⚙️ 110800 McDonnell & Miller 7B Proportioning Switch – 135 Ohm
Potentiometer Slide Wire Control for Low Water Cut-Off and Valve Actuation
The McDonnell & Miller 110800 7B is an automatic reset proportioning switch designed to maintain precise water levels in steam and hot water boilers. Featuring a 135 ohm potentiometer slide wire, it provides a proportional signal to control electric valves and maintain a constant water line. Ideal for use with multiple McDonnell & Miller low water cut-offs, the 7B switch ensures reliable system operation and safety.
✅ Key Features
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✅ Proportional Signal Control – Maintains consistent water level by modulating valve operation.
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✅ Automatic Reset – Restores function after low water conditions are corrected.
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✅ Single Pole Double Break Switch – Supports multiple functions, including alarms, valve actuation, or low water cut-off.
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✅ Wide Compatibility – Works with 93, 193, 94, 194, 162300, 163400, 165200, 166600 low water cut-offs.
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✅ Robust Construction – Built to OEM standards for long-lasting reliability.
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✅ Precise Potentiometer – 135 ohm slide wire allows fine-tuned proportional control.
📊 Specifications
| Specification | Detail |
|---|
| Manufacturer |
McDonnell & Miller |
| Part Number |
110800 |
| Model |
7B |
| Type |
Proportioning Potentiometer Slide Wire Switch |
| Resistance |
135 Ohms |
| Switch Type |
Single Pole Double Break |
| Reset Type |
Automatic |
| Application |
Low Water Cut-Offs, Electric Valve Actuation, Alarm Systems |
| Compatible LWCO Models |
93, 193, 94, 194, 162300, 163400, 165200, 166600 |
| Function |
Proportional control of water level via valve signal |
| Installation |
Mounts directly on compatible LWCO assemblies |
⚠️ Common Symptoms When Replacement Is Needed
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Valve fails to proportionally control water level
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Alarm or cut-off function does not activate correctly
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Electrical contacts worn or corroded
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Inconsistent water line maintenance
❓ FAQ
Q: What does “proportional signal” mean?
A: It means the switch varies its output voltage or resistance to proportionally control an electric valve, maintaining a constant water line rather than simply turning the valve fully on or off.
Q: Which low water cut-offs is this compatible with?
A: Compatible with 93, 193, 94, 194, 162300, 163400, 165200, 166600 McDonnell & Miller LWCOs.
Q: Does it require manual reset after a low water condition?
A: No — the 7B is automatic reset.
Q: Can this be used to trigger alarms?
A: Yes — the single pole double break switch allows multi-function use, including alarms, valve actuation, or LWCO operation.
🛒 Shopping Tips
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Verify your LWCO model before purchasing to ensure compatibility.
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Use OEM McDonnell & Miller parts for reliable proportional control and safety compliance.
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Ideal for maintaining precise water levels in both residential and commercial boiler systems.
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Check that your valve operator matches the 135 ohm potentiometer rating.
