to September 2003 (03J) may require a complete head replacement to accommodate this snap-action geometry. The dual-circuit design allows for simultaneous burner control and alarm activation. Ensure the rocker is correctly aligned with the float mechanism roller during seat-in to prevent mechanical binding. This McDonnell & Miller replacement part is built to handle specific electrical loads, typically up to 7.4A at 120 VAC, ensuring robust performance in demanding commercial and industrial boiler rooms.
Key Benefits:- Direct OEM Compatibility: Specifically designed for McDonnell & Miller 150S/157S series, ensuring exact mounting and terminal alignment.
- Manual Reset Safety: Integrated manual reset prevents automatic burner restarts, crucial for compliance and identifying the root cause of low water events.
- High-Pressure Tolerance: Field-proven to operate reliably in steam systems with pressures up to 150 psi (10.5 kg/cm²).
- Snap-Action Reliability: Features high-quality internal contacts that provide a crisp, positive break to prevent arcing and premature wear.
- Simplified Field Service: Designed for rapid replacement to minimize system downtime during critical heating seasons.
Is the SWA-150S-M compatible with older mercury switch controls?
No. This snap-action assembly is strictly for "S" models and is not interchangeable with the older mercury-style Series 150/157 controls.
Do I need to replace the entire head assembly for this switch?
If your current head was manufactured before September 2003, a full head replacement is required. Units manufactured after October 2003 (03K) allow for the switch-only replacement.
What are the electrical ratings for this manual reset assembly?
The assembly is typically rated for 7.4A at 120 VAC or 3.7A at 240 VAC. For higher current draws, always use a motor starter or relay to protect the switch contacts.
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: $488.78
-65%$488.78
$171.07McDonnell & Miller 354089 Switch Assembly
The McDonnell & Miller 354089 Switch Assembly, also designated as the Model SWA-150S-M, is a critical replacement component engineered specifically for Series 150S and 157S low water cut-offs and pump controllers. For technicians servicing steam boilers, this snap-action switch assembly is the standard for maintaining precise liquid level control and ensuring high-limit safety. Featuring a manual reset mechanism, this assembly requires professional intervention after a low water condition, preventing the burner from cycling until the system is checked. This switch is rated for applications up to 150 psi and is designed for a direct fit on modern "S" prefix head mechanisms, providing a significant upgrade in reliability over older mercury-style iterations.
When installing the SWA-150S-M manual reset switch, verify the manufacturing date of the existing unit; models produced prior to September 2003 (03J) may require a complete head replacement to accommodate this snap-action geometry. The dual-circuit design allows for simultaneous burner control and alarm activation. Ensure the rocker is correctly aligned with the float mechanism roller during seat-in to prevent mechanical binding. This McDonnell & Miller replacement part is built to handle specific electrical loads, typically up to 7.4A at 120 VAC, ensuring robust performance in demanding commercial and industrial boiler rooms.
Key Benefits:- Direct OEM Compatibility: Specifically designed for McDonnell & Miller 150S/157S series, ensuring exact mounting and terminal alignment.
- Manual Reset Safety: Integrated manual reset prevents automatic burner restarts, crucial for compliance and identifying the root cause of low water events.
- High-Pressure Tolerance: Field-proven to operate reliably in steam systems with pressures up to 150 psi (10.5 kg/cm²).
- Snap-Action Reliability: Features high-quality internal contacts that provide a crisp, positive break to prevent arcing and premature wear.
- Simplified Field Service: Designed for rapid replacement to minimize system downtime during critical heating seasons.
Is the SWA-150S-M compatible with older mercury switch controls?
No. This snap-action assembly is strictly for "S" models and is not interchangeable with the older mercury-style Series 150/157 controls.
Do I need to replace the entire head assembly for this switch?
If your current head was manufactured before September 2003, a full head replacement is required. Units manufactured after October 2003 (03K) allow for the switch-only replacement.
What are the electrical ratings for this manual reset assembly?
The assembly is typically rated for 7.4A at 120 VAC or 3.7A at 240 VAC. For higher current draws, always use a motor starter or relay to protect the switch contacts.
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 McDonnell & Miller 354089 Switch Assembly, also designated as the Model SWA-150S-M, is a critical replacement component engineered specifically for Series 150S and 157S low water cut-offs and pump controllers. For technicians servicing steam boilers, this snap-action switch assembly is the standard for maintaining precise liquid level control and ensuring high-limit safety. Featuring a manual reset mechanism, this assembly requires professional intervention after a low water condition, preventing the burner from cycling until the system is checked. This switch is rated for applications up to 150 psi and is designed for a direct fit on modern "S" prefix head mechanisms, providing a significant upgrade in reliability over older mercury-style iterations.
When installing the SWA-150S-M manual reset switch, verify the manufacturing date of the existing unit; models produced prior to September 2003 (03J) may require a complete head replacement to accommodate this snap-action geometry. The dual-circuit design allows for simultaneous burner control and alarm activation. Ensure the rocker is correctly aligned with the float mechanism roller during seat-in to prevent mechanical binding. This McDonnell & Miller replacement part is built to handle specific electrical loads, typically up to 7.4A at 120 VAC, ensuring robust performance in demanding commercial and industrial boiler rooms.
Key Benefits:- Direct OEM Compatibility: Specifically designed for McDonnell & Miller 150S/157S series, ensuring exact mounting and terminal alignment.
- Manual Reset Safety: Integrated manual reset prevents automatic burner restarts, crucial for compliance and identifying the root cause of low water events.
- High-Pressure Tolerance: Field-proven to operate reliably in steam systems with pressures up to 150 psi (10.5 kg/cm²).
- Snap-Action Reliability: Features high-quality internal contacts that provide a crisp, positive break to prevent arcing and premature wear.
- Simplified Field Service: Designed for rapid replacement to minimize system downtime during critical heating seasons.
Is the SWA-150S-M compatible with older mercury switch controls?
No. This snap-action assembly is strictly for "S" models and is not interchangeable with the older mercury-style Series 150/157 controls.
Do I need to replace the entire head assembly for this switch?
If your current head was manufactured before September 2003, a full head replacement is required. Units manufactured after October 2003 (03K) allow for the switch-only replacement.
What are the electrical ratings for this manual reset assembly?
The assembly is typically rated for 7.4A at 120 VAC or 3.7A at 240 VAC. For higher current draws, always use a motor starter or relay to protect the switch contacts.
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.
